Man-made lakes and man-made diseases

SW. Sci. Med. Vol. 16. pp. I I27 to I 145. 1982 Printed m Great Britain. All rights reserved

0277-9536/82;1 I I l27-19SO3.OQ~O Copyright Q 1982 Pergamon Press Ltd

MAN-MADE LAKES AND MAN-MADE DISEASES

TOWARDS A POLICY RESOLUTION

JOHN M. HUNTER*. LUIS F&Y+ and DAVID SCOTTS

Abstract-Throughout the tropical world, in Africa. Asia and Latin America. the construction of water impoundments, for irrigation and other purposes. in areas of endemic water-related diseases. has inexor- ably intensified community levels of infection. and also created new areas of transmission. The clearest ‘indicator’ disease is schistosomiasis. but others are involved such as malaria and the filariases. An assessment for the future suggests a worsening situation because of population growth, the demand for food production. and the increased technological capacity of the ‘bulldozer revolution’ to effect earth impoundments. The typical sectoral dichotomy in which a department of agriculture creates a disease outbreak through its development activity. leaving its counterpart department of public health to cope on a curative basis, where possible. is strongly deplored. A policy position is offered whereby disease prevention measures are integrated with development projects from the beginning and infrastructural investment and operational costs for health maintenance are identified and incorporated in the total benefit-cost analysis. The need for a communications network on ecological and health effects is pointed out; and a typology for registration of dams is offered in support of policy implementation.

RETROSPECTz ECOLOGICAL DISRUPTION

AND DISEASE

The construction of dams, formation of man-made lakes and development of irrigation projects in tropical areas introduce important changes in the environment and, in parallel, produce a number of risks to human health, apart from the evident benefits brought to the macroeconomy of a country or the production of some specific economic advance. With reference to environmental changes, water resources development projects tend in general to cause some degradation of the environment through the destruc- tion of forest galleries, increased soil erosion, and the production of biotopes more favorable than before to intermediate hosts or vectors of parasitic or infectious diseases.

At a local level, the inhabitants of submerged or requisitioned lands are affected by economic and social disturbances. even when resettlement programs have been implemented to minimize these problems. Children and pregnant women are particularly exposed to risk during the years between the aban- donment of cultivated lands and the necessary adaptation to a new situation. This adaptation is often associated with changes in life style and activities, and equilibrium with the new ecosystem may not be attained for some years.

Population migrations induced by actual or possible ‘opportunities for work provided during construction of water development projects can aggravate the

*Department of Geography and Department of Com- munity Health Science. Michigan State University. East Lansing. Ml. 48824. U.S.A.

tWH0 consultant parasitologist. Brazil. Present address: c/o O.M.S.. Caixa Postal 377. Mauuto. Mozambique.

:Formerly ProJect Manager. UNDP.‘WHO Project for Research on the Epidemiology and Methodology of the Control of Schistosomiasis in Man-Made Lakes (TDR-304). Present address: P.O. Box M 217. Accra. Ghana.

local conditions of life through housing difficulties, overcrowding, rising costs of living, commercial speculation, prostitution and other social problems, as well as the introduction of new sources of diseases (or new diseases) and immigrants immunologically susceptible to the endemic diseases prevailing in the area of development.

In Brazil. for instance, important risks to human health and welfare appearing in circumstances such as those described above, include: (a) occupational disks: accidents, some occupational diseases; (b) infections in adults: respiratory diseases, many parasitic diseases such as malaria, Chagas’ disease, venereal diseases, leishmaniasis, schistosomiasis and filariasis, yellow fever and other arbovirus infections; (c) infections in children: respiratory and virus infections. diarrhoea hookworm and other intestinal parasites. schistosomiasis, malaria, Chagas’ disease. leishmaniasis (kala- azar), etc.; (d) non-infectious conditions in children: malnutrition, deficient development, perinatal mor- tality, domestic and other accidents; and (e) general social risks: inadequate relocation procedures, loss of traditional economic activities, failure in adaptation of the resettled population. unemployment, social insecurity and insufficiency of the family budget with its consequences on educational, hygienic and nutritional conditions.

In general. risks appear, or sometimes disappear. in a sequential order, those immediately following the implementation of a water resources development project being qualitatively or quantitatively different from those arising during the construction period ‘or those occurring in the normal operation of an hydro- electric plant and its catchment area.

Limitations of‘data

The risk of spread of parasitic infections associated with the development of water resources has been stressed on many occasions. Some of these warnings are contained in documents prepared during the plan-

1127

1128 JOHN M. HUNTER rr al

ning stages of particular schemes. others are found in papers dealing more generally with the health hazards of water development. The conditions most frequently listed as being most apt to spread in tropical zones are schistosomiasis, malaria, bacterial and helminthic intestinal infections, arbovirus infections. and other specific infections which have a regional distribution, e.g. filariasis, trypanosomiasis. and dengue haemorr- hagic fever.

Evidence of the impact on health would be most valuable where a direct comparison can be made between pre- and post-development data (qualitative and quantitative) relating to parasitic diseases in a particular area. There are, however, few instances where such comparison is possible and two main reasons for this are: (i) the absence of pre- and post- development data, or the availability of data which are inadequate for the purpose of comparison; (ii) a natural reluctance on the part of governments to pub- lish reports which indicate that water resources development projects have resulted in any deterioration of the health of the local residents or immigrants. This latter situation, in itself, suggests the need for a sys- tematic study of the health hazards associated with new water impoundment and irrigation schemes.

Where direct comparison of pre- and post-development data is impossible, an alternative technique is to contrast the distribution and prevalence of selected parasitic infections in the area affected by the development with the situation in a nearby undeveloped but otherwise comparable locality. Again there are few examples where this has been done.

Finally, examination of post-development data alone indicate that the prevalences of particular infections are ‘high’, i.e. higher than in some other part of the country or in the country as a whole, and it is often this quality of information which must rightly serve to incriminate water development schemes as a hazard to health.

It would be expected that the group of infections described as ‘water-related’ would become increas- ingly prevalent as uncontrolled use of water increases, and as the association between man and water becomes closer. The best illustration of this is found in the high prevalences of schistosomiasis existing in endemic areas, the Nile Valley providing an excellent example of the consequences of intensive water use. In the case of other water-related infections, however, such a clear association is not so apparent, or at least is not so well documented. Schistosomiasis claims prior attention for a number of reasons: an increase in prevalence associated with greater use of water in the endemic areas has been an experience common to many countries in Africa now engaged in water development schemes; it is observed simultaneously across the whole African continent; these increases have often been of a very high magnitude, are relatively easy to detect, and have frequently caused a public outcry to a dramatic sign of the infection, i.e. intense haematuria in a large proportion of the children. With the other parasitic infections, if an increase of prevalence has resulted from a new closer contact with water, it has apparently been more localized, not so readily associated with the cause, and probably less dramatic.

The purpose of this presentation is to examine evi-

.

dence that water development projects have resulted in increased prevalence in specific parasitic infections.

Ajrica

The number of instances where a comparison has been made between disease distribution and intensity in pre- and post-development situations are relatively few and relate almost exclusively to schistosomiasis.

Egypt. Construction of the Low Dam at Aswan in the early 1930s allowed perennial irrigation in a number of provinces in Egypt. This was followed by an increase of Schistosoma haematobium between 1934 and 1937 in four areas which were investigated; levels of prevalence varying from 2-119; rose to 4475”, [l]. The new high dam at Aswan. which has produced more extensive perennial irrigation, has also resulted in a change of schistosomiasis transmission patterns in both Upper and Lower Egypt. The malaria epi- demic of 1942/1943 which occurred in Upper Egypt and caused 130,000 deaths was due to an invasion of Anopheles gambiae from the Sudan [Z] and must be seen as a consequence of water development.

Ghana, Lake Volta. Large-scale surveys for urinary schistosomiasis were undertaken over much of Ghana in the decade before the Akosombo Dam was built. Low prevalences (5-10x in children) were found around the area which was later impounded. Within a year of the lake reaching its maximum level (1968). very high prevalences (up to 90% and over in children aged 10-14 years) were found in lakeside communities. There are some 150,000 people living along the lakeshore. This example provides irrefutable evidence of a major hazard of the rapid spread of urinary schistosomiasis at an explosive level and on a large scale resulting from a water resources development program. Further proof of the impact of the lake was given by a study of prevalence in hinterland communities lying away from the lake. The prevalence fell progressively along a transect of 7 km, and was related to a decreasing degree of dependence on the lake for domestic water needs [3].

Ivory Coast. The dam across the Bandama Valley to impound Lake Kossou was completed in 1972. It is claimed that there has since been a marked rise in urinary and intestinal schistosomiasis in the Ivory Coast but the data on which this statement is based would have to be examined.

Kenya. Mosquito surveys in the irrigated and non- irrigated areas of the Kano Plain project, Nyanza Province, showed a reduction in the number of species and a change in the composition of the population with about a Cfold increase in the house-entry rate in the irrigated areas. It would be expected that following the increase of settlement in the area, there would be an increase in malaria transmission, but there appears to be no data on this point. In the same province, some 10,fMlO small ponds were dug with the aim of increasing fish production. They resulted in considerable breeding of malaria vectors, but no assessment of the effect on public health seems to have been made.

Mali. In the Cercle de Bandiagara (population 160,000) urinary schistosomiasis has been known for a long time. In recent years a program to build about 50 small dams was begun, with about 20 having been completed in 1977. No surveys were made before this

Man-made lakes and man-made diseases 1129

work started. But a comparison of the first two studies made in 1976 and 1977 showed an increase in the prevalence, from 79.4 to 93.40/, during the year in the same population. In addition, the local transmission of 5. mansoni was demonstrated for the first time in the 1977 survey. It can be concluded that the barrage system has probably enhanced transmission. Surveys carried out by the Organisation de Coordin- ation et de Cooperation pour la lutte contre les Grandes Endemies (OCCGE) have demonstrated high levels of schistosomiasis associated with the cultivation of rice along the flood plain of the Niger.

Nigeria. Dazo and Biles [4, 51 carried out studies of schistosomiasis prevalence and intensity at Kainji Lake in 1970 and 1971. They examined three small communities living on the lakeshore and one, New Bussa. which had been resettled well away from the lake. Prevalence, intensity of infection and incidence were much higher in the lakeshore villages than in New Bussa.

Sudan. Irrigation of the Gezira by the construction of the Sennar Dam in 1924 and extension of the irrigation system after 1950 has resulted in a progressive increase in schistosomiasis. The prevalence of S. hae- matohium rose from less than 1% in the period 19241944 to 21% in adults and 45% in children in 1952. 5. mansoni prevalences were 5% in 1947. 8.8% in 1952, and between 77 and 86% in the 7-9 year old age-group in 1973 [6,7].

Asia

In Asia, clear evidence of the adverse effects on health of water impoundment schemes, drawn by a comparison of pre- and post-development data on the distribution and prevalence of parasitic diseases, is not often found [S]. The reasons for this situation have been suggested above, in the discussion on data limitations.

Three main types of water resource development in Asia may be found: (i) multipurpose projects for hydro-electric power, irrigation and flood control; (ii) irrigation projects; and (iii) water supply projects. There would seem to be practically no health problems associated with water supply developments, or surpris- ingly, with irrigation schemes where the land irrigated is less than 16.000 ha. Of the 15 most important diseases endemic in the region. all have some potential for spread in water development schemes from (in order of importance) malaria. dengue haemor- rhagic fever. Japanese B. encephalitis. filariasis. soil transmitted helminths, schistosomiasis. liver, lung and intestinal flukes. to cholera and dysenteric infections.

Indonesia. The recent development of water resources in Indonesia has lagged behind that of Malaysia, the Philippines and Thailand, despite the fact that its population is greater than that of the other three countries combined. There is however a considerable program of development for the future. In Indonesia, as in the other three Asian countries considered. there is very little precise information available on the prevalence and distribution of parasitic diseases. and only a few surveys have been undertaken. Malaria and filariasis are considered to constitute a threat of spread in development schemes. Prevalence rates of intestinal helminths (ascariasis. tri-

churiasis and hookworm infections) range from 70 to 80%. Diarrhoeal disease of unidentified etiology is common and cholera is prevalent in some areas.

5. japonicum has been found in two small, almost adjacent. areas in Central Sulawesi Island which un- fortunately lie close to the only water development project (irrigation) in this island (population 9.4 million).

Malaysia. In West Malaysia, no studies have been made of the health problems relating to communities associated with the water development projects. Instead. profiles of parasitic diseases are based on data from health centers in the provinces in which the schemes are situated. In East Malaysia. i.e. Sabah and Sarawak. where there is great potential for water resources development. projects are planned but not yet implemented. Formerly malaria and filariasis were major public health problems, but control programs of recent years have greatly reduced the prevalences so that today the main problems are intestinal helminthiases (ascariasis. hookworm and trichuriasis) with bacterial intestinal infections resulting from poor environmental sanitation.

Schistosomiasis (i.e. 5. japonicum) is not endemic in Malaysia but one case was found in an aboriginal in Pahang State in 1974 and since then 11 more cases of infection have been detected: no intermediate snail host has yet been identified. As in Thailand, there may be a risk of spread of this infection throughout the vast water resources schemes either in operation or in the planning stage.

Dams built for hydro-electric power, and there are many, are considered to be relatively free from health hazards, being sited in uninhabited mountainous areas or perhaps otherwise protected. Irrigation schemes present a greater risk for the spread of infeo tions. However, the small schemes in the States of Perlis and Negeri Sembilan, for example, are said to be insignificant in their effects on public health. (This contrasts markedly with the situation in Africa where schistosomiasis is endemic and small impoundments have a considerable potential for the spread of the infection.)

The example of the Muda irrigation scheme in the State of Kedah demonstrates certain features of large water resources development projects: completed in 1970, it provides irrigation for 105,000 ha on which 60.000 families reside with 1.5 ha each; no information on the health of these families is available but in the State of Kedah filariasis was reduced from 26.7% in 1957 to 0.7% in 1966. as a result of a control program. A study carried out among 435 persons in 6 villages showed a low prevalence of malaria, up to 1.03%; stool examinations showed Ascaris and Tri- churis (although not hookworm) but the prevalences are not given. A number of studies on the impact of water impoundments on health are planned and will include a sequence of surveys among people living in the development areas; some of these surveys have begun.

Philippines. Water development schemes are com- paratively recent in the Philippines. but a vast future program is being envisaged. There are 39 schemes in operation. 12 are under construction and a further 812 are being planned or considered. Many of the dams already built are solely for the generation of

1130 JOHN M. HUNTER rt a/.

hydro-electric power and relatively few are for irrigation purposes.

On the relationship of water development projects to health, Harinasuta et al. [8] state:

“Since there (are) no studies on the intestinal parasitic infections in the indigenous people residing in the vicinity of any dam areas. and also no available valid data from the health centers on the Islands where those dams are situated, the review of the parasitic diseases of the gastrointestinal system in the Philippines reported by Cabrera in 1971 (see Ref. [9]) is used as a model representing the intestinal parasitic infections among inhabitants in the dam areas. The report revealed the prevalences of these infections in the endemic areas as follows: ascariasii 84.1 percent, trichuriasis 34.6 percent, hookworm infection 13.6 percent, strongyloidiasis 1.6 percent, amoebiasis 9.3 percent. These prevalences remained much the same as those found in many surveys which have been made since 1908”.

Account must be taken of the presence of S. japonicum in the Philippines. There is an endemic belt across the eastern, southern islands, Southern Luzon, Leyte, Mindanao and Jolo, estimated to have over 200,000 cases of the infection. For obvious reasons no water development schemes have been carried out in the endemic areas but a threat of extension of S. japonicum into the system of dams as the program de- velops momentum is very real.

Neither malaria nor filariasis are considered to be serious problems in the Philippines at present, but they could become important if water development projects permitted uncontrolled breeding of the mosquito vectors. The number of cases of infective hepa- titis is increasing.

Thailand. The risk of spread of the various parasitic infections is to be emphasized, with schistosomiasis being the major public health problem in water resources development. S. japonicum is not established as an endemic disease in the country. A small focus of infection (50 cases) was found 18 years ago in the Ta Pee river basin in southern Thailand but, in spite of intensive searches, the intermediate’snail host was not discovered. In 1974 two more cases were diagnosed (in Bangkok) from the same locality. Recently a few cases have been reported from Ubol Province and from Central Thailand; the infection has been shown to be by S. mekongi (more correctly termed S. japonicum) and the intermediate host is Lithoglyphopsis aperta (Temcharoen). This snail has been found in abundance in Ubol Province in the Mun river which drains into the Mekong river. There clearly exists a very real risk of the spread of this infection into water development projects in the area. There is also a risk of spread of venereal disease by importation in migrants in water development schemes, as has occurred, for example, during the construction of the Bhumiphol dam. None of the data on parasitic disease found in the epidemiological records of the health centres in the provinces refer specifically to the situations obtaining in association with water development projects.

A contrast between the situations in Aji+ca and Asia

In Africa, schistosomiasis is endemic over much of the populated areas of the continent. Its transmission is undoubtedly enhanced by an increase in man-water

contact and, from the data at present available. the infection clearly constitutes the greatest single immediate threat to health in the development of water resources. Other parasitic infections may also be increasing but they have received less attention. for resources are limited. and it is understandable that these should be largely devoted to monitoring the most sensitive index of impact, schistosomiasis. rather than used in the surveillance of infections showing changes in the levels of transmission which may occur less frequently, and be more localized and less dramatic in their effect.

In contrast, schistosomiasis in the countries considered in Asia is contained within a few relatively small endemic foci and it has been possible, in each of the four countries, to construct a large system of water resources development projects in infection-free areas without the introduction of S. japonicum. As a consequence, the impact of water related projects on health must be measured by less satisfactory parameters than those provided by schistosomiasis; and findings may be obscured by long-term operations against, for example, malaria and hlariases. Thus in Asia where impoundment schemes have been in operation for a considerable period there does not appear to be any documentary evidence that their impact on health has been examined specifically. The risks of schistosomiasis becoming established in the future. however, are undoubtedly grave.

Latin America

The changes introduced by dam construction and other water resources development projects can create or aggravate health risks in different ways that can be simplified by a grouping into two categories: one where the ecosystem is fundamentally concerned, the other where demographic or socioeconomic factors are preponderant. In the first group, parasitic and infectious diseases take pride of place.

Aggravation of health risks due to changes in the ecosystem. In the Parana Paraguay basin, malaria, leishmaniasis, and yellow fever are endemic problems that can be aggravated by water impoundments and irrigation projects through increasing the number of breeding places for anophelines or through bringing people in closer contact with the ecological niches of phlebotomine and culicine vectors of sylvatic infections. Another feared risk is the introduction of schistosomiasis in the project areas because endemic foci already exist in some aflluents of this hydrographic basin. Raising the water table and, possibly. a higher atmospheric humidity will increase soil-borne parasitic and protozoan infections that will also be simultaneously favored by the anticipated increase in population density. In the Sio Francisco basin, the same problems exist but with lesser risks for yellow fever and greater ones for schistosomiasis. Kala-azar and plague are still present in this region. In the Amazon basin, where the construction of man-made lakes is just starting, malaria is highly endemic and the control projects aim at eradication only in the long term. Here, every lake will multiply the breeding places of Anophekes darlingi, the most important vector. Other anthropodborne diseases of relevance in this large equatorial region are yellow fever, encephalitis and


certain other virus infections, cutaneous, muco-cutaneous and visceral leishmaniasis, and also filariasis, with onchocerciasis in the north-central part of the Amazon region and bancroftian filariasis in the orien- tal part. Hookworm, ascaris and trichuris infections are highly prevalent and widely distributed throughout the area. Ecologically and epidemiologically, the Araguaia-Tocantins basin resembles that of the Ama- zon, particularly where the Tucurui Dam is being constructed. In that area. there has been an aggravation of the malaria incidence in recent years, and during the first half of 1978 an exacerbation of sylvatic yellow fever produced 16 confirmed cases. Equivalent risks are found in many places of northern South America as well as in Central America and the Carib- bean islands.

Aggravation of’ health risks due to demographic and socioeconomic fhctors. Migratory movements, population resettlement, and working conditions created by water resources development projects, are other sources of risk. The increase in the density of the human population and the invasion of sylvatic eco- systems has exacerbated the transmission of a number of the diseases discussed above. Yet other diseases are due to poor living conditions. Crowding is responsible, for instance, for a high incidence of respiratory infections and for a relatively high rate of tubercu- losis. The scarcity of water in the houses and the absence of sanitary facilities in most of the residential areas around dam building sites explain the excep- tional frequency of enteritis and other diarrhoeal diseases, as well as one of their consequences, dehy- dration. In houses made of dried mud, the invasion and colonization of the triatomid vectors of Chagas’ disease is a permanent risk over the entire continent. with very limited free areas. The massive arrival of immigrants has everywhere caused housing problems, increases in rents and food costs, and employment instability as well as unemployment. All these factors contribute to a lowering of nutritional status and to increased susceptibility to infections. A predominance of single men in the labor population has stimulated prostitution and produced high frequencies of venereal diseases, particularly gonorrhea and syphilis.

If these risks have not resulted in dramatic situations in most of the dam construction areas in Latin America, it is because the existence of preventive health services and their active engagement in control measures have contributed to the containment of the risks to low levels. Sometimes, the high costs of control operations have been supported by those in charge of the project, as for example in Itaipu or in Sobradinho. These costs have been particularly important when the risks were not foreseen and reduced by preventive measures.

A true appreciation of the influence of water resources development projects on health risks requires a specific survey including pre- and post- impoundment data, or some other statistical analyses that can avoid the dilution of a higher rate of prevalence in the project zone with the lower prevalences existing outside this area. An example can be found in the study conducted by the Superintend2ncia de Cam- panhas de Saude Publica [IO] on the influence of the transamazonian road on the prevalence of malaria (see Table 1).

Table 1. Influence of the transamazonian road on the distribution of malaria prevalence

Prevalence of malaria* Transamazonian road Other areas

area of the state State (7;) (7,)

Maranhio 12.3 5.0 Para 14.5 3.9 Amazonas 17.7 7.4 Acre 22.8 1.9

*Percentage of positive blood examinations.

In general, health risks are greater in highly endemic areas of disease with economically weak populations. Organizational and budgetary resources for an appraisal of the future risks and early preventive intervention are not expected in projects of medium or small capacity. In countries or regions without adequate infrastructures for the control of health risks, these may in turn effectively damage the local population and later require more costly procedures to cope with the situation.

In the foregoing discussion of disease effects in Africa, Asia and Latin America, the general acceler- ation of disease transmission in water impoundments and irrigation schemes has been described. Old endemic foci of infection have been greatly enlarged and exacerbated and new diseases have sometimes been introduced. The patterns of disease intensification that have emerged reflect man’s efforts to change the environment for purposes of economic development.

PROSPECT: ‘FUTURE SHOCK

Construction growth rates

Apart from the currently serious situation. the implications for the future are exceedingly grave unless the necessary ameliorating and counteractive steps are taken. This prognosis is based upon what can be ascertained regarding the present rate of dam construction and future plans and feasibility studies. Information on Africa. Asia and South America is discussed later, but, in general. growth trends in the rates of construction would seem to be following an exponential curve. According to the International Commission on Large Dams [ll]. over 350 dams with a height of over 15 m come into existence each year thereby adding to a current inventory of lO,OOO-12,000 such dams [12]. Regarding the construction of megadams, with a surface area exceeding 1000 km, three existed before 1950, 8 were built in the next decade, 1950-1959, and 21 in 1960-1969 [13]. Lake Volta, the world’s largest man-made impoundment. is 15 times larger than Lake Geneva; and the great river basins such as Amazonia Zaire and Mek- ong have hardly been tapped. McJunkin [12] argued that only 227(, of Africa’s potentially arable land was cultivated, and the corresponding proportion for South America was a mere I I’:,. He claimed that millions of hectares of land would be brought under irrigation in the years to come.

Undoubtedly. it is the pressure of population increase in the developing world that demands an

1132 JOHN M. HUNTER et al.

expansion of agricultural production. This is achiev- able through intensification of water impoundment and irrigation. Worthington [14] cited the example of Mexico, an arid country, with its population increasing at a phenomenal rate of 3.6% per year. Indeed, faced with food demands for the world’s increasing population, extended water management, i.e. more land under irrigation, appears inevitable. An estimate by Houston [lS] suggested that in addition to the existing 50 million hectares of land in the world under irrigation (including irrigated areas that need to be improved or rehabilitated), an additional 23 million hectares of irrigated land will be added, i.e. an increase of 46% by 1985 giving an enormous increase of production. Thus man-water contact, vector populations, and disease incidence will predictably rise sharply and, furthermore, will appear on a quantitatively greater scale than ever before. This is truly a ‘future shock’ situation. A pessimistic but probably not unrealistic view may be expressed that developing countries have just reached the ‘foothills’ of the disease transmission and water problem, and that the ‘mountains’ lie ahead.

The ‘bulldozer revolution’ and small impoundments

Small impoundments tend to serve more purposes than do large dams. A small multi-purpose project may be used for fishing, water supplies, cattle and livestock watering, irrigation, and flood control. Usually, population and animal contact with water is high, so that disease transmission rates are correspondingly increased. Some specific examples are given below for Africa, Asia and Latin America, but in general large regions in the developing countries are found to be dotted with small dams. In aggregate they are highly significant in agricultural production and probably exceed large dams in importance of disease effects.

Comprehensive data are not available. However, it Seems certain that the rate of construction of small dams is increasing rapidly. One reason for this increase, apart from improved knowledge of agronomic and hydrological techniques and from the accruing production benefits, is the ‘bulldozer revolution’: that is to say, the ready availability of ‘bulldozers’ and other earth-moving equipment for purchase, loan, lease, rent or shared ownership has led to considerable earth-moving capability at local community levels. The results are that, in addition to government- supported agricultural projects, village communities and farmer cooperatives in the tropical world can, on their own initiative, construct small water impoundments. Even churches, missions and voluntary agencies are able to participate in this activity.

Without denying their agricultural benefits, the small impoundments are hazardous to health since they generate a high risk of disease transmission and are usually totally without provision of health care measures. Furthermore, small impoundments, especially when they are not financed by the government, are often affected by problems of maintenance, seepage and water discipline, all of which favor the extension of vector habitats. The rapid increase of construction of small dams, desirable as it is, constitutes an ominous threat to health. The development

of disease prevention programs is therefore urgently needed around these constructions, as well as support for maintenance of earthworks.

Time-lag between infection and pathology

In the case of schistosomiasis, public awareness emerges slowly because of the insidious onset of the disease and rather slow appearance of grosser clinical manifestations. Depending on variable intensities of infection, the full pathologies in severe cases may not develop for l&20 years. Thus there is a long time-lag between the onset of infection. which can be rapid. say a year or two, in a new irrigation scheme, and the onset of disabling sickness. Peasant stoicism bringing, as it does, a phlegmatic acceptance of disease. com- pounded by ignorance of etiology and an absence of politicization, generally prevents public outcry. The community demand for health care services is accord- ingly muted and the proliferation of new schemes continues, often recklessly disregarding future health costs. In this respect, the role of health agencies is to help prevent ‘future shock by creating an informed body of opinion that will insist on the inclusion of adequate health-care infrastructures in all future schemes of water impoundment and irrigation.

Aji+ca

Water impoundment schemes vary in size and for the sake of simplicity can be graded into large. medium and small, using either the classification of the Knoxville International Symposium on Man- Made Lakes [16] or that of the most recent World Register of Dams prepared by the International Com- mission on Large Dams [l 11. Information on national programs for the construction of large and medium impoundments is easier to obtain that for small dams; the larger impoundments are fewer, require central funds and other resources, and are directed perhaps to a national objective, while small dams generally derive from local needs, decisions and inputs. Thus the rate of increase in the number of impoundments can be gauged by examining fairly ac- curate and complete data on large dams and by aug- menting these with the rare, incomplete but often im- pressive statements on the numbers of small impoundments being constructed.

Large impoundments. In Table 2, which is based on the World Register of Dams [ll]. the number of dams and the time of their construction are presented: (a) for 29 out of the 31 listed countries of Africa, Zimbabwe and South Africa being the two exceptions; and (b) for the 25 countries lying between latitude 23”3O’N and 23”3O’S, i.e. in tropical Africa.

These figures suggest that in the countries of tropical Africa the rate of increase in large dam construction between one decade and the next is now at least 50% and may be higher. Since 1973, several new impoundments have been proposed in Ghana. Mali and Nigeria and some, which are not listed in the World Register of Dams [l I], are already under construction. Nigeria has recently allocated 10 million Naira (approx. US $17.500.000) for feasibility studies and engineering design alone, for proposed dams and irrigation schemes in 9 river basins [17]. In the Sudan. a

Man-made lakes and man-made diseases

Table 2. Rate of construction of large dams in Africa (pre-19X&1971)

1133

Number of dams constructed Countries Pre-1950 1951-1960 1961-1970 1971*

(a) In 29 countries 26 28 38 28 (b) In 25 ‘tropical’ countries 5 19 28 18

*Figures according to information gathered up to 1972 but including projects for the future.

Table 3. Names and dates of construction of some of the major dams in Africa

. Dam (country) Date of completion

of construction

Aswan. low dam (Egypt) 1933 Owen Falls (Uganda) 1954 Kariba (Zambia/Zimbabwe) 1959 Akosombo (Ghana) 1965 Kainji (Nigeria) 1968 Aswan, high dam (Egypt) 1970 Kafue (Zambia) 1971 Kossou (Ivory Coast) 1972 Cabora Bassa (Mozambique) (1980):’ Kpong (Ghana) (1981)?

large new irrigation system. the Rahad, has been developed and further irrigation extensions to the Gezira are planned.

The huge Gezira irrigation system comprises 850,000 ha and consists of the original Gezira scheme of 1925 and the Managil extension finished in 1962. The scheme, with some 2 million people, is divided into 14 groups which are further subdivided into 107 blocks, the basic irrigation units. Additional to the Gezira area proper, several large towns are situated within or in close proximity to the’ area, e.g. Wad Medani, Hassaheisa and Sennar. Tenant farmers in the Gezira live in small villages of about 1000 people each. and there are numerous unregistered villages of Fellata from Nigeria and immigrants from the western Sudan. During the cotton season there exist in addition many temporary camps built by seasonal laborers who may number as many as half a million people.

Small irnpoItrtdr,l~llrs. In Ghana, for example. about 120 small dams are being constructed in the Upper Region with foreign aid. Recently technical assistance has been proposed for the construction of 20 dams in order to support an agricultural program in the Northern Region. Some further indication of the scale on which small dams are being constructed comes from Nyanza Province in Kenya where a program began in 1957; within 3 years SO.OBO had been built. In Mali. a system of 50 small dams is being established in the Cercle de Bandiagra (population 160,000) to promote vegetable growing. By 1977 about 20 of these had been completed or were under construction [18]. Another example would be the construction. with foreign technical assistance. of 57 small dams in an area of northern Cameroun where numerous

water-related diseases are endemic and where, in consequence, a considerable disease impact may be expected. No health measures are included in the project [ 191.

Asia

Two sources of information on water resources development projects relating to Indonesia, Malaysia, Philippines and Thailand have been available for this review: (i) the World Register of Dams [ll] which lists only large impoundments; and (ii) the report by Harinasuta et al. 183 which describes projects in each country. Relevant information contained in the World Register of Dams [l l] is summarized in Table 4 which presents the number of large dams by the decade of their construction for each country. These figures show a considerable increase in the construction of large dams between the two decades 1951-1960 and 1961-1970. For the period 1971-1976, the data are necessarily incomplete and several of the 10 dams in Thailand were still under construction.

Such useful information as could be readily extracted from the report by Harinasuta et al. [S] is summarized in the following sections by country [20]. In general three main types of dam are described for these countries: the multipurpose dam for hydro-electric power, irrigation and flood control: the dam pri- marily for hydro-electric power; and the dam for irrigation projects.

Indonesia. In the last 10-15 years the Government has been greatly concerned with the development of water resources. Most of the new projects are sited on the Island of Java (Table 5) where 647: of the country’s population of 137 million live.

Malaysia. A number of water development projects from the current Development Plan (19761980) are indicated below. In East Malaysia one major hydro- electric project will be implemented soon in Sabah. and similar projects are proposed for Sarawak. but they are still being studied. In West Malaysia. some of the projects are already in operation or about to be implemented: (i) 2 irrigation projects for 75,OOB ha of agricultural land in Perak State; (ii) 5 impoundments for hydroelectric power and irrigation of the Pahang river basin: (iii) the Kenyir multipurpose project in the Trengganu river basin for hydro-electric power and irrigation of 198.000 ha: (iv) a project to increase irrigation to cover 48.000 ha in the agriculture project in North West Selangor; (v) in Selangor. a hydro- electric project (Gambak) and relatively small water supply schemes; (vi) a major development in the Kelantan river basin for hydro-electric power and irrigation of over 100.000 ha: and (vii) a number of water supply schemes in the Southern States.

1134 JOHN M. HUNTER rt al.

Table 4. Rate of construction of large dams in four countries of Asia (pre-195Ck1971)

Country Pre-1950 1951-1960 1961-1970 1971’

Indonesia 13 3 8 - Malaysia 2 1 8 Philippines 2 3 2 - Thailand - 9 27 10 Total 3 3 z i-d

*Figures according to information gathered up to 1972 but including projects for the future.

Philippines. The rate of growth to be expected in water development projects in the Philippines is clearly Seen from an inventory of projects made in 1978 by the National Water Resource Council. Out of a total of 861 dams, reservoirs and irrigation systems: (i) 39 are in operation, 12 under construction, 177 awaiting construction; (ii) 31 are under investigation and study and 361 have been identified for investigation and study; and (iii) feasibility studies have been completed on 12 projects and tentative planning studies have been made on a further 229.

ThniluM. An important program has already been carried out for the development of water resources in Thailand. In the Fourth Five-Year Development Plan for the period 1977-1981 proposals were made for further schemes to be undertaken. (i) Northern Region. One small scale multipurpose dam (Mae Gnud) is due for completion in 1980; three others were built between 1964 and 1973. Two small scale dams are at present under construction to irrigate 47,520 ha; the total number of these dams will then be 131, irrigating 294,000 ha. (ii) Central Region. A second large multipurpose dam (Srinagarind) is due to be commissioned in 1980, providing hydra-electric power and water to irrigate 500,000 ha of agricultural land. Many small irrigation dams have been constructed in the last 20 years; one, the Phitsanulok dam, is under construction and should be completed in 1984; it will irrigate 187,500 ha. (iii) North-East Region. Four large multipurpose dams and several large and small dams for irrigation have already been provided in the region. No further projects are being undertaken during the current Development Plan. (iv) Southern Region. One large multipurpose dam is due to be completed in 1981, to produce hydro-electric power and to irrigate 48,000 ha in the first phase and 20,000 ha in the second phase. There are also plans to construct three dams in the Ta Pee river basin, to irrigate 100,000 ha.

Latin America

The number of man-made lakes being constructed in Latin America is continually increasing, as can be seen in Table 6 which summarizes data from the World Register of Dams [l 11. In Brazil, for instance, future developments can be anticipated if it is considered that, from the estimated total hydro-electric potential of 80,000 MW. only about 18,000 MW are presently harnessed, through the activity of more than 400 hydra-electric plants. Two giant plants are currently under construction: Itaipu (12,600 MW) on the Parana river and Tucurui (8000 MW) on the Tocan- tins river. The rate of new construction is around 10 important lakes per year.

Numerous small and medium sized impoundments (some 800 in the northeastern part of Brazil only) have been built for irrigation or other purposes. There will always be new ones as the cultivated areas increase or agricultural technology is improved. In 1976 in Venezuela. there were 54 man-made lakes, 4 were under construction and 8 others planned. The irrigated surface, which was 64,914 ha in 1968. increased to 74,251 ha in 1972. Since then, about 5000 ha of irrigated land have been added to that of the preced- ing year. In 1975, more than 90,000 ha were under irrigation. The Quinquennial Programme of Hy- draulic Resources for 19761980 considered the possibility of attaining a total of 246,916 ha of cultivated land under irrigation by the end of this decade.

CONSIDERATlONS OF POLICY AND IMPLEMENTATION

The dilemma

National and international efforts to improve the quality of life in the developing world through the provision of better nutrition and the generation of

Table 5. Numbers of water resources projects on Java and other islands (1965-1978)

Number of projects

Implemented Under construction Proposed

Type of Other Other Other dam Java islands Java islands Java islands

Multipurpose 2 3 1 Hydro-electric - 2 13 - 1rriga:ion I - 1


Table 6. Rate of construction of large dams in 21 countries of Latin America (pre-1950-1971)

Pre-1950 1951-1960 1961-1970 1971* Total

1. Argentina 2. Brazil 3. Chile 4. Cuba 5. Colombia 6. Costa Rica 7. Dominican Republic 8. El Salvador 9. Ecuador

10. Haiti 11. Honduras 12. Jamaica 13. Mexico 14. Nicaragua 15. Panama 16. Paraguay 17. Peru 18. Surinam 19. Trinidad and Tobago 20. Uruguay 21. Venezuelat

22 119 34

2 - -

- - - -

2 75

- 2

- 35 -

1 9

13 111

7 2 5

- 2

-

- - 45

1 - -

5 -

2 2

IO

16 15 97 93 10 15 17 28 18 42 2 1

- 1 1 1 1 1

- - I 1

- - 132 7 - 3

2 1 1 1

13 23 1 -

- - - - 22 25

66 420

66 49 65 4 1 4 2 1 2 2

259 4 5 2

76 1 3 3

66

Total 302 207 334 258 1101

*Figures according to information gathered up to 1972 but including projects for the future. Nevertheless. the numbers here represent in general only a fraction of the projects currently planned or the dams under construction.

tupdated according to Direction General de Recursos Hidraulicos [21].

more income are highly laudable. Such ‘development’ efforts necessarily take the form of interventions to change the status quo ante and to alter the existing order of man-environment relationships. The ensuing change requires adaptations which are inherently stressful. Responses to stress may be adaptive and beneficial rather than negative, depending upon circumstances including time. However, in the developing world, observation reveals many seriously mal- adapted responses to the forces of change created by development activity. Furthermore, developmental interventions have produced unexpected consequences, all of which bear negatively on the health of populations.

It is now widely known that economic development activities mediated through the introduction of radi- cal changes of man-environment relationships may also disrupt disease patterns by creating new areas of prevalence. new foci and, often, serious outbreaks of disease. Indeed there are very few newly introduced economic activities that are entirely free of adverse repercussions on health. Thus, ironically, economic activity, under the banner of ‘development’, is creating ill health, which is a strange form of societal self- abuse. Water management schemes are particularly implicated because they set off a series of ecosystem disturbances that involve parasitic and infectious disease transmission cycles. The literature of medical science is now replete with accounts of dramatic increases in water-related diseases such as malaria and schistosomiasis in water impoundment schemes in the tropical world. Furthermore. given the present rate of water impoundment. and in view of known future plans in many countries. it appears that the problem

of disease generation will become exponentially more serious unless the necessary preventive measures are taken.

The premise of’ complementarity. It is argued that economic development and health are wholly interde- pendent ; indeed they are indivisible. Economic growth through the dissemination of production benefits should promote good health rather than create illness and disease, as is frequently the case today. It is thus conceptually unacceptable that economic development planning and health maintenance should appear to be antagonistic rather than complementary entities. Increasing illness will ultimately jeopardize economic development no matter how suc- cessful the latter appears to be in the short run. The policy position maintained here is that health and development are mutually reinforcing. one promoting the other, both enhancing the quality of life.

Disregard of ComplementaritJ. It is dysfunctional and counter-productive in economic development planning to ignore the health-sequelae of water impoundment schemes. Time-lag effects do not minimize this responsibility. Some decades ago. it could be argued that those engaged in water development planning were innocently unaware of the health consequences of their actions, that the arts and sciences of development planning using water impoundment were uninformed. ecologically naive. and ill-equipped to anticipate the unknown and the unintended. Such excuses no longer exist. Much is known and there is a widespread consciousness of ecological sequelae of water impoundment. Sufficient evidence has now accumulated to show that the ecological consequences of water resources development. including


the increase of parasitic and infectious diseases, are predictable empirically. It is argued also that refuge cannot be taken in narrow sectoral planning compart- ments because the real world is not disaggregated in this way. It is untenable to divide the problems of river basin development into separate administrative and bureaucratic entities. Furthermore, it appears highly unethical to create and then ignore health hazards. This may also be regarded as a misallocation of real costs.

Ma/distribution of risks and benefits. Typically, in those water impoundment schemes involving irrigation and power production, significant regional asym- metries of benefit and risk are found. People living in towns and participants in the wider national economy enjoy electricity, wage employment and other economic benefits generated through the water development scheme, whereas people at the lake-side suffer from increased disease and are even worse off than before. Through this inequity of distribution of benefits, the effect of the water impoundment scheme is to exaggerate social and economic disequilibrium in different parts of the country. Environmental degradation in one place, the lake area, stands in stark contrast to improvement in the quality of life elsewhere. To remedy this situation national planning mechanisms must be established with the purpose of reducing regional inequalities through both risk reduction and the better spread of benefits.

It is argued that the absence of coordination among administrative bureaucracies such as the Ministries responsible for agriculture, water supply, electricity, education and health, is inefficient and wasteful of national resources. Such institutional separatism usually results in water impoundment schemes being implemented by relatively capital-rich bureaucracies that unintentionally create outbreaks of disease; and then the cost of managing these disease out-breaks is transferred to the capital-poor, under-financed and infrastructurally weaker health-care services. In other words, the agencies that create the problem do not share the subsequent disease costs; whereas, in justice, populations enjoying the scheme’s wider benefits should assist those suffering from it; or better yet, help avoid the problem in the first place.

DeJning the basic challenge. How should the economic premise that disease burdens are the inescapable price of progress-in this case, of increased energy generation and agricultural production through irrigation-be regarded? One view is that the construction of many new dams and reservoirs is imperative, that environmental and health costs are inevitable and therefore must be absorbed in order to secure overall benefits [12]. The case is cited of a foreign journalist becoming persona non grata in country ‘X for critically exposing the schistosomiasis problem, allegedly inflating its importance beyond that of food production. Putting aside the question of responsible reporting, it is not an ‘either or’ situation: preventive health care measures can be introduced into water development projects without impairing their efficiency and there is a distinct possibility that such measures will increase production efficiency. In any case is it econometrically valid to omit future health costs from the debit-credit balance?

Continuing experience in the tropical world shows

that the apparent interests of water impoundments and irrigation schemes on the one hand and of human health on the other are allowed to function as inimi- cal, antagonistically opposed entities. Worthington [14] admits that irrigated agriculture and health are actually seen as opposed, in the narrow view, but argues that they can be made complementary. To make them complementary is a basic challenge. Full policy recognition of the essential complementarity of economic development and health would afford the opportunity for coordinated planning for prevention or minimization of health hazards emerging from water impoundment schemes. This would share the benefits and the costs over the nation as a whole. Preventive measures would also promote greater economic production efficiency. Furthermore, as preventive health care costs are lower than curative costs. the total real costs to the country would be reduced. Continuing transgressions of the essential complementarity of development and health cannot be allowed to go unchallenged.

A policy solution

The principle should be established that, ideally, economic development shall not create sickness thus paralleling the physician’s Hippocratic oath primum non nocere. This goal, which obtains within reasonable limits and circumstances, follows from the premise of complementarity. The major position held here is that water development projects should take into account health protection through all the stages of planning, design, building and subsequent operation of a project. This would ensure that developmental interventions be evaluated in their ecological entirety so as to avoid or minimize the negative consequences to human health.

Integrated regional planning. Health services should not be developed separately in a water impoundment scheme, but should be an integral part of regional, spatial land-use planning. In this sense it is not sufficient to prevent disease: health care must be part of a wider plan for the lake, its surroundings, and broader spheres of influence, the whole being considered as a geographical and economic entity. The ‘global’ approach, or integrated regional planning incorporating health care, will, at the same time, serve the cause of environmental protection. Afforestation. fauna1 and floral maintenance, ecosystem stability and prevention of eutrophication, and pollution of the lake and of the downstream area by industrial efflu- ents, of agriculturally introduced herbicides and pesti- cides, would all be considered conjointly.

Incorporation of health costs. The infrastructural costs of health care services and health maintenance should be incorporated with the engineering and public works infrastructural costs of the water impoundment scheme. Capital costs thus aggregated will more realistically reflect total costs. Health maintenance costs, after the completion of the impoundment scheme, will be supported from the gross income of that scheme or from some proportionate equivalency of it, as for example, I or 0.5% of gross income from power generation or from cotton or sugar production. This income would cover the regular, recurrent costs of the operation of health maintenance services and would be chargeable to the gross income of the


scheme. In this way, the economic benefits generated by the scheme will also cover health maintenance. Such support would exist on a continuing, permanent basis and could cover the costs of screening, surveillance. prevention, treatment. education and vector and intermediate host control.

Preventive measures. The existence of adequate health services and of an infrastructure for the control of some endemic diseases, can. in certain areas, reduce or eliminate specific risks and make the genera1 health situation apparently normal. In such cases, the less dramatic problems will probably remain unnoticed, and the slow-developing risks such as those depen- dent on eutrophication. on cumulative pollution. or on the deterioration of human living conditions, will not be predicted. Many risks can be prevented at lower costs than those of curative medicine, and, if preventive measures are taken sufficiently early, they will require less personnel, less equipment and less material than after the breeding areas of disease vectors or intermediate hosts have expanded, the prevalence rates of diseases have increased or. simply, the number of people in need of protection has multi- plied. While economies can be gained on reductions of sick-leave, of consultations, and of medical care, perhaps increased work productivity and social tran- quility are more important benefits.

Policy implementation

A national auhoriry. A national authority might be created with responsibilities for overseeing water impoundments and irrigation systems, e.g. a national water development authority. Ideally the authority would be at a very high administrative tier, say cabi- net or presidential level. It would thus be administratively superior to the individual departments responsible for public works, power, agriculture, education, health, transport and other functions. It would be constituted so’as to be in a position to advise and guide lesser, administratively more narrow sectoral interests. Its expertise would comprise a combination of physicians, public health specialists. parasitologists. microbiologists, engineers, biologists, ecologists, agri- culturalists, economists and other related professionals and administrators. It would have the responsibility to set national goals and priorities for water impoundment and irrigation schemes including economic interests and health maintenance. Encour- aging precedents for the creation of national water impoundment and irrigation authorities may be found in the success achieved by certain bi-national water development organizations. such as those embracing the frontier river basins of Paraguay- Brazil and Argehtina-Uruguay.

Impact assessment. Each proposed scheme should be preceded by a survey with analysis and evaluation of the findings relating to the potential impact upon health as well as the economic outcome. Such a review would necessarily have to be holistic and multidisciplinary. It would identify the unintended negative side effects on health which could be anticipated, along with cost-benefit analyses of prevention. treatment and control measures. The preparation of appropriate guidelines for such impact assessment statements could be developed with the collaboration of scientists in developing countries and of inter-

national scientific and technical agencies, including the World Health Organization.

Integrated development. A further concept arises out of national and international experiences. The necessary protection of the environment to ensure the greatest longevity of man-made lakes. to maintain the quality of water and to avoid most of the health risks produced by these projects. requires also an adequate utilization of the land which is geographically and economically influenced by the lake. This means that the use 3f the land around the impoundment, the establishment of new settlements and the industrial, agricultural or other activities must be planned and regulated in accordance with ecological principles and sanitary and social interests. This type of planning activity is the most economic and efficient way to prevent or to control risks to health. as well as to improve the quality of life in the area. One of the purposes of the planning activity is to ensure that a reasonable part of the investment and of the benefits produced by the water-resources development project is administered in such a way that local development could be financed and guided adequately. It is time to alter the former tendency of generating with each such project an asymmetry in the distribution of benefits and risks, that is, the risks occurring around the man-made lake, with the benefits occurring in industrialized urban areas.

Aspects of integrated development includes: (i) Multisectoral planning. Only through integrated, multisectoral planning activity, evolving around the water impoundment scheme, will it be possible to achieve an effective resolution of the varying goals of power production. increased agricultural production and improved health. (ii) Health guidelines. Guidelines eventually leading to specific technical manuals, will have to be established to promote integrated development planning, including health planning measures. Health guidelines should aim at being concise. explicit and widely applicable. Recommendations for the creation of multidisciplinary planning teams would be included. Any technical manuals subsequently developed should be multidisciplinary and strongly integrated by the application of systems methodology. (iii) Sectoral synthesis. It will be necessary to integrate sectoral planning for agronomics. ecology, economics, environmental monitoring, health services, clinics, health surveillance, housing, hygiene. hydrology, lim- nology, social activity, vector biology, wildlife ecology, and so on. (iv) Regional synthesis. Just as sectoral synthesis is necessary in integrated development planning, so is regional, i.e. geographical or spatial. synthesis essential. In this spatial sense, an integration of planning should be effected between areas above and below the dam. around the impoundment in the different parts of the watershed, and also beyond watershed boundaries. The impact of impoundment projects typically affects population migration from distant areas. new marketing zones. and. higher levels of spatial integration within the national spatial economy. (v) Cost synthesis. Along with regional and sectoral syntheses, cost synthesis should be effected by aggregating all components of infrastructural COStS

plus the components of operational and maintenance costs. Appropriate health related costs for such aggre- gation will be identified in all the different sectors of

* 1138 JOHN M. HUNTER et al.

the scheme such as water impoundment, agricultural production, housing and population activity, and vector biology and control.

National regulations. An impact statement might be considered a prerequisite for the planning activity and for authorization of continuation of planning. The proposed strategies for integrated development should conform to national guidelines and national regulation where these exist. These should constitute further approved steps in the authorization of continuation of planning. Regulations should be developed to cover the continuous evaluation of health impact, as well as other forms of environmental evaluation of the impoundment schemes after their construction. In other words, the regulations should extend beyond the initial creation of the scheme into its continuing, long-term operation.

Conditional financing and provision of‘ funds. Appli- cations for funding support and offers of grants should be regarded as invalid unless they conform with national regulations. The planning steps for integrated development should constitute a prior con- dition for the negotiation of loans from the World Bank and other international financing bodies. The disbursement of nationally generated funds for impoundment schemes should also comply with the conditions.

Capital costs of the necessary health care infrastructures such as buildings, clinics and outpatient facilities in rural areas, should be included in the integrated capital costs. In addition, the costs of recruit- ing and training the necessary teams of health care professionals for rural areas which are usually deficient in such personnel, should be included in the initial ‘start-up’ costs. In a developing country, additional health care personnel will not normally be available to meet the extra demands created by new projects. Recurring costs for health services, screening treatment, vector control and health education, should be included in the standard budget planning for recurrent operational costs of the scheme as a whole. These latter funds should be derived directly or indirectly from the gross income of the scheme. This should be done as needed or on some equivalency basis such as a proportion of the income equivalency of power generation, or of agricultural production. The recurrent costs should also include the costs of regular health surveillance and evaluation, as well as environmental monitoring.

‘Future risk’ research. Except for some evident or explosive problems, health protection in general requires the existence of a multidisciplinary team which has an active work-program and which can initiate the necessary surveys, interpret the resultant data, and plan or implement programs for prevention or control of actual disease risks. Such a team using suitable ecological and epidemiological techniques, must be able to estimate disease risks with sufficient precision to recommend. if necessary, essential changes in the plans of the water resources development project or in the organization and use of land under the influence of the future lake in such a way that risks would be eliminated or that the preventive measures proposed could minimize their consequences. This eco-epidemiological team should be represented in every water-resources development

project or group of projects under the same authority from the beginning of the enterprise and should have a voice at the decision-making level.

Essential for policy implementation will be the ability to respond rapidly to problems as they arise. An effective response capability can be developed upon the basis of information provided by an ongoing research program that will measure disruptions in the ecosystem. Projects would include ecosystem research involving the dynamics of change of flora. fauna. hydrology, agriculture and human social and health conditions. These could be small-scale, modestly funded. and at a pilot level.

The rate of water impoundment in the tropical world should be recognized. The great majority of such impoundments do not appear on national and international registers. Indeed, within any one given country, the Ministry of Health may not be informed by the Ministry of Agriculture of the existence of many such schemes nor of plans to create new ones in the near future. Comprehensive data are extremely difficult to obtain. Nevertheless’given the population pressure and the increasing demand for food supplies, together with what is known directly and indirectly of national plans for water impoundments, it is essential that health planners recognize that the problem of water-related diseases is rapidly increasing in magnitude. After the normal lapse of time required for the build-up of reservoirs of infection, the impact on human health will be correspondingly enlarged.

Scientific attention has focused almost exclusively on the largest of the water bodies in the tropical world. These are not only important as problems in their own right, but also have symbolic value for human achievement. However, it is likely that small water impoundments, in an aggregate quantitative sense, have equally great or even greater significance for human health. For instance, the intensity of cercarial infestation and of water contact per unit of shore line and per unit volume of water is greater in small impoundments than in large lakes, and therefore small impoundments can become intense foci of schistosomiasis transmission. It is recommended that future risk research be directed towards the problems of disease transmission in small impoundments.

It is also recommended that organizational steps be taken to compile national registers of small impoundments and to develop regulations and integrated planning strategies for preventive health measures. These may have to be modified and adapted from the integrated planning strategies developed for major impoundments. ‘Future risk’ research should involve continuous evaluation and comparison of different preventive and control strategies in both large and small impoundments. Organizational mechanisms should be developed to cycle research findings back into integrated planning strategies, and national regulations, through the appropriate national authorities. This could be described as the research feed-back loop.

Communications network on ecological and health effects

Need. At present there is no international scientific or technical network that addresses itself in a holistic fashion to the problems of ecology and health in


water development schemes. Research is slow and piecemeal in its progress and suffers from lack of both coordination and exchange of information. With the increasing use of dams, the need for an international communications network is clearly felt. In particular, there is no international register of water impoundment schemes. There is of course the valuable ICOLD register of large dams but this necessarily excludes the smaller impoundments and is limited to engineering data on the dam itself.

Among the numerous international scientific and technical organizations concerned with water development, hydrology, dams and irrigation, there exists a considerable degree of institutional separatism. In this sense, matters of the environment and of ecology, including health, are neglected. It would be useful therefore for international coordination to be effected to monitor the growing problems of water impoundment. ecology and health.

Objectives. The first objective of the proposed network would be to create an international register of water development schemes. This register would cover all large schemes and as many of the small impoundments as can be identified and recorded. The second objective would be to establish an international clearing house for the exchange of scientific and technical information. This would help solve some of the problems such as lack of information flow, gaps in information, and other communications deficiencies which inhibit the vigorous development of international thought and the design of constructive responses. The third objective of the network would be to develop a functional typology of water impoundments and irrigation schemes. Such a typology would offer many advantages, some of which are: (i) a research data base; (ii) the generation of international projects. Precedents in this area include the Soil Map of the World (FAO/UNESCO), the World Atlas of Salt-affected Soils (UNESCO), the World Map of Desertification. and the World Map of Soil Deteriora- tion; (iii) an information base for ecosystem modelling in ecology and health aspects of water related development schemes; (iv) an information base for training and education; (v) an early warning system for threats to public health; and (vi) a data base for the generation of problem response capability.

Structure. The scientific and technical disciplines involved in the network will include among others agronomy, biology, botany, climatology, ecology, economics, engineering, hydrology, geography. meteorology, soil science, zoology and related social sciences such as anthropology, demography and sociology. as well as systems analysis. The medical and biomedical sciences together with health care planning disciplines. prompted and assisted through the World Health Organization, will have a particularly important role to play in identifying and re- sponding to problems of ecology and health.

FAO

UNDP

Food and Agriculture Organiz- ation United Nations Development Pro- gram

Leadership: Key members: The environment: UNEP United National Environment

Program UNESCO- United Nations Educational,

MAB Scientific and Cultural Organiza- tion-Man and the Biosphere Pro- gram

ICSU-SCOPE International Council of Scientific Unions-Scientific Committee on Problems of the Environment [22]

Leadership: Key members: Financial support: World Bank African Development Bank Asian Development Bank Inter-American Development Bank

ScientiJic and technical international membership: COWAR Committee on Water Research IAH International Association of Hy-

drogeologists IAHS International Association of Hy-

drological Science IBP International Biological Program ICID International Commission on Irri-

gation and Drainage ICOLD International Commission on

Large Dams IGU International Geographical Union IHP International Hydrological Pro-

gram ISSS International Society of Soil

Science IUBS International Union of Biological

Sciences IWRA International Water Resources As-

sociation SIL International Association of Lim-

nology WMO World Meteorological Organiz-

ation

National organkations with international programs:

ACSAD Arab Centre for the Study of Arid Zones and Dry Lands

ASCE American Society of Civil Engin- eers

AWWA American Water Works Associ- ation

NAS National Academy of Sciences ORSTOM Office de la Recherche Scientifique

et Technique Outre-Mer USDA United States Department of Agri-

culture Membership. A nucleus of international groups for

collaboration in order to create a register and func- Bilateral aid programs: donor countries

tional typology or water impoundme& is suggested Multilateral aid programs: all to be included below. Numerous additions are to be made.

Typolog),fbr registration

Leadership: Ke_v members: Agricultural production and The purposes of this section are to suggest: (i) a health: tentative outline for registration of water impound-

WHO World Health Organization ments; (ii) a starting point for the development of a


rudimentary, functional typology, which should be subsequently refined and rendered more technically specific; (iii) an organizational basis for the maintenance of national and international registers, with accompanying provision of services to participating countries; (iv) a basis for global monitoring of health effects around water impoundments, both large and small; and (v) that a register and typology will aug- ment the research data base for the examination of health effects around water impoundments.

Need. There is a growing awareness of the need to understand both current and projected growth rates in the Construction of water impoundment schemes, particularly in the developing tropical world. Lack of cognizance of such development is becoming increas- ingly disquieting to health officials concerned with the disease effects produced by water impoundments. In particular, the dimensions, that is to say, the quantitative basis of the phenomena, need to be established. Data are lacking on numbers, size, and other specific characteristics of impoundments and irrigation schemes, including engineering, hydrological, agronomic, and human health characteristics. Specific quantitative data should be collected on a continuing basis. Water-related ecological and health phenomena regarding human diseases, zoonoses and vectors, need to be identified. The proposed register would assist in this respect ‘and in specific problem recognition. A functional typology that identifies different categories of impoundments for different purposes would help to identify problems, priorities, and needs in the promotion of toth health services and disease research at the international level.

Size-ordering of lakes. Size-ordering of lakes is of medical significance. For example, schistosomiasis transmission reflects cercarial infestation per unit volume of water and per linear unit of shoreline and thus small water impoundments are potentially more dangerous in aggregate than large lakes. In this way, a number of small impoundments will collectively transmit more schistosomiasis than a large lake of equal total size. There are also other significant ecological differences that obtain by lake size. For example the proliferation of rooted or floating vegetation which provides a substrate for the intermediate snail hosts of schistosomiasis tends to be correlated with size of water habitat. The construction of small water impoundments is growing at a rapid rate in many developing countries. Yet in fact little is known about these impoundments. They are not registered because they are not large, and because they are built not only by different branches of government but also by voluntary and lo&l-organizations, with no centralized information available. Size-ordering registration will draw attention to the importance of small lakes and impoundments.

The Knoxville Symposium in 1971 [16] suggested criteria for differentiating between ponds, lakes, and large lakes, recommending depth thresholds of 3 and lOm, and size thresholds of 10 and 100 km*. How- ever, from the disease transmission point of view, more attention should be focused on smaller impoundments. For this reason, six size groups are proposed in Table 7.

By about 1970, it is estimated that there were about 260 ‘size 5’ dams in the world. and 40 ‘size 6’ dams.

Lake Volta. at approx. 8500 km’. is at present the largest.

Aerial photography and remote sensing ,fi)r monitoring water impoundments. Each country could easily effect the physical counting of impoundments. particularly small impoundments. through monitoring by aerial photography and by remote sensing. At the simplest level, this would provide the numbers of impoundments, their geographical location, and calcula- tions of surface area. The method would be efficient. inexpensive and comprehensive. It could also be used as a basis for the design of sample field investigations of disease areas as well as for other forms of enquiry. (See Appendix 1 for more detail.)

Descriptive variables for registration. In the data registration process, it will be useful to recognize different groups or clusters of descriptive variables that will define the varying characteristics of water development schemes. These will be considered for possible use in registration and for the development of a health-related typology of water impoundment projects. A list of headings is given below and is amplified in Appendix 2: (1) gross size variables of water body; (2) limnological variables of water body; (3) irrigation design and practice; (4) irrigated crop production; (5) non-irrigated crop production; (6) livestock production; (7) game biomass; (8) aquatic biomass; (9) forestry production; (10) ecosystem characteristics: soils, rainfall, vegetation; (11) power production; (12) lake transport and communications; (13) population: settlement and demography variables; (14) population: employment and occupational activities; (15) human disease variables; (16) zoonoses; (17) vector biology variables; and (18) health care services. The above list is open-ended, comprising merely suggestions for discussion, evaluation and review. In all cases, technically and scientifically appropriate parameters are to be identified.

A size-ordering of descriptive characteristics is appropriate. The foregoing descriptive variables and groups of variables, which are detailed in Appendix 2, may be size-ordered in categories for convenience of data retrieval and analysis. A log scale of five class- intervals would cover most needs, i.e. -x, x. 10x. 100x, 1000x. This would assist retrieval capability in a matrix framework.

Central registration authority. An international multi-agency, coordination body could be established to operate a continuing program of registration. It should embrace FAO, WHO, the World Bank and other agencies and foundations, together with insti-

Table 7. Proposed size-ordering of man- made lakes for health risks registration

and surveillance

Size-order

Size 1 lake Size 2 lake Size 3 lake Size 4 lake Size 5 lake Size 6 lake

Depth Area

(m) (km?

<3 <I <3 >l <3 > IO >3 > 10

> IO >loo > 10 >looo


tutions in developing countries such as the National Academy of Sciences and Ministries responsible for health and agriculture. The registration authority would establish and maintain a central international register, and make its scientific and technical content available to governments, scientific bodies, and development agencies. An important role of the proposed central authority would be to establish guidelines for registration. Scientific and technical descriptions would have to be standardized, including the design of registration forms.

Participation by yocernments. Participation by governments would of course be optional and would vary from country to country. It would be normal to expect incomplete and partial registration of data. The considerable difficulties that will be faced by governments in assembling the data should be recognized, even for basic information such as the name of the impoundment, its location and its surface area. The more technical and scientific parameters will require the establishment of survey and monitoring systems. These would have long-term benefits in terms of limnological, ecological and health research; but technical assistance would be necessary to set up the systems. Categories of reporting could be developed such as ‘first order’, ‘second order’, ‘third order’. and so on in decreasing levels of detail; according to priority and interest levels, and program capability and support. If it is effectively demonstrated that a water impoundment registry and data bank will have utility in agricultural planning and management and will be beneficial for ecology and health monitoring, then active cooperation of governments will be more readily forthcoming, despite the difficulties of data collection.

Operarional ~~ff~ome~. In terms of service. an international registration authority could and should give considerable assistance to the participating countries. If requested, data-processing services could be provided. Health information including disease prevalence would be included. The authority would develop data storage, retrieval and access capabilities and would provide standardized information. It would also specifically meet technical requests for planning purposes and research management. There would thus be a direct feed:back to participating countries as a service in support of the planning and management of water bodies. ‘On-line’ service would be provided where possible to governments and to the scientific and technical community.

In terms of monitoring. the authority would serve as a centralized information conduit, and would promote a worldwide monitoring of the health and ecological status of water schemes on the register. The registration authority would also provide a funda- mental data base that would assist in research design and in research strategies. The on-line data base, with all of the variables attached by impoundments. would facilitate cross-referencing of findings and would pro- mo&e multi-disciplinary research, with obvious implications for health studies. Data retrieval could be made by any particular groupings of key variables: by the proposed six size categories. by wet tropical areas or by dry tropical areas. or by any other criteria or aggregates of criteria, including diseases. This retrieval capability would provide a direct feed-back to

S.S.M. 16 I I -_(

those engaged in health planning. management and research. The end result should be assistance in the prevention and control of disease and promotion of better health in the developing world.

CONCLUSION

Although the presentation of evidence above is necessarily selective and incomplete, it is well known and clearly established that water development projects aggravate health risks in the tropical world. Furthermore. increasing rates of construction of impoundments. both large scale and small. offer a dis- maying prospect of continued serious deterioration of health in the future. Hitherto. medical services have been left to cope on a curative basis. where possible. with the disease outcomes of development; but it is argued that programs of disease prevention. integrated with the development projects. would effect much better maintenance of human health. Invest- ment and operational costs for health would be incorporated in the planning budgets. Major decisions of policy and implementation need to be formulated by governments, and by international and bilateral technical assistance agencies. to address this problem. A communications network on ecological and health effects, together with registration of and access to information, are vehicles that will assist in determining strategies for disease control in the context of development planning. Above all, however, governments and agencies need to make a policy commitment to recognize the processes that inadvertently generate adverse health risks. and to attempt to minimize them through integrated multisectoral planning.

Acknowledgmlrnrs-This paper is adapted from a report which was- first prepared at the request of the Parasitic Diseases Program. World Health Organization. Geneva. The authors’-views. however. are personal. and do not necessarily reflect the position of the World Health Organ- ization. We are deeply indebted to Dr A. Davis. Chief. Parasitic Diseases Program. and Dr .I. Deom. Schistoso- miasis and Helminthic Infections. World Health Organiz- ation. for their stimulus. encouragement and support.

I.

2.

3.

4.

5.

6.

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Khalil Bey M. The national campaign for the treatment and control of bilharziasis from the scientific and economic aspects. JI R. Egypt. med. Ass. 32. 820. 1949. Farid M. A. Irrigation and malaria in arid lands. In Worthington E. B. op. cir.. pp. 413-419. 1977. UNDP/WHO Research on the epidemiology and methodology of schistosomiasis control in man-made lakes (RAF/71/217)-Ghana and Egypt. Project findings and recommendations. Unpublished WHO document PDPi79.2. 1979. Dazo B. C. and Biles J. E. Schistosomiasis in the Kainji Lake area, Nigeria. Report on a survey made in Octo- ber-December 1970. Unpublished document WHO’ SCHIST0/72.21, 1972. Dazo B. C. and Biles J. E. Follow-up studies on the epidemiology of schistosomiasis in the Kainii Lake area. Nigeria (November-December 19711. Unpub- lished document WHO/SCHIST0!73.29. 1973. Amin M. A. Problems and effects of schistosomiasis in irrigation schemes in the Sudan. In Worthington E. B. op. cit.. pp. 407-41 I, 1977.

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ings of the 7th SEAMEO Tropical Medicine Seminar on Infectious Diseases of the Gastrointestinal System in Southeast Asia and in the Far East, Taipei, 1970 (Edited by Cross J. H.), pp. 39-52. 1971. SUCAM. A SUCAM na area do projeto de Sobradinho, incluindo agrovilas de Born Jesus da Lapa. Unpublished document, Ministri of Health, Setor Bahia, Brazil, April. 1976; SUCAM. Situacao de saude na area de infl&ncia da hidrelectrica de Itaipu Unpublished document, Ministry of Health, Brazil, 1976; SUCAM Erradicacio e controle de endemias. Unpublished document, Ministry of Health, Brazil. 1978. ICOLD World Register of Dams-Registre Mondial des Barrages. 998 pp. International Commission on Large Dams, Paris, 1973; ICOLD World Register of Dams- Reaistre Mondial des Barrages, 299 pp.. First Updat- ing, 31 December 1974. International Commission on Lame Dams. Paris. 1976: ICOLD World Reaister of Dams-Registre M&dial des Barrages, 322 pp.; Second updating, 31 December 1977. International Com- mission on Large Dams, Paris, 1979. McJunkin F. E. Water. engineers, development and disease in the tropics. Schistosomiasis Engineering Applied to Planning, Design. Construction and Oper-

ation of Irrigation. Hydroelectric and Other Water De- velopment Schemes, 182 pp. Agency for International Development. Department of State, Washington, DC 1975. Fels E. and Keller R. World register on man-made lakes. In Ackermann W. D. et ul., op. cit., pp. 43-49. 1973. Worthington E. B. (Ed.). Arid land irrigation in developing countries. Environmental problems and effects. Based on the International Symposium, 16-21 February 1976. Alexandria. Egypt, 463 pp. Pergamon Press, Oxford, 1977. Houston C. E. Irrigation development in the world. In Worthington E. B.-op. cit., pp. 4255432, 1977. Ackermann W. D.. White G. F. and Worthington E. B. (Eds). Man-made lakes: their problems and environmental effects. Proceedings of an Inrernationul Sym- posium on Man-Made Lakes, Knoxcille, 1971. 847 pp., Geophysical Monograph Series No. 17. American Geophysical Union, Washington. DC, 1973. West Africa, 4 April p. 688, 1977. Scott D. and Chu K. Y. Schistosomiasis research project on man-made lakes (IR/MPD/028). Visit from the project to Mali, 1629 September 1977. Unpub- lished WHO document, 1977. Ripert C.. Ekobo S. and Palmer D. Environmental assessment: The potential health impact of the construction of 57 dams in the Mandara Mountains, North Cameroun. Unpublished USAID document. Mandara Mountains Water Resources Project No. 631412, 1977. It should be noted that the report by Harinasuta et al. (1979) was not intended to provide precise data on the evolution of the water development programs. In some instances there is no clear indication of whether an impoundment has been completed, is in the construction stage, or is only proposed: dates of construction are rarely given for irrigation systems. Direction General de Recursos Hidraulicos. Grandes

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Presas de Venezuiela. El Agua. Caracas. Ministerio de Obras publicas. 2 (numero especial). 1976: Direction General de Recursos Hidraulicos. Progruma quinquenul de recursos hidraulicos (period0 1976-l 9X0). Exposition

de motipos, Ministerio de Obras Publicas. Caracas, 1976. SCOPE/ICSI-J. Man-made lakes as modified eco- systems, SCOPE Report No. 2. 76 pp. Scientific Com- mittee on Problems of the Environment/International Council of Scientific Unions. Paris. 1972. Personal communication by Dr R. Le Berre. Oncho- cerciasis Control Program. World Health Organiz- ation. Other References consulted: Abdallah A. (Ed.) Proceedings of the Internutionul Con- ference on Schistosomiasis, Cairo, 1975. 2 vols, 819 pp. Ministry of Health, Egypt. 1978. Andradk R. Milward de. Nota ecologica sobre o Lago de Pampulha (Belo Horizonte, M. G.). corn especial refer&&a aos planorbideos (Pulmonata, Planorbidae), Rep. bras. Malar. 21, 59-l 16, 1969. Bradley D. J. The health implications of. irrigation schemes and man-made lakes in tropical environments. In Wastes and He&h in Hot Climates (Edited bv Fea- them R., McGarry M. and Mara D.). pp. 18-29. Wiley, London, 1977. Bras&Paraguay/Itaipu Binacional. Hidrelectrica de

Itaipu. Plano basic0 para conseraaccio do meio umbiente. Itaipu Binacional, Rio de Janeiro-Assuncao, 1975. Brasil-Paraguay/Itaipu Binacional. Estatistica de aci- dentes. Unpublished document-November. 1978. Brown A. W. A. and Deom 1. 0. Summary: health aspects of man-made lakes. In Ackerman, W. D. et al..

op. cit., pp. 755-764. 1973. Companhia Hidro-Electrica do Sio Francisco. Relu-

torio da Directoria 1977. Recife, CHESF, 1978. Coumbaras A. Travaux hydrauliques et problemes de Sante dans les pays en voie de developpement. Actu

trop. 34, 229-248, 1977. Coumbaras A. and Picot H. Hydraulic projects and health problems: directives for study, prevention and control. Unpublished WHO document MPD/PPD- December, 1975. Davis A. Epidemiology and control of schistosomiasis. In Epidemiology and Community Health in Warm Cli- mare Countries (Edited by Cruickshank R., Standard K. L. and Russell H. B. L.). pp. 223-242. Churchill Livingstone. Edinburgh, 1976. Davis A. Schistosomiasis. Unpublished WHO document TDR/WP/76.8, 1976. Deom J. The role of the World Health Organization. In Stanley N. F. Alpers M. P., op. cit. pp. 387-400, 1975. Deom J. Water resources development and health. A selected bibliography. Unpublished WHO document MPDl76.6, 1976. Deom J. Water resources development and health. A selected bibliography. 1st addendum. Unpublished WHO document MPDl77.7, addendum 1 to MPD/ 76.6, 1977. Deschiens R. and Cornu M. Commentaires ecologi- ques et tpidtmiologiques concernant les bilharzioses et le lac deretenue de Kossou (Cote d’Ivoire). Bull. Sot. Path. exot. 69, 163-169, 1976. Hughes C. C. and Hunter J. M. Diseases and “development” in Africa. Sot. Sci. Med. 3, 443493, 1970. Hunter J. M. Man-environmental holism as an approach to the study of disease transmission and con- t&l. Assignment report. Unpublished WHO document MPD/RCT-TDR-Auaust. 1976: Institute Brasileiro -de Geographia e Estatistica. Annuario estutistico do Brosil, 1977. IBGE, Rio de Janeiro, 1978.

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Lanoix J. N. Relation between irrigation engineering and bilharziasis. Bull. W/d Hlrh Org. 18, 1011-1035, 1958. Lowe-McConnel R. H. (Ed.). Man-made lakes. Pro- ceedings of a Sq’mposium Held ar the Royal Geographi-

cal Society, 30 September-18 October 1965. Symposia of the Institute of Biology No. 15, 218 pp. Academic Press. London. 1966. Miller M. J. (Ed.). Schisrosomiasis. Proceedings of a Symposium on the Future of Schistosomiasis Control.

135 pp. Tulane University, New Orleans. 1972. Odingo R. S. (Ed.). Multipurpose river basin develop ment in developing countries. Report of an Inter- national Workshop. 139 pp. Department of Geogra- phy, University of Nairobi, Nairobi. 1975. OMS/OPS. Impactos de la construction de la presa de Itaipu sobre la salud en Paraguay. lnforme de un grupo de estudio de la OPS’ 21 Marzo-I Abril 1977. Unpublished OMS/OPS document. 1977. Papema I. Study of an outbreak of schistosomiasis in the newly formed Volta Lake in Ghana. 2. Tropenmed.

Parasit. 21. 411425. 1970. Picot H. Etude des problimes sanitaires lits P la crCa- tion des lacs artificiels. Rapport de mission. 16 sep tembre-21 decembre 1974. Unpublished WHO document MPD/PPD. 1975. Rey L. Report on a travel to South America to visit man-made lakes in Brazil, and to establish preliminary contacts to prepare a seminar on health environment and development in projects for water resources utilization to be held in Argentina or Uruguay. Mission report, l-23 December 1978. Unpublished report to WHO, 1978. Rey L. er al. Development of water resources and health risks. Studies for the establishment of a fore- casting and preventing methodology. Mission report, 12 March-12. April 1977. Unpublished WHO document PDP/79.1, 1979. Rubin N. and Warren W. M. (Eds). Dams in Africa. An Interdisciplinary Study of Man-Made Lakes in Africa.

188 pp. Cass. London, 1968. Stanley N. F. and Alpers M. P. (Ed.). Man-Made Lakes

and Human Health. 515 pp. Academic Press, London, 1975. Vogel L. C. et (I/. (1974) Healfh and Disease in Kenyu. East African Literature Bureau, 529 pp. Dar-es- Salaam, Kampala, Nairobi, 1974. White G. F. (Ed.). Enuironmenral Eflecrs of Arid Land

Irrigution in Deceloping Counrries. ?ech&al Notes 8. 67 pp. UNESCO-Man and the Biosphere (MAB), Paris, 1978.

APPENDIX 1

AIR PHOTOGRAPHY AND REMOTE SENSING

Surceillance tecAnolog,b

Levels of accuracy in remote sensing are rapidly increasing. More detailed, scientifically valuable information is becoming retrievable through these mechanisms. Resolu- tion in Landsat imagery has improved recently from I to 0.25 hectare. Literally thousands of satellites are in orbit representing a great capacity for the collection of scientific information. For example, it is possible to identify vegetation and land-use patterns as well as changes in those patterns over time. Such environmental information is closely related to the habitat of vectors and of intermediate hosts and to zoonotic reservoirs. There is a distinct need to engage in this frontier of technology in order to develop techniques for the monitoring of disease risk. The opportunity awaits scientific leadership in this area of health applications research. A first step would be to develop an experimental. prototype program.

UIilil)

There are three primary goals of aerial photography and remote sensing: (i) immediate practical applications. There is immediate utility for project management at the practical level through appropriate information retrieval on a daily, weekly or monthly basis. A good example would be the proposed utilization of teledetection and teletransmission by the Onchocerciasis Control Program in the Volta River Basin in support of their spraying campaign against Simu- lium in West Africa [23]. (ii) Planning and program design. A second goal of remote sensing is the assembly of an inventory and data base for planning the future development of natural resources. (iii) Research. Specifically focused projects. related to health, can effectively utilize remote sensing technology. For example. it is possible, at the prototype level at least, to identify malaria habitats. Applications of remote sensing for data collection and surveillance of man-made lakes including small impoundments should be considered.

Aerial dara accumulation

(i) Types of data. (a) Aerial photoyraphy and phorograrn- metry. These are photographic images taken from aero- planes; they are appropriate for the detailed study of small areas. Great precision can be achieved at scales of, for example 1: 5000. (b) Remote sensing, sarellite imagery and telederection. This is an area of innovation and technological growth. Magnetic tape retrieval is available to all developing countries. Machine print-out capability of the data recorded by the satellites includes computer mapping in color (e.g. land .use and crop regions in rural tropical areas). (c) Automated relerransmission. Networks of terres- trial stations can be established. for example around lakes, in river basins, in ecological zones. and by country. These stations would be identified by telemetric code. would operate automatically and would send signals to satellites overhead giving environmental parameters such as water level and amount of rainfall. Through teletransmission, data could be rapidly collated in different ways as required for the near-instantaneous provision of information to be used in research and project management. (d) Direct ques- tioning. A further capability to be derived from a network of automated telemetric monitoring stations would be to fly over such stations by helicopter and. by signal. to ask them direct questions. This would provide immediate, localized data, which are valuable if needs demand. though more costly infrastructurally.

(ii) Uriliry jbr disease control. (a) Register. Remote sensing is available at low cost and could be utilized for the basic identification of lakes. establishing their numbers. size and geographical coordinates. This would be especially valuable for the large numbers of smaller impoundments that escape the registration process. (See text for note on monitoring for registration.) (b) Encironmental moniroriny. Remote sensing is extremely valuable for ecological analysis. Environmental status and environmental changes can be monitored around large lakes, and also in regions of extensive use of small impoundments. (c) Human hahitar. Remote sensing can be used to collect information on settlements and settlement trends. on location of villages and changes of locations, and on agricultural systems and areas of cultivation, grazing. and burning practices. (d) Dis- ease habitats. With the appropriate development of research methodologies and the design of prototype programs. it would be possible to identify disease habitats. i.e. environmental areas of high risk of disease transmission. In particular. the capability of automatic monitoring of water- body levels and of other habitat characteristics over wide areas in the developing world could eventually be related. effectively. to parameters of insect populations. snail vet- tars and other man-disease habitat relationships.

1144 JOHN M. HUNTER cf al.

APPENDIX 2

DESCRIPTIVE VARIABLES

The following lists of groups of descriptive variables of water development schemes are intended to serve (a) as guidelines for a national and international registration program, and (b) as a representative set of descriptors for the 1 preparation of a functional health-related typology of water control schemes. In all cases. these lists are merely preliminary suggestions for review, and technically and scientifically appropriate parameters will need to be identified.

I. Gross six variables of‘ water body

Area. km2 Depth. m Shoreline length, km Grassline volume-high water. 106, m’ Grassline volume-low water. 10”. m3 Volume per unit of surface area Seasonal flux coefficient IO year flux coefficient.

2. Limnological variables of water body

Water chemicals Water pH Water suspended particles Water trace-elements Water thermal characteristics Water movements and currents Water stratification Water photo-sensitivity characteristics Water phyto-plankton Water zoo-plankton ‘Age’ of lake.

3. Irrigation design and practice

Water irrigation volume-high water. ha/m Water irrigation volume-low water, ha/m Storage capacity Offtake capacity Pipes, pumps. gravity Bow. open or covered channels Sub-impoundments Networks of channels. aquaducts Spray, sprinkler systems Periods of irrigation by areas, and duration of flow Drawdown area km2, lo6 ha Discrete hydrological units Unified hydrological units Water table characteristics ‘Age’ of irrigation areas.

4. Irrigated crop production

Areas by crop type, e.g. cotton, sugar, vegetables, tree crops

Water need characteristics: applications, durations, amounts. by crop by time of day by season (relevant for water contact)

Crop micro-climate characteristics (relevant for vector control).

5. Non-irrigated crop production

Crop-type and other characteristics.

6. Livestock production

Livestock watering capacity: numbers. aggregate or bovine equivalents

Carrying capacity: numbers Herder families and dependents, numbers Area definitions of cattle raising activity (zoonotic Con-

tact).

7. Game biomass

Area definitions to be determined Sustained yield offtake per year in defined areas around

the lake. kg/km’ Hunters and gatherers. families and dependents.

numbers (zoonotic contact) Other biomass characteristics.

8. Aquatic biomass

Fish: sustained yield offtake, fish harvests. kg per year Other aquatic foodstuffs Fishermen: families and dependents. numbers (water

contact).

9. Forestry production

Area definitions to be determined Sustained yield harvesting by species defined per unit

area around the lake Other forest products Numbers engaged (relevant for zoonotic health risks).

IO. Ecosystem characteristics: soils. rainfall, Fegetation

Ecosystem area definitions to be determined both upstream and downstream, within the watershed, and beyond

Rainfall, mm/year Rainfall. number of dry and/or wet months per year Temperatures per month and per year Evaporation Evapotranspiration Soil distributions, catenas. profiles Watershed: monitoring of erosion sources; protection:

reserves, fences. barriers. boundaries Water-table characteristics; seasonal flux, and time-

trends, run-off, parameters. seasonal and other vari- ations

Vegetation patterns, floristic communities, species, stability and flux. measures. fauna1 communities. eco- types.

1 I. Power production

Service areas both regional and national to be defined Consumer type definitions also to be established Power potential. MW, Head-m Spillway characteristics Other engineering characteristics.

12. Lake transport and communications

Service areas to be defined Wider connections to be defined People per km per year by type of lake vehicle Volume of goods per km per year by type of lake ve-

hicle Value of goods per km per year by type of lake vehicle Type of goods volume per year lake transport Schedules, formal commercial Schedules, informal commercial Other Transportation axes by direction by distance.

13. Population: settlement and demography variables

Appropriate area definitions to be made for each population group

Numbers displaced and relocated, ‘relocatees’ Numbers involved in ‘host’ communities Numbers of ‘immigrants’ Numbers not moving and not receiving ‘relocatees’.

viz. ‘stable residual population’ Numbers, densities per unit area defined Time-related net population balance per unit area

defined: equilibrium Population numbers within 1 km of lake-shore, 2 km,

5km


Migration source areas Migration. ‘source’ regional characteristics Age, sex. demographic characteristics of the four popu-

lation groups. viz. relocatees. hosts, immigrants, and the stable. residual communities

Geographical spheres of influence of the water impoundment scheme

Villages. towns, settlement patterns. by lake location Settlements by other environmental and population

characteristics Settlement patterns of populations at disease risk.

14. Population: employment und occuporionul acfiriries

Area specific definitions necessary Numbers and characteristics: fishing Number and characteristics: irrigation project. work by

field plots and by techniques (occupational water contact)

Numbers and characteristics: traditional livestock raising

Numbers and characteristics: traditional hunting and gathering activities

Numbers and characteristics: power production employment

Numbers and characteristics: trading activities Numbers and characteristics: artisan activities.

15. Human disease wriuhks

Area definitions to be made Types of diseases Presence or absence Prevalences lncidences Other variables.

16. Zoonosrs Area definitions to be determined Zoonoses to be listed Other variables.

17. Vector hiologr wriahles

Area definitions to be determined Species to be listed Data on prevalence and intensities and infectivity

levels.

18. Health care sercices

Area definitions to be determined Health care services infrastructure Health care services personnel Population vaccination levels Utilization of traditional health care services Other information.

Documents

Man-made lakes and man-made diseases