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14
CHAPTER 2
STUDIES ON DROUGHT ASSESSMENT
2.1 GENERAL
History of any concept will give an idea about the aspects which
are not yet covered, present requirements and a future direction for research.
It will throw light on the state of the art of knowledge and enlighten the future
course of study. In the case of droughts, several studies were completed the
world over in tropical as well as humid countries. Drought is fundamentally
the resultant of an extended period of reduced precipitation. It is viewed
through its impacts such as soil moisture, streamflow, crop yields, etc. As
such, the question of predictability of drought must extend to those quantities
as well. Nevertheless, in developing an understanding of drought and its
predictability, it is useful to first consider the physical mechanisms that cause
precipitation deficits and how they vary by time scale.
Availability of varied definitions of drought reflects the complexity
of the natural disaster cum hydrologic extreme. Studies were conducted on
drought assessments using different techniques (conventional such as
estimation of relevant hydrologic parameters and advanced such as Remote
Sensing technique, GIS software, etc.) in varied domains of dry land
agriculture, rural / urban contexts, etc. There is a need to analyse the drought
implications in an irrigated agriculture with inputs from Participatory
irrigation management. The following sections cover a review of literature
that are relevant to the objectives of this study.
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2.2 ESTIMATION OF CROP WATER REQUIREMENT
Information on crop water requirements is imperative in the planning
and operation of soil and water management strategies. Water used by the
crops is predominantly lost by transpiration (T) but there are also evaporative
(E) losses from the soil and plant surfaces. The amount of water used by
plants together with water losses through evaporation is called
evapotranspiration (ET). Other potential areas of water loss are due to many
meteorological factors such as humidity, wind speed, temperature etc.
Estimating evapotranspiration in a locality is a difficult task because it
involves equipments which are considered to be quite costly. A lot of research
has been undertaken to estimate a kind of reference ET from meteorological
data and convert this to the actual ET. There are various methods to calculate
ET such as directly using lysimeters, indirect methods of meteorological
factors and pan evaporation data.
A study sponsored by the United Nations indicates that irrigated
agriculture will need to provide 70% of the world’s increased food
requirements in future (Report of United Nations, 2005). Postel (1999)
indicates that food production levels needed in 2025 could require upto 2,000
cubic kilometers of additional water for irrigation. Water management and
crop yields can be improved by means of increased use of reliable methods
for estimating crop evapotranspiration (ET). More than a score of methods
have been proposed and used over the past 50 years. Selection of the preferred
ETo method should be based on the time step required, site aridity, equipment
costs and operation and maintenance requirements, quality of the weather data
available and the required simplicity of computations.
Where equipment cost is a consideration, where data quality is
questionable or where historical data are missing, both the reduced set FAO-
PM and the Hargreaves (Hargreaves and Allen, 2003) methods are
16
recommended, since the two methods are surprisingly equivalent over a wide
range of climates. When the weather data site is not located within a large and
well-watered area, the Hargreaves method will generally have less aridity-bias
impact in the estimate of ETo as compared to the combination equations.
Daily estimates by the Hargreaves equations are subject to error caused by the
influence of the temperature range caused by the movement of weather fronts
and by large variations in wind speed or cloud cover. Therefore, the
Hargreaves methods are recommended for use with five-day or longer time
steps.
Allen et al (2005) report that the measurement of evaporation in the
initial stage of the crop by semi theoretical integrated function to predict the
average Kc ini representing the initial period of a growing season when the
soil is mostly bare. This incorporates factors like wetting frequency,
evaporative demand and water-holding capacity of the upper soil layer. The
procedure can be used to produce graphical figures similar to that introduced
in FAO-24 for Kc ini. The model is based on a two stage evaporation process,
where evaporation during the second stage is predicted in proportion to
cumulative evaporation depth during the second stage. The model served as
the basis for figures in FAO-56. The Kc max value has been shown by several
studies to range from 1 to 1.3 for grass reference ETo, so that this value can
be predicted with relatively small error in evaporation estimates.
Singh and Irmak (2009) presented a modified approach towards
estimating Kc values from remotely sensed data. The surface energy balance
algorithm for land model was used for estimating the spatial distribution of
ETc. Land use map was used for sampling and profiling the Kc values from
the satellite overpass. Finally, a regression model was developed to establish
the relationship between the normalized difference vegetation index (NDVI)
and the ETr based crop coefficients Kcr. There was a good correlation
17
between the NDVI estimated Kcr and the Bowen ratio energy balance system
based Kcr with a R2 of 0.74 and a low root mean square difference of 0.21.
This can be a very useful tool for a large watershed or regional scale
estimation of evapotranspiration using the crop coefficient and reference
evapotranspiration approach.
Sabziparvar and Tabari (2010) used digital elevation model (DEM )
and GIS assisted methods to generate a regional distribution of monthly ETo
using the best performed model and multiple linear regressions. The
comparison of model results showed that the HG model presented the best
performance for estimation of monthly ETo values in arid and semiarid
regions northeast of Iran. Besides, the input variables are available at all of
the meteorological stations in the study area. These suggest that the model can
be a good candidate for prediction of monthly ETo in arid and semiarid
regions, where comprehensive measurements of meteorological data are not
available. The statistical analyses showed that the mean air temperature was
well correlated with altitude and latitude. When the correlations averaged over
all 12 months, a reasonable coefficient of determination 0.76 was obtained.
The maximum and minimum temperatures were also affected by altitude and
latitude of the region. The predicted ETo values showed both temporal and
spatial variations in the region. The estimated monthly ETo increased
southward because of drier climate in the south. Though PMF-56
evapotranspiration model was considered as the reference, standard method
for validating the predicted ETo data, the use of field lysimeter data can
improve the model estimates.
Murali and Prasad (2011) have done a study which is especially
relevant in a changing climate where there is a need to see how changes occur
in croplands, their implications on water use and strategies for adaptability to
ensure food security. The outcome of this research highlights the value of
18
using time-series data and advanced methods like spectral matching
techniques in the study of agricultural cropland changes in large river basins.
Ram Karan and Pawar (2011) conclude that by giving due importance to both
criteria’s viz. R2 based analysis and statistical indicators (RMSD, MBE and t-
statistics) based analysis, that Priestley-Taylor and FAO 24 Blaney-Criddle
method can be used for ETo predictions under wide range of climatic
conditions when limited data is available or reliability of data is in question.
Nandagiri and Kovoor (2012) provide guidance on the choice of the
most appropriate ETo equation to be adopted in a particular Indian climate
when input data are insufficient to apply the preferred FAO-56 PM method,
alternative ETo methods were ranked on the basis of SEE, STDEV, R2 and
also on the basis of an overall rank that considered all the performance
statistics.
2.3 DROUGHT ASSESSMENT
Agricultural drought occurs when soil moisture and rainfall are
inadequate during the growing season to support healthy crop growth to
maturity and cause extreme crop stress and wilt. Agricultural drought can be
estimated directly using conventional demand supply gap or indirectly using a
few approaches such as Remote Sensing.
Rama Prasad (1990) tried to quantify the water deficiency during a
drought and the method considers the soil moisture in the form of an
Antecedent Precipitation Index (API). The difference between the actual API
on a given time period and the API value necessary (crop water requirement
for the time period) to ensure that the crop water demand is fully met is
defined as the deficit for the day. The cumulative value of the deficits in a
water year is calculated as total deficit. The total deficit for each water year is
plotted with the crop yield data and a straight line is fitted. The drought
19
severity classification is made based on the normalised yield values that were
noted from the plotted line against the corresponding deficit for each year.
Byun (1999) analyzed the common weaknesses of current drought
indices. First, most of the current indices are not precise enough in detecting
the onset, end and accumulated stress of drought. Second, they do not
effectively take into account the aggravating effects of runoff and
evapotranspiration, which build up with time. Third, they have a limited
usefulness in monitoring ongoing drought because they are based on a
monthly time step. Fourth, most of them fail to differentiate the effects of
drought on surface and subsurface water supply. A new series of indices are
proposed to solve these weaknesses and to improve drought monitoring. New
quantified definitions on drought and its onset, end and duration are proposed.
Wilhite (1991 and 1994) focuses on the definition of drought and
the quantification of its intensity and duration. Most drought indices are based
on meteorological or hydrological data. They include indices developed by
Palmer (1965), McKee et al (1993) and Subramanyam (1964). Of all the
indices, the Palmer Drought Severity Index is still the most widely used and
recognized index on an operational bases.
Panu and Sharma (2002) studied the challenges in drought research.
Major challenge of drought research is to develop suitable methods and
techniques for forecasting the onset and termination points of droughts. An
equally challenging task is the dissemination of drought research results for
practical usage and wider applications. The statistical and mathematical
algorithms of forecasting are reasonably well developed, whereas the
phenomenal and causative aspects are far from satisfactory. One major
application of drought forecasting is in the planning of measures to mitigate
the impacts of drought by governments and related agencies. The spatial
coverage of drought duration, severity and/or intensity is of significant
20
importance in planning measures towards mitigating impacts of droughts.
Drought impacts should be handled using the risk-based approach rather than
the crisis-based approach, as is the practice today in most countries.
Svoboda (2000) focuses on discussion about the drought plans
which normally contain three basic components: monitoring & early warning,
risk assessment & mitigation and response. A 10-step drought planning
process illustrates how these components of a plan are addressed during plan
development. An example of a new climate monitoring product, the Drought
Monitor, is presented to illustrate how climate parameters and indices are
being used in the United States to produce a weekly comprehensive
assessment of drought conditions and severity levels. A critical component of
planning for drought is the provision of timely and reliable climate
information, including seasonal forecasts, that aids decision makers at all
levels in making critical management decisions. This information, if properly
applied, can reduce the impacts of drought and other extreme climate events.
Drought differs from other natural hazards in several ways. First,
since the effects of drought often accumulate slowly over a considerable
period of time and may linger for years after the termination of the event, the
onset and end of drought is difficult to determine. Because of this, drought is
often referred to as a creeping phenomenon (Tannehill 1947). Although
Tannehill first used this terminology more than fifty years ago, climatologists
continue to struggle with recognizing the onset of drought and scientists and
policy makers continue to debate the basis (i.e., criteria) for declaring an end
to a drought. Second, the absence of a precise and universally accepted
definition of drought adds to the confusion about whether or not a drought
exists and, if it does, its degree of severity. Realistically, definitions of
drought must be region and application (or impact) specific. Third, drought
impacts are nonstructural, in contrast to, the impacts of floods, hurricanes and
21
most other natural hazards. These characteristics of drought have hindered the
development of accurate, reliable and timely estimates of severity and impacts
and, ultimately, the formulation of drought contingency plans by most
governments.
Drought severity is dependent not only on the duration, intensity,
and spatial extent of a specific drought episode, but also on the demands made
by human activities and vegetation on a region’s water supplies. The
characteristics of drought, along with its far-reaching impacts, make its effects
on society, economy, and environment difficult to identify and quantify.
Improved understanding of a region’s drought climatology will provide
critical information on the frequency and intensity of historical events.
Identifying the factors that explain who and what is at risk and why (i.e., the
underlying factors behind the vulnerability) can lead to the development and
implementation of a wide variety of mitigation actions and programs to
reduce impacts from future drought events.
Droughts differ from one another in three essential characteristics:
intensity, duration, and spatial coverage. Intensity refers to the degree of the
precipitation shortfall and/or the severity of impacts associated with the
shortfall. It is generally measured by the departure of some climatic index
from normal and is closely linked to duration in the determination of impact.
Many indices of drought are in widespread use today, such as the decile
approach (Gibbs and Maher 1967) used in Australia, the Palmer Drought
Severity Index and Crop Moisture Index (Palmer 1965, Alley 1984) in the
United States and the Yield Moisture Index in the Philippines and elsewhere.
A relatively new index that is gaining increasing popularity in the United
States and worldwide is the Standardized Precipitation Index (SPI), developed
by McKee et al. (1993).
22
Another distinguishing feature of drought is its duration. Droughts
usually require a minimum of two to three months to become established but
then can continue for months or years. The magnitude of drought impacts is
closely related to the timing of the onset of the precipitation shortage, its
intensity and the duration of the event. Droughts also differ in terms of their
spatial characteristics. The areas affected by severe drought evolve gradually
and regions of maximum intensity shift from season to season.
Ray Motha (2000), dealt with establishing an effective national
drought information delivery system, a coordinated effort must be undertaken
to bring more systematic data networks to rural and tribal areas. A
comprehensive information gateway must be established to provide users with
free and open access to observational network data and drought monitoring,
prediction, impact, assessment, preparedness and mitigation measures. The
key elements of an effective national drought policy include planning,
proactive mitigation, risk management, resource stewardship and public
education. All of these elements require detailed knowledge of observational
data and research products that form the foundation for efforts to reduce
drought impacts on society.
Sinha Ray (2000) have dealt with monsoon variability and the
impact of global and regional scale parameters on summer monsoon rainfall
and the prediction of summer monsoon rainfall through numerical models.
The advisories regularly issued by the India Meteorological Department
(IMD) and the National Centre for Medium Range Weather Forecasting
(NCMRWF) can be made more user oriented and a better feedback
mechanism may evolve. Proper validation of remotely sensed data in
coordination with IMD scientists, scientists from other agencies, and policy
makers for proper and timely monitoring of drought in smaller areas has been
emphasized. Better communication between farmers, policy makers, and
23
researchers to improve the nature and quality of information provided to the
users also has been stressed.
To assess the utility and impact of operational weather services to
farmers, feedback can be obtained through conferences, workshops of
forecasters, agrometeorologists, agriculturists, extension workers and farmers.
Feedback is obtained by various means, such as questionnaires. The
questionnaires usually include (1) general information (e.g., name of unit,
main crops and main cultural operations), (2) information regarding farmers’
awareness of meteorological forecasts and agromet advisories, and (3)
information regarding the language of advisories (e.g., whether the language
is easy or difficult to follow), reliability of forecasts and usefulness of
warnings. Regular surveys for this feedback information are essential for the
improvement of our forecasting at such a level, so that the user community
can correctly interpret the advisories to their best advantage.
Studies by Smith (1978) and Singh and Kriplani (1987) have shown
that the 30-50 day mode has strong interannual variability, which may in turn
affect the variability of the monsoon season rainfall through active-break
monsoon episodes. They prepared a time series of the drought area index.
They defined the moisture index as the ratio of departure of rainfall from the
monthly mean and standard deviation of monthly rainfall. The epochal
behavior of drought has been discussed by Joseph (1978).
Appa Rao (1981 & 1987) classified the drought-prone areas and
chronically drought-affected areas. Most of the drought-prone areas identified
above are in either arid or semiarid regions where droughts occur more
frequently. Sinha Ray and shewale (2001) have shown a decreasing trend in
the area affected by drought in India. They made a detailed study of the
variability of drought incidence over districts of Maharashtra. Shewale (2001)
have determined the probability of occurrence of drought on the basis of
24
summer monsoon rainfall data for the period 1875-1999. Probability of
occurrence of severe drought was found to be greatest in Saurashtra and
Kutch, followed by Gujarat and West Rajasthan. He also studied the effects of
El NiZo on summer monsoon rainfall of various subdivisions of India.
The National Natural Resource Management System (Jeyaseelan
2002) has been set up to monitor the progress of remote sensing applications
to natural resources management in the country. To pursue and guide remote
sensing application development in the agriculture sector, the Standing
Committee on Agriculture and Soils (SC-AS) has been created. The SC-AS is
entrusted with the responsibility of examining the role of remote sensing
technology in addressing various issues related to management of agricultural
resources. They are assessing the present and future capabilities of that
technology to develop procedures to retrieve agromet parameters from space
borne systems and disseminate agromet information for farmers’ advisory
services. Recent efforts to combat drought through policies formulated by
governmental agencies include: 1. Crop weather watch groups at the national
and state level, 2. Food security through buffer stocks, 3. Priority to the most
seriously affected areas for “food for work”/National Rural Employment, 4.
Project and other programs, 5. High priority to food production in the most
favorable/irrigated areas as compensatory, 6. Programs, 7. Optimum input
use, 8. Rural godowns to avoid crash sales, and 8. Crop insurance schemes.
The space-based National Agricultural Drought Assessment and
Monitoring System (Jeyaseelan 2002), which has been operational since 1989
under India’s Department of Agriculture, provides scientific information at
the district level for most of the states and sub district levels in a few states.
The NADAMS program needs to be strengthened with interdepartmental
support. The Drought Prone Area Development Programme (DPAP) and
25
Desert Development Programme (DDP) should use the action plans prepared
on the basis of integrated resource estimation from remote sensing data.
Premier government institutions like the Central Arid Zone
Research Institute (CAZRI),Jodhpur; Indian Grassland and Fodder Research
Institute (IGFRI), Jhansi; Central Soil Salinity Research Institute (CSSRI),
Karnal; and research stations of the Ministry of Agriculture in various states
have developed some ameliorative measures. These practices are region
specific, and after proper implementation, they have the potential of bringing
forth productive green cover on otherwise marginal degraded lands.
2.4 DROUGHT STUDIES USING REMOTE SENSING AND GIS
National Remote Sensing Agency of India (Thiruvengadachary,
1988) has assessed the drought based on the analysis of vegetation index map
and the greenness map as well as vegetation index statistics for bimonthly
periods for each taluk. The satellite based drought assessment and monitoring
methodology was developed based on the relationship obtained between
previous years Normalized Difference Vegetation Index (NDVI) profiles with
the corresponding agricultural performance available at district level and their
relative difference in the current year. The National Agricultural Drought
Assessment and Monitoring System (NADAMS) in a view of the whole
country coverage, envisages the use of data from NOAA satellites with
1.1 km resolution, for generation of weekly composited Normalized
Difference Vegetation Index (NDVI) maps of country. The NDVI is a
transformation of reflected radiation in the visible and near infrared bands of
NOAA AVHRR and is a function of green leaf and biomass.
The various approaches presented above have not tried to quantify
the water deficiency during an agricultural drought, which is relevant from the
water resources engineering point of view. Rama Prasad (1990) tried to
26
quantity the water deficiency during an agricultural drought and the method
considers the soil moisture in the form of an Antecedent Precipitation Index
(API).
Krishnaveni (1993) reported that in case of drought assessment, the
important parameters that may be influencing drought are rainfall,
groundwater levels, stream flows, soils, land use etc. These parameters
possess temporal and spatial characteristics. Geographic Information System
software provides tools to incorporate spatial and temporal variations.
Therefore, GIS can be advantageously used for the analysis of drought.
Tiruvengadachari et al (1987) in their case study in Tadipatri taluk
of Anantapur District in Andhra Pradesh, India, reported that the NDVI
response over the taluk was compared between two years, supported by
ground reports on agricultural conditions. NDVI comparisons over specific
sites around rain gauges and anomalous areas provided an improved
understanding of the NDVI response specially as applied to taluk level
drought assessment. It is suggested that in addition to total vegetated area, the
NDVI response averaged over the total geographic area of the taluk or the
product of vegetated area and NDVI response could be significantly used as
drought indicators. They were found to be more effective than the mean
NDVI response over vegetated areas.
Chanzetal (2003) developed the procedure to form the image to
express the unavailability of water during periods of drought for a selected
drainage basin. Based on the method of truncation level, truncated values of
precipitation and stream flows were estimated at each gauging station. These
truncation levels were used to reflect the levels of drought severity. The
stream flow image from precipitation was subtracted to obtain drought
severity at each level. These were done on a cell by cell basis to create new
attribute values for the new image to represent the unavailability of water at
27
each level of drought severity. He discusses the future perspective of the
applications of GIS technology for agricultural resources management. Land
use suitability analysis is carried out as a part of the study and land use
classification is given. The drought mitigation and management and spatial
variation of drought conditions are explained. It offers in-depth analyses of
regional drought conditions.
Mongkolsawat et al (2000) modeled the drought risk area with a set
of themes using remotely sensed data and GIS. The underlining concept of the
paper is that the severity of drought can be considered as being a function of
rainfall, hydrology and physical aspect of landscape. Each theme of the
drought consists of a set of logically related geographic features and attributes
are used as data input for analysis. The matrix overlay operation of the
drought risk layers was performed. They are then classified into 4 drought
classes of drought risk: very mild, mild, moderate and severe.
Nagarajan and Subrata Mahapatra (2000) developed the Land
Based Information System for drought to store information of past, compared
it with the current data and to assess the vulnerability of an area using orbital
temporal remotely sensed and ancillary data in understanding the situation
and decided on the mitigation planning. This study provides an overall
picture about drought information requirement for decision makers. This
study highlights the land information based system developed for this purpose
for the drought prone Marathwada region.
Wilhelmi (2002) explains the agro-climatological factors of
vulnerability to agricultural drought. Evapotranspiration (ET) values were
estimated based on the relationship between ET, water use efficiency and crop
yield. Probability values were assigned by spatial interpolation and classified
using GIS. The classifications included low, moderate, high and very high
probability of seasonal crop moisture deficiency. The results of this study
28
formed the basis for a comprehensive, GIS-based agricultural drought
vulnerability assessment for Nebraska.
Ajay and Baldev Sahai (1986) have described the role of remote
sensing in drought detection and its quantification. Different types of drought
have been discussed. It is stated that the steady rise in temperature, absence or
the deficiency of rainfall over a fairly long period form the basic characteristic
of drought. In addition, the study provides the information on useful spectral
bands and indices used for the assessment of drought like NDVI, Stress Degree
Day, Temperature Stress Days and Crop Water Stress Index. The study
concluded that the problem of drought/crop condition assessment may use a
hybrid approach which uses both comparatively high resolution earth resources
satellite data together with coarse resolution meteorological satellite data.
Thiruvengadachari and Gopalakrishna (1993) developed an
Integrated Data base Environment for Assessment of Drought (IDEA),
primarily meant to provide operational assistance to the National Agricultural
Drought Assessment and Monitoring System (NADAMS) in the analyses and
interpretation of NDVI data derived from the NOAA AVHRR satellite sensor.
IDEA has been used to derive two indices namely Seasonal Vegetation Index
(SVI) and Peak Vegetation Index (PVI) that are used in tandem to
characterize the drought prone taluks of the Karnataka State. A weighting
model was used to show relative drought proneness of the Karnataka taluks.
The ground variables taken into account were, percentage irrigation support,
percentage forested area, percentage rainfed area and normal seasonal rainfall
for each taluk.
Bora et al (1995) studied the integrated resource survey using
remote sensing to combat drought in a part of Nagaur district of Rajasthan
State, India using False Colour Composite (FCC) of IRS-1A LISS-II of
October 1988 and January 1989. Based on visual interpretation, it is
29
concluded that remote sensing technique is a useful tool for inventory of
resources of any area and the integration of database of resources led to
scientific planning and alternate land uses for combating drought menace.
Tripathy et al (1996) attempted to evaluate the indicators of
desertification process in semi-arid lands of Shahapur and Shorapur taluks of
Gulbarga district of Karnataka State, India by making use of temporal satellite
information (Landsat-4 MSS 1984 & 1985 and IRS-1A LISS-II 1988 & 1991)
along with the surface and statistical data with the aid of GIS. A
desertification severity map was produced by integrating meteorological,
hydrological and biological indicators. The study concludes that the average
severity of desertification is moderate and aggravated by human activity.
A study for monitoring the regional drought of South American
continent using AVHRR data was carried out by Liu and Kogan (1996).
Drought areas are delineated with certain threshold values of NDVI and
Vegetation Condition Index (VCI). It has been reported that drought patterns
delineated by NDVI and VCI agreed quite well with rainfall anomalies
observed from rainfall map. The results showed that NDVI images provided a
useful tool to study large scale climatic variability, while VCI images
provided a useful tool to analyse the temporal and spatial evolution of
regional drought as well as to estimate the crop production qualitatively.
Seiler et al (1998) carried out a study on AVHRR based Vegetation
and Temperature Condition indices for drought detection and impact
assessment on agricultural yields in Cordoba province of Argentina. It is
concluded that the VCI and TCI are useful to assess the spatial characteristics,
the duration and severity of drought, and were in a good agreement with
precipitation patterns.
30
Bayarjargal Yu et al (2000) carried out a study on drought and
vegetation monitoring in the arid and semi arid regions of the Mongolia using
NOAA/AVHRR satellite data. Drought affected regions were detected by
calculating the Normalised Difference Vegetation Index (NDVI) and Land
Surface Temperature (LST) values of the drought and wet years. Due to
moisture stress on the vegetation, NDVI (LST) value recorded in the dry
years should be lower (higher) than those values recorded in a normal year. It
is concluded that the AVHRR based NDVI and LST can provide valuable
information for operational drought detecting and monitoring.
Hostert et al (2001), made a study on monitoring and assessment of
desertification using remote sensing and GIS. The study provides the
additional value that can often be added through integrating remote sensing
derived information with auxiliary data through GIS approach. The study
outlined the importance of integrating socio-economic boundary conditions
and anthropogenic influences. The study further highlights the perspectives of
future developments and their likely implications on Remote Sensing and GIS
based desertification research.
Jayaseelan (2002) has described the recent trends in remote sensing
applications to drought assessment and monitoring with a case study on
National Agricultural Drought Assessment and Monitoring System
(NADAMAS). After the country wide drought in 1987, the emphasis on using
space technology for drought monitoring grew and in 1989, NADAMAS was
set up at National Remote Sensing Agency (NRSA), India. Organizations
involved in the functioning of NADAMS are National Remote Sensing
Agency (NRSA), India Meteorological Department (IMD), Central Water
Commission (CWC) and State Agricultural Departments. The project covers
14 agriculturally important and drought vulnerable states of the country,
which include Tamil Nadu State. NADAMS monitors drought during June to
31
October, the main cropping season in the country. The NADAMS uses
NOAA AVHRR data to monitor country level vegetation dynamics. Bi-
weekly NDVI time series is used to monitor the vegetation phenology through
out the season. For regional drought monitoring (State level), NADAMS uses
Wide image Field Sensor (WiFS) data of IRS-1C/1D and IRS-P3.
Singh Ramesh et al (2003) carried out a study on monitoring
drought over India by studying VCI and TCI of NOAA AVHRR data. Time
series of satellite data during 1985-1996 over various Indian regions have
been used for mapping vegetation cover and classification employing NDVI.
The VCI quantifies weather component which varies from 0 to 100,
corresponding to changes in vegetation condition from extremely
unfavourable to optimal. The study has reported that VCI and TCI can be
used for drought detection and mapping. The TCI alone can not be used alone
to predict drought due to stressed vegetation and wetting of land. The VCI
coupled with TCI may be employed as a tool to monitor both drought and
excessive wetness.
Lei and Peters (2003) presented a study for assessing the vegetation
response to drought in Northern Great Plains using AVHRR data during 1989
to 2000. The derived vegetation condition and moisture availability for the
grassland crop land in the Northern Great Plains fits very well with the
predicted and observed NDVI values in most cases. It is concluded that the
NDVI is a good indicator of moisture condition and can be an important data
source when used for detecting and monitoring the drought. However,
seasonality may be an important factor for decision makers to consider.
Wan et al (2004) carried out studies for drought monitoring in
Southern Great Plains, USA. The NDVI derived from Terra Moderate
Resolution Imaging Spectroradiometer (MODIS) of 2001 and Land Surface
Temperature (LST) has been used in this study. These two are called
32
Vegetation Temperature Condition Index (VTCI) which ranges from 0 to 1.
Lower the value, higher is the occurrence of drought. The study concluded
that VTCI is physically interpreted as the ratio of LST differences among the
specific NDVI values in an area large enough to provide wide ranges of
NDVI and soil moisture at surface layers. Drought monitoring approach by
VTCI integrates the remotely sensed land surface reflectance and thermal
properties and gives the emphasis on changes in both LST and NDVI over a
region. VTCI is time dependant and usually region specific and is useful
during plant growing seasons.
Symeonakis and Drake (2004) studied the monitoring
desertification and land degradation over sub-Saharan Africa using AVHRR
data of 1996. This study emphasized the role of soil erosion that has resulted
due to natural processes, such as drought and human activities, such as
irrigation, agriculture, deforestation and urbanization. The regional land
degradation is assessed by the estimation of vegetation cover which is linearly
related with NDVI. Soil erosion, the chief indicator is estimated using a
model parameterized over land flow, vegetation cover, the digital soil map
and a digital elevation model. The most susceptible degraded land is
highlighted by combining the effects of all the four indicators.
Bhuiyan (2004) used multi-sensors data to deduce surface and
meteorological parameters (vegetation index, temperature, evapotranspiration)
of Aravalli region for the years 1984-2000 together with actual ground data
(rainfall, temperature, ground water level) for detailed drought analysis. The
Standardised Precipitation Index (SPI) has been used to quantify the
precipitation deficit. A standardized Water-level Index (SWI) has been
developed to assess groundwater recharge deficit. Vegetation drought index
has been calculated using NDVI values obtained from Global Vegetation
Index (GVI) of NOAA AVHRR data. Spatial and temporal variations in
33
meteorological, hydrological and vegetative droughts in the Aravalli terrain
have been analysed and correlated for monsoon and non-monsoon seasons
during the years 1984-2000. Based on the results, it is concluded that, none of
the drought indices follow any particular spatial and temporal pattern in this
region. The analysis reveals that meteorological, hydrological and vegetative
droughts are not linearly inter-related and suggests that combination of
various indices offer better understanding and monitoring of drought
conditions for hilly and semi-arid terrains such as Aravalli of Western India.
Nageswara Rao et al (2005) used METEOSAT-5 thermal infrared
(TIR) data for assessing the spatial and temporal distribution of rainfall and
impact of successive agricultural droughts in the state of Karnataka. It is
emphasized that there is a need for an independent system that can provide
the severity, duration and aerial extent of drought and its impact on the actual
condition of the crops/vegetation so that the authorities concerned can take
appropriate relief measures. A comparison of NDVI for the years 2000, 2001
and 2002 has been made. Districts having permanent vegetation, like forests
and agricultural land under irrigation did not show much variation between a
normal year (2000), drought year (2001) and a severe drought year (2002). It
is concluded that the NDVI is a good indicator of agricultural drought but the
reduction in green cover due to drought may be inferred and interpreted
carefully by comparing the NDVI values of the year under study with a
normal year.
Wipop and Sirirat (2006) carried out a study on drought risk area
analysis in Bandanlanhoi district, Sukhothai province based on stepwise
regression model from spatial data. QUICKBIRD satellite images were used
for creation of spatial data. Geographic Information System was applied to
simulation spatial data such as rainfall, rainy days, relative humidity,
temperature, groundwater potential, distance from water body, elevation and
34
soil drainage data. The model showed that the well soil drainage and rainfall
are important parameters for the determination drought risk area. The drought
risk area was divided into four classes viz., No risk, low risk, moderate risk
and high risk. The study concluded that, though the result was shown quite
low accuracy, the technique is good enough for using with GIS.
Rasheed and Venugopal (2009) attempted to map the agro-
ecological units for Vellore district of Tamil Nadu and derive the crop-zone
map for the four corps namely, paddy, sugarcane, groundnut and millets. The
study has demonstrated the application of agro-ecological units for
sustainable land use planning of a region. The basic theory of FAO
framework for land evaluation was adopted to define the suitability of crops.
Land quality details like terrain, soil and climatic characteristics are necessary
for evaluating agro-land suitability of crops and for delineating the agro-
ecological units. Agro-ecological units map was generated by overlaying the
agro-edaphic and agro-climatic map layers in GIS. The agro-land suitability
map was generated by matching the crop requirement details with the land
qualities. The results of the suitability evaluation, when compared with the
current land use statistics of these crops showed that area cultivated is less
than the area suitable for these crops.
2.5 IRRIGATED AGRICULTURE AND PARTICIPATORY
IRRIGATION MANAGEMENT
Agriculture is closely linked to water resource management issues.
Worldwide, 70% of water use is related to agriculture, climbing to 95% in
several developing countries. It is estimated that freshwater usage for
agricultural purposes will increase 14% over the next 30 years to meet the
growing food demands of an increasing population (Report of UN, 2005).
35
Irrigated agriculture, of which 58% of the world‘s total is in Asia,
inevitably comes under intense pressure to improve efficiency of water use in
response to scarce water resources. To promote the efficiency of water use,
there needs to be a focus on enhanced governance and capacity building at all
levels that integrates the basic principles of transparency, subsidiary, and
equity. Decentralizing water governance in agriculture and developing
equitable cost-sharing mechanisms within irrigation systems assists in
achieving more effective use of water.
Irrigation has been the primary engine for the agricultural growth of
developing nations such as India. Notwithstanding the massive public
expenditures, under performance of irrigation systems are a major concern for
such nations. Ineffective irrigation management is due to the non participation
of farmers from the process of planning and implementation. Often, lack of
social and political commitments are identified as the main reasons for the
slow progress in irrigation management. To address the issue, concepts of
Participatory Irrigation Management (PIM) involving the farmers in various
levels of decision making processes has been attempted in various
countries.PIM is a process for improving productivity and sustainability of
irrigation systems. It was during the late 1970’s and early 1980’s, India began
to focus, initiate and support programmes that would later lead to PIM. But,
this has happened after several other countries have examined with it and
became wiser in the use of it.
There are several studies carried out in past by several researchers
on Participatory Management of Irrigation system all over the world. The first
and the best-documented nation-wide programme to build participation in
irrigation management, as a corner stone of irrigation policy, occurred in
Philippines (Bagadion, 1988). The process of institutionalizing this approach
entailed workshops, training programmes, and information dissemination
36
within the agency and the farming community. This learning process was
carried out with the help of outside consultants, academic researchers and
donors, but initiative came from within agency (Bagadion and Korten, 1985).
Participatory Irrigation Management (PIM) is one approach to improve water
allocation, and effective water use being tested within agriculture systems that
are striving to be more sustainable. PIM refers to the participation of water
users at all phases of irrigation management, such as the planning, operation,
maintenance, monitoring, and evaluation of the system. The common
problems of irrigation, including inequitable water distribution, poor irrigation
system maintenance, inadequate water availability, and lack of incentives for
saving water, can be considered through a PIM approach. However,
employing PIM simply by decentralization and transfer of authority to local
water user organizations (WUOs) does not guarantee automatic success.
Institutional capacity building needs to be done step by step.
In Sri Lanka, reports have shown that out of 30 percent of increase in
the flow of water to the downstream, half of the Minipe scheme within the
first year of introducing a farmer’s organization (Uphoff, 1998). In Thailand,
in Norway scheme the farmer’s organization reportedly raised cropping
intensity from 50percent to 90 percent in two years. In Philippines, when a
participatory approach was taken to expand the Buhi-Lalo scheme, engineers
with farmers advised that concurrence would be rendered to the planned
length of field channel by 12 percent, thereby saving substantial costs. The
construction work by farmers was completed four months ahead of schedule
and the project engineer judged the quality of work as good.
In Malaysia, Muda Irrigation Scheme has lined tertiary channels
which have been constructed at government expenses to avoid field to field
irrigation and at the same time group farming has been encouraged and
37
farmers cooperatives have been formed to handle subsidized agricultural
inputs (Report of IIMI,1994).
Robert Chambers’ (1994) participatory action research (PAR) has
been parallel and overlapping with participatory research, and has had strong
associations with industry and agriculture (Whyte, 1991).Participatory Rural
Appraisal (PRA) describes a growing family of approaches and methods to
enable local people to share enhance and analyze their knowledge of life and
conditions, to plan and to act. PRA has sources in activist participatory
research, agro ecosystem analysis, applied anthropology, field research on
farming systems, and rapid rural appraisal (RRA). In RRA information is
more elicited and extracted by outsiders; in PRA it is more shared and owned
by local people. Participatory methods include mapping and modeling,
transect walks, matrix scoring, seasonal calendars, trend and change analysis,
well-being and wealth ranking and grouping, and analytical diagramming.
PRA applications include natural resources management, agriculture, poverty
and social programs, and health and food security. Dominant behavior by
outsiders may explain why it has taken until the 1990s for the analytical
capabilities of local people to be better recognized and for PRA to emerge,
grow and spread.
Ruth Meinzen-Dick (2002) identifies factors affecting organization
and collective action among water users in major canal irrigation systems in
India. Policies of devolving management of resources generally assume that
users will organize and take on the necessary management tasks. Water users’
organizations increase the likelihood of collective maintenance work by
farmers, but do not affect the likelihood of collective representation, or
lobbying activities, which seem to happen more spontaneously. The
devolution of responsibility and control over natural resources from
government agencies to user groups has become a widespread policy trend
38
that cuts across countries and natural resource sectors, encompassing water
(especially irrigation), forests, rangelands, fisheries and wildlife. One such
programs go by a range of names (e.g., Community-based Natural Resource
Management, co management, or management transfer), and range from those
that simply try to increase users’ involvement in management as a supplement
to state management (participatory management or co management), to those
that transfer full responsibility and control over resources to organized users.
A common feature, however, is the emphasis on increasing the participation
of resource users in the management of the resources.
Iskandar Abdullaev (2009) reports that the formation of the UWU has
improved the transparency of water management, helped to improve
responsiveness of water managers to the water users’ complaints, generated
support on canal de-silting, helped to reduce illegal water withdrawals from
the canal and WUAs have seen UWU as their advocate organization.
Establishment of UWUs provided a higher platform for the representation of
water users than common WUAs at the on-farm, secondary canal level. The
results of the water users’ surveys before and after UWU has been formed
have not shown a considerable improvement on water distribution. This will
bring long expected sustainability to irrigation water management. The
inclusion of water users will also engender more transparent practices and as a
result reduce the transaction costs of water management. The implementation
of the above approach on a basin scale will require a huge effort to mobilize
water users and re-organize the irrigation water management structure. Water
allocation approaches should also be revised with more inclusion of water
users’ voice in the process. This requires goodwill from state agencies, which
has to be emphasized and managed as a key element in the process.
United Nations Development Programme Report (Report of UN,
2005) captures the global water crisis in the following way: Unlike wars and
39
natural disasters, the global crisis in water does not make media headlines.
Nor does it galvanize concerted international action. Like hunger, deprivation
in access to water is a silent crisis experienced by the poor and tolerated by
those with the resources, the technology and the political power to end it. Yet
this is a crisis that is holding back human progress, consigning large segments
of humanity to lives of poverty, vulnerability and insecurity.
Accounting for 60% of the world‘s population, Asia currently
experiences the acute pressure of inadequate regional water resources supplies
because it only possesses 36% of global water resources. By 2025, nearly two
billion people will be living in countries or regions with absolute water
scarcity, and two-thirds of the world population could be under what the UN
terms stress conditions. Coming to terms with this water crisis will be one
of the greatest two challenges faced by every nation on the earth during early
21st century (Report of UN, 2005).
2.6 DROUGHT MONITORING AND VULNERABILITY
ASSESSMENT
Droughts are periods of time when natural or managed water
systems do not provide enough water to meet established human and
environmental uses because of natural shortfalls in precipitation or stream
flow. Drought management is a subset of water supply planning. The
distinction between a “drought” problem and a “water supply” problem is
essentially defined by the nature. Attempts to understand and address the
failings of water management during drought would be unsuccessful unless
shortcomings in the larger context of water management are also understood
and addressed. This was also one of the conclusions drawn by the Corps of
Engineers in the first year of the National Drought Study (William, 1994).
40
The purpose of assessing vulnerability is to identify appropriate
actions that can be taken to reduce vulnerability before the potential for
damage is realized. The need for vulnerability assessment is noted in the
scientific literature (Anderson, 1994; Hewitt, 1997; Keenan and Krannich,
1997; Downing and Bakker, 2000). However, because of the complexity of
the issue of vulnerability, assessments are commonly subjective and vary
between regions and hazards. Mapping vulnerability to drought is a
challenging task, because drought is also a very complex and the least
understood phenomenon, which lacks universal definition and onset criteria.
Wilhelmi and Wilhite (2002) presented a method spatial,
Geographic Information Systems-based assessment of agricultural drought
vulnerability in Nebraska. It was hypothesized that the key biophysical and
social factors that define agricultural drought vulnerability were climate, soils,
land use, and access to irrigation. The framework for derivation of an
agricultural drought vulnerability map was created through development of a
numerical weighting scheme to evaluate the drought potential of the classes
within each factor. The results indicate that the most vulnerable areas to
agricultural drought were non-irrigated cropland and rangeland on sandy
soils, located in areas with a very high probability of seasonal crop moisture
deficiency.
The spatial characteristics of agricultural drought vulnerability in
China were investigated using a GIS-based agricultural drought vulnerability
assessment model, which was constructed by selecting three agricultural
drought vulnerability factors,( Wu et al, 2002). Seasonal crop water
deficiency, available soil water-holding capacity and irrigation were identified
as the main indicators of agricultural drought vulnerability in China. The
study showed that the distribution of seasonal crop moisture deficiency
showed significant differentiation in both north–south and east–west
41
directions, and the agricultural drought vulnerability presented a similar trend.
At a regional scale, southern and eastern China typically has a low- and
moderate-vulnerability to drought, while high and very high vulnerability to
agricultural drought is observed in northern and western China.
Kiumars et al (2012) assessed drought vulnerability across three
drought intensities (very high, extremely high, and critical) areas in Western
Iran for the case of wheat farmers in Western Iran. A survey study was
applied and 370 wheat farmers who all experienced drought during 2007–
2009 were selected through a multi-stage stratified random sampling method.
Face to face interviews were used to collect data on vulnerability indices from
the farmers. Me-Bar and Valdez's vulnerability formula was applied to assess
the vulnerability of wheat farmers during drought. Results revealed that the
farmers' vulnerability is influenced mainly by economic, socio-cultural,
psychological, technical, and infrastructural factors. The results also indicated
that the farmers in Sarpole-Zahab township were most vulnerable compared
to those in the Kermanshah township as the least vulnerable.
IMD’s long-range forecasts should be available on a smaller spatial
and temporal scale, which will be helpful for sustainable agriculture. Agromet
parameters estimated from remote sensing data need to be validated with
ground based observation and turned into a usable product. Agrometeorology
of ICAR and IMD should have a linkage with the NADAMS project of the
Department of Space to provide periodic crop/pest/disease information at
subdistrict to national levels. The Agromet advisory service issued from
NCMRWF and AGRIMET of IMD should coordinate the space-based
program on NADAMS and use the spatial maps for strengthening the present
advisory services on crop pest/disease monitoring. The Drought Prone Area
Programme (DPAP) and the Desert Development Programme (DDP) require
improved management of land and water resources to avoid land degradation
42
like salinity, alkalinity, and water logging. Each state should be equipped with
a drought management system, linking district administration with state and
national departments that provide services. Agromet information for farmers’
advisory services should be made more user-oriented, and frequent feedback
may be obtained from farmers for further improvement. Use of the Internet
may be exploited for more efficient feedback (Sinha Ray, 2000).
Sivakumar et al (2011) calls for pro-active future actions to cope
with droughts. National governments must adopt policies that engender
cooperation and coordination at all levels of governments in order to increase
their capacity to cope with extended periods of water shortages due to
drought. Despite the repeated occurrences of droughts throughout human
history and the large impacts on different socio-economic sectors, no
concerted efforts have ever been made to initiate a dialogue on the
formulation and adoption of national drought policies. The time is ripe for
nations to move forward with the development of a pro-active, risk-based
national drought policy. Without a coordinated, national drought policy that
includes effective monitoring and early warning systems to deliver timely
information to decision makers, effective impact assessment procedures, pro-
active risk management measures, preparedness plans aimed at increasing the
coping capacity, and effective emergency response programs directed at
reducing the impacts of drought, nations will continue to respond to drought
in a reactive, crisis management mode.
According to Bryant (1991), drought ranks first among all natural
hazards who ranked natural hazard events based on various characteristics,
such as severity, duration, spatial extent, loss of life, economic loss, social
effect, and long-term impact. Drought produces a large number of socio-
economic impacts as water is integral to produce goods and provide certain
services. The socio-economic impacts of droughts may arise from the
43
interaction between natural conditions and human factors, such as changes in
land use and land cover, water demand and use. Excessive water withdrawals
can exacerbate the impact of drought. Some direct impacts of drought are
reduced crop, rangeland, and forest productivity; reduced water levels;
increased fire hazard; increased livestock and wildlife death rates; and
damage to wildlife and fish habitat. A reduction in crop productivity usually
results in less income for farmers, increased prices for food, unemployment,
and migration. There is growing evidence that the frequency and extent of
drought has increased as a result of global warming.
The fraction of land surface area experiencing drought conditions
has risen from 10-15 percent in the early 1970s to more than 30 percent by
early 2000 (Dai et al 2004). A global analysis has shown that abrupt changes
in rainfall are more likely to occur in the arid and semi-arid regions, and that
this susceptibility is possibly linked to strong positive feedbacks between
vegetation and climate interactions (Narisma et al 2007).
Ray Motha (2000) depicts the key elements of a drought plan, which
include 1) Monitoring, Assessment and Prediction, 2) Preparedness and
Mitigation, 3) Response and 4) Communications. From the public hearings,
more than one hundred people testified on behalf of urban and rural water
associations, tribes, federal agencies, state and county governments,
municipalities, livestock producers and farmer associations, and conservation
groups. A clear assessment of the findings became very conclusive from all
sectors of society affected by drought. Preparedness, including drought
planning, plan implementation, proactive mitigation, risk management,
resource stewardship, consideration of environmental concerns, and public
education must become the cornerstone of a national drought policy. To
ensure preparedness, there must be fundamental principles of a national
drought policy. There must be an adequate national observation network to
44
provide the basis for an effective drought monitoring program. A national
drought information “gateway” needs to be accessible to the entire user
community. The benefits of high quality research must be focused on
information and technology that are fundamental to drought preparedness,
with research results as well as the transfer of technology more effectively
implemented in drought programs.
Zuqiang Zhang (2011) says that effective and efficient drought risk
management is difficult to accomplish without the comprehensive
involvement of stakeholders and the public. Non-governmental organization
and volunteers are encouraged to join the efforts of drought management. The
agriculture insurance services have been proved to be a useful approach of
risk transfer for drought relief and recovery. Charities also play an active role
in drought relief, and the government has adopted measures, in terms of the
preferential taxation system, to encourage public donations. Capacity building
in self-reliance of the public from the drought impact has recently received
more attentions from the government. Relevant training opportunities and
financial assistances are offered to the public to enhance their self-reliant
capability in alleviating the impact of drought. The agricultural sector will
evaluate the possible impact of drought on the crop growth and production
and then prepare some tailored measures for the drought risk management.
Philippe Roudier and Gil Mahe (2010) conducted Study on Bani
River (Niger basin, Mali) about water stress and droughts with indicators
using daily data water deficit (drought) was logically addressed using the
Standardized Precipitation Index at a 10 days time step. The inadequacies in
the Standardized Precipitation Index while estimating water deficit within the
basin based on technical issues result in the usage of the Effective Drought
Index (EDI). Vulnerability is a very wide concept, with several definitions
(Füssel and Klein, 2006), that demand several dataset, if satisfactory
45
assessment of a region vulnerability to climate change is to be attained. This
is evident in Water Poverty Index computation (and its evolution: Climate
Vulnerability Index) by Sullivan and Meigh (2005). Precipitation threshold
parameter is highly useful due to its practical application while studying
drought event and while addressing issues relating to irrigation water
management. The structure of the precipitation threshold map is similar to
annual isohyets, especially for the extreme drought values.
Todisco et al (2009), allows a new classification of the drought
phenomenon on the seasonal time scale a distinction is made between
potential and actual agricultural drought on the inter-seasonal time scale a
distinction is made between agricultural drought and agricultural aridity.
Janki Jiwan (2012) reports that Sustainable Drought Management
implies reconciliation of short term and long term strategies. Long term
strategy entails drought preparedness, prevention and management of natural
resources in watershed framework with active participation of the people.
Short term strategy is contingent upon timely government initiatives in the
form of relief measures in drought affected areas Monitoring and declaration
are the primary tasks to agricultural drought management. Central and State
Weather-Crops Watch Group (CWCWG and SWCWG) keeps vigil on
drought like condition across the country based on data supplied by
specialized agencies like India Meteorological Department (IMD), National
Agricultural Drought Assessment and Monitoring System (NADAMS) and
National Centre For Medium Range Weather Forecasting (NCFMRF)
(National Disaster Management Authority, NDMA 2010).
Traditionally, response to drought throughout the world has been
through a reactive, crisis management approach. This approach to drought
management responds to the impacts of drought once they occur in an attempt
to speed the recovery process. This crisis management approach has been
46
noted to be costly, largely untimely, poorly coordinated, and often results in
resources or assistance being misdirected. Drought impacts illustrate the
vulnerability of societies to drought and programs that provide assistance to
those affected by drought are essentially treating the symptoms of
vulnerability rather than the causes. Many assistance programs, in fact, result
in increased vulnerability to future drought events by making individuals and
societies more reliant on government programs or assistance from donor
organizations. As a consequence of an increased frequency of drought and
societal vulnerability to extended period of water shortages, the economic,
social and environmental impacts of droughts have increased significantly
worldwide. Because of their long-term socio-economic and environmental
impacts, droughts are by far the most damaging of all natural disasters.
The Intergovernmental Panel on Climate Change Fourth
Assessment Report (Concept Note, 2011) states that the world indeed has
become more drought-prone during the past 25 years, and that climate
projections for the 21st century indicate increased frequency of severe
droughts in many parts of the world. Whether due to natural climate
variability or climate change, there is an urgent need to improve drought
management strategies that will lead to improved coping capacity. These
strategies must be science based and directed at managing the risks and
mitigate the effects of drought.
Drought Management Centre for Southeastern Europe (Report of
DMCSEE, 2006) lists out some its objectives for effective drought
management as (i) to assess the data available for effective drought
monitoring and early warning system; (ii) to evaluate and select the most
effective and reliable indices and indicators for drought assessment; (iii) to
conduct a drought risk assessment; (iv) to identify the specific training needs;
(v) to develop and implement a data and information delivery system on
47
drought management; (vi) to develop a comprehensive network of experts and
institutions to assist the Drought Management Centre; (vii) to ensure
communication and user feedback and (viii) to establish the permanent
drought management centre and ensure its sustainable functioning and
operations.
2.7 SUMMARY
The different classifications, definitions and the various
methodologies for meteorological, hydrological, agricultural drought
assessments and forecasting were reviewed. The above review has given a
much greater understanding of the drought and its characteristics. It also
helped to have information and to perceive importance of the present scenario
of the drought problem to be analysed in detail. Existing methods of drought
analysis either have qualitative assessments or use only a few drought causing
parameters and data intensive.
From literature review, it is understood that the use of GIS
technique might enhance the spatial analysis of drought distribution across the
study area. Understanding the drought occurrences in various parts of the
study area, it is proposed to analyse the vulnerability of different areas for
agricultural drought in an irrigated area.
Recommended