G.M. Bandaranayake G.M. Bandaranayake Department of Geography Department of Geography University of USJP University of USJP Sri LankaSri Lanka

Tank Cascading System of Sri Tank Cascading System of Sri

LankaLanka

What is a tank cascade ?What is a tank cascade ?¤ A Cascade is a chain of tanks connected by water, flows ¤ A Cascade is a chain of tanks connected by water, flows from one to another, located in the downstream. from one to another, located in the downstream. ¤ A tank cascade is a connected series of tanks organized ¤ A tank cascade is a connected series of tanks organized within the meso-catchment of the dry zone landscape within the meso-catchment of the dry zone landscape

¤ cascade is a system of water storage, using the drainage ¤ cascade is a system of water storage, using the drainage courses within a definite watershed boundary courses within a definite watershed boundary

¤ cascade is a means of storing,conveying,distributing and ¤ cascade is a means of storing,conveying,distributing and utilizing water from first or second order empherenial utilizing water from first or second order empherenial streams streams

¤ cascade is a small storage reservoir system with ¤ cascade is a small storage reservoir system with hydrologic interlinkage by water, flows through the same hydrologic interlinkage by water, flows through the same valley valley

¤ Irrigation tanks, interconnected forming cascades allowing ¤ Irrigation tanks, interconnected forming cascades allowing surplus flow from the upstream tanks(s)and return flow from surplus flow from the upstream tanks(s)and return flow from the upstream commond area, to reach the tank that is the upstream commond area, to reach the tank that is immediately downstream.immediately downstream.

A typical tank cascadeA typical tank cascade

How cascades originatedHow cascades originated

* * Early settlers who settled down in river valleys, first used water directly drawn Early settlers who settled down in river valleys, first used water directly drawn from the streams from the streams

* Latter, they made small tanks, like ponds in valley bottoms to store water. Streams * Latter, they made small tanks, like ponds in valley bottoms to store water. Streams were dammed and converted water through canals to tanks. were dammed and converted water through canals to tanks.

* When population expanded and when they realized that water is a seasonal resource * When population expanded and when they realized that water is a seasonal resource they constructed tanks damming accross rivers. Settlements attached the tanks they constructed tanks damming accross rivers. Settlements attached the tanks spread over the valleys from lower to the upper parts. spread over the valleys from lower to the upper parts.

* When Buddhism and paddy culture were incoporated, a hydraulic civilization * When Buddhism and paddy culture were incoporated, a hydraulic civilization based on triple elements called tank+village+ temple was developed based on triple elements called tank+village+ temple was developed

*Ancient king’s main task was the building of tanks and temples, considering it as a *Ancient king’s main task was the building of tanks and temples, considering it as a meritatious task meritatious task

* When ancient people got a well awareness on the topography of the land * When ancient people got a well awareness on the topography of the land they built tanks at every possible sites of the valleys for different purposes in they built tanks at every possible sites of the valleys for different purposes in different size different size

Tank typesTank types

Choronicles refer 3 types of tanks Choronicles refer 3 types of tanks 1.Kulu wew (spring tanks) 1.Kulu wew (spring tanks) 2.Rada wew(very deep tanks) 2.Rada wew(very deep tanks) 3.Talaka wew (ponds in the jungle) 3.Talaka wew (ponds in the jungle) 4.Dana wew(large tanks) 4.Dana wew(large tanks)

Parker (1909) and Brohier (1941) Parker (1909) and Brohier (1941) identified different ancient tanks made by identified different ancient tanks made by ancient people for many purposes ancient people for many purposes 1. Jungle tanks for wild creatures 1. Jungle tanks for wild creatures 2. Mountian tanks for 2. Mountian tanks for chenachena (shifting) (shifting) cultivation cultivation 3. Slope tanks for soil erosion controlling 3. Slope tanks for soil erosion controlling 4. Village tanks for human settlements4. Village tanks for human settlements

Location of tanksLocation of tanks

1.In the uppermost parts of rivers: small tanks 1.In the uppermost parts of rivers: small tanks 2.in the middle parts: midium tanks 2.in the middle parts: midium tanks 3.in lower valleys: larger tanks3.in lower valleys: larger tanks

Evolution of the Evolution of the Cascading SystemCascading System

* * Most jungle tanks were destroyed when shifting cultivation was extensively practiced Most jungle tanks were destroyed when shifting cultivation was extensively practiced * * By the 11th centuray, most tanks had been destroyed by outside invations and abandoned By the 11th centuray, most tanks had been destroyed by outside invations and abandoned as the kingdom shifted to the wet zoneas the kingdom shifted to the wet zone

* During the period of Dutch administration (1650-1796), some attempts were made to * During the period of Dutch administration (1650-1796), some attempts were made to restore canal anicuits irrigation systems, but tanks in the dry zone were completely restore canal anicuits irrigation systems, but tanks in the dry zone were completely neglected. neglected.

* When British occupied the country (1796), the tank irrigation system was badly in * When British occupied the country (1796), the tank irrigation system was badly in function . They made a vigorous effort on restoration and repairing of tanks .They wanted function . They made a vigorous effort on restoration and repairing of tanks .They wanted the North Central Province to be re-created. the North Central Province to be re-created.

* They launched an immense program on tank restoration, but used an approach of * They launched an immense program on tank restoration, but used an approach of selecting individual tanks rather than the whole cascade system. selecting individual tanks rather than the whole cascade system.

* During the period of post- independence,(1948-1954) local political leaders made a special * During the period of post- independence,(1948-1954) local political leaders made a special attention on the buiding of large scale river diversion projects called colonization schemes. attention on the buiding of large scale river diversion projects called colonization schemes. Therefore, small tank systems were further neglected Therefore, small tank systems were further neglected

* After 1970s, national attention was focused on the Mahaweli Diversion Scheme. Small * After 1970s, national attention was focused on the Mahaweli Diversion Scheme. Small tanks were neglected and even some small village tanks were physically damaged by the tanks were neglected and even some small village tanks were physically damaged by the costruction of massive irrigation channels network of the Mahaweli scheme. costruction of massive irrigation channels network of the Mahaweli scheme.

Recent trendsRecent trends

*Recently, some development programs have focused attention on villge *Recently, some development programs have focused attention on villge tanks tanks

¤ Integrated Rural Development Program(IRDP) 1986 ¤ Integrated Rural Development Program(IRDP) 1986 (Selected village tanks were restored)(Selected village tanks were restored) ¤ Village Irrigation Rehabilitation Progeam(VIRP) 1990 ¤ Village Irrigation Rehabilitation Progeam(VIRP) 1990 (irrigation channels, anicuits and sluices of tanks) (irrigation channels, anicuits and sluices of tanks) ¤Village Community Rehabilitation (VCRP) 1994¤Village Community Rehabilitation (VCRP) 1994 (community participation on restoring of tanks) (community participation on restoring of tanks) All these programes dealt with individual tank restoration, not utilized All these programes dealt with individual tank restoration, not utilized

an approach of overall cascade an approach of overall cascade

Today, SriLankan Government has launched a program of Thousands Today, SriLankan Government has launched a program of Thousands Tanks Restoration. It is also based on the restoration of selected tanks Tanks Restoration. It is also based on the restoration of selected tanks island wide, not concerns with the tank cascading system. island wide, not concerns with the tank cascading system.

Previous researches undertaken on tank Previous researches undertaken on tank

cascading systems cascading systems Brohier (1946) studied the technical set-up of tank systems from an irrigation and Brohier (1946) studied the technical set-up of tank systems from an irrigation and engineering perspectives.( location,dam characteristics and irrigation channels. engineering perspectives.( location,dam characteristics and irrigation channels.

Parker(1909),Nicholas(1960) studied the historical backaground of the tank systems. Parker(1909),Nicholas(1960) studied the historical backaground of the tank systems. How originated? How originated?

MaddumaBandara(1985) - significance of tank catchments. Some aspects of land and MaddumaBandara(1985) - significance of tank catchments. Some aspects of land and water resources managements water resources managements

IIMI of Sri Lanka conducted many researches on the view of making framework for IIMI of Sri Lanka conducted many researches on the view of making framework for rehabilitation of tanks within cascades. Based on basin hydrology. rehabilitation of tanks within cascades. Based on basin hydrology.

Somasiri (1997) emphasised the importance of village tanks as an agricultural Somasiri (1997) emphasised the importance of village tanks as an agricultural resources.A case study.Water crops and land relationship. resources.A case study.Water crops and land relationship.

Panabokke(1999) dealing with the nature and properties of small tanks, has Panabokke(1999) dealing with the nature and properties of small tanks, has attempted to identify the sustainable production threshods of village tanks. attempted to identify the sustainable production threshods of village tanks. Calculation of water and crop yield. Calculation of water and crop yield.

Previous researches cont..Previous researches cont..

Itakura(1995) attempted to build aItakura(1995) attempted to build a water water balance model for planing rehabilitation of tank balance model for planing rehabilitation of tank cascades. A similar study has been done by cascades. A similar study has been done by

Shinori (1998). Utilizing Hydrological parametersShinori (1998). Utilizing Hydrological parameters

Tasuma (1999) has studied how returnTasuma (1999) has studied how return flows of flows of tanks act as an input of water to other tanks of tanks act as an input of water to other tanks of the cascade system (water behaviour)the cascade system (water behaviour)

IIMI of Sri Lanka studied the the possibility of IIMI of Sri Lanka studied the the possibility of predicting water availability of cascade system predicting water availability of cascade system using a water balance model. using a water balance model.

Author (2003) has carried out a reaesrch on Author (2003) has carried out a reaesrch on socio-ecological significance of tank villages of socio-ecological significance of tank villages of Sri Lanka based on a case study concerning with Sri Lanka based on a case study concerning with

some social and environmental values of tanksome social and environmental values of tank villages.villages.

Gaps and missing aspects of Gaps and missing aspects of previous researchesprevious researches

Most researches emphazised the produtivity of Most researches emphazised the produtivity of

tanks,irrigation and water management, physical tanks,irrigation and water management, physical renovations,rehabilitation dealing with technical,physicalrenovations,rehabilitation dealing with technical,physical or or human aspects alone, regarding mostly with individual human aspects alone, regarding mostly with individual tanks,sometimes, based on cascades tanks,sometimes, based on cascades

But the But the problem of efficient use of waterproblem of efficient use of water is a combination is a combination of many factors of physical and social relating to the whole of many factors of physical and social relating to the whole system. system.

Therefore, it is more essential to adopt an integrated Therefore, it is more essential to adopt an integrated approach concerning both physical and social aspects approach concerning both physical and social aspects

Most practically, in the context of dry zone tank cascades, Most practically, in the context of dry zone tank cascades, there is a tight interationship of physical and social factors there is a tight interationship of physical and social factors

As shown in the next slide. As shown in the next slide.

Inter-relationship of Physical Inter-relationship of Physical and social factorsand social factors

Sedimentation

in tanks

Land form changes

Increasing population

Catchment land use

Changes in stream flow

Less water storageIncreasing

Landuse under tanks

Increasing demand on water

Many researches have missed this Many researches have missed this integration of the water problem of integration of the water problem of cascade system cascade system thus thus My research problem is My research problem is

How the past functional How the past functional mechanism of the cascading mechanism of the cascading system was operated to be system was operated to be achieved the sustainable use of achieved the sustainable use of waterwater and and How the system has been How the system has been changed due to integrated socio- changed due to integrated socio- physical factors at present physical factors at present

MethodologyMethodology

* Initial set-up and physical formation of tank systems will be studied * Initial set-up and physical formation of tank systems will be studied by topo-maps, sattellite images, and archaeological evidencesby topo-maps, sattellite images, and archaeological evidences * Initial functional characteritics of tanks will be examined by historical * Initial functional characteritics of tanks will be examined by historical evidences, evidences, * present land use, stream runoff, landform changes will be studied by * present land use, stream runoff, landform changes will be studied by

field field observation, aerial photo and sattellite images interpretation observation, aerial photo and sattellite images interpretation * Sedimentation of tanks is measured at the field * Sedimentation of tanks is measured at the field * infomation on present water and land utilization are collected by field * infomation on present water and land utilization are collected by field surveys surveys

Outcome and Importance of Outcome and Importance of

the researchthe research

Findings of experiences from the Findings of experiences from the

past,constrains in the present, past,constrains in the present, could be jointly used in making an could be jointly used in making an appropiate framework for the appropiate framework for the sustainable water resources sustainable water resources development planning for the dry development planning for the dry zone Sri Lanka. zone Sri Lanka.