The importance of the small-tank cascade system for the sustainable production of water in the dry zone of Sri Lanka

Abstract

Proper operation and maintenance of water resources in the dry zone of Sri Lanka is a pre-requisite to ensure sustainable development. Of particular concern in these regards is the case of the ‘Rajarata’ cascade system of interconnected small irrigation tanks which are spread all over the north central province and extend up-to the northernmost limits of the Vavuniya district. From a sustainable consumption and production perspective, these cascade systems function as recharging mechanisms that help to maintain sustainable and optimum stocks of fresh groundwater for human and agriculture utilization. This paper focuses on a case-study of the small-tank based cascade system in the Vavuniya Urban Council limits - where due to increases in human population, and subsequent disturbances that have occurred in such systems; the sustainable maintenance of the groundwater aquifer has become a critical management issue. A GIS based spatial modeling approach was adopted to understand the state of the small-tank cascade system at present. In these regards, terrain modelling and the modeling of the network of cascades within the Urban Council limits were done using the data acquired from Google Earth Pro services and field observations to assess the pattern and functioning of cascades for mapping the groundwater potential. This modeling approach provides the water resources manager with the facility to visualize, comprehend and simulate scenarios pertaining to management options for the system of concern. Results indicate that human-induced disturbances that have occurred in the cascades have reduced the sustainable production of water. It is suggested that an ecosystem based integrated water resource management method is the most effective option to enhance the water stock towards sustainable production of water resources in the dry zone of Sri Lanka.