A Case Study on the Retention Tanks in the Walawe Ganga River Basin, Sri Lanka

Village tanks have been used for irrigation purposes from a longer period of time and its behavior as a cascade system can be considered as an efficient methodology towards a sustainable water management system. Though it’s not vividly addressed in recent studies, some tanks are present in a cascade system with a mere intention of retaining water for the downstream tanks and, are being called as retention tanks. Nevertheless, in the present day, those are being used to fulfill human water needs instead of their initial use as retention tanks. Due to this reason, the overall working capacity of village tank cascade systems is being diminished. And in this case study, a methodology is proposed to identify retention tanks using five cascade systems in Walawe ganga river basin.