A study by Colombo-based International Water Management Institute (IWMI) fusing ancient technology and modern science explored this balancing act. Hydrological models of the Malwatu Oya basin, and its multiple tank cascades, and the Kalu Ganga basin, with its single reservoir, simulated river flows and estimated how different reservoir types would impact how much water is available, and at which time, for people as well as ecosystems.
The results illustrated ways in which the number, size, location, water withdrawals and water releases of reservoirs in different parts of a river basin can be orchestrated to make reservoir development more holistically sustainable. The right mix can maximise benefits from storage while minimising negative impacts on aquatic ecosystems and ecosystem services.