Integrated Water Resource Analysis of the Deduru Oya Left Bank Considering Traditional and Modern Systems

The Deduru Oya reservoir which was commissioned in 2014 is primarily planned to improve the livelihood of farmers in parts of the North Western Province of Sri Lanka by increasing the productivity of its land and water resources by regulating and diverting water to irrigation systems through two main canals in both riverbanks. This irrigation project is an example of integration of modern irrigation systems and traditional irrigation systems to improve cropping intensity and resilience. In this study, a model for water management in the left bank (LB) canal development area of the Deduru Oya irrigation project is developed. Hydrologic Modeling System (HEC-HMS) of Hydrological Engineering Center, US Army Corps Engineers is used for runoff estimation, and CROPWAT model of FAO is used for the estimation of crop water requirements. Water available for paddy cultivation in the area from each of the traditional irrigation systems is estimated, and the additional requirement of water from the Deduru Oya reservoir through the LB canal to satisfy the irrigation demand in the area is estimated. Simulation carried out for the past 10 years reveals that the Deduru Oya reservoir project which functions incorporating the existing traditional irrigation systems would supply the irrigation water requirement for paddy cultivation in the LB canal irrigation area without failure.