Model Development for Assessment of Unmet Irrigation Water Demand in Left Bank Development Area of the Deduru Oya Reservoir Project

Abstract

Abstract: Rainfall in Deduru Oya basin has a significant temporal variation and thus the Deduru Oya carry flash floods during rainy season and very low flows during dry season. The multi-purpose Deduru Oya reservoir project with a reservoir of a capacity of 75 Million Cubic Meters (MCM) augments water resources in 136 existing tank based irrigation systems in the Deduru Oya Left Bank through a Left Bank (LB) canal and also diverts water to the Iginimitiya tank in the Mee Oya basin through a Right Bank (RB) trans-basin canal. This study is focused on the setting up of WEAP21 version 3.43 (Water Evaluation And Planning) model to study the water management including diversion requirement from the Deduru Oya reservoir through the LB canal to supplement LB irrigation demand. Hydrological Engineering Center-Hydrological Modeling System (HEC-HMS) is used for runoff estimations and CROPWAT model is used to estimate crop water requirements. WEAP model is used for water balance simulations in Deduru Oya LB canal development area and to calculate water requirements from LB canal for the period of recent 10 years. The study reveals that the annual unmet demand varies from 26 MCM to 41 MCM without Deduru Oya reservoir project and from 0.44 MCM to 1.07 MCM with Deduru Oya reservoir project, for the study period from 2000 to 2010. The developed model can be used as a tool for irrigation water management and drought impact assessment in the LB development area of the Deduru Oya reservoir project.