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.
