3th WCSET-2014 at Nepal
Civil Engineering / Environmental / Architecture / Planning Session:
Title:
Analysis of the diversion requirements from the Deduru
Oya reservoir in Sri Lanka
Authors:
Sampath D. S., Weerakoon S. B., Mishra B., Herath S.
Abstract: The
Deduru Oya reservoir project which is under construction
is aimed to improve the livelihood of farmers in parts
of the North Western Province by increasing the
productivity of its land by regulating and diverting the
Deduru Oya water by two main canals. The proposed Left
Bank (LB) canal which is 44.1 km long with a discharge
capacity of about 7.1 m3 /s at the intake will supply
water to augment about 136 existing storage-based minor
irrigation systems in the left bank of the Deduru Oya
river. This study is focused on the analysis of the
diversion requirements of the proposed reservoir. For
each of the 136 rain-fed minor reservoirs(tanks) that
will be supplied water by the LB canal, the relevant
catchment areas, storage areas, natural streams, land
use patterns and cascades were identified for modeling
the system. Topographic, geology and land use details
were collected from the digital data of the Survey
Department of Sri Lanka and Arc GIS 9.2 was used as a
tool for spatial analysis. HEC-HMS (Hydrologic
Engineering Center– Hydrologic Modeling System) version
3.0.1 was calibrated and verified for the Tittawella
Tank, which is a minor tank in Kurunegala District and
also for the Deduru Oya river Catchment. HEC-HMS model
was then used to develop rainfall runoff model for each
of the rain-fed irrigation tank catchment and the Deduru
Oya reservoir catchment. WEAP21 version 3.43 (Water
Evaluation And Planning) model was used to study the
water requirement from LB canal. The LB development area
would require 62 MCM annually through the LB canal as a
supplement to meet the LB irrigation demand of the
existing and proposed new development areas in dry year
while annual RB trans-basin diversion is 79 MCM, and
annual downstream release for hydropower, irrigation and
environmental requirements is 502 MCM in 2009. With long
term forecast rainfall data, the WEAP model can be used
for predictability studies in the Deduru Oya LB
development areas. The model developed is a useful tool
for planning water resources development in the Deduru
Oya reservoir project.
Keywords: Deduru Oya
Project, HEC-HMS, WEAP, Irrigation development
Pages:
091-093