Abstract:
Water resources are vital components for a country's development important to the country's
growth and transformation. .The abstraction of water from the river without proper basin plan
as well as without considering middle stream and downstream water users. The main aim of
this study was to conduct surface water potential assessment and evaluation of water demands
of Gogara watershed. The Gogara river sub-basin receives an estimate mean annual
precipitation of = 873.464 mm. HEC-HMS evaluates surface water resources availability by
analyzing their presence and quantity. WEAP assesses factors affecting water availability,
identifying optimal allocation policies based on changes in demand, development activities,
and climate conditions for efficient water management. CROPWAT calculates crop water
requirements by considering factors like crop type, weather, soil characteristics, and
irrigation methods, ensuring optimal growth and development. The estimated mean annual
runoff in the whole watershed is 159.2MCM which is correspond to mean annual depth of
surface runoff is mean annual precipitation. The mean annual water balance shows that the
significant number of the mean annual precipitation (69.4%) received by the watershed were
lost via evapotranspiration. The remaining parts of annual precipitation (172.2mm which
accounts about 15.9%) received by the watershed infiltrates to the soil to recharge GW
aquifers as well as to contribute to base flow (24.2mm as lateral flow and about 140.35mm as
return flow). The model was calibrated and validated by using 1995 to 2007 and 2008 and
2014 respectively years stream flow data. The performance was found good during calibration
[correlation coefficient, R 2 = 0.6, Nash-Sutcliffe efficiency, NSE = 0.658) and validation
R 2=0.6, NSE = 0.609). The mean annual future surface water resources potential of the
catchment was estimated as 267.75MCM and 318.35MCM under RCP4.5 and RCP8.5
respectively. The estimated surface water potential was 159.609 MCM. The scenarios were
developed to evaluate the future demands based on different sets of “what if” situations up to
the 2030. The environmental flow requirement is required more detailed studies of water
allocation patterns within the basin.
