ANALYZING EXTREME STREAM FLOW EVENTS AND DEFINING ENVIRONMENTAL RIVER FLOW REQUIREMENTS FOR DOWN STREAM ECOSYSTEM: (A CASE STUDY OF KULFO WATERSHED

Abstract

Analyzing of river flow events and defining environmental river flow requirements for the downstream ecosystem have not yet been widely investigated over the world. As the result of this scarcity of water, on the other hand uncontrolled flood causes a great damage on living and nonliving things. The simulated stream flow was used to reduce an error that was developed by the large missing gaps. In the simulation process spatial data DEM, land use land cover map, soil map and time series data were used to estimate flow at gauging station which was taken as an outlet. SWAT model was selected as it utilizes various spatial parameters to simulate runoff at required scale and easy availability. Sensitivity analysis has shown that the base flow alpha factor (days) and curve number are the most sensitive parameters that affects the hydrology of the watershed particularly runoff generation. The model was calibrated using flow data from 2005 to 2010 and validated for the period 2011 to 2013. The model was checked by statistical model performance indicators such as the coefficient of determination (R2 ) is 0.84 and 0.82 for calibration and Nash-Sutcliffe model Efficiency (ENS) is 0.82 and 0.75 for validation respectively. The simulated output of SWAT2012 was used in the process of the selection of fit distribution by easy fit and flow event was determined. Peak yearly Discharge Prediction for the watershed were determined by Gen. extreme value for 2,10,20,,50,100.200,500, returned periods to be found 59.17,109.72,132.92,166.73,195.18,226.5,272.88. Finally the river environmental flow required for downstream was calculated by using Global environmental flow calculator (GEFC) software. Instream flow allocated to the river of EMC class Largely modified (class D) was 89.72 MCM (i.e., equivalent to 23.5 % of the natural MAR).