WATER BALANCE STUDY OF PANJ AMU RIVER BASIN IN AFGHANISTAN

Abstract

Water is a limited natural resource and its management determines its prospective capability to sustain growth and development related aspirations of the society. The planning, development and operation of water resources is very much depending upon the availability of water in required quantity. Study of water balance of a river basin is necessary for various development activities. The current work involves the study to see the feasibility of available water for a watershed, which is part of Panj-Amu river basin in Afghanistan. The catchment area under study is about 37605 square km and located on the north part of Hindukush Mountain in the northeast of Afghanistan. For the purpose of water balance study, and water availability on the study area, long-term (1984-2015) daily climatological data have been collected from NASA Prediction of Worldwide Energy Resource (POWER) and based on these data, rainfall trend analysis carried out by application of Modified Mann-Kendall method and Sen’s Slope estimator test. Also, rainfall variability in monthly, annual and seasonal wise; drought analysis using SPI have been carried out. In this study, Soil and Water Assessment Tools (SWAT) has been used to analyse and quantify the water balance of basin. SWAT is an integrated physically based distributed watershed model. SWAT model has been in use world over during the recent past. It has the high efficacy to address wide range of river basin problems at different spatial and temporal scales. SWAT model uses DEM, land use, soil and climate data as input. The sensitivity analysis of the model has been carried out to understand the most sensitive parameters which help in parameter reduction at the calibration phase. Then the model has been calibrated by using SWAT CUP, based on observed river flow, on the outlets of sub-basins and main outlet of the basin. Manual calibration has been performed. The calibration efficiency has been tested by Nash-Sutcliff efficiency, coefficient of determination and PBIAS. The results showed the observed and simulated runoff in calibration (2008-2015) to match well for the Pul-i-Chogh site (sub-basin 3) with high values of R2 = (0.98), NSE= (-7.22/0.86) and low values of PBIAS = (-28.41/-24.79). . In overall water balance study, it was also noticed that, the contribution of ET, surface water and ground water was 59.4 percent, 31.8 percent and 8.6 percent respectively. However, the weighted average curve number value and number of HRUs to be found as 86.66 and 88 respectively.