Effects of climatic factors on the sedimentation trends of Tarbela Reservoir, Pakistan

The study explores the factors affecting the sedimentation trends in the surrounding catchment area of the Tarbela Dam for the period 1980–2017, specifically rain and temperature. Furthermore, this study also investigates the seasonal effects of sediment loads coming into the reservoir from 2007 to 2012. The statistical techniques were applied for the estimation of the effects of climate (rainfall and temperature) on the sedimentation and the inflow of Tarbela Dam and its surrounding catchment area. The results revealed that sediment deposition pattern points toward the greater bed elevation at 7–12 range lines that lie near the Main Embankment Dam, also that Barandu River carried more bulk of inflow to the Indus, as compared to Siran River and thus contributed a greater amount of sediments to the reservoir. Summer monsoon season also contributed to the greatest bulk of sediments to the Tarbela Dam and its surrounding catchment area. The regression confirmed that for one degree increase in temperature there will be a 7 Million Acre Feet (MAF) increase; for a 1 mm (mm) increase in rainfall there will be a 1 MAF decrease and for a 1 Cusec increase in the inflow coming into the reservoir, there be a 4 MAF increase in sedimentation of the reservoir. Thus, the contribution of the temperature in sediment generation is found to be greater than rainfall. The study recommended that for the proper functioning of Tarbela Dam, the shift in the climate of the Upper Indus Basin (UIB) might be regularly monitored as rising temperatures in UIB would result in greater glacial melt and hence greater sediments to settle down into the reservoirs downstream.