Hydrological Modelling of Sediment Yield in the Upper Basin Region of Kirkuk City Watershed

Abstract

Mountain sedimentation and undue erosion provide significant challenges for dams since materials accumulate within reservoirs that hold water, reducing the capacity for storing living water, which is the most important goal of dam building. Iraq is one of the nations that will have a big problem getting sufficient water because its water requirement continues to climb, and the supplying countries provide less water to Iraq. The present research focuses on the upper basin of the Kirkuk City watershed in northeastern Iraq. The largest watershed region, spanning approximately 420 km² within Al-Sulaymaniyah and Kirkuk Provinces. The objective is to quantify and foresee the sediment yield in this basin using 43 years of daily environment information and various rainstorm events with various intensities. The model was adjusted and confirmed by comparing it to the monthly mean surface flow and sediment readings obtained at the Kirkuk gauging station. The Soil and Water Assessment Tool (SWAT) model was utilized to simulate the upper basin region of Kirkuk City. The aforementioned model uses the geographic information system (GIS) software to analyse necessary information from GIS layers of the electronic contour modelling kind of soil, using of land, and coverage by integrating it with the appropriate climatic information. The kinematic erosion (KINEROS) and runoff model can simulate intricate watershed behaviour by precisely adjusting for the geographical variation of soils, distribution of rainfall sequences, and vegetation. The hydrological features of the Kirkuk city basin reveal that the subdivisions with the highest erosion rates cannot transport the debris or deposits to the reservoir, primarily due to propagation damages, percolating, and other smaller barriers. The optimal curve number (CN) was determined to be between 84 and 88, while the land cover factor (C) ranged from 0.005 to 0.04. The model validation results indicate that the Kirkuk Dam reservoir received a total volume of water estimated at 118.7 million cubic metres (MCM) and a total silt yield of 0.85 million tonnes. The “KINEROS” simulation modelling for the sediment yield closely matches the upper basin of Kirkuk watershed's deformation and sedimentation behaviour during singular rainfall events; this is particularly true for parts of watersheds located near the watershed area entrance.