Multiple modeling to estimate sediment loss and transport capacity employing hourly rainfall and In-Situ data: A prioritization of highland watershed in Awash River basin, Ethiopia

Abstract

In present study, the sediment yield/loss and Transport Capacity (TC) has been estimated in a highland watershed of Adama Woreda, part of Awash River Basin in Ethiopia. For the study, average hourly 14 years rainfall data obtained from different gauging stations in the study area during 2001–2014 was utilized to calculate rain erosivity (R factor). Subsequently, soil erodibility K, length-slope LS factors of Revised Universal Soil Loss Equation (RUSLE) were adopted for the calculation of WATEM/SEDEM sediment delivery algorithm. The average R factor value for the watershed was evaluated as 2075.27 MJ/ha mm/year. The grid based KTC (Transport Capacity Coefficient) was determined for the WATEM/SEDEM sediment transport estimation through the results of Soil Water Assessment Tool (SWAT) and Revised/Modified USLE. The SWAT simulated suspended solids (SS) versus two years (2013 and 2014) rainfall measured records at single observatory was used for the SWAT calibration and validation. The SWAT sediment yields and Transport Capacity (TC) were used to determine the KTC at each sub-watershed. The mean value of KTC was estimated 8.033 and minimum and maximum values were found 0.080 and 51.49 respectively. Moreover, the Sediment Deliver Ratio (SDR) model equation was calculated and resulted values were found >0.7 in the main streams. For the prioritization, sediment yield and loss estimated values using Sediment Yield Index (SYI) and RUSLE along with SWAT models were employed. The results generated through these models were averaged and accordingly the ranks and severity classes were determined.