Efficacy of Time-Area Method in simulating temporal variation of sediment yield in Chehelgazi watershed, Iran

Abstract

Efficacy of Time-Area Method in simulating temporal variation of sediment yield in Chehelgazi watershed, Iran The proper prediction of temporal and spatial variation of sediment yield from the watershed is a need for sediment control, river engineering and soil and water conservation studies. The present study was therefore planned to simulate the sediment graphs for Chehelgazi watershed in Gheshlagh dam upstream in Kurdistan Province, Iran, by using Time-Area Method. Towards this attempt, the study watershed was divided into 7 time-area segments based on the time of concentration. The soil erosion in each segment was estimated using the USLE and then routed to the main outlet using sediment delivery ratio as a function of land slope in two adjacent time-areas. The temporal variation of sediment was ultimately predicted with the help of lag time of sediment arrival to the outlet and the concept of superposition for 11 storm events, which occurred during winter 2006 and spring 2007. The comparison between estimated sediment graphs with corresponding observed ones verified the weak capability of the model in simulation of sediment graphs under consideration. The results also verified the calibration necessity of the model to achieve appropriate estimation for important components of the sediment graphs. The results of the calibration finally proved the considerable capability of the model in predicting of total volume of sediment yield with respective estimation and verification errors of 30.93 and 33.40%.