Evaluation of sediment yield in PSIAC and MPSIAC models by using GIS at Toroq Watershed, Northeast of Iran

Abstract

Regarding the importance of watersheds in arid and semi-arid regions, it is necessary to better protect water supplies such as dam reservoirs. The most efficient way of conserving water sources is to apply proper management to decrease erosion and sedimentation. The first step of this process is to be aware of sediment yield (Qs)/production and identify erosive zones in upper reach of reservoirs. The present study aims to evaluate Qs and production in Pacific Southwest Inter-Agency Committee (PSIAC) and modified PSIAC (MPSIAC) models by using satellite data, GIS analysis, and field observations. According to the results, the study area can be categorized into five erosive classes: very high, high, moderate, low and negligible. The east part of the watershed is slightly eroded due to its hard surface geology and relatively flat topography characteristics, while the northern and southern parts of the basin are highly eroded because of the high erodibility potential of soil and intensive cultivation of the area. A comparison of the output maps from PSIAC and MPSIAC models showed that the calculated Qs in most parts correspond well in both models and with field observations. The results of regression between main determining factors (surface geology, soil, topography and land cover) and Qs derived from each model indicated moderate to strong correlation coefficient (R2 = 0.436−0.996 to 0.893–0.998) after PSIAC and MPSIAC models, respectively.