The Effect of Gardens Terracing on Reducing Water Turbidity (Case study: Manshad Watershed, Yazd Province, Iran)

Abstract

One of the main factors to decrease water quality in rivers is land use changes. This study was conducted to choose the best way for land use management in order to increase water quality related to the least turbidity. So, the effect of land use changes on turbidity was investigated for 2 to 100-year periods using GIS and HEC-HMS model in the Manshad watershed. The amount of CN and land use planning model were variable parameters in each simulation stage. After preparing CN map, HEC-HMS model was calibrated for observed rainfall-runoff events using CN method. Finally, the best model was chosen among linear and non-linear sediment rating curves. The results showed that there are a lot of conformity between present land use and land use planning model. Terrace removing in land use planning model (as a scenario) increased turbidity in the peak discharge (11.02%) compared to the current land use. Therefore, according to the results, gardens terracing in allowable slopes help to manage water and soil in Watershed.