Effect of wet and dry periods on the amount of specific sediment (Case study: Karkheh watershed)

Determination the effects of a drought or wet in the area، is one of the essential needs for environmental and economic plans، particularly for water resources management plan. One of the most important influences is affecting on the suspended sediment، which is very important in river engineering and water resource. The purpose of this study is the impact of drought and wet periods on the amount of sediment in Karkheh basin. With Studying of data in Meteorological and hydrometric stations and select of 18 stations، identified the drought and wet periods with using of five-year moving average. Then fitted Sediment rating curves and estimation of sediment for each of sub watershed. The result shows that in the dry periods sediment has decreased trend and in the wet period the sediment has increased trend. In wet year the sediment was 1. 57 dry year، that between 0. 9 and 5. In this year’s spatially sediment was 1. 12 spatially sediment in total periods While the in dry periods spatially sediment was 0. 74 spatially sediment in total periods.