Assessment of Flow and Sediment Regime Properties in Arid and Semi Arid Catchment Areas (Case study: Lorestan province)

Study the behavior of the rivers at arid and semi arid areas is of the main and basic activities in the country (since a great portion of Iran has arid and semi arid climate). The main differences of arid areas from humid areas are the different climatic factors including the precipitation amount and pattern. This issue can cause the change of flow regime and sedimentation regime (FSR) and their ratios in these areas. Also temporary flood ways of arid areas, in which the water flow is limited to heavy rainy and wet seasons, has a great influence on flow and sediment regime (FSR). In this research, by statistical review of flows discharge in arid and semi arid areas at the west part of country, it is tried to review the effect of climate on flow and sediment regime.For this purpose, flood discharge with different return periods were estimated by the best statistical distribution of 21 hydrometric stations. Then by using rating flow of sediment, sediment amount was measured in different return periods. At the next step, flow and sediment regime was calculated and the relationship between flow and sediment regime and the area of relevant up stream sub-catchment areas was determined. Also the results of this study show that the relation of up stream sub-catchment areas of each station will increase with FSR increase in high return periods.