Modelling of estmation of the suspended Load in Ardabil Darehrud basin

The suspended load of a comprises mineral and organic matter is dispersed through the flow by turbulence. typically، the mineral load is dominant & Consists of grains ranging is siz from clay up sand grade. The suspeded load is quantified in terms of its concentration، discharge،sediment mass flux Per unit time- also referred to as the “load” -،& Particle-size distribution (pro-portions of the load in given size fractions). Theclay -silt fractions (ofen termed”wash load”) are largely sourced from erosion Processes outside the river channel،being moreeasily suspended، they are well mixed through the flow& travel long distances in suspention. Darehrud basin، as one of subbasin of arax، discharges a high bulk of sedimentsto Caspian sea iran’s northwest mountains that located in Ardabil & eastern Azarbaija provinces. this basin carry materials resulting from denudation in various forms toward base – level which apart of these sediments includes soft & fine texture deposites in form of suspended sediment. On the other hand the existence of three reservoir dams (Yamchi، Saghezchi and sabalan) in this basin makes it necessary to study and recognize the potential of sediment creation and erosion of this with approach of increasing the useful life of mentioned dams. In this research data and information related to discharge and sediment of 31 hydrometry stations that are located in baisn have been analysed. this way that at first darehrud river’ s basin morphometry goes to the place of stations has been calculated and then the correlation equations of sediment and discharge are owned by using existing data and finally the amount of annual sediment for each river has been calculated and has been completed by using FAO method foraperiod of thirty years. The limitation existence consists; lacking hydrometery and sampling from sediment mineral density in throughout basin and necceray sediment estimation in basin lacking statistic. Accordingly،estimate of correlation sediment and and discharge in Dareh Rud basin and subbasin and also estimate of sediments suspended load for the basins lacking statistic according regional eqations base on the result of research and the development of the eqation is one the main objectives of the present study. The amount of estimated sediment of suspended burden for the basin was 8. 7 million ton per year. and amount of discharge specificl of sediment was 624 ton per year in each square kilometer. At least the regional equations of sediment estimate for Darehruod river basin and sub-basins of Qarahsuo and Ahar chay has been presented on the basis of basin area; channel length، and special of sediment. Also according to calculations performed on the suspended load passing at hydrometery stations over a 30-year period (which shows significant correlating with river discharge) and the calculation the average suspended load in the mentioned points، their is asignificant correlation between morphometery subbasins Dareh Rud and river and sediment rate. Finally، the final equation of suspended sediments estimate has been presented on the basis of basin’s morphometry charactristic for basins with less and more than 500 square km area.