برآورد حجم رسوب گذاري در مخازن سدهاي كرج و دز و مقايسه آن با نتايج هيدروگرافي

Estimation of sediment volumes in Karaj and Dez Reservoirs and their comparison with Hydrographic surveying

Erosion and sediment transportation are phenomenons that are occurred in the courses of rainfall conversion to runoff and in the flow of water in stream. Parts of the transporting material settled down in dam reservoirs which have not only some technical trouble, but also economic and even social disasters. So it is important to estimate the amount of sedimentation accurately, before and during of reservoir operation. On the other hand, determination of the actual amount of erosion or sedimentation is too difficult, but different methods of estimation have been suggested. To estimate the amount of input and output sediments discharge from these dams, we have used monthly sediment rating curves (SRC) which are established in up and down streams stations. Then by using the equations and based on the daily flow discharge, the daily input and output sediment discharges were estimated during hydrographic surveying period. Besides the estimation method mentioned above, to estimate the input and output sediment discharge, the artificial neural network (ANN) was used and the best arrays of network and model were founded. For both methods the volumes of sediments were estimated base of specific density of sediments. Besides the estimation methods (SRC & ANN), the volumes of sediments in each of reservoirs are also determined based of hydrographic surveying and compared with the results of different estimations. The results indicated that the sediment rating curves (SRC) were estimated the amount of sediment as 70 percent and %97 of the actual volume in Dez and Karaj dams respectively. By using the artificial neural network (ANN), these estimations were %115 for Dez and %94 for Karaj. To find the efficiency of these methods, we suggest that these methods will be applied to some other reservoirs with different climatic and hydrological regimes.