Uncertainty Analysis of Reservoir Sedimentation

Estimation of reservoir sedimentation volume is necessary for design and hydraulic structure management purposes where different empirical and mathematical methods are employed in this regard. Due to different factors effecting sedimentation process and their stochastic process, uncertainties arise which cause failure and may force designers to consider safety factors in their designs. Therefore, uncertainty analysis may introduce a better understanding of the effect of different input parameters and their separate contributions to the whole output error. In this research, the sediment discharge rate was estimated by employing different methods such as USBR, average of classes, and the FAO modification coefficient. In these methods data collected from Yalfan hydrometry and Shakhe Dovom SAD stations were used. To calculate the trap efficiency the Brown method, and for specific weight Lane & Koelzer and Miller methods were used. The results of the FAO modification coefficient on average of classes and specific weight of Miller method compared to other corresponding methods show better agreement with the measured ones. In this research, Mont Carlo Simulation and Har's methods were investigated. Calculation of The Mont Carlo method and the uncertainty contribution of each parameter were conducted by a FORTRAN computer program introduced by the author. The results show that the sediment discharge rate and the flow rate introduce the highest contribution to the whole uncertainty of sedimentation volume, respectively. Also, Har's method show less uncertainty value compared to the Mont Carlo method.