Hydrologic Analysis and Optimal Release of the Qeshlaq Dam Reservoir, Based on Drought analysis of River Basin

Dam reservoirs supply potable, agricultural, and industrial water in most cities of Iran. Due to lack of proper operational rules or unbalanced demand versus water resources volume, (along operating time) correction in operational rules is required to fulfill current situations. Hence the goal of this study is to optimize the Qeshlaq Dam reservoir operation rules to maximize the water release for agricultural demand with considering to maintain reservoir capacity to allocate 100% of potable water demand. For this purpose a linear optimization program was developed in MATLAB. Herbst method was used to assess drought intensities and periods. Based on Herbst method, a critical period of 51 month (October 1987 – Septamber2012) was determined and an optimal release of 1.334 MCM was estimated for agricultural use. Based on downstream potential agricultural demand, this released water is supplied only 60% of the agricultural demands. So there will be shortage in supplying agricultural demands for months July (2.2MCM), August (2.47MCM) and September (2.29MCM). The correlation coefficient of R2 = 0.84 was obtained between modelled and actual monthly reservoir storage. Results showed that the probability of the maximum long term storage of 162 MCM (equal to 0.75 of reservoir capacity) is 50%. Also statistical distribution analysis revealed that spillway discharge data are agree with Gumbel distribution more accurately than other distributions. In general, the results of the optimization showed that linear programming can be used for optimal water resources allocation for agriculture and industry use.