Evaluating the effect of water reservoirs on groundwater level, Case study: Gorganroud watershed of Golestan Province

By studying changes in the water levels of 359observation wells before and after the construction of 251 water reservoirs in Gorganroud watershed of Golestan province, water reservoirs effects were evaluated in improving the groundwater level. In this study some water reservoirs were selected that there were observation wells around them. All wells in which the water table levels were lower than the water levels of water reservoirs were evaluated. Among these, 31 Water reservoirs clearly showed there effects on 33 observation wells. Therefore, 12.4 percent of Water reservoirs have a positive effect on the level of groundwater. With providing a distribution map of all water reservoirs and observation wells and adapt them to each other and having observational data before and after the water reservoirs construction the effect of water reservoirs on the aquifer improvement were evaluated. In this study, parameters for evaluating effect of water reservoirs on the improving of aquifer included time of influencing the water level on observation wells levels, annual water rise and annual compensation of the water level. In this study the results show that water reservoirs had a positive effect on the groundwater level at the distance of 3.8 km, increasing the maximum groundwater level by 114 cm. The amount is of the annual compensation of the water level was 184 cm. Based on a rating scale the evaluation criteria were graded and so the performance of the water reservoirs at levels low (31.2%), average(20.4%), good(17.2%), good (21.5%) and excellent (9.7%) was evaluated.