Simulating Run-off of Abbandans in Mazandaran Province using SWMM Model to Increase their Capacity Through Harvesting Rainwater

Abbandans are man-made reservoirs constructed by excavating and creating borders of soil dykes around them. Dredging Abbandan is done to increase storage capacity and provide greater flexibility in water allocation during droughts. For this purpose, the catchment runoff for different return periods was calculated using the SWMM model. Subsequently, the Abbandans’ conditions were examined to change their dimensions to increase the volume. The increase in Abbandans' volume was investigated by increasing its depth and utilizing the genetic algorithm. One model is presented that maximizes agricultural net benefits. Various allowable dredging ratios are used in the model for the case study. According to the results, for return periods of the 2, 5, 10, 25, and 50 years, 5.4%, 8.3%, 12.1%, 29.9%, and 37.4% of precipitation at the Abbandan upstream was transformed into runoff, respectively. Increasing the cultivated area or planting second crops can be considered as additional management practices for optimizing water usage. Based on the results, dredging and improving of all Abbandans in the region will cause the collection of runoff from rainfall events up to a 50-year period. The model shows that the maximum net financial benefit for agricultural increases as the ratio increases. It reaches its highest value (on average $81010) when the ratio is 0.5. Also, the area of cultivated fields irrigated by the Abbandan increased from 124 to 193 hectares.