JWSS - Journal of Water and Soil Science

In the present study, the SWAT hydrological model was developed for the upstream of the Zayandehrood dam to evaluate the inflow to this dam. Accordingly, after entering the meteorological and hydrometric information of the region, the runoff simulation was performed. Due to the high volume of entrances to the Zayandehrood Dam, Shahrokh Castle hydrometric stations were selected as the base station for calibration and validation during the statistical period of 1990-2015. After hydrological simulation and accuracy of results, climate prediction was performed using the fifth model of the climate change for the RCP scenarios. According to the forecast, by using climate change models, the temperature could be assumed to increase in all models and the highest rate of increase would occur under the RCP 8.5 climate scenario. After evaluating climate change in different diffusion scenarios, the runoff of the basin was simulated in the SWAT model. The simulation results of runoff in the catchment area showed that although the amount of rainfall was increased in the region, increasing the temperature had a greater effect, reducing the amount of runoff in the basin. Based on the results of climate change, hydrological simulation was performed using the SWAT model. The results showed that the effect of diffusion scenarios in the region was different, causing an increase in temperature and precipitation. The highest increase was observed in the RCP8.5 scenario, which was consistent with the nature of this emission scenario, with the highest emission of greenhouse gases and carbon dioxide. Then, the evaluation of the hydrological model was done; the results showed that although the amount of rainfall in the region had been increased, the increase in temperature of this basin had a greater effect and efficiency in reducing the amount of runoff.

The application of simulation-optimization models is a valuable tool for selecting the appropriate cropping pattern. The main objective of this research is to develop a two-objective simulation-optimization model to determine the pattern of cultivation and water allocation. The model performs the optimization with the multi-objective metamorphic algorithm (MOALO) after simulating different states of the cultivation pattern. The decision variables including land and water allocated to ten-day periods of plant growth were designed in a way that the minimum utilization of water resources and economic maximization were identified as target functions. The developed model was used to simulate and optimize the cultivation pattern with an area of ​​5500 hectares and water allocation of Semnan plain with renewable water at the rate of 60.8 million cubic meters. Harvesting scenarios of 80 (GW80) and 100 (GW100) percent of renewable groundwater and scenarios of change in existing cropping pattern of 30 (AC30) and 60 (AC60) percent were considered and each scenario was simulated with the MOALO algorithm. Optimization using the proposed model in four scenarios improved the water and economic objective functions compared to the initial simulation performance. The results showed that the four proposed scenarios were obtained by minimizing the water objective function and maximizing the economic objective function relative to the current situation (simulation). In general, the proposed model had a good performance despite its simplicity, which is a specialized tool to optimize the crop pattern with water allocation.