The disparate temporal and local distribution of freshwater and the rapid growth of the population in recent decades have led to problems in providing water resources for various applications. Hence, the supply of water in many countries such as Iran has become one of the most important challenges of the present century. Modern mathematical models have been developed for studying the complex hydrological processes of a watershed. The application of conceptual hydrological models is an important issue in watersheds for researchers, especially in arid and semiarid regions. The hydrological behaviors are complicated in such watersheds, and their calibration is more difficult. In this research, the conceptual and semidistributed SWAT model is used for Samalqan watershed, Iran, with 1148 km² area. Streamflow simulation is considered for 13 years. Samalqan watershed modeling led to 22 subbasins and 413 hydrologic response units. Water balance components have been computed, the results have been calibrated with the SUfI2 approach in the SWAT-CUP program, and finally, the performance of the model is evaluated. The sensitivity analysis was conducted using 26 SWAT parameters. The most sensitive parameters were CN2 (moisture condition II curve number), GWQMN (threshold water level in shallow aquifer for base flow), GW_Delay (delay time for aquifer recharge), GW_REVAP (Revap coefficient), and ESCO (Soil evaporation compensation coefficient). The model was calibrated from 2004 to 2012 and validated from 2012 to 2014. The coefficient of determination (R²) and Nash and Sutcliffe efficiency (NSE), On monthly basis, were between 0.60–0.80 and 0.80–0.95 respectively, for calibration, and 0.70–0.90 and 0.70–0.80, respectively, for validation periods, which indicates that the model results are satisfactory. Results show that the SWAT model can be used efficiently in semiarid regions to support water management policies and development of sustainable water management strategies. Due to the arid and semiarid climate of Iran and water resources constraints, the need for modeling is clear. It can be concluded that determination of the existing water potential is necessary for water planning and management of water resources in the watershed.

中文翻译：

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使用SWAT模型在萨马拉干流域（伊朗）中模拟水平衡方程组件

近几十年来，淡水的时空分布和局部分布以及人口的快速增长导致了为各种应用提供水资源的问题。因此，伊朗等许多国家的水供应已成为本世纪最重要的挑战之一。已经开发出现代数学模型来研究流域的复杂水文过程。概念性水文模型的应用是研究者在流域中的重要问题，特别是在干旱和半干旱地区。在这种流域中，水文行为复杂，标定难度更大。在这项研究中，概念性和半分布式SWAT模型用于伊朗萨马干流域，长1148 km ²区。流量模拟被考虑了13年。萨马干流域建模导致了22个子流域和413个水文响应单元。计算了水平衡成分，在SWAT-CUP程序中使用SUfI2方法校准了结果，最后评估了模型的性能。使用26个SWAT参数进行了灵敏度分析。最敏感的参数是CN2（湿度条件II曲线编号），GWQMN（基本流量的浅层含水层中的水位阈值），GW_Delay（含水层补给的延迟时间），GW_REVAP（Revap系数）和ESCO（土壤蒸发补偿系数） 。该模型于2004年至2012年进行了校准，并于2012年至2014年进行了验证。确定系数（R ²）和Nash和Sutcliffe效率（NSE），按月计算，分别在0.60–0.80和0.80–0.95之间，用于校准，在验证期分别在0.70–0.90和0.70–0.80之间，这表明模型结果是满意的。结果表明，SWAT模型可以在半干旱地区有效使用，以支持水资源管理政策和制定可持续的水资源管理策略。由于伊朗的干旱和半干旱气候以及水资源的限制，显然需要建模。可以得出结论，确定现有的水潜力对于水的规划和流域水资源的管理是必要的。