The objective of this study was to investigate impacts of climate disturbance and watershed management operations on hydrologic functioning of the Kordan watershed in Iran. Soil and water assessment tool was used and evaluated for an 18-year monthly stream discharge. Statistical and graphical analysis of the calibrated and validated model presented appropriate fit to the measured data (NSE and R² were more than 0.80), allowing reproduction of the historic hydrological conditions of the watershed for future analysis. A 12-month timeframe was achieved from correlation between standardized precipitation index and standardized runoff index to quantify drought characteristics and define drought disturbance scenarios. Replacing normal periods in terms of precipitation amount with extreme and severe periods up to 40% resulted in declining monthly flow out by 24% and 21%, respectively. Pasture restoring scenarios resulted in a significant decline in amount of surface runoff. Replacing 50% of poor rangeland areas with moderate rangeland caused monthly amount runoff to decline by 16%. The percentage of runoff decline raised up to 44% by replacing moderate rangeland thoroughly. Furthermore, land-use scenarios increased amount of subsurface flow considerably. Impacts of constructing hydraulic structures were assessed in each sub-basin separately. Results showed decline in yearly surface runoff varied from 50 to 97%, depending on the volume of structures and sub-basin characteristics. The findings would be beneficial to decision makers which contribute to better understanding of natural and man-made activities on hydro-power potential of watersheds.

本研究的目的是调查气候扰动和流域管理操作对伊朗科丹流域水文功能的影响。使用土壤和水评估工具对 18 年的每月河流流量进行评估。校准和验证模型的统计和图形分析显示了与测量数据的适当拟合（NSE 和R ²大于 0.80），从而可以再现流域的历史水文条件以供将来分析。通过标准化降水指数和标准化径流指数之间的相关性，获得了 12 个月的时间范围，以量化干旱特征并定义干旱扰动情景。用极端时期和严重时期降水量代替正常时期的降水量高达40%，导致月流量分别减少24%和21%。牧场恢复情景导致地表径流量显着下降。用中等牧场取代 50% 的贫困牧场导致月径流量下降 16%。通过彻底替代中度牧场，径流下降率提高到44%。此外，土地利用情景大大增加了地下流量。分别评估每个子流域修建水工建筑物的影响。结果显示，年地表径流下降幅度从 50% 到 97% 不等，具体取决于建筑物的体积和次流域特征。研究结果将有益于决策者，有助于更好地了解自然和人为活动对流域水电潜力的影响。