Climate change, besides global warming, is expected to intensify the hydrological cycle, which can impact watershed nutrient yields and affect water quality in the receiving water bodies. The Mahabad Dam Reservoir in northwest Iran is a eutrophic reservoir due to excessive watershed nutrient input, which could be exacerbated due to climate change. In this regard, a holistic approach was employed by linking a climate model (CanESM2), watershed-scale model (SWAT), and reservoir water quality model (CE-QUAL-W2). The triple model investigates the cumulative climate change effects on hydrological parameters, watershed yields, and the reservoir’s water quality. The SDSM model downscaled the output of the climate model under moderate (RCP4.5) and extreme (RCP8.5) scenarios for the periods of 2021–2040 and 2041–2060. The impact of future climate conditions was investigated on the watershed runoff and total phosphorus (TP) load, and consequently, water quality status in the dam’s reservoir. The results of comparing future conditions (2021–2060) with observed present values under moderate to extreme climate scenarios showed a 4–7% temperature increase and a 6–11% precipitation decrease. Moreover, the SWAT model showed a 9–16% decline in streamflow and a 12–18% decline in the watershed TP load for the same comparative period. Finally, CE-QUAL-W2 model results showed a 3–8% increase in the reservoir water temperature and a 10–16% increase in TP concentration. It indicates that climate change would intensify the thermal stratification and eutrophication level in the reservoir, especially during the year’s warm months. This finding specifies an alarming condition that demands serious preventive and corrective measures.

除全球变暖外，气候变化预计会加剧水文循环，这会影响流域养分产量并影响受纳水体的水质。由于流域养分输入过多，伊朗西北部的马哈巴德大坝水库是一个富营养化水库，气候变化可能会加剧这种情况。在这方面，通过将气候模型 (CanESM2)、流域尺度模型 (SWAT) 和水库水质模型 (CE-QUAL-W2) 联系起来，采用了一种整体方法。三元模型研究气候变化对水文参数、流域产量和水库水质的累积影响。SDSM 模型缩小了 2021-2040 年和 2041-2060 年期间温和（RCP4.5）和极端（RCP8.5）情景下气候模型的输出。研究了未来气候条件对流域径流和总磷 (TP) 负荷的影响，进而对大坝水库的水质状况产生影响。将未来条件（2021-2060 年）与中度至极端气候情景下的观测现值进行比较的结果显示，温度升高 4-7%，降水减少 6-11%。此外，SWAT 模型显示同期流量下降 9-16%，流域 TP 负荷下降 12-18%。最后，CE-QUAL-W2 模型结果表明，水库水温增加了 3-8%，TP 浓度增加了 10-16%。这表明气候变化会加剧水库的热分层和富营养化水平，特别是在一年中温暖的月份。