Evaluation of hydrological response to future climate change is essential for water quality risk assessment and adaptive management implementation within a watershed context. In this study, we present a modeling framework that integrates a hydrological model with projections of General Circulation Models (GCMs). Temperature and precipitation projections of six GCMs with two downscaling methods are used to force the Soil and Water Assessment Tool (SWAT) model in the Hamilton Harbour watershed in Ontario, Canada. A flow-based weighting strategy was developed to integrate the projections of multiple GCMs based on their ability to recreate empirical flow frequency distributions in multiple monitoring sites. Our study renders support to the ability of the weighted model ensemble to draw meaningful hydrological forecasts. Nonetheless, we also note that the ensemble strategy understates the frequency and magnitude of flow extremes, and therefore the domain that is collectively delineated by individual GCMs can still provide complementary planning information. Climate change is projected to trigger a distinct increase in air temperature and precipitation during the late winter-early spring period, which in turn will likely result in an earlier snowmelt and changes in the magnitude and timing of peak flow events. Analysis of the water cycle shows that the sensitivity of the individual hydrological components to climate change may vary along the urban-to-agriculture gradient. The projected declining soil–water content in agricultural catchments highlights the likelihood of more intensified drought conditions in the croplands. Evapotranspiration rates will likely increase across the entire watershed, whereas surface runoff could be reduced but less so in urbanized locations. Overall, our findings suggest that any future planning exercise to ameliorate the prevailing water quality conditions will only be insightful if we consider the interplay between climate change and urbanization processes in the area.

对流域范围内的水质风险评估和适应性管理的实施，评估对未来气候变化的水文响应至关重要。在这项研究中，我们提出了一个建模框架，该模型将水文模型与一般环流模型（GCM）的预测相结合。在加拿大安大略省的汉密尔顿港流域中，采用两种降尺度方法对六个GCM的温度和降水预测进行了推论，以推导土壤和水评估工具（SWAT）模型。制定了基于流量的加权策略以整合多个GCM的预测是基于它们在多个监控站点中重建经验流频率分布的能力。我们的研究为加权模型集合得出有意义的水文预报的能力提供了支持。尽管如此，我们还注意到，整体策略低估了流量极值的频率和大小，因此低估了单个GCM共同划定的范围仍然可以提供补充的计划信息。预计气候变化将在冬末至春初期间引发气温和降水的明显增加，这反过来又可能导致融雪更早，以及高峰流量事件的大小和时间发生变化。对水循环的分析表明，各个水文要素对气候变化的敏感性可能随城市到农业的梯度变化。预计农业流域土壤水含量的下降突显了农田中干旱加剧的可能性。整个流域的蒸散速率可能会增加，而地表径流可能会减少，但在城市化地区的减少幅度较小。总体，