Small topographic depressions are ubiquitous in the glaciated terrain of the Northern Prairies characterized by a cold semiarid climate. Groundwater recharge in this region is focused in topographic depressions, which receive lateral inputs of snowmelt runoff in addition to vertical inputs of precipitation. The response of depression-focused recharge to climate change is largely unknown due to the difficulty of representing the complex interaction between depressions and surrounding uplands in hydrological models. This study evaluates climate change effects on recharge using a process-based hydrological model and the pseudo-global warming (PGW) approach representing a climate of 2092–2100, which has a higher mean annual temperature (+4.9 °C) and precipitation (+135 mm or +27%) compared with the present climate. The recharge model is conditioned using field data from an instrumented grassland site in the Canadian Prairies. Under the present climate, snowmelt runoff occurred in March–April over frozen soil, which accounted for the majority of water transfer from the upland to the depression. Under the PGW scenario, the amount of snowmelt runoff in March–April decreased due to lower snow accumulation and shorter periods of frozen soil. Instead, runoff occurred in midwinter and also in summer months due to increased intensity and duration of summer storms. Despite the increased precipitation, mean annual recharge rates decreased from 10.2 to 3.2 mm yr^–1, indicating the importance of considering the complex effects of warmer and wetter climate on hydrological processes in cold semiarid regions.

中文翻译：

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气候变化对加拿大大草原以洼地为中心的地下水补给的影响

在以寒冷的半干旱气候为特征的北方大草原的冰川地形中，小的地形洼地无处不在。该地区的地下水补给集中在地形洼地，除了垂直输入降水外，这里还接受融雪径流的横向输入。由于难以在水文模型中表示洼地与周围高地之间复杂的相互作用，以洼地为重点的补给对气候变化的响应在很大程度上是未知的。本研究使用基于过程的水文模型和代表 2092-2100 年气候的伪全球变暖 (PGW) 方法评估气候变化对补给的影响，该气候具有较高的年平均温度 (+4.9 °C) 和降水 (+ 135 毫米或 +27%）与当前气候相比。补给模型使用来自加拿大大草原仪器仪表草地现场的现场数据进行调节。在目前的气候下，3-4 月冻土上出现融雪径流，其中大部分水从高地转移到洼地。在 PGW 情景下，由于积雪较少和冻土时间较短，3-4 月融雪径流量减少。相反，由于夏季风暴的强度和持续时间增加，径流发生在仲冬和夏季月份。尽管降水量增加，但年平均补给率从 10.2 毫米降至 3.2 毫米 这占大部分水从高地转移到洼地。在 PGW 情景下，由于积雪较少和冻土时间较短，3-4 月融雪径流量减少。相反，由于夏季风暴的强度和持续时间增加，径流发生在仲冬和夏季月份。尽管降水量增加，但年平均补给率从 10.2 毫米降至 3.2 毫米 这占大部分水从高地转移到洼地。在 PGW 情景下，由于积雪较少和冻土时间较短，3-4 月融雪径流量减少。相反，由于夏季风暴的强度和持续时间增加，径流发生在仲冬和夏季月份。尽管降水增加，但年平均补给率从 10.2 毫米下降到 3.2 毫米^–1，表明考虑温暖和潮湿气候对寒冷半干旱地区水文过程的复杂影响的重要性。