Data from: Evapotranspiration is resilient in the face of land cover and climate change in a humid temperate catchment

In temperate humid catchments, evapotranspiration returns more than half of the annual precipitation to the atmosphere, thereby determining the balance available to recharge groundwaters and support stream flow and lake levels. Changes in evapotranspiration rates and therefore catchment hydrology could be driven by changes in land use or climate. Here we examine the catchment water balance over the past 50 y for a catchment in southwest Michigan covered by cropland, grassland, forest, and wetlands. Over the study period about 27% of the catchment has been abandoned from row-crop agriculture to perennial vegetation and about 20% of the catchment has reverted to deciduous forest, and the climate has warmed by 1.14°C. Despite these changes in land use, precipitation and stream discharge, and by inference catchment-scale evapotranspiration, have been stable over the study period. The remarkably stable rates of evapotranspirative water loss from the catchment across a period of significant land cover change suggest that rainfed annual crops and perennial vegetation do not differ greatly in evapotranspiration rates, and this is supported by measurements of evapotranspiration from various vegetation types based on soil water monitoring in the same catchment. Compensating changes in the other meteorological drivers of evaporative water demand besides air temperature—wind speed, atmospheric humidity, and net radiation—are also possible, but cannot be evaluated due to insufficient local data across the 50-y period. Regardless of the explanation, this study shows that the water balance of this landscape has been resilient in the face of both land cover and climate change over the past 50 y.

在温带湿润流域(catchment)中，蒸散发(evapotranspiration)将超过一半的年降水量返还至大气，由此决定了可用于补给地下水、维持径流与湖泊水位的水量平衡。蒸散发速率乃至流域水文的变化，可能由土地利用或气候变化驱动。本研究针对密歇根州西南部一处覆盖耕地、草地、森林与湿地的流域，分析了其过去50年的流域水量平衡。研究期内，该流域约27%的区域从大田作物耕作转向多年生植被覆盖，约20%的区域恢复为落叶林，同时区域气候升温1.14℃。尽管土地利用发生了上述变化，但研究期内的降水量、径流量，以及据此推断的流域尺度蒸散发均保持稳定。在土地覆被发生显著变化的时期内，流域蒸散发水量损失速率仍保持极高的稳定性，这表明雨养一年生作物与多年生植被的蒸散发速率差异极小；这一结论得到了同一流域内基于土壤水监测的不同植被类型蒸散发实测数据的支撑。除气温外，影响蒸发需水量的其他气象驱动因子——风速、大气湿度与净辐射——也可能存在补偿性变化，但由于50年研究期内本地数据不足，无法对其进行评估。无论具体成因如何，本研究均表明，在过去50年里，该区域的水量平衡在面临土地覆被与气候变化时仍保持了韧性。