Most of the population and economic growth in the United States occurs in megaregions as the clustered metropolitan areas, whereas climate change may amplify negative impacts on water and natural resources. This study assesses shifts in regional hydroclimatology of fourteen US megaregions in response to climate change over the 21st century. Hydroclimatic projections were simulated using the Variable Infiltration Capacity (VIC) model driven by three downscaled climate models from the Multivariate Adaptive Constructed Analogs (MACA) dataset to cover driest to wettest future conditions in the conterminous United States (CONUS). Shifts in the regional hydroclimatolgy and basin characteristics of US megaregions were represented as a combination of changes in the aridity and evaporative indices using the Budyko framework and Fu’s equation. Changes in the climate types of US megaregions were estimated using the Fine Gaussian Support Vector Machine (SVM) method. The results indicate that Los Angeles, San Diego, and San Francisco are more likely to experience less arid conditions with some shifts from Continental to Temperate climate type while the hydroclimatology of Houston may become drier with some shifts from Temperate to Continental climate type. Additionally, water yield is likely to decrease in Seattle. Change in the hydroclimatology of Denver and Phoenix highly depends on the selected climate model. However, the basin characteristics of Phoenix have the highest sensitivity to climate change. Overall, the hydroclimatic conditions of Los Angeles, San Diego, Phoenix, Denver, and Houston have the highest sensitivity to climate change. Understanding of future shifts in hydroclimatology of megaregions can help decision-makers to attenuate negative consequences by implementing appropriate adaptation strategies, particularly in the water-scare megaregions.

美国的大部分人口和经济增长发生在作为聚集的大都市区的大区域，而气候变化可能会放大对水和自然资源的负面影响。本研究评估了 21 世纪美国 14 个大区域的区域水文气候变化以应对气候变化。水文气候预测是使用可变渗透能力 (VIC) 模型模拟的，该模型由来自多元自适应构造类似物 (MACA) 数据集的三个缩减气候模型驱动，以涵盖美国本土 (CONUS) 未来最干燥到最潮湿的条件。使用 Budyko 框架和 Fu 方程，美国大区域的区域水文气候和盆地特征的变化被表示为干旱和蒸发指数变化的组合。使用精细高斯支持向量机 (SVM) 方法估计美国大区域气候类型的变化。结果表明，洛杉矶、圣地亚哥和旧金山更有可能经历较少干旱的条件，从大陆气候类型到温带气候类型的一些转变，而休斯顿的水文气候可能会随着从温带气候类型向大陆气候类型的一些转变而变得更加干燥。此外，西雅图的产水量可能会下降。丹佛和凤凰城的水文气候变化高度依赖于所选的气候模型。但凤凰的盆地特征对气候变化的敏感性最高。总体而言，洛杉矶、圣地亚哥、凤凰城、丹佛和休斯顿的水文气候条件对气候变化的敏感性最高。