Shifts away from the historical hydroclimate in populated regions can have dire consequences for water management. Regions like the state of California—where highly engineered, geographically interconnected, and inflexible water management systems are predicated on particular spatiotemporal patterns of water availability—are particularly vulnerable to hydroclimate shifts. However, much of the analysis of hydroclimate sensitivity to anthropogenic climate change has focused on gross metrics like annual mean precipitation, which is highly uncertain at the regional scale. This perceived uncertainty has deterred adaptation investments and quantitative integration of climate projection data into regional water management. Here, we assess projected future shifts in the state of California in a range of hydroclimate metrics critical to water management, using data from 10 statistically downscaled global climate model and two emissions scenarios currently used by the state. We find substantial inter-model agreement under both emissions scenarios—and > 80% inter-model agreement under the more severe climate change scenario—across metrics that collectively point toward an increasingly volatile, temporally concentrated, and extreme precipitation future for the state. We show, via hydrologic and operations modeling, that accounting for shifts in these more nuanced metrics reduces the projected reliability and sustainability of current water management practices to a greater degree than would be inferred from changes in total annual precipitation alone. These results highlight both the viability and critical importance of incorporating climate change projections quantitatively into water management decisions in California and other regions vulnerable to hydroclimate shifts, and underscore the need to develop integrated climate-hydrologic-operations models and decision-making protocols capable of accounting for all projected hydroclimate shifts.

中文翻译：

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关于对水资源管理至关重要的加利福尼亚水文气候特征的预测变化的模型间协议

人口稠密地区远离历史水文气候会对水资源管理产生可怕的后果。像加利福尼亚州这样的地区——那里高度工程化、地理上相互关联且不灵活的水资源管理系统取决于特定的可用水资源时空模式——特别容易受到水文气候变化的影响。然而，大部分关于水气候对人为气候变化的敏感性的分析都集中在年平均降水量等总指标上，这在区域尺度上是高度不确定的。这种感知到的不确定性阻碍了适应投资和将气候预测数据定量整合到区域水资源管理中。在这里，我们评估了加利福尼亚州在一系列对水资源管理至关重要的水文气候指标中预计的未来变化，使用来自 10 个统计缩小的全球气候模型和国家目前使用的两个排放情景的数据。我们发现两种排放情景下的模型间一致——并且在更严重的气候变化情景下大于 80% 的模型间一致——跨指标共同指向该州的一个越来越不稳定、时间集中和极端降水的未来。我们通过水文和运营模型表明，考虑到这些更细微的指标的变化，与仅从年降水总量的变化中推断出的相比，在更大程度上降低了当前水资源管理实践的预计可靠性和可持续性。