Climate change impacts on hydrological services in southern California
Climate change impacts on hydrological services in southern California
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DOI：
10.1088/1748-9326/aaeb59
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发表时间：
2018-12
影响因子：
6.7
通讯作者：
E. Underwood;A. Hollander;L. Flint;A. Flint;H. Safford
中科院分区：
文献类型：
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作者：
E. Underwood;A. Hollander;L. Flint;A. Flint;H. Safford
水的可用性是南加州面临的最关键问题之一。因此，供水的公共土地上的完整流域的作用和管理是至关重要的。我们在南加州的四个国家森林——洛杉矶、洛杉矶教士、克利夫兰和圣贝纳迪诺进行了气候对水文服务（径流、补给和气候缺水）的第一个区域研究。我们利用RCP8.5下的三种环流模式（GCMs），将1981-2010年的当前条件与本世纪中叶（2040-2069）和世纪末（2070-2099）进行了比较，评估了水资源的暴露、敏感性和脆弱性。在中度GCM （CCSM4）模式下，从现在到本世纪末，预计有一半的研究区域在10%-30%的年份将超过2015年的干旱状况，在更热、更干燥的预测模式下，预计有三分之一的研究区域在50%的年份将超过2015年的干旱状况。在中等预测下，到本世纪末，3个国家级森林的平均径流量增加了1.2倍，而所有森林的平均补给量减少了0.9倍。预计本世纪末气候水分亏缺平均增加1.1倍。我们通过比较当前和未来气候的预估平均变化与当前使用三种脆弱性的年际变率来评估流域的脆弱性。在中等预测下，385个流域中有三分之一对径流和补给的变化处于中等脆弱状态（+/ - 0.2至+/ - 1倍当前年际变率的标准差），约12个流域处于高度脆弱状态，表明到本世纪末将出现一个新的水文条件时代。林务局优先管理的流域中有一半具有中等或高度的径流和补给脆弱性。水文服务及其脆弱性的空间数据可以直接帮助进行气候智能型规划，从而评估拟议的管理行动及其对水文服务的影响之间的权衡。
Water availability is one of the most critical issues facing southern California. Consequently, the role and management of intact watersheds on public lands that supply water are paramount. We undertake the first regional study of climate impacts on hydrological services (runoff, recharge, and climatic water deficit) across the four national forests of southern California—the Angeles, Los Padres, Cleveland and San Bernardino. We assess the exposure, sensitivity, and vulnerability of water resources by comparing current conditions (1981–2010) to mid-century (2040–2069) and end-of-century (2070–2099) using three general circulation models (GCMs) under RCP8.5. Half of the study area is projected to exceed 2015’s drought conditions in 10%–30% of the years between now and end-of-century under the moderate GCM (CCSM4), and one-third of the area is projected to exceed 2015 in 50% of the years under the hotter, drier projection (MIROC-ESM). Under a moderate projection, mean runoff increased by 1.2× by the end-of-century for three of the national forests, while mean recharge decreased by 0.9× across all forests. Projected end-of-century climatic water deficit increased on average 1.1× across the four forests. We assessed the vulnerability of watersheds by comparing the projected mean change between current and future climates with the current inter-annual variability using three categories of vulnerability. Under the moderate projection, one-third of the 385 watersheds were moderately vulnerable to changes in runoff and recharge (+/−0.2 to +/−1× the standard deviation of current inter-annual variability) and ∼12 watersheds were highly vulnerable, suggesting an era of new hydrological conditions by the end-of-century. Half of the Forest Service’s priority management watersheds had moderate or high vulnerability for runoff and recharge. Spatial data on hydrological services and their vulnerability can directly assist in climate-smart planning, allowing tradeoffs to be assessed between proposed management actions and their effect on hydrological services.