Contrasting warming and drought in snowmelt-dominated agricultural basins: revealing the role of elevation gradients in regional response to temperature change
Contrasting warming and drought in snowmelt-dominated agricultural basins: revealing the role of elevation gradients in regional response to temperature change
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对比融雪主导的农业盆地的变暖和干旱：揭示海拔梯度在区域对温度变化响应中的作用
DOI：
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发表时间：
2018
影响因子：
6.7
通讯作者：
R. Maxwell
中科院分区：
文献类型：
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作者：
J. M. Gilbert;R. Maxwell
对于加州圣华金这样以雪为主的盆地，气温上升会影响水文过程，并对支撑宝贵的灌溉农业和城市人口的水资源造成压力。最近在加利福尼亚州看到的降水的年际大幅波动，突显了更好地了解未来潜在变暖与这种极端的多年降水变化相结合的影响的必要性。在这项研究中，我们使用一个综合水文模型(PARFLOW-CLM)来研究在最近一个干湿循环(2009年-2013年)中，年平均变暖2 °C和4 °C对水文响应的影响。在圣华金盆地上空以1 公里的分辨率进行模拟，以评估连接当地和盆地尺度的水文响应，这是该区域许多以前研究的共同之处。在流域尺度上，较暖的气温减少圣华金河径流量的数量与当代干旱年份一致：除了最潮湿的年份外，对于所有年份，气温每升高4 °C，模拟径流量就会减少到模拟最干旱年份的基准值。这种径流损失可以归因于抵消了气候变暖导致的年蒸散量的增加，而在干旱年份，蒸散量由地下蓄水补贴。在局部地区，水文对气候变暖的响应表现为沿海拔梯度的变化。流域范围内的径流减少是局部增减的净平衡，它遵循一个复杂的高程函数：所有高程都可能出现负的平均径流敏感性，但在2000 m和3500 m高程之间的特定位置存在正的径流敏感性。相反，气候变暖增加了内华达山脉所有海拔的平均蒸散量，最大增幅在1000 m到3000 m之间。当地径流和蒸散量的平均增加结合在一起，减少了内华达山脉各处根带以下的渗漏，同时将事件尺度的补给增加转移到中央山谷河道。
For snow-dominated basins like the San Joaquin in California, warmer temperatures affect hydrologic processes and stress water resources that support valuable irrigated agriculture and urban populations. Large inter-annual swings in precipitation, seen recently in California, highlight the need to better understand the effects of potential future warming combined with such extreme multi-year precipitation variability. In this study we use an integrated hydrologic model (ParFlow-CLM) to examine the effects of mean annual warming of 2 °C and 4 °C on hydrologic response over a recent wet-dry cycle (2009–2013). Simulations are performed at a 1 km resolution over the San Joaquin basin to assess the hydrologic response that bridges the local and basin scales common to many previous studies of the region. At the basin scale, warmer temperatures reduce San Joaquin River runoff by an amount consistent with the contemporary dry years: for all but the wettest year, an increase in temperature of 4 °C reduces simulated runoff to the baseline value of the next driest year simulated. This runoff loss can be attributed to offsetting warming-induced increases in annual evapotranspiration, subsidized in dry years by subsurface storage. Locally, hydrologic response to warming manifests as variation along an elevation gradient. The basin-wide reduction in runoff is the net balance of local increases and reductions that follow a complex function of elevation: negative mean runoff sensitivity can occur at all elevations, yet a positive runoff sensitivity exists for select locations between 2000 m and 3500 m elevation. In contrast, warming increases mean ET at all elevations in the Sierra Nevada, with the highest increase between 1000 m and 3000 m. The average increase in local runoff and ET combine to reduce percolation below the root zone in locations across the Sierra Nevada while shifting event-scale increases in recharge to Central Valley river channels.