Winter Inputs Buffer Streamflow Sensitivity to Snowpack Losses in the Salt River Watershed in the Lower Colorado River Basin
Winter Inputs Buffer Streamflow Sensitivity to Snowpack Losses in the Salt River Watershed in the Lower Colorado River Basin
复制标题
科罗拉多河流域下游盐河流域冬季输入缓冲水流对积雪损失的敏感性
作者：
M. Robles;J. Hammond;S. Kampf;J. Biederman;E. Demaria
最近科罗拉多河上游流域的流量下降，引起了人们对4000万人供水对气温上升的敏感性的担忧。然而，美国西部河流流域的其他研究提出了一个悖论：流量并没有随着变暖和降雪量的减少而持续下降。这种缺乏一致性的一个可能的解释是，当潜在的蒸发损失较低时，变暖引起的冬季径流的产生。这种机制更可能在海拔较低或纬度相对温暖的冬季温度和间歇性积雪的盆地。我们测试这是否占9个计量流域的盐河及其支流，这是一个子流域在较低的科罗拉多河流域（LCRB）的径流模式。我们开发了一个流域尺度的模型，分离雪和降雨输入，并模拟积雪和融化的温度，降水量和相对湿度。尽管从1968年到2011年显著变暖，许多流域的积雪减少，但年度和季节性流量并没有下降。年径流量的25%和50%之间产生于冬季（NDJF），此时径流率通常较高，潜在蒸散损失是春季潜在损失的三分之一（MAMJ）。冬季输入的次年度径流响应比春季和夏季响应更大，更有效，1968-2011年的频率和幅度比1929-1967年增加。总的来说，75%的最大的冬季事件与大气河流有关，这可以产生大的冷季流量峰值。我们的结论是，冬季水文输入和径流量的增加减缓了LCRB子流域温度引起的积雪损失。
Recent streamflow declines in the Upper Colorado River Basin raise concerns about the sensitivity of water supply for 40 million people to rising temperatures. Yet, other studies in western US river basins present a paradox: streamflow has not consistently declined with warming and snow loss. A potential explanation for this lack of consistency is warming-induced production of winter runoff when potential evaporative losses are low. This mechanism is more likely in basins at lower elevations or latitudes with relatively warm winter temperatures and intermittent snowpacks. We test whether this accounts for streamflow patterns in nine gaged basins of the Salt River and its tributaries, which is a sub-basin in the Lower Colorado River Basin (LCRB). We develop a basin-scale model that separates snow and rainfall inputs and simulates snow accumulation and melt using temperature, precipitation, and relative humidity. Despite significant warming from 1968–2011 and snow loss in many of the basins, annual and seasonal streamflow did not decline. Between 25% and 50% of annual streamflow is generated in winter (NDJF) when runoff ratios are generally higher and potential evapotranspiration losses are one-third of potential losses in spring (MAMJ). Sub-annual streamflow responses to winter inputs were larger and more efficient than spring and summer responses and their frequencies and magnitudes increased in 1968–2011 compared to 1929–1967. In total, 75% of the largest winter events were associated with atmospheric rivers, which can produce large cool-season streamflow peaks. We conclude that temperature-induced snow loss in this LCRB sub-basin was moderated by enhanced winter hydrological inputs and streamflow production.