Event to multidecadal persistence in rainfall and runoff in southeast Arizona
Event to multidecadal persistence in rainfall and runoff in southeast Arizona
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亚利桑那州东南部降雨和径流的数十年持续性事件
DOI：
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发表时间：
2008
期刊：
影响因子：
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通讯作者：
R. Scott
中科院分区：
文献类型：
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作者：
D. Goodrich;C. Unkrich;T. Keefer;M. Nichols;J. Stone;L. Levick;R. Scott
流域降雨的时空变异性直接影响到几乎所有流域尺度上的水文响应。由于当地固有的变异性和气候变化的某种组合，几十年来降水制度的变化可能会导致植被、供水的变化，并在更长的时间尺度上导致景观演变。美国农业部核桃沟实验流域(WGEW)位于亚利桑那州东南部的农业研究服务处的密集雨量网络的日、季和年降水量和强度，利用1956至2006年的观测资料，评估了一系列流域尺度(1.5公顷至149平方公里)上的降水量和降雨量强度的数十年趋势。比较了40年间(1966-2006年)同一空间尺度上的降雨量、径流量和径流量变异性。本研究的主要发现是，累积降水量的空间变异性随时间呈指数递减，平均而言，经过20年的降水累积后，空间变异性变得更加均匀。高强度、产流降水的空间变异性也呈指数级下降，但51年后变异性仍远高于测量误差。流域尺度的降水量没有明显的时间趋势。从1966年到1998年，像WGEW这样的短暂支流的径流量长期减少，可能是由于更高强度的、产生径流的降雨的变化，导致较大的圣佩德罗河夏季流量减少的一个关键因素。
Spatial and temporal rainfall variability over watersheds directly impacts the hydrologic response over virtually all watershed scales. Changes in the precipitation regime over decades due to some combination of inherent local variability and climate change may contribute to changes in vegetation, water supply, and, over longer timescales, landscape evolution. Daily, seasonal, and annual precipitation volumes and intensities from the dense network of rain gauges on the Agricultural Research Service, U. S. Department of Agriculture Walnut Gulch Experimental Watershed (WGEW) in southeast Arizona are evaluated for multidecadal trends in amount and intensity over a range of watershed scales (1.5 ha to 149 km2) using observations from 1956 to 2006. Rainfall and runoff volume and rate variability are compared over the same spatial scales over a 40 year period (1966–2006). The major findings of this study are that spatial variability of cumulative precipitation decreases exponentially with time, and, on average, became spatially uniform after 20 years of precipitation accumulation. The spatial variability of high‐intensity, runoff‐producing precipitation also decreased exponentially, but the variability was still well above the measurement error after 51 years. There were no significant temporal trends in basin scale precipitation. A long‐term decrease in runoff from 1966 to 1998 from ephemeral tributaries like the WGEW may be a critical factor in decreasing summer flows in the larger San Pedro due to changes in higher‐intensity, runoff‐producing rainfall.