Model‐estimated monthly water balance components (i.e., potential evapotranspiration, actual evapotranspiration, and runoff (R)) for 146 United States (U.S.) Geological Survey 8‐digit hydrologic units located in the Colorado River Basin (CRB) are used to examine the temporal and spatial variability of the CRB water balance for water years 1901 through 2014 (a water year is the period from October 1 of one year through September 30 of the following year). Results indicate that the CRB can be divided into six subregions with similar temporal variability in monthly R. The water balance analyses indicated that approximately 75% of total water‐year R is generated by just one CRB subregion and that most of the R in the basin is derived from surplus (S) water generated during the months of October through April. Furthermore, the analyses show that temporal variability in S is largely controlled by the occurrence of negative atmospheric pressure anomalies over the northwestern conterminous U.S. (CONUS) and positive atmospheric pressure anomalies over the southeastern CONUS. This combination of atmospheric pressure anomalies results in an anomalous flow of moist air from the North Pacific Ocean into the CRB, particularly the Upper CRB. Additionally, the occurrence of extreme dry and wet periods in the CRB appears to be related to variability of the Atlantic Multidecadal Oscillation and the Pacific Decadal Oscillation.

中文翻译：

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科罗拉多河流域的水年水量平衡

146个美国（美国）地质调查局使用模型估算的每月水平衡分量（即，潜在的蒸散量，实际的蒸散量和径流（R）），使用位于科罗拉多河盆地（CRB）的8位水文单元来检查1901年至2014年水年（水年是一年的10月1日至次年9月30日的时间）的CRB水平衡的时空变化。结果表明，CRB可以分为六个子区域，每个子区域的每月R具有类似的时间变异性。水平衡分析表明，仅一个CRB分区就产生了约75％的总水年R，而大部分R盆地是由盈余（衍生小号在10月至四月的月产生的）水。此外，分析表明，S的时间变化主要受西北端美国（CONUS）上负气压异常和东南CONUS上正气压异常的控制。大气压力异常的这种组合导致湿空气从北太平洋异常流入CRB，特别是上部CRB。此外，CRB中极端干燥和潮湿时期的出现似乎与大西洋多年代际涛动和太平洋年代际涛动的变化有关。