The atmospheric freezing level (Z_FL) determines the rain‐snow transition zone at the surface, how much rainfall is available for runoff, and the flood risk during a precipitation event. An accurate Z_FL forecast is thus critical for reservoir operation, especially in mountain watersheds with narrow elevation bands like the Feather and North Fork Yuba in California, where a 500‐m elevation gain can amount to >50% of the watershed area. Using a ±350‐m Z_FL forecast error, we find inflow volume uncertainties of <10% to >50% of the flood pool storages at Lake Oroville and New Bullards Bar reservoirs, depending on the Z_FL, antecedent moisture condition, and the precipitation event magnitude. The uncertainties can increase by up to >3% per inch (25.4 mm) of precipitation, depending on the Z_FL and antecedent moisture condition. This result substantiates the significant impact of Z_FL forecast error and the critical need of Z_FL forecast accuracy to support reservoir flood control operations in the two watersheds.

中文翻译：

---

冻结水平预测错误可能会消耗水库的防洪存储：加利福尼亚州奥罗维尔湖和新布拉德斯酒吧水库的潜力

大气冻结水平（Z _FL）决定了地表的雨雪过渡区，可用于径流的降雨量以及降水事件期间的洪水风险。因此，准确的Z _FL预测对于水库运行至关重要，尤其是在海拔范围较窄的山区流域，例如加利福尼亚的Feather和North Fork Yuba时，500 m的海拔增量可以达到流域面积的50％以上。使用±350-m的Z _FL预测误差，我们发现Oroville湖和New Bullards Bar水库的洪水池入库量的不确定度<10％至> 50％，具体取决于Z _FL，先前的湿度条件和降水事件的大小。取决于Z _FL和先前的湿度条件，每英寸降水量（25.4 mm）的不确定性可能增加> 3％。该结果证实了Z _FL预报误差的重大影响以及Z _FL预报精度对支持两个流域的水库防洪行动的迫切需求。