白鹤滩水电站坝区小时极端降水特征

Hourly extreme precipitation characteristics in the dam area of Baihetan hydropower station

摘要

为揭示白鹤滩水电站坝区短时极端降水的时空分布特征，基于2011−2023年白鹤滩水电站坝区11个地面气象站小时降水数据，选取12项极端降水指数，采用一元线性回归及P值检验，从年际、月际、日内变化3个时间尺度研究坝区短时极端降水时空特征及其随高程变化的规律。结果表明：坝区各站点极端降水指标年际变化均不显著且空间分布不均；坝区各站年强降水量（R₉₅）和极强降水量（R₉₉）对年总降水量（P_TOT）贡献率超过1/3和1/8，上村梁子、新田、葫芦口大桥及旱谷地站弱降水小时数（H_LP）占降水小时数（R_{1 h}）比例超80%；坝区极端降水指标集中出现在6−9月，且7−8月对P_TOT贡献最大；坝区日平均小时降水量和降水频次多出现在0∶00−8∶00，呈“夜雨多、昼间少”的日内分布特征；强降水量阈值（P₉₅）和极强降水量阈值（P₉₉）随海拔增高微弱下降；H_LP和R_{1 h}与海拔呈显著正相关，高海拔地区更易出现持续性、低强度降水。研究结果可为坝区防洪调度、山地灾害风险评估及水电站安全运行提供科学依据。

Abstract

The Baihetan hydropower station, located in the lower reaches of the Jinsha River, is a key power supply hub of China's "West-to-East Electricity Transmission" project. Its safe and stable operation is directly related to China's energy security and regional socioeconomic development. However, the dam area is characterized by complex topography and fragile geological conditions, where extreme precipitation not only threatens power generation stability but also significantly increases the risk of secondary hazards such as landslides and debris flows. Therefore, a thorough studying of the spatiotemporal characteristics of short-duration extreme rainfall in this area is essential for improving flood control scheduling and disaster prevention. This study aimed to fill this gap by long-term hourly precipitation observations to reveal the extreme characteristics of hourly precipitation in the Baihetan dam area. It utilized hourly precipitation records from eleven meteorological stations in the Baihetan dam area during 2011 to 2023. Twelve extreme precipitation indices were selected to comprehensively characterize rainfall intensity, frequency, and persistence, including annual total precipitation (P_TOT), maximum 1-hour precipitation (R_{x1 h}), maximum 12-hour precipitation (R_{x12 h}), hours of light precipitation (H_LP), hours of heavy precipitation (H_{HP15 mm}), hours of very heavy precipitation (H_{HP20 mm}), total precipitation hours (R_{1 h}), simple hourly intensity index (I_SDⅡ), annual heavy precipitation amount (R₉₅), annual very heavy precipitation amount (R₉₉), heavy precipitation threshold (P₉₅), and very heavy precipitation threshold (P₉₉). Linear regression analysis was employed to examine temporal trends, andP-value significance testing were conducted at three different temporal scales (interannual, monthly, and diurnal) and the spatial dimension of elevation, thereby depicting the spatiotemporal characteristics of short-duration extreme precipitation in the Baihetan dam area. The results reveal pronounced spatiotemporal heterogeneity of short-duration extreme precipitation in the Baihetan dam area. Interannually, none of the indices exhibited statistically significant trends at individual stations, but substantial spatial differences were observed among stations. Heavy precipitation (R₉₅) and very heavy precipitation (R₉₉) contributed more than one-third and one-eighth of the annual total precipitation (P_TOT), respectively, highlighting the dominant role of extreme events in shaping annual rainfall totals. In contrast, light-precipitation hours (H_LP) accounted for approximately 80% of total precipitation hours (R_{1 h}), indicating that low-intensity rainfall occurs frequently and persistently. Seasonally, extreme precipitation indices were strongly concentrated during June and September, with July to August contributing the largest fraction to annual precipitation. At the diurnal scale, both precipitation amount and frequency exhibited a clear nocturnal maximum, with peak values occurring mainly between 00:00 and 08:00, especially around 03:00–04:00, forming a distinct "more rainfall at night and less during daytime" pattern. Regarding elevation effects, the thresholds of heavy and very heavy precipitation (P₉₅ and P₉₉) showed a slight decreasing tendency with increasing elevation, whereas H_LP and R_{1 h} were significantly and positively correlated with elevation, suggesting that high-altitude areas are more prone to persistent but low-intensity rainfall. This study demonstrates that short-duration extreme precipitation in the Baihetan dam area exhibits strong seasonal concentration, pronounced nocturnal dominance, and marked spatial heterogeneity driven by topographic effects. Extreme rainfall events play a disproportionate role in annual precipitation totals. The significant positive relationship between precipitation duration and elevation implies that high-altitude regions are more susceptible to prolonged low-intensity rainfall. These findings provide scientific support for optimizing flood control scheduling, improving disaster early-warning systems, and enhancing the operational safety of large hydropower stations in mountainous terrain.

关键词

小时降水 / 极端降水指标 / 时空分布特征 / 高程影响 / 白鹤滩水电站

Key words

hourly precipitation / extreme precipitation indice / spatiotemporal distribution characteristics / impact of elevation / Baihetan hydropower station

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基金资助

国家自然科学基金青年基金项目(52209032)

白鹤滩水电站坝区暴雨预警及实时校正技术研究项目()