基于1991—2024年洞庭湖流域内湖南、贵州、重庆、湖北、江西及广西等省（区、市）129个国家基本气象站点的逐月降水观测数据，本研究首先采用泰森多边形加权平均法计算各二级流域面雨量，统计各子流域年均面雨量和汛期（3—9月）占比等气候态特征；采用Mann-Kendall趋势检验和Sen斜率估计分析各序列的变化趋势，利用Pettitt突变检验识别潜在突变点；应用快速傅里叶变换（FFT）提取各序列的主周期，对年序列和季节序列分别进行周期分析；基于Getis-Ord Gi统计量识别多年平均降水的空间聚集异常区（热点与冷点）。结果表明：（1）各子流域年均面雨量介于1323.1~1495.4 mm之间，汛期降水占全年总量的75.6%~79.7%，降水集中度较高。（2）面雨量趋势分析显示，5个子流域中4个呈下降趋势，仅沅水表现为微弱上升趋势，资水下降最为明显，但所有趋势均未通过显著性检验（p>0.05）；Pettitt突变检验亦未检测到显著的突变年份。（3）FFT周期分析表明，洞庭湖、澧水、湘江、资水主周期为3.8~4.2年（年际尺度），沅水主周期为17.0年（年代际尺度）；分季节周期呈"春夏为纯年际型、秋冬为混合型"的特征。（4）Getis-Ord Gi*空间热点分析识别出4个显著热点和2个显著冷点，热点主要集中于湘江上游（广西境内），冷点集中于沅水上游（贵州境内）。本研究揭示了洞庭湖流域降水"西增东减"的趋势格局、年际与年代际并存的多尺度周期特征，以及"湘江上游多雨、沅水上游少雨"的空间分异规律，为流域水资源管理和旱涝灾害防御提供了科学依据。

[Objective] Against the backdrop of global climate change, precipitation patterns in the Dongting Lake Basin have undergone notable shifts, with increases in both the frequency and intensity of extreme rainfall events. Accurately assessing long-term trends in areal rainfall and deciphering their spatiotemporal evolution are therefore fundamental to improving fine-scale precipitation forecasting, and are critical for rational reservoir operation and flood-drought risk management. This study aims to systematically characterize the climatic baseline, interannual-interdecadal trends, multi-scale periodic oscillations, and spatial differentiation of areal rainfall across the secondary sub-basins of the Dongting Lake Basin, with particular emphasis on clarifying the inter-sub-basin differences in precipitation abundance and deficit and their temporal stability. The findings are intended to fill the existing gap in a comprehensive, multi-dimensional understanding of areal rainfall variability in this basin, and to provide robust scientific support for optimal water resource allocation, coordinated reservoir group operation, and flood-drought early warning and risk mitigation. [Methods] Using monthly precipitation records from 1991 to 2024 collected at 129 national basic meteorological stations distributed across Hunan, Guizhou, Chongqing, Hubei, Jiangxi, and Guangxi within the Dongting Lake Basin, this study first calculated areal rainfall for each secondary sub-basin via the Thiessen polygon weighted average method, and derived climatological metrics including multi-year mean annual areal rainfall and the proportion contributed by the flood season (March-September). Trend analysis was performed using the Mann-Kendall test and Sen's slope estimator, while the Pettitt test was employed to detect potential abrupt change points. Dominant periods were extracted via fast Fourier transform (FFT) for both annual and seasonal series. Spatial clustering of multi-year mean precipitation was assessed using the Getis-Ord Gi* statistic to identify significant hotspots and coldspots.[Results] (1) Multi-year mean annual areal rainfall across the sub-basins ranged from 1323.1 to 1495.4 mm, with the highest value in the Xiangjiang (1495.4 mm) and the lowest in the Yuan River (1323.1 mm), yielding a spatial gradient of 172.3 mm. The flood season (March-September) contributed 75.6%-79.7% of the annual total, indicating a high degree of seasonal concentration—highest in the Lishui (79.7%) and lowest in the Xiangjiang (75.6%). (2) Over the study period, annual areal rainfall exhibited a west-east dipole trend: the western Yuan River showed a slight upward tendency (+3.01 mm/decade), whereas the eastern sub-basins experienced decreasing trends, most pronounced in the Zishui (−44.30 mm/decade), followed by the Lishui (−42.88 mm/decade) and the Dongting Lake area (−38.29 mm/decade), with the Xiangjiang showing the smallest decline (−4.37 mm/decade). None of these trends reached statistical significance (p > 0.05), and the Pettitt test detected no significant abrupt change points. (3) Multi-scale periodic oscillations were evident. At the annual scale, the Xiangjiang, Zishui, and Dongting Lake sub-basins shared a dominant period of 3.8 years, the Lishui exhibited a 4.2-year period (both interannual), while the Yuan River showed a distinct interdecadal period of 17.0 years. Seasonally, spring and summer rainfall displayed purely interannual periodicities across all sub-basins, whereas autumn and winter exhibited mixed signals—the Xiangjiang and Zishui dominated by 2.6-year interannual cycles, and the Dongting Lake, Lishui, and Yuan River by 17.0-year interdecadal cycles. (4) The Getis-Ord Gi* analysis identified four significant hotspots and two significant coldspots. Hotspots were predominantly concentrated in the upper Xiangjiang (within Guangxi), while coldspots were centered in the upper Yuan River (within Guizhou). [Conclusions] This study reveals three salient features of precipitation variability in the Dongting Lake Basin: a west-east dipole trend pattern, the coexistence of interannual and interdecadal periodicities, and a stable spatial dichotomy characterized by wetter conditions in the upper Xiangjiang and drier conditions in the upper Yuan River. These findings fill a critical gap in systematic, multi-dimensional research on areal rainfall dynamics in this basin. The marked heterogeneity among sub-basins underscores the need for region-specific water resource management and differentiated flood-drought response strategies. The results are directly applicable to coordinated reservoir group operation and early warning of extreme hydro-meteorological events. Future work should integrate atmospheric circulation drivers (e.g., ENSO, PDO), reanalysis datasets, and extreme precipitation indices, together with local topographic effects and the seasonal progression of the East Asian monsoon, in a multi-factor attribution framework to further elucidate the mechanisms governing the observed rainfall patterns and their evolution.