鄱阳湖作为通江湖泊,其洪水大小由多因素共同决定,湖区洪灾频繁。鄱阳湖水利枢纽工程建设后将对洪期复杂水动力过程造成影响。为评估其影响,建立了包括鄱阳湖湖区和尾闾以及长江九江到八里江段在内的平面二维水动力模型,对1954年大洪水和1991年倒灌2种灾害型洪期过程进行情景模拟,分析了枢纽对长江和湖区可能造成的影响。结果表明:枢纽工程使湖口出流过程更加平缓,具有一定的削峰作用,对长江洪水位基本无影响;1954年大洪水过程,枢纽使湖区水位升高,代表水文站水位壅高最大值为0.021 m;1991年倒灌过程,枢纽使湖区水位降低,湖区水位变化的趋势与湖口流量变化趋势一致,相位稍滞后于流量过程。研究成果可为江湖水安全管理提供技术支撑。

受自然因素变化和人类活动的双重影响,近年来鄱阳湖出现了极端的洪枯水文情势。2020年汛期鄱阳湖最高水位突破历史极值,2022年鄱阳湖出现历史罕见的“汛期反枯”现象,多站出现历史最低水位。极端的洪枯水文情势给湖区乃至长江下游地区防汛抗旱工作带来了严重影响。为应对新水沙及气候条件下鄱阳湖流域洪旱灾害,根据鄱阳湖流域水文、大气环流资料和三峡工程运行信息,对上述2次极端洪枯事件进行总结分析。 结果表明: 厄尔尼诺和拉尼娜现象下副热带高压影响降雨、湖区出入流是鄱阳湖出现极端洪枯水文情势的主要原因,长江上游干支流水库调节也对极端洪枯水文情势产生了一定影响。研究成果有助于提升鄱阳湖流域水旱灾害应对能力。

鄱阳湖接纳流域内来水，其洪水的形成和发展受鄱阳湖流域来水和长江洪水的双重影响，造成该地区在特定时段极易引发特大洪水。文章分析了江湖作用机制，并基于1959-2009年汉口和湖口洪水资料，统计分析了江湖洪水遭遇及长江洪水倒灌入湖频次；通过构建鄱阳湖-长江干流二维水动力模型，对江湖顶托加剧情景、江湖顶托相持情景、长江洪水倒灌情景等典型洪水过程进行了重演与分析，将模拟结果与实测水位过程进行验证与误差分析，并应用该模型对1998年极端洪水遭遇过程进行模拟分析。研究结果表明：鄱阳湖洪水一般早于长江洪水出现，两者遭遇主要在6-7月；长江倒灌情景一般发生在长江主汛期，通过统计分析长江洪水的倒灌天数及倒灌水量，反映了江湖顶托强度在年代际尺度上处于此消彼长的波动状态；模型对江湖洪水遭遇典型水位过程与1998年极端洪水遭遇过程的模拟预测精度较高，效果较好，说明模型能够很好地处理鄱阳湖洪水与长江洪水遭遇的高动态变化问题，可为鄱阳湖地区的经济建设和防洪治理提供理论支撑。

. Poyang Lake receives incoming water from the basin， and its flood formation and development are influenced by both incoming water from Poyang Lake basin and Yangtze River flood. This makes the area extremely vulnerable to severe flooding at a certain time of the year. Based on the flood data of Hankou and Hukou from 1959 to 2009， this paper analyzes the flood occurrence of Yangtze River and Poyang Lake and the frequency of Yangtze River flood inpouring into Poyang Lake. By constructing a two-dimensional hydrodynamic model of Poyang Lake and Yangtze River mainstream， this paper reviews and analyzes typical flood processes such as the intensification scenario of Yangtze River and Poyang Lake overburden， the equilibrium scenario of Yangtze River and Poyang Lake overburden， and the extreme scenario of Yangtze River flood flowing backwards into Poyang Lake overburden. The simulation results are verified and errors are analyzed with the measured water level process， and the extreme flood encounter process in 1998 is simulated and analyzed with this model. The results show that the flood of Poyang Lake generally occurs earlier than the flood of Yangtze River， and the two floods mainly occur in June to July. The backflow of Yangtze River flood into Poyang Lake generally occurs in the main flood season of Yangtze River. Through statistical analysis of the number of days and water volumn of backflow， it shows that the intensity of Yangtze River and Poyang Lake overburden fluctuates in interdecadal scale. The model has high accuracy and good effect in simulating and predicting the typical water level process of the flood encounter of Yangtze River and Poyang Lake and the extreme flood in 1998， indicating that the model can well deal with the highly dynamic changes of Poyang Lake flood and Yangtze River flood， and can provide theoretical support for the economic construction and flood control in Poyang Lake Region.

为探讨鄱阳湖流域洪水过程的变化特征和规律,系统分析流域洪水量级、频率、发生时间的变化特征,利用核密度估计分析洪水发生率的非平稳性,运用月频率法评价洪水集聚性特征,并探讨低频气候因子对洪水变化的影响。研究表明：① 鄱阳湖流域各水文站点年、秋季和冬季最大洪水及POT超阈值洪水以增加趋势为主。② 洪水发生率年内集聚性显著,主要集中在4~7月;年际洪水发生次数呈现非平稳泊松分布,洪水发生率出现明显的年际集聚性特征。③ ENSO、IOD对下年洪水量级及洪水发生次数有明显影响,洪水发生次数与年最大洪水量级异常现象通常是ENSO和IOD协同作用结果。

Changing properties of floods in the Poyang Lake have been thoroughly investigated in terms of flooding magnitude, occurrence rates and timing. These characteristics were obtained from annual and seasonal maximum flow (AMF) and sampling the flood series based on the Peak-over-Threshold (POT) method. Kernel estimation technique and Bootstrap method were used in detection of nonstationary of flooding processes. Monthly frequency have been used in analysis of changing properties of floods in terms of annual and international viewpoints. Moreover, impacts of ENSO, NAO, IOD and PDO on floods in the Poyang Lake Basin have been widely analyzed. Results indicated that: 1) Annual maximum streamflow and POT-based flood events are generally in increasing tendency at annual and seasonal (winter and autumn) time scales. The change points of AMF at hydrological stations of the lake basin were mainly in 1980s-1990s, except Lijiadu station where the change point of AMF was 1966. The flood magnitude increased by 19%, 13%, 22% and 16% after the change points at Lijiadu, Meigang, Hushan and Wanjibu stations. Autumn AMF and Winter AMF in all stations are increased or significantly increased. The average increase rate of Autumn AMF and Winter AMF are 113% and 40.5%, respectively, after the change points. 2) Clustering effects of floods were evident and floods were active during April and July, which were significant at 5% significance level, implying that the time interval from April to July is the active flood period.Massive occurrences of heavy floods during a certain period usually trigger high flooding risk and which poses serious challenges for human mitigation to flood hazards. 3) Annual occurrence rates of floods follow nonstationary poisson distribution with evident interannual clustering properties. Further, two periods having higher occurrence rates of floods were identified, i.e. in the late 1960s and the early 1970s, and the mid 1990s. However, the highest occurrence rates of floods are observed mainly during the 1990s. Active flood activities can usually be observed at most hydrological stations in the Poyang Lake Basin. 4) ENSO and IOD have coincident impacts on flooding magnitude and occurrence rates of floods of the subsequent years. ENSO usually have negative impacts on floods of the same year during Spring seasons and have a significant impact on the flood occurrence rate and on annual maximum streamflow during Spring in the subsequent years. IOD has a significant positive relation with the occurrence timing of floods in the same year. Positive IOD phase usually delayed occurrence timing of floods. PDO and NDO have no significant impacts on flood processes of the lake basin. the warm phase of ENSO together with the warm phase of IOD combine to intensify precipitation extremes of the next year in the Poyang Lake Basin and hence increase peak flood flow and flood occurrence rate across the basin. The results of this study are of great scientific and practice merits in terms of human mitigation to floods and also management of flood hazards, conservation of ecological environment of the Poyang Lake Basin.

The retention lake often plays an important role in flood mitigation through the water storage and the lake–river interactions. However, the evolution of real-time flood regulation capacity remains poorly characterized. Using wavelet decomposition and flood peak removing ratios, this study presents a comprehensive evaluation of the characterization, mechanism, and impacts of the flood regulation capacity in Dongting Lake. The results indicate that the change of flood regulation effect of the lake can be well reflected by the multi-year changes in the variances of the inflow and outflow runoffs. The wavelet decomposition indicates that the flood regulation of the lake is mainly functioned on the high-frequency floods with durations less than 32 days. The average yearly flood peak removing ratios range from 0.13 to 0.56, but no significant tendency changes on the effect of the flood regulation capacity has happened during the study period. The changes in maximum regulation volume reveal that the flood regulation of the Dongting Lake is mainly a passive process decided by the complex river–lake relationship and the interactions among different processes of discharge and sediment. The impacts from the large volume reduction caused by sedimentation in the lake is compensated by the increased flood controlling water level, which in turn have resulted in the new phenomenon of “normal discharge, high water level and disaster” in the lake regions after the 1990s. The significant impacts on the lake–river relationship caused by the sediment reallocation from the operation of the Three Gorges Reservoir (TGR) have further changed the hydrological regimes between the lake and the Yangtze River. Influenced by the new lake-river interaction pattern the discharge passing capacity downstream the outlet of the lake is becoming a key factor that affects the flood regulation capacity, which is leading to a shift of the flood pressures from the lake region to the downstream of Yangtze in the near future.

The flow of plain-type river-connected lakes is affected by both upstream and downstream rivers, and the hydrological conditions are very complex. Poyang Lake, situated in Jiangxi Province, is the largest river-connected lake in the Yangtze River Basin. Its unique geographical features and complex hydrological conditions have made it a heavy disaster area and a frequent area of floods since ancient times. As typical mitigation measures of Poyang Lake, semi-restoration polder areas and flood storage and detention areas play a crucial role in the flood control of Poyang Lake. Taking Poyang Lake as an example, this article studies the flood characteristics of Poyang Lake based on the measured hydrological data. Furthermore, by using the weir (gate) outflow formula to construct the hydraulic model of semi-restoration polder areas and DHI MIKE to construct the hydrodynamic model of Kangshan flood storage and detention area, the flood diversion capacity of the two, and the flood diversion effect under the super-historical flood in 2020 are analyzed. The results show that compared with the non-use of mitigation measures, the maximum cumulative reduction in Xingzi water level can be reduced by 0.68 m and 0.48 m when semi-restoration polder areas and Kangshan flood storage and detention areas are used alone. Finally, the article puts forward some thoughts and suggestions on the flood control of Poyang Lake. The research results can offer some reference to the flood risk management of plain-type river-connected lakes.