Water Security-based Hydrological Regime Assessment Method for Lakes with Extreme Seasonal Water Level Fluctuations：A Case Study of Poyang Lake,China

Extreme seasonal water level fluctuations characterize natural floodplain lakes in monsoon regions, which are crucial for ensuring lake water security, including flood prevention water supply and health of aquatic ecosystem. In order to achieve this goal, we established a hydrological regime assessment method based on a set of hydrological indicators for lakes with heavy seasonal water level fluctuations. The results suggest that time-sensitive hydrological indicators and specific time scales for various water security aspects must be considered. We discovered that it is more practical and meaningful to combine the water level classification derived from statistical analyses with characteristic hydrological values linked to water security. The case study of Poyang Lake results show that there are no discernable trends of Poyang Lake water regime status over the last 35 years, and the two periods of poor status are in accordance with climate variation in the lake basin area. Scholars and policy makers should focus on both floods and droughts, which are the main water security problems for Poyang Lake. It is hoped that this multi-scale and multi-element hydrological regime assessment method will provide new guidelines and methods for other international scholars of river and lake water assessment.

Variation of Floods Characteristics and Their Responses to Climate and Human Activities in Poyang Lake, China

The Poyang Lake is one of the most frequently flooded areas in China. Understanding the changing characteristics of floods as well as the affecting factors is an important prerequisite of flood disaster prevention and mitigation. The present study identified the characteristics variations of historical floods in the Poyang Lake and their tendencies based on the Mann-Kendall(M-K) test, and also investigated the related affecting factors, both from climate and human activities. The results revealed that the highest flood stages, duration as well as hazard coefficient of floods showed a long-term increasing linear trend during the last 60 years with the M-K statistic of 1.49, 1.60 and 1.50, respectively. And, a slightly increasing linear trend in the timing of the highest stages indicated the floods occurred later and later during the last six decades. The rainfall during the flood season and subsequent discharges of the Changjiang(Yangtze) River and runoff from the Poyang Lake Basin were mainly responsible for the severe flood situation in the Poyang Lake in the 1990 s. In addition, the intensive human activities, including land reclamation and levee construction, also played a supplementary role in increasing severity of major floods. While, the fewer floods in the Poyang Lake after 2000 can be attributed to not only the less rainfall over the Poyang Lake Basin and low discharges of the Changjiang River during flood periods, but also the stronger influences of human activity which increased the floodwater storage of the Poyang Lake than before.

A general multi-objective programming model for minimum ecological flow or water level of inland water bodies

Assessment of ecological flow or water level for water bodies is important for the protection of de- graded or degrading ecosystems caused by water shortage in arid regions, and it has become a key issue in water resources planning. In the past several decades, many methods have been proposed to assess ecological flow for rivers and ecological water level for lakes or wetlands. To balance water uses by human and ecosystems, we proposed a general multi-objective programming model to determine minimum ecological flow or water level for inland water bodies, where two objectives are water index for human and habitat index for ecosystems, respectively Using the weighted sum method for multi-objective optimization, minimum ecological flow or water level can be determined from the breakpoint in the water index-habitat index curve, which is similar to the slope method to de- termine minimum ecological flow from wetted perimeter-discharge curve. However, the general multi-objective programming model is superior to the slope method in its physical meaning and calculation method. This model provides a general analysis method for ecological water uses of different inland water bodies, and can be used to define minimum ecological flow or water level by choosing appropriate water and habitat indices. Several com- monly used flow or water level assessment methods were found to be special cases of the general model, including the wetted perimeter method and the multi-objective physical habitat simulation method for ecological river flow, the inundated forest width method for regeneration flow of floodplain forest and the lake surface area method for eco- logical lake level. These methods were applied to determine minimum ecological flow or water level for two repre- sentative rivers and a lake in northern Xinjiang of China, including minimum ecological flow for the Ertix River, minimum regeneration flow for floodplain forest along the midstream of Kaxgar River, and minimum ecological lake level for the Ebinur Lake. The results illustrated the versatility of the general model, and can provide references for water resources planning and ecosystem protection for these rivers and lake.

Effect of hydrological variability on diatom distribution in Poyang Lake, China

Poyang Lake is the largest freshwater lake in China, and it has a seasonal flooding cycle that significantly changes the water level every year. The aim of this paper was to explain how these hydrological changes influence diatom populations in Poyang Lake. The yearly hydrological cycle can be divided into 4 phases: low water-level phase, increasing water-level phase, high water-level phase and decreasing waterlevel phase. Variations in the abundance of planktonic diatoms were studied using quarterly monitoring data collected from January 2009 to October 2013. Generally, diatoms were dominant in Poyang Lake and accounted for more than 50% of the total phytoplankton biomass except in July 2009(26%) and January 2012(35%). Aulacoseira granulata and Surirella robusta were the predominant species in all four phases, and they accounted for 25.02% to 56.89% and 5.07% to 14.78% of the total phytoplankton biomass, respectively. A redundancy analysis(RDA) showed that changes in physico-chemical parameter were related to the water level, and changes in diatom biomass were related to nitrite levels and p H. These results indicate that changes in environmental parameters related to both seasonal variations and water-level fluctuations caused variations in diatom biomass and community composition in Poyang Lake. Furthermore, extreme hydrological events can have different influences on the diatom community composition in the main channel and lentic regions. This research provides data on the diatom variations in Poyang Lake and will be useful for establishing biological indicators of environmental change and protecting Poyang Lake in the future.

Impact of Accumulated Temperature on Wetland Vegetation Area in Poyang Lake

Accumulated temperature,which is now widely used in agronomy,is an important ecological factor to the growth of plants,but few relative studies have been found on the vegetation area of floodplain grasslands in Poyang Lake.This research used the classification and regression tree(CART)to classify normalized vegetation area index derived from MODIS LAI(Moderate Resolution Imaging Spectroradiometer Leaf Area Index)images from 2008 to 2014,according to different climate indexes,such as mean daily air temperature(n),accumulated temperature(jw),daily maximum temperature(g),daily minimum temperature(d),accumulative precipitation(j),water level(s)and average water level for 20 days preceding(a).The results showed that:(1)The accumulated temperature and the 20-day average WL(water level)were found to have the greatest impact on variation in wetland vegetation area,and they both dominated the classification process twice;(2)Two classification thresholds of accumulated temperature were 790°C and 1784°C,approximately corresponding to the beginning of April and midMay;(3)790°C could also be used as a threshold to select remote sensing images to analysis the annual variability of vegetation,i.e.while accumulated temperature is lower than 790°C,remote sensing images of similar accumulated temperature rather than similar date should be selected from different years for comparison.We also found that,effects of different hydrological factors on area of floodplain grasslands showed stage characteristics:(1)From January to March,water level changes slowly with less rainfall,as a result,the 20-day average WL which can interpret the hydrologic characteristics smoothly showed significant importance in this stage;(2)While entering April,intense rainfall make accumulative precipitation to be the dominating factor of classification;(3)From late April to mid-May,in condition of accumulative precipitation higher than 405 mm,daily water level is of most importance,because to the flood recession process as well as rapid water level fluctuations.

Non-stationary water-level fluctuation in China＇s Poyang Lake and its interactions with Yangtze River

Seasonal water-level fluctuations （WLF） play a dominate role in lacustrine ecosys- tems. River-lake interaction is a direct factor in changes of seasonal lake WLF, especially for those lakes naturally connected to upstream and downstream rivers. During the past decade, the modification of WLF in the Poyang Lake （the largest freshwater lake in China） has caused intensified flood and irrigation crises, reduced water availability, compromised water quality and extensive degradation of the lake ecosystem. There has been a conjecture as to whether the modification was caused by its interactions with Yangtze River. In this study, we investi- gated the variations of seasonal WLF in China＇s Poyang Lake by comparing the water levels during the four distinct seasons （the dry season, the rising season, the flood season, and the retreating season） before and after 2003 when the Three Gorge Dam operated. The Water Surface Slope （WSS） was used as a representative parameter to measure the changes in river-lake interaction and its impacts on seasonal WLF. The results showed that the magni- tude of seasonal WLF has changed considerably since 2003; the seasonal WLF of the Poy- ang Lake have been significantly altered by the fact that the water levels both rise and retreat earlier in the season and lowered water levels in general. The fluctuations of river-lake in- teractions, in particular the changes during the retreating season, are mainly responsible for these variations in magnitude of seasonal WLF. This study demonstrates that WSS is a rep- resentative parameter to denote river-lake interactions, and the results indicate that more emphasis should be placed on the decrease of the Poyang Lake caused by the lowered water levels of the Yangtze River, especially in the retreating season.

鄱阳湖水利枢纽工程施工和运行对湖区及尾闾洪水动力的影响

鄱阳湖是长江水系中的两大通江湖泊之一,在调节长江水位、涵养水源、改善当地气候和维护周围地区生态平衡等方面都起着巨大的作用。鄱阳湖水利枢纽的修建可能导致湖泊水文情势和水动力的变化。本文基于MIKE 21构建鄱阳湖二维水动力模型,选取1954年和1998年特大洪水年以及1991年长江倒灌年作为运行期的典型年,选取1995年作为施工期典型年,按照规划中的鄱阳湖水利枢纽工程施工及运行调度方案,计算水利枢纽修建前后鄱阳湖水位和流量的变化,定量分析枢纽工程对长江干流、鄱阳湖湖区及尾闾附近洪水动力的影响。结果表明:不同典型年鄱阳湖水利枢纽对长江干流、湖区及尾闾的洪水动力影响相似,其中洪水期、倒灌期及施工期一期对长江防洪、湖区及尾闾附近的影响较小,施工期二期湖区水位壅高幅度最高达0.237 m,对鄱阳湖湖区及尾闾附近防洪有一定影响;枢纽工程对星子、都昌、康山等湖区水文站水位影响幅度较为接近,且越靠近尾闾,影响越小。整体而言,鄱阳湖水利枢纽的修建会导致洪水年鄱阳湖湖区水位壅高,倒灌期湖区水位降低,湖区流速降低,但变化幅度均较小,故枢纽工程施工期和运行期对汛期行洪影响不大。

基于MODIS影像的鄱阳湖湖面积与水位关系研究

利用统计分析的方法,根据2001年获取的13景鄱阳湖区无云MODIS影像中的9景提取的水体面积,并结合同步观测的水文数据分别采用线性、对数和指数3种模型模拟湖面积-水位之间关系。结果显示对数模型相关性最好(R2=0.918),其次为线性和指数模型。利用另外4景MODIS影像对模型进行检验表明,该模型精度较高,模拟的最大误差为3.36%。本研究显示,可根据鄱阳湖水位观测值,利用该模型预测鄱阳湖洪涝期洪水淹没面积,以弥补云天状况下光学遥感难以监测到洪水淹没范围的不足。本研究为利用遥感影像实时监控鄱阳湖水情空间动态变化提供了可行的方法,对湖泊、水库的泛洪监测、调洪功能分析具有重要意义。

基于SPI的鄱阳湖流域干旱时空演变特征及其与湖水位相关分析

以标准化降水指数(SPI)为工具,以鄱阳湖流域为研究对象,选择流域内13个气象站共50a的逐月降水量和5个水位站共50a的逐日水位为实验数据,通过Mann-Kendall检验方法和Kriging插值方法,分析了鄱阳湖流域干旱的时空演变特征,以Spearman秩相关系数为评价指标,比较了流域不同时间尺度的SPI值与各站湖水位、不同时间尺度干旱强度与各站年最低水位之间的相关程度。研究表明:鄱阳湖流域的干旱具有明显的季节性特征,春季和秋季具有较为明显的干旱化趋势;鄱阳湖的干旱覆盖面较广,干旱在不同区域内的不同时期都有可能发生和转移;鄱阳湖流域的气象干旱对湖水位具有较为显著的相关性,湖水位对3个月尺度和6个月尺度的SPI值响应最为明显,其与湖水位的相关程度,自近出湖口地区向远离湖口地区递增。

鄱阳湖水利枢纽对江湖洪期水动力过程的影响

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。

基于GMS鄱阳湖拟建枢纽对地下水影响探讨

针对拟建鄱阳湖水利枢纽工程对地下水影响问题．选择赣江三角洲为代袁区，采用资料收集、野外调查、统计分析和数值模拟等方法进行研究。依据地质钻探资料、地下水与河流动态关系、区域数字高程模型，结合鄱阳湖历史形成与演化过程确定研究区边界条件．运用GMS模拟软件建立了研究区地下水三维运动模型。依据推荐的枢纽调度方案．利用数值模型计算枢纽运行后对地下水运动影响的时空变化规律。结果表明：枯水年份影响大，距离河流、坝址近的地方影响大，反之亦然。影响幅度范围0～2m．地下水径流交替因此减弱．丰水年份土壤潜育化面积增加9.3％。

基于Sentinel-3A SRAL 2级产品的鄱阳湖水位评估与校准

Sentinel-3A卫星合成孔径雷达高度计(SRAL)因其时空分辨率优势在水位监测上应用潜力较大。基于2016—2018年Landsat-8与Sentinel-2光学遥感获取鄱阳湖星子站邻近水域,提取湖上Sentinel-3A SRAL 2级产品卫星测高点,提出一种卫星测高水位计算与校准方法,并结合实测水位进行评估。结果表明:Sentinel-3A SRAL 2级产品在鄱阳湖的过境数据有效率为64%,3—9月有连续覆盖数据,12月至次年2月受水位低或湖滩出露影响无有效数据;不同高程系统下的卫星观测水位与实测水位序列的一致性极显著,皮尔逊相关系数为0.999,在0.001水平上显著相关,实测水位变化量与卫星观测水位变化量的皮尔逊相关系数为1,二者的平均偏差为−0.175 m,标准差为0.084 m,其中降轨统计指标值优于升轨,枯水期则优于丰水期,以降轨枯水期指标值为最优:平均偏差、均方根误差、标准差分别为−0.082、0.107和0.076 m。以2016—2017年、2017—2018年、2016—2018年卫星测高水位与实测数据的平均偏差作为校准参数,校准水位的平均绝对偏差都为0.073 m,皮尔逊相关系数为1。研究验证了卫星测高数据计算和校准河湖水位方法的有效性,该类数据可应用于水文、气候变化研究与洪旱监测等。

大湖演算模型在裕溪河流域的适用性分析

为探究大湖演算模型在裕溪河流域是否适用,采用大湖模型和误差自回归模型,对2020年汛期裕溪河闸闸上水位一次涨水过程进行模拟研究,发现大湖模型对该流域的洪峰模拟精度较高,对水位的整体涨落过程预测较好,经过实时误差修正后,模型精度进一步得到提升。结果表明,大湖模型在裕溪河流域有一定的适用性,可为裕溪河流域今后防洪调度预报工作提供参考。

基于MODIS的鄱阳湖区水位遥感估算研究

以鄱阳湖区为研究对象,利用MODIS数据对湖区水位进行了遥感估算研究。

鄱阳湖流域水沙变化及出湖水沙模拟研究

自20世纪50年代以来,鄱阳湖流域气候发生显著变化,人类活动日益频繁,降水、产流能力和产沙能力都发生了明显变化。基于鄱阳湖流域“五河”入湖控制站以及湖口水文站数据,运用Mann-Kendall检验法和双累积曲线法确定了年输沙量突变时间点,再利用累积量斜率变化分析法量化降水、产流能力和产沙能力对鄱阳湖入湖沙量的影响;在此基础上,提出了变分模态分解、LSTM神经网络和完全逐步抽样技术等多方法耦合的水沙模拟模型及其评价方法,并建立了研究区域鄱阳湖湖口站水沙模拟模型。研究结果表明:不论是“五河”入湖沙量变化,还是湖区泥沙淤积量变化,以降水变化为代表的气候变化因素对其影响较小,主要影响还是来自人类活动因素;但在具体的变化规律上却存在差异,人类活动对入湖沙量的贡献率呈上升趋势,但对同期鄱阳湖湖区淤积沙量的影响贡献率则呈现先降后升的趋势。水沙模拟分析表明,湖口站出湖月径流量、出湖月输沙量的模拟过程与实测过程较为吻合,取得了较高模拟精度,湖口、星子站水位对模拟精度的提升贡献较小。

T-S模糊模型在锅炉汽包水位建模中的应用

对实际对象进行数学建模来加以分析和处理是非常重要的,电厂锅炉汽包水位控制系统是火力发电中的一个重要组成部分,维持锅炉汽包水位在一定的范围内是机组安全运行的主要条件。本文将T-S模糊神经网络模型应用到锅炉汽包水位对象的数学建模中,通过对模型的参数学习,得到锅炉汽包水位的仿真模型。

Potential influence of water level changes on energy flows in a lake food web

Large seasonal water-level fluctuations may influence isotopic signatures of primary producers and the types and amounts of these potential food sources accessible to aquatic fauna of Poyang Lake,the largest freshwater lake in China.In this study,the isotopic signatures of primary producers and consumers were determined,stable carbon and nitrogen isotope analysis and mixing models were combined to investigate the influence of water levels on the diet and isotopic composition of Poyang Lake fish and invertebrates.Five potential food sources (seston,benthic organic matter,aquatic macrophytes,attached algae,and terrestrial plants),4 species of invertebrates,and 10 species of fish were collected from the lake area during dry and wet seasons between January 2009 and April 2010.The δ 13C values of invertebrates and most fish were within the range of δ 13C values of the potential food sources for both seasons.The δ 13C values of invertebrates and most fish were lower in the dry season than in the wet season,whereas the δ 15N values exhibited different patterns for different species.Mixing models indicated that the most important food sources for common lake fauna were seston in the dry season and aquatic macrophytes and terrestrial plants in the wet season.The fauna were more omnivorous in the wet season than in the dry season.The food web dynamics of Poyang Lake are strongly influenced by changes in the abundance and accessibility of different basal food sources that occur because of seasonal flood pulses.The trophic links within the aquatic communities of Poyang Lake are modified by water-level fluctuations.

基于WASP模型的水质模拟研究——以鄱阳湖南矶山断面为例

WASP是美国环保局推荐使用的水质预测软件。为分析南昌市水体达标方案工程项目实施后对鄱阳湖南矶山断面水质改善效果,采用WASP水质分析模拟程序对鄱阳湖南矶山断面达标年(2020年)的水质进行分析,并进行水质目标可达性分析。

Impact of continuous low water stage on the breeding environment of Oncomelania hupensis: a case study of Poyang Lake area in China

Background Oncomelania hupensis is the only intermediate host of Schistosoma japonicum and plays a decisive role in its transmission.The variation of water level greatly affects the reproduction and growth of snails.Therefore,in this paper,we analyze the variations of water level in the Poyang Lake region from 1993 to 2016 combined with satellite imagery to elucidate the evolution of the snail breeding environment.Methods By employing remote sensing data from 1993 to 2016(April–June and September–November),the vegetation area of Poyang Lake and the vegetation area at different elevations were extracted and calculated.Moreover,the average daily water level data from the four hydrological stations(Hukou station,Xingzi station,Tangyin station and Kangshan station)which represent the typical state of Poyang Lake were collected from 1993 to 2016.The variance of the monthly mean water level,inundation time and the average area were analyzed by variance to find a significance level ofα=0.05.Results According to hydrological data before and after 2003,the average water level after 2003 is significantly lower than that before 2003 in Poyang Lake.After 2003,the time of inundateing the snail breeding period was later in April to June than that before 2003,while the time of wate-falling stage in September to November moved forward after 2003 than before 2003.Of them,the lowest water level affecting the breeding and growing period of O.hupensis in the northern part of Poyang Lake decreased from 11 m to 9 m.After 2003,the expansion of meadow area in the north part of Poyang Lake was mainly concentrated in the elevation of 9–11 m,and the newly increased infested-meadow in the lake area was mainly concentrated in the north part of Poyang Lake.Conclusions By comparing the change of water level characteristics in different parts of the Poyang Lake area as well as changes in meadow area before and after 2003,it is found that the water level changes mainly affect the snail breeding area in the northern part of Poyang Lake.The results are helpful for improving scientific measures for snail control in Jiangxi Province.This approach could also be applicible to Dongting Lake area and other lake areas affected by water level changes and can bring significant guidance for snail control in lake areas.

鄱阳湖水位对沉积物磷释放的影响及总磷考核建议

为探讨干湿交替对湖泊沉积物内源磷释放的影响,结合基础资料和模拟试验,研究了鄱阳湖水位波动及其驱动下沉积物中磷的释放过程,并对湖区总磷(TP)考核提出建议。结果表明:2020~2022年鄱阳湖星子站水位高幅波动,最高水位差分别为15.01,11.42 m和12.69 m,导致水面面积也呈现高度动态性,最低水位时的裸露面积分别达到3433.92,3442.40 km^(2)和3618.36 km^(2),大面积沉积物会经历干湿交替过程;沉积物磷释放模拟试验结果显示,南矶山和青岚湖断面沉积物经历裸露-暴晒-淹水后,淹水初期沉积物TP的平均释放通量分别高达16.67 mg/(m^(2)·d)和13.23 mg/(m^(2)·d);综合考虑鄱阳湖水体中TP组成特征和水位波动的影响,建议湖区国控断面以活性磷酸盐(SRP)或者溶解性总磷(TDP)替代TP作为磷考核指标,并动态调整磷考核标准的阈值,当星子站水位低于11.00 m时以河流标准考核。