鄱阳湖湖口、外洲、梅港三站水沙变化及趋势分析(1955-2001年)

对鄱阳湖流域三个主要控制站湖口、外洲和梅港多年(1955-2001年)水沙数据进行了统计分析,利用滑动平均法,Spearman秩次相关检验、线性回归检验方法对三个测站的水沙变化趋势进行了分析检验,结果表明,鄱阳湖泥沙出湖集中于长江大汛前的2-6月,在长江7-9月大汛期间,会出现长江泥沙倒灌鄱阳湖的情况．湖口站近期(1990-2001年)径流量和输沙量变幅都非常大,同上世纪80年代相比,年均径流量增加255．3×10~8 m~3．年均减少沙量0．29×10~8 t;外洲站近期的输沙量明显减少,沙量分别为70年代前、70年代、80年代的49．6%、48．7%和52．3%;梅港站径流量略微增加沙量无明显变化趋势．从入湖径流来看,赣江和信江占52．4%,入湖泥沙量占了76．0%以上．从赣江和信江水沙总体变化趋势来看,赣江径流量变化趋势不明显,而输沙量具有明显减少的趋势;信江径流量增加趋势明显,输沙量基本无明显趋势．鄱阳湖流域水沙变化主要受人类活动的影响．土地利用方式的改变和流域水利工程设施的修建极大地影响了流域水沙特征及其变化趋势．     

湖北长湖富营养化状况及时空变化(2012-2013年)

为评估长湖水体富营养化程度,2012-2013年分4个季度对全湖区20个采样点的物理、化学和生物要素进行监测,在评价水质现状的基础上采用综合营养状况指数法和浮游植物细胞丰度指数法综合评价水体营养状况,并应用典型相关分析(CCA)方法揭示水体富营养化状况与湖泊理化要素之间的典型相关性.结果显示:4个季节长湖全湖区的水质均处于地表水IV类~劣V类水标准;综合营养状态指数值在49.54~82.55之间,浮游植物细胞丰度在2.88×106~61.73×106cells/L之间,均显示其处于富营养化状态;长湖富营养化状况的分布呈现一定的时空差异性;CCA分析显示,长湖理化要素变量可解释68.6%的水体富营养化状况变量的变异,影响其富营养化状况的主要理化因素有水体总磷、总氮、溶解氧、亚硝态氮、硝态氮浓度,水深和沉积物总磷、总氮含量.长湖水体富营养化主要是由于外源的磷污染,其次是氮污染,富营养化最严重的夏、秋季浮游植物的生长主要受氮营养限制,而冬、春季则部分受磷营养限制,部分属于过渡类型.因此,建议大力削减围网/围栏养殖量,同时考虑结合水生植物栽种等生态工程建设措施以降低长湖水体发生严重富营养化的风险,并进一步改善长湖的水质现状.     

鄱阳湖入湖、出湖污染物通量时空变化及影响因素(2008-2012年)

研究鄱阳湖入、出湖污染物通量是加强鄱阳湖及长江水功能区限制纳污红线管理的前提,是建立鄱阳湖水质预测模型的基础.基于2008-2012年鄱阳湖8条主要入湖河流、出湖口的逐月水量、水质同步监测资料,根据污染源特征优选算法,计算总磷(TP)、氨氮(NH3-N)、高锰酸盐指数(CODMn)的入、出湖污染物通量,并分析时空变化特征及影响因素.结果表明:(1)出湖口和乐安河入湖口断面的NH3-N、TP及昌江入湖口断面的TP,以点源污染为主,采用每月瞬时通量作为月平均通量的算法更准确;其余以非点源污染为主,采用瞬时污染物浓度与月平均流量之积来计算月平均通量更准确.(2)2008-2012年CODMn、NH3-N和TP年平均人湖通量分别为304398、53063和9175 t,年平均出湖通量分别为367436、45814和8452t.8条入湖河流每年的入湖水量、CODMn通量和个别年份的NH3-N、TP通量小于出湖,这主要是因为未计算区间产流及相应排污和采砂引起的内源污染.(3)入、出湖污染物通量在年际间主要受水量影响而呈现W型波动变化趋势,CODMn、NH3-N、TP入湖通量及CODMn出湖通量均集中在汛期,NH3-N、TP出湖通量则是冬季较多(低水位下湿地植被净化作用受限).入湖TP、NH3-N、CODMn通量主要来自赣江、信江、乐安河,而NH3-N、TP浓度最高的是乐安河、信江.     

洪泽湖出入河流及湖体氮、磷浓度时空变化(2010—2019年)

基于2010-2019年洪泽湖湖体水质逐月监测数据,筛选出影响湖体水质的主要污染物指标为总氮（TN）和总磷（TP）;选取洪泽湖周边25条主要入湖河流和2条出湖河流在2019年10月2020年9月的监测数据,探讨河流外源性输入对不同湖体区域氮磷的影响及其水期变化规律.结果发现：①湖体TN、TP浓度长期居高不下,年均浓度范围分别在1.39~1.86、0.080~0.171 mg/L波动.主要入湖河流TN、TP时空平均浓度（1.92~5.70和0.114~0.181 mg/L）,均高于同区域湖体（1.15~1.46和0.088~0.101 mg/L）,其中北部入湖河流肖河、马化河和五河与临近湖区TN、TP浓度呈现显著正相关,是影响北部湖体TN、TP浓度的主要河流;南部入湖河流维桥河和高桥河是临近湖区非极端降雨期TN、TP的主要来源.②调水工程对湖体及入湖河流TN、TP浓度分布影响显著,调水期湖体沿调水方向TP浓度逐渐上升,TN浓度则呈现先降后升的趋势,南部入湖河流维桥河和高桥河TN浓度达到水期峰值,分别为10.69和9.90 mg/L.③极端降雨期入湖河流的TN、TP浓度显著高于其它水期,由于湖体对TN、TP的富集作用不同,TP浓度呈现中间高,四周低,而TN浓度呈现沿洪水流向逐渐降低的规律.     

Nonstationarity-based evaluation of flood risk in the Pearl River basin: changing patterns,causes and implications

Nonstationary GEV-CDN models considering time as a covariate are built for evaluating the flood risk and failure risk of the major flood-control infrastructure in the Pearl River basin, China. The results indicate: (1) increasing peak flood flow is observed in the mainstream of the West River and North River basins and decreasing peak flood flow is observed in the East River basin; in particular, increasing peak flood flow is detected in the mainstream of the lower Pearl River basin and also in the Pearl River Delta region, the most densely populated region of the Pearl River basin; (2) differences in return periods analysed under stationarity and nonstationarity assumptions are found mainly for floods with return periods longer than 50 years; and (3) the failure risks of flood-control infrastructure based on failure risk analysis are higher under the nonstationarity assumption than under the stationarity assumption. The flood-control infrastructure is at higher risk of flood and failure under the influence of climate change and human activities in the middle and lower parts of Pearl River basin.

EDITOR D. Koutsoyiannis

ASSOCIATE EDITOR G. Thirel     

Flood frequency under the influence of trends in the Pearl River basin,China: changing patterns,causes and implications

Using a nonstationary flood frequency model, this study investigates the impact of trends on the estimation of flood frequencies and flood magnification factors. Analysis of annual peak streamflow data from 28 hydrological stations across the Pearl River basin, China, shows that: (1) northeast parts of the West and the North River basins are dominated by increasing annual peak streamflow, whereas decreasing trends of annual peak streamflow are prevailing in other regions of the Pearl River basin; (2) trends significantly impact the estimation of flood frequencies. The changing frequency of the same flood magnitude is related to the changing magnitude or significance/insignificance of trends, larger increasing frequency can be detected for stations with significant increasing trends of annual peak streamflow and vice versa, and smaller increasing magnitude for stations with not significant increasing annual peak streamflow, pointing to the critical impact of trends on estimation of flood frequencies; (3) larger‐than‐1 flood magnification factors are observed mainly in the northeast parts of the West River basin and in the North River basin, implying magnifying flood processes in these regions and a higher flood risk in comparison with design flood‐control standards; and (4) changes in hydrological extremes result from the integrated influence of human activities and climate change. Generally, magnifying flood regimes in the northeast Pearl River basin and in the North River basin are mainly the result of intensifying precipitation regime; smaller‐than‐1 flood magnification factors along the mainstream of the West River basin and also in the East River basin are the result of hydrological regulations of water reservoirs. Copyright © 2014 John Wiley & Sons, Ltd.     

近50a淮河流域汛期降水日数和强度的分布与变化特征

选用1961-2010年淮河流域145个地面气象站的观测资料,分析淮河流域汛期(5-9月)降水的时空变化规律.结果表明:淮河流域汛期降水的空间分布不仅受到地理位置和地形的影响,而且与湿度和风速的空间分布具有较好的相关性;在时间变化上,雨日出现频率有下降的趋势,但暴雨日比重和暴雨日平均降水量均有升高的趋势.淮河流域汛期暴雨日出现频率以及各类型雨日的平均降水量均有上升的趋势,强降水时空变化呈现局地性和频发性.     

珠江流域西江支流贺江水体硅藻群落结构、分布和评估

综合运用TWINSPAN数量分类和DCA排序方法评估了贺江流域硅藻群落,结合硅藻生物指数(IBD)、硅藻属指数(IDG)、硅藻营养化指数(TDI)和特定污染敏感指数(IPS)对其结果进行进一步验证.结果显示,TWINSPAN将贺江流域的38个样点分为4组,且群落Ⅰ到群落Ⅳ其生境质量逐渐变得单一,人为干扰程度逐渐加大;划分的四组群落在DCA排序图上有明显的界限,依据Van Dam硅藻生态指示意义,水环境污染程度从群落Ⅰ到群落Ⅳ逐渐加剧,有争议的样点7、8和24在DCA排序图上也倾向于群落Ⅲ.4种硅藻指数都是显著相关的,但IBD、IPS、IDG在硅藻群落的箱型图中明显呈现出合理的趋势.以上研究表明,划分的硅藻群落较好地反映了贺江流域的生态质量,IBD、IPS、IDG适合于贺江流域生物监测与评价.     

Variability of water levels and impacts of streamflow changes and human activity within the Pearl River Delta,China

Abstract

The Pearl River Delta (PRD) is a complicated criss-cross river network. The booming economy and intensifying human activity have greatly altered the natural water levels, which threatens regional sustainable development. The Mann-Kendall trend test and the kriging interpolation method were used to detect the spatial and temporal patterns in the trends of extreme high/low water levels related to different magnitudes of streamflow, in order to explore the impacts of hydrological processes on the water-level changes throughout the PRD. The results indicate that: (a) streamflow changes at the Sanshui and Makou stations exhibit different characteristics. No significant trend can be identified in the streamflow changes at Makou station; however, the streamflow at Sanshui station shows a significant increasing trend, especially in low-flow periods. The decreasing Makou/Sanshui streamflow ratio exerts tremendous impacts on the water-level changes in the hinterland of the PRD region. (b) Extreme high/low water levels exhibit similar changing patterns. The extreme high/low water levels in the high/normal flow periods are decreasing in both the upper PRD and the hinterland of the PRD region. Increasing extreme high/low water levels in low-flow periods can be identified in the hinterland of the PRD region. The coastal regions are characterized by increasing extreme high/low water levels. (c) Extreme high/low water levels for high/normal flow periods in the hinterland of the PRD are heavily impacted by topographic changes due to in-channel dredging. Increasing extreme high/low water levels along the coastal regions are mainly backwater effects caused by serious siltation and rising sea level. This study has scientific and practical merits in regional fluvial management and mitigation of natural hazards.

Citation Zhang, Q., Xu, C.-Y. & Chen, Y. D. (2010) Variability of water levels and impacts from streamflow changes and human activity within the Pearl River Delta, China. Hydrol. Sci. J. 55(4), 512–525.     

Temporal trends of hydro‐climatic variables and runoff response to climatic variability and vegetation changes in the Yiluo River basin,China

The Yiluo River is the largest tributary for the middle and lower reaches of the Yellow River below Sanmenxia Dam. Changes of the hydrological processes in the Yiluo River basin, influenced by the climatic variability and human activities, can directly affect ecological integrity in the lower reach of the Yellow River. Understanding the impact of the climatic variability and human activities on the hydrological processes in the Yiluo River basin is especially important to maintain the ecosystem integrity and sustain the society development in the lower reach of the Yellow River basin. In this study, the temporal trends of annual precipitation, air temperature, reference evapotranspiration (ET₀) and runoff during 1961–2000 in the Yiluo River basin were explored by the Mann‐Kendall method (M‐K method), Yamamoto method and linear fitted model. The impacts of the climatic variability and vegetation changes on the annual runoff were discussed by the empirical model and simple water balance model and their contribution to change of annual runoff have been estimated. Results indicated that (i) significant upwards trend for air temperature and significant downwards trend both for precipitation and ET₀ were detected by the M‐K method at 95% confidence level. And the consistent trends were obtained by the linear fitted model; (ii) the abrupt change started from 1987 detected by the M‐K method and Yamamoto method, and so the annual runoff during 1961–2000 was divided into two periods: baseline period (1961–1986) and changeable period (1987–2000); and (iii) the vegetation changes were the main cause for change of annual runoff from baseline period to changeable period, and climatic variability contributed a little to the change of annual runoff of the Yiluo River. Copyright © 2009 John Wiley & Sons, Ltd.     

珠江流域东江干流浮游植物叶绿素a时空分布及与环境因子的关系

为了解珠江流域东江干流水体叶绿素a的时空分布及与环境因子的关系,于2012年6月(丰水期)和12月(枯水期)对东江干流进行采样调查分析.结果表明,东江水体叶绿素a含量具有明显的时空分布特征,其全年变化范围为0.84~14.93μg/L,整体均值为3.60±2.45μg/L,丰水期叶绿素a含量显著高于枯水期;而丰、枯水期叶绿素a含量空间分布特征相似,上游河段显著低于下游河段.相关性与主成分分析结果显示,水体中总氮浓度、总磷浓度、有机物含量、水温和水流流速等都是影响东江浮游植物生长的重要因素,其中以总磷的影响最为显著,表明磷可能是东江浮游植物生长的限制因子.     

Floodplain stratigraphy of the ice jam dominated middle Yukon River: a new approach to long‐term flood frequency

Floodplain stratigraphy is used as a new method for reconstructing ice jam flood histories of northern rivers. The method, based on reconstruction of the sedimentary record of vertically‐accreting floodplains, relies on stratigraphic logging and interpretation of floodplain sediments, which result from successive ice jam floods, and radiocarbon dating of inter‐flood organic material for chronology. In a case study along a reach of the Yukon River that straddles the Yukon–Alaska border, the method is used to develop a record of ice jam flooding for the last 2000 years. Detailed chronostratigraphic logs from three sites along the Yukon River indicates that the long‐term recurrence interval varies depending on location, but ranges from approximately once in 25 years to once in 38 years (or a probability of ca 3–4% in any given year). This is broadly similar to the 4·5% probability of recurrence calculated from archival and gauged data at Dawson City, Yukon Territory, for the period 1898–2006. Two of the three study locations, with sufficient chronology, suggest a decrease in flood frequency in the last several hundred years relative to the preceding period at each site, broadly corresponding to the Little Ice Age, suggesting climate exerts some control over long‐term ice jam flood frequency. This study demonstrates that the floodplain sedimentary record offers the potential to extend records of ice jam flooding in remote, ungauged northern rivers and provides a broader temporal context for assessing the frequency and variability of ice jam flooding. Copyright © 2008 John Wiley & Sons, Ltd.     

Abrupt changes in the discharge and sediment load of the Pearl River,China

The abrupt changes in the streamflow and sediment load at nine hydrological stations of the Pearl River basin were systematically analysed by using the simple two‐phase linear regression scheme and the coherency analysis technique. Possible underlying causes were also discussed. Our study results indicated that abrupt changes in the streamflow occurred mainly in the early 1990s. The change points were followed by significant decreasing streamflow. Multiscale abrupt behaviour of the sediment load classified the hydrological stations into two groups: (1) Xiaolongtan, Nanning and Liuzhou; and (2) Qianjiang, Dahuangjiangkou, Wuzhou, Gaoyao, Shijiao and Boluo. The grouped categories implied obvious influences of water reservoirs on the hydrological processes of the Pearl River. On the basis of analysis of the locations and the construction time of the water reservoirs, and also the time when the change points occurred, we figured out different ways the water reservoirs impacted the hydrological processes within the Pearl River basin. As for the hydrological variation along the mainstream of the Pearl River, the water reservoirs have considerable influences on both the streamflow and sediment load variations; however, more influences seemed to be exerted on the sediment load transport. In the North River, the hydrological processes seemed to be influenced mainly by climate changes. In the East River, the hydrological variations tended to be impacted by the water reservoirs. The study results also indicated no fixed modes when we address the influences of water reservoirs on hydrological processes. Drainage area and regulation behaviour of the water reservoirs should be taken into account. The results of this study will be of considerable importance for the effective water resources management of the Pearl River basin under the changing environment. Copyright © 2011 John Wiley & Sons, Ltd.     

Projection of extreme flood inundation in the Mekong River basin under 4K increasing scenario using large ensemble climate data

Projecting changes in the frequency and intensity of future precipitation and flooding is critical for the development of social infrastructure under climate change. The Mekong River is among the world's large-scale rivers severely affected by climate change. This study aims to define the duration of precipitation contributing to peak floods based on its correlation with peak discharge and inundation volume in the Lower Mekong Basin (LMB). We assessed the changes in precipitation and flood frequency using a large ensemble Database for Policy Decision-Making for Future Climate Change (d4PDF). River discharge in the Mekong River Basin (MRB) and flood inundation in the LMB were simulated by a coupled rainfall-runoff and inundation (RRI) model. Results indicated that 90-day precipitation counting backward from the day of peak flooding had the highest correlation with peak discharge (R² = .81) and inundation volume (R² = .81). The ensemble mean of present simulation of d4PDF (1951–2010) showed good agreement with observed extreme flood events in the LMB. The probability density of 90-day precipitation shifted from the present to future climate experiments with a large variation of mean (from 777 to 900 mm) and SD (from 57 to 96 mm). Different patterns of sea surface temperature significantly influence the variation of precipitation and flood inundation in the LMB in the future (2051–2110). Extreme flood events (50-year, 100-year, and 1,000-year return periods) showed increases in discharge, inundation area, and inundation volume by 25%–40%, 19%–36%, and 23%–37%, respectively.