Temporal Variations of Water Discharge and Sediment Load of Huanghe River,China

Based on the data from gauging stations, the changes in water discharge and sediment load of the Huanghe （Yellow） River were analyzed by using the empirical mode decomposition （EMD） method. The results show that the periodic oscillation of water discharge and sediment load of the Huanghe River occurs at the interannual, decadal, and multi-decadal scales, caused by the periodic oscillations of precipitation, and E1 Nifio/Southern Oscillation （ENSO） af- fects water discharge by influencing precipitation distribution and contributes to periodic varations in precipitation and water discharge at interannual timescale. The water discharge and sediment load of the Huanghe River have decreased since the 1960s under the influence of precipitation and huamn activities, and human activities attribute more than precipitation to the reduction in the water discharge and sediment load, furthermore, water abstraction and water-soil conservation practices are the main causes of the decrease in water discharge and sediment load, respectively. The reduction in sediment load has directly impacted on the lower reaches of the Huanghe River and the river delta, causing considerable erosion of the river channel in the lower reaches since the 1970s along with River Delta changing siltation into erosion around 2000.

Response of delta sedimentary system to variation of water and sediment in the Yellow River over past six decades

In order to find out the variation process of water-sediment and its effect on the Yellow River Delta, the water discharge and sediment load at Lijin from 1950 to 2007 and the decrease of water discharge and sediment load in the Yellow River Basin caused by human disturbances were analyzed by means of statistics. It was shown that the water discharge and sediment load into the sea were decreasing from 1950 to 2007 with serious fluctuation. The human activities were the main cause for decrease of water discharge and sediment load into the sea. From 1950 to 2005, the average annual reduction of water discharge and sediment load by means of water-soil conservation practices were 2.02×10^9 m^3 and 3.41×10^8 t respectively, and the average annual volume by water abstraction for industry and agriculture were 2.52×10^10 m^3 and 2.42×10^8 t respectively. The average sediment trapped by Sanmenxia Reservoir was 1.45×10^8 t from 1960 to 2007, and the average sediment retention of Xiaolangdi Reservoir was 2.398×10^8t from 1997 to 2007. Compared to the data records at Huanyuankou, the water discharge and sediment load into the sea decreased with siltation in the lower reaches and increased with scouring in the lower reaches. The coastline near river mouth extended and the delta area increased when the ratio of accumulative sediment load and accumulative water discharge into the sea （SSCT） is 25.4-26.0 kg/m^3 in different time periods. However, the sharp decrease of water discharge and sediment load into the sea in recent years, especially the Yellow River into the sea at Qing 8, the entire Yellow River Delta has turned into erosion from siltation, and the time for a reversal of the state was about 1997.

Sediment Load of Asian Rivers flowing into the Oceans and their Regional Variation

Study of the major Asian rivers discharge to the ocean reveals variations of their water discharges and sediment loads, and local characteristics of river sediment concentrations. On the basis of this, the Asian rivers fall into three regions, including Eurasia Arctic, East Asia, Southeast and South Asia Regions. The Eurasia Arctic Region is characterized by the lowest sediment concentration and load, while the East Asia Region is of the highest sediment concentration and higher sediment load, and the South-East and South Asia Region yields higher sediment concentration and highest sediment load.The sediment loads of these regions are mainly controlled by climate, geomorphology and tectonic activity. The Eurasia Arctic rivers with large basin areas and water discharge, drain low relief which consists of tundra sediment, thus causing the lowest sediment load. The East Asia rivers with small basin areas and lowest water discharges, drain extensive loess plateau, and transport most erodible loess material, which results in highest sediment concentration. The SE and South Asia rivers originating from the Tibet Plateau have large basin areas and the largest water discharges because of the Summer Monsoon and high rainfall influence, causing the highest sediment load.In Asia, tectonic motion of the Tibet Plateau plays an important role. Those large rivers originating from the Tibet Plateau transport about 50% of the world river sediment load to ocean annually, forming large estuaries and deltas, and consequently exerting a great influence on sedimentation in the coastal zone and shelves.

Temporal variability of water discharge and sediment load of the Yellow River into the sea during 1950-2008

Based on hydrological data observed at Lijin gauging station from 1950 to 2008, the temporal changes of water discharge and sediment load of the Yellow River into the sea were analyzed by the wavelet analysis, and their impacts on the estuary were investigated in different periods based on the measured coastline and bathymetry data. The results show that： （1） there were three significant periodicities, i.e. annual （0.5-1.0-year）, inter-annual （3.0-6.5-year） and decadal （10.1-14.2-year）, in the variations of water discharge and sediment load into the sea, which might be related to the periodic variations of El Nino and Southern Oscillation at long-term timescales. Variations of water discharge and sediment load were varying in various timescales, and their periodic variations were not significant during the 1970s-2000s due to strong human disturbances. （2） The long-term variation of water discharge and sediment load into the sea has shown a stepwise decrease since the 1950s due to the combined influences of human activities and precipitation decrease in the Yellow River Basin, and the human activities were the main cause for the decrease of water discharge and sediment load. （3） The water discharge and sediment load into the sea greatly influenced the evolution of the Yellow River Estuary, especially the stretch rate of coastline and the deposition rate of the sub-aqueous topography off the estuary which deposited since 1976.

Multi-scale variability of water discharge and sediment load into the Bohai Sea from 1950 to 2011

This paper examines the changes in the time series of water discharge and sediment load of the Yellow River into the Bohai Sea. To determine the characteristics of abrupt changes and multi-scale periods of water discharge and sediment load, data from Lijin station were analyzed, and the resonance periods were then calculated. The Mann-Kendall test, order clustering, power-spectrum, and wavelet analysis were used to observe water discharge and sediment load into the sea over the last 62 years. The most significant abrupt change in water discharge into the sea occurred in 1985, and an abrupt change in sediment load happened in the same year. Significant decreases of 64.6% and 73.8% were observed in water discharge and sediment load, respectively, before 1985. More significant abrupt changes in water discharge and sediment load were observed in 1968 and 1996. The characteristics of water discharge and sediment load into the Bohai Sea show periodic oscillation at inter-annual and decadal scales. The main periods of water discharge are 9.14 years and 3.05 years, whereas the main periods of sediment load are 10.67 years, 4.27 years, and 2.78 years. The significant resonance periods between water discharge and sediment load are observed at the following temporal scales： 2.86 years, 4.44 years, and 13.33 years. Water discharge and sediment load started to decrease after 1970 and has decreased significantly since 1985 for several reasons. Firstly, the precipitation of the Yellow River drainage area has reduced since 1970. Secondly, large-scale human activities, such as the building of reservoirs and floodgates, have increased. Thirdly, water and soil conservation have taken effect since 1985.

Regional variation of sediment load of Asian rivers flowing into the ocean

Study of Asian major rivers discharge to the ocean reveals variations of their water discharges and sediment loads, and local characteristic of river sediment concentrations. On the basis of this, the Asian rivers can be divided into three regions: Eurasia Arctic, East Asia, Southeast and South Asia Region. The Eurasia Arctic Region is characteristic of the lowest sediment concentration and load, while the East Asia Region is of the highest sediment concentration and higher sediment load, and the Southeast and South Asia Region yields higher sediment concentration and highest sediment load.The sediment loads of these regions are mainly controlled by climate, geomorphology and tectonic activity. The Eurasia Arctic rivers have large basin areas and water discharge, drain low relief which consist of tundra sediment, thus causing the lowest sediment load. The East Asia rivers have small basin areas and lowest water discharges, drain extensive loess plateau, and transport most erodible loess material, which results in highest sediment concentration. The Southeast and South Asia rivers originating from the Tibetan Plateau have large basin areas and the largest water discharges because of the summer monsoon and high rainfall influence, causing the highest sediment load.In Asia, the tectonic motion of the Tibetan Plateau plays an important role. Those large rivers originating from the Tibetan Plateau transport about 50% of the world river sediment load to the ocean annually, forming large estuaries and deltas, consequently exerting a great influence on sedimentation in coastal zones and shelves.

长江上游水沙变化对三峡水库泥沙淤积的影响

1956-2015年通过宜昌站的径流量变化不大,输沙量却大幅减少至2003-2015年的43 mt/a,同期三峡水库拦沙率为75.8%。长江上游大型水库拦沙使三峡入库泥沙锐减,尤其是向家坝和溪洛渡水库运行后,2013-2015年的年均入库泥沙量较2003-2012年减少了64.8%,至71.4 mt/a,向家坝站年均输沙仅占入库总量的2.2%。三峡库区泥沙淤积呈不连续片状分布,主要分布在宽谷和弯道河段(D50<0.01 mm),且呈沿程细化,水库细沙淤积速度减缓但淤积率并未降低,细沙发生了絮凝沉积。

1956-2010年三江源区水土流失状况演变

为研究三江源区水土流失状况变化及其可能成因,基于1956—2010年三江源区水文、气象观测资料以及遥感数据,借助Mann-Kendall趋势检验法分析了输沙量的年际变化,并采用双累积曲线、RUSLE(修正的通用土壤流失方程)分析了水土流失状况变化的可能成因.结果表明:1三江源区输沙量表现为黄河源区>长江源区>澜沧江源区,输沙量最大值均出现在6—8月,最小值均出现在12月—翌年1月.2各流域输沙量的年际变化较大,并且均以20世纪80年代为最大.2005—2010年黄河源区输沙量较多年平均值减少32.25%,而长江源区和澜沧江源区分别相应增加24.76%和41.86%.黄河源区土壤水蚀量增加明显,长江源区不同河段各有增减,澜沧江源区土壤水蚀强度降低.3引起水土流失状况变化的原因主要包括气候变化和生态工程两个方面.即1降雨量的增加导致降雨侵蚀力和径流量增加,使得土壤水蚀量和河流输沙量有所增加;2生态工程实施后,土壤中w(有机质)虽有所增加,但仍明显低于1980年的水平.尽管植被覆盖度有所提高,但对水土保持功能起重要作用的根系层恢复却较为缓慢,因此,土壤保持功能基本上未得到提高.

近50年来浙江入海河流水沙通量变化过程

基于1961—2012年浙江主要入海河流年径流量和输沙量的时间序列资料，结合流域降水量和相关人类活动，通过数理统计，阐述了河流入海水沙通量的多尺度变化过程。结果表明：1961—2012年浙江入海河流径流量基于多年平均值上下波动、无明显趋势性变化，降水量的波动是径流量年际变化的主要影响因素。近50年来，河流的输沙量年际波动比较剧烈，整体呈减少的态势。径流模数和输沙模数双累积拟合陆线表明，输沙量存在2—5个不等的时间尺度变化特征，各阶段输沙量明显减少与人类活动关系密切，流域的水土保持、水利枢纽兴建、人为采砂等活动改变了河流的水沙过程。

气候变化和人类活动对长江径流泥沙的影响研究

采用长江干流寸滩、宜昌、汉口和大通四个控制站的径流量和输沙量资料,应用Mann-Kendall检验、滑动t检验和有序聚类检验等方法,分析水沙变化趋势及突变特征,运用气候弹性系数法以及累积量斜率变化率法,定量分解气候变化与人类活动对径流泥沙的影响。结果表明:近60年来长江干流径流量年际变化相对平稳,而输沙量年际变化剧烈,四个站的年输沙量均呈现显著减少趋势,大多数站点的年径流量和年输沙量在1968年前后和21世纪初期发生了突变。变异Ⅰ期为1969-2002年,人类活动对四个站的径流量和输沙量变化的贡献率分别为31.98%~70.04%和75.40%~95.33%。变异Ⅱ期为2003-2015年,人类活动引起四个站的径流量和输沙量变化的贡献率分别为59.75%~80.04%和91.94%~99.17%,显示人类活动的作用强度增大。

黄河口冲淤演变及治理研究综述

综述了黄河口来水来沙条件的变异特点、河口演变的大小循环、河口改道后的滞后响应特征及近期河口冲淤演变的新特点,总结了以往关于黄河口演变对下游河道的影响、河口冲淤的临界水沙条件、未来河口水沙条件及河口生态等方面的研究成果。以往多数研究认为河口延伸引起的溯源淤积可影响到下游艾山或泺口河段,而对艾山以上河道是否受溯源淤积的影响争议较大,仍需深入研究不同时间尺度黄河口演变对下游河道的影响;以往研究认为维持黄河口造陆与侵蚀平衡的临界来沙量为2.74亿~4.21亿t/a,维持清水沟冲淤平衡的临界来沙量约为1.5亿t/a,后续研究需从径流、潮汐、海洋、海岸和河口河道边界条件等各因素相互作用的物理机理出发,建立统一的临界水沙量的计算方法。此外,需深入开展自然和人为因素影响下黄河口未来水沙通量的预测研究及河口生态响应研究。

近50年来黄河入海水沙的多时间尺度特性分析

基于黄河入海水沙对黄河三角洲及其生态系统平衡的重要性,研究从实时性、全面性地掌握黄河入海水沙序列演变规律的角度出发,以黄河入海口的控制测站—利津站1964年以来的实测径流量、输沙量和水沙系数为研究对象,以Matlab为软件平台,以复值Morlet连续小波变换为研究方法,开展近50a以来的黄河入海水沙序列的多时间尺度特征分析,并应用小波方差对研究结果进行了检验。研究发现,1964—2012年黄河入海水沙序列都存在明显的多时间尺度特性,且以年均水沙系数的多时间尺度特性最强,其次为年径流,最后是年输沙。黄河入海年均水沙系数以年代际周期振荡为主,且具有全域性,以33a为尺度中心的是主周期振荡,以18a为尺度中心的是次周期;黄河入海年径流和年输沙亦以具有全域性的年代际周期振荡最强,前者以大于45a的年代际周期振荡最强,后者以大于36a的年代际周期振荡最强;以4a为尺度中心的年际周期振荡都表现出局域范围内振荡能量最强的特征,但都仅限于1970s前期。在大的丰水期和高含沙量期的主控下,黄河河道以低于次饱和状态的冲刷作用为主,且未来这种趋势将会进一步加强。

2006年特大枯水期间长江中下游河床沙与悬沙沿程变化特征

基于2006年10月长江中下游沿程不同断面的河床沙、悬沙以及流速等相关水文泥沙现场观测资料,采用数理统计学与泥沙运动力学相结合的方法,对极端气候与流域重大工程作用下,长江中下游水沙的沿程变化以及悬沙与河床沙交换等进行分析。流量自宜昌向下游方向总的趋势是沿程增大,观测时段与多年同期平均流量(33 500 m3/s)相比少了近57%,而在沙市河段流速最大值达1.1 m/s;近底层水体含沙量较低,平均值为0.079kg/m3,与多年平均(50年)含沙量相比减少了90%。大通站实测悬沙含量与多年10月平均相比减少了近86%;河床沙组成以细砂和中砂为主,悬沙组成以粘土和粉砂类为主。与多年平均值相比,河床沙变化并不大,悬沙显著细化。中游河段河床沙中略细的粘土和细粉砂组分含量较上下游为多,而悬沙中略粗的中粗粉砂组分含量较上下游为多,断面垂向差异大;同时,从水流、含沙量、河床沙和悬沙颗粒组成及河道类型等多因素同步分析,表明长江中游河道泥沙交换相对频繁,河床稳定性相对较差,下游河道泥沙交换相对较少,河床稳定性相对较好。

三门峡水库蓄清排浑运用以来库区冲淤演变初步分析

水库蓄清排浑运用以来 ,黄河潼关 1974～ 1986、1987～ 1995、1996～ 2 0 0 2年均水量较 195 0～ 195 9年减少9 1% ,35 5 %、5 5 5 % ,沙量减少 4 0 9%、4 9 6 %、6 6 2 %。潼关以下三个时段年均淤积量为 0 0 4 2、0 16 1、0 2 0 8亿m3。呈水沙量递减 ,淤积量递增趋势。潼关同流量水位 2 9年升高 2 31m ,受上游冲淤下延影响升高 1 0 5m占 4 5 5 % ,其他因素影响升高 1 2 6m占 5 4 5 %。小北干流非汛期冲刷、汛期淤积格局未变 ,反映了水库运用对小北干流没有明显影响。渭河华县站 1974～ 1986年水量较大 ,渭淤 1～ 10断面仅淤积 0 0 6 5亿m3,华县同流量水位升高 0 0 3m。以 1974～ 1986年为准 ,1987～ 1995年、1996～ 2 0 0 2年华县年均水量减少 2 2 8%、5 6 2 % ,年均沙量减少 11 6 %、34 4 %。渭淤 1～ 10断面 1987～ 1995年淤积 1 72亿m3,特别是 1994和 1995年的中小洪水 ,汛期淤积 0 85亿m3主河槽萎缩 ,华县同流量水位升高 1 0 7m。

黄河在调水调沙影响下的入海泥沙通量和粒度的变化趋势

基于1950—2013年的黄河水文泥沙资料,系统研究了黄河实施调水调沙以来入海泥沙在通量、粒度组成和时间分布上的变化特征,揭示了调水调沙影响下黄河入海泥沙的变化趋势。在2002年黄河实施调水调沙以来,6—11月平缓均衡的持续性高水沙量取代了调水调沙之前7—10月峰值尖瘦的汛期特征,汛期与非汛期差异减小,入海水沙通量的季节性特征显著改变。随着调水调沙的逐年实施,河床泥沙颗粒粗化,临界起动功率不断增大,而调水调沙期间的径流量峰值基本稳定,径流对下游河床冲刷效率不断降低,导致入海泥沙通量持续降低、泥沙颗粒变细。可以预见,黄河河口的淤积将会大大减缓,入海的泥沙将更多地沉积在远离河口的区域,维持河口三角洲叶瓣冲淤平衡的临界泥沙量将会加大。

黄河尾闾河道平滩流量变化对来水来沙的响应

通过分析1976年清水沟流路以来黄河河口尾闾河道冲淤变化及河槽萎缩特点,探讨了利津平滩流量变化对来水来沙及河口延伸的关系。结果表明:河口区平滩流量变化不仅与来水量、洪峰流量、水沙搭配系数、河口河长相关,而且与前期河床条件有关。给出了维持河口河道4 000 m3/s平滩流量需要的水量、洪峰流量及水沙搭配的定量关系以及河口延伸长度的限制条件,为河口尾闾河道的综合治理提供一定的参考。

长江干流监利站水沙特性分析

监利河段位于长江中下游14个重点河段之一荆江河段的下段。根据对该河段代表水文站——监利水文站多年统计资料分析,监利站年径流量变化过程与年输沙量变化过程均呈不规则周期性变化,且以20世纪80年代末期为界,明显地分为2个阶段,2006年为长江枯水少沙年份,径流量、输沙量均为历年来最低值。监利站径流量年内分配与输沙量基本一致,均集中于汛期5-10月,且输沙量更为集中。水沙关联性分析结果表明,监利站来水来沙总体呈正相关性,即径流量越大,输沙量也就越大。监利站的水沙变化除了受长江上游来水来沙变化的影响外,下荆江裁弯工程、荆江三口分流分沙变化及三峡工程等水利枢纽建设,均是主要影响因素。

长江中游荆江监利河段水沙特性分析

对荆江监利河段的水沙特性进行了初步概括，以期抛砖引玉。根据监利河段代表水文站一监利水文站多年统计资料（1950－2006年），监利河段年径流量变化过程与年输沙量变化过程均呈不规则周期性变化，水沙过程变幅略大，2006年为长江枯水少沙年份，径流量、输沙量均为历年来最低值。河段径流量年内分配与输沙量基本一致，均集中于汛期5～10月。通过分析可知，监利河段来水来沙总体呈正相关性，即径流量越大，输沙量也就越大，而2000年以来年径流量序列与年输沙量序列无相关性，河段输沙量呈现明显减少趋势。监利河段的水沙变化除了受长江上游来水来沙变化的影响外，下荆江裁弯工程、荆江三口分流分沙变化、三峡工程等水利枢纽建设及洞庭湖出流顶托等，均是主要影响因素。

黄河中游水沙变化特征分析

黄河具有水少、沙多、水沙关系不协调的特点,其治理的主要难题在于处理径流量和输沙量的关系.近60年来,黄河中游水沙关系加剧恶化.因此,揭示黄河中游水沙变化特征及其影响因素是水沙研究的首要任务.采用滑动平均法、Manner-Kendall检验法对比分析黄河中游4个主要水文站(龙门、花园口、华县、白家川)在1950—2010年的水沙变化趋势.结果表明:黄河中游水沙量呈显著减少趋势,尤其是20世纪70年代以后;气候变化、降雨、水利工程、水土保持措施等是水沙变化的主要驱动因素,人类活动正成为影响水沙变化的最根本因素.

基于小波分析的汀江水沙通量变化规律研究

利用1951-2007年月平均水沙通量资料,采用Morlet小波函数,对汀江上杭水文站近60年来的年际和年代际变化特征进行小波分析,揭示了汀江水沙通量的多时间尺度变化特征和突变点,并根据小波能量谱(能量集中区)所对应的主周期进行了趋势分析。计算结果表明,洪季水沙通量的多时间尺度振荡趋势和位相与水沙通量的年变化特征相一致;洪季(4-9月)和年径流量均存在18年左右时间尺度的主振荡周期,6-9年时间尺度的次主周期;洪季(年)沙通量均存在28年左右时间尺度的主振荡周期,16年时间尺度的次主周期;经小波趋势分析,未来10-20年,汀江水沙通量与正常值相比呈降低趋势。