Impacts of Water-Sediment Regulation Scheme on Chromophoric Dissolved Organic Matter in the Lower Yellow River

As a river with more than 3000 reservoirs in its watershed,the Yellow River has been affected by dams not only on the sediment load,but also on the water quality.Water-sediment regulation scheme(WSRS),which has been carried out annually in the Yellow River since 2002,is a typical human activity affecting river water quality.Chromophoric dissolved organic matter(CDOM)in river is susceptible to changes in ecological and environmental conditions as well as human activities.Here,we report variations in dissolved organic carbon concentrations,compositions and sources of CDOM in time series samples in the lower Yellow River during WSRS.In addition,a parallel factor fluorescence analysis(PARAFAC)method is applied to identify different fluorescent components in water samples during WRSR,showing four major components including tryptophan-like component(C1),microbial humic-like component(C2),terrestrial humic-like component(C3)and tyrosine-like component(C4).In general,C1 increased after water regulation,while C2 and C3 increased after sediment regulation,indicating that the water and sediment released by the dam have different effects on CDOM compositions.Under the impacts of the dam,source of CDOM in the lower Yellow River is mainly autochthonous related to microbial activities,and is regulated by the terrestrial input during WSRS period.Sediment resuspension inhibits microbial activities and reduces the production of autochthonous CDOM.Overall,human activities especially WSRS,as exemplified here,significantly alter the quality and quantity of CDOM in the lower Yellow River,affecting CDOM dynamics and biogeochemical processes in the estuarine environment.

The influence of water-sediment regulation on macrobenthic community structures in the Huanghe River(Yellow River)Estuary during 2012–2016

To determine if water-sediment regulation has affected macrobenthic community structure in the Huanghe River Estuary,China,macrobenthic samples were collected following regulation events from 2012 to 2016.We identify seven phyla and 138 macrobenthic species from within samples throughout the survey area,over time.Species richness and abundance in 2012 were significantly higher than in 2016.Biomass did not differ significantly during 2012–2016.Dominant species were mostly small polychaetes,with mollusks,arthropods,and echinoderms all being relatively rare.In 2016,dominant species were small polychaetes.MDS reveals macrobenthic communities at all surveyed distances from the estuary to have become the same community structure over time.Shannon-Wiener diversity and Margalef richness indexes trended down over time.CCA reveals the most dominant sediment-dwelling species to prefer lower dissolved oxygen,sulfides,and pH,and sediments with high D50 and low clay content.We speculate that water-sediment regulation has affected seabed communities,particularly Region A in our survey area.

Impact of the water-sediment regulation and a rainstorm on nutrient transport in the Huanghe River

Dissolved nutrient concentration in the Huanghe （Yellow） River at Lijin was monitored during a water-sediment regulation period and a subsequent rainstorm from 14 June to 19 July, 2005. This study provides detailed information on nutrient concentrations in the Huanghe River during the water-sediment regulation and rainstorm periods, and is of significance for the downstream area of the Huanghe River and the Bohai Sea. The average concentrations of nitrate, nitrite and ammonia were 304.7 μmol/L, 0.19 μmol/L, and 1.10 μmol/L, respectively, while the average concentrations of dissolved inorganic phosphorus （DIP） and dissolved silicate （DSi） were 0.23 gmol/L and 122.9 ktmol/L, respectively. Nutrient concentrations during the water-sediment regulation period were mainly influenced by the dilution effect, floodplain effect and sediment resuspension while dilution and erosion effects were the main factors during the rainstorm. The fluxes of dissolved inorganic nitrogen （DIN）, DIP and DSi during the water-sediment regulation and rainstorm periods accounted for 20.4%, 19.5%, 16.7% and 4.97%, 6.45%, 5.47% of the annual nutrient fluxes, respectively. Discharge was the main factor influencing the fluxes of nutrients during both the water- sediment regulation and the rainstorm periods.

Effect of water-sediment regulation and its impact on coastline and suspended sediment concentration in Yellow River Estuary

Implementation of the water-sediment regulation(WSR) scheme, mainly focused on solving the sedimentation problems of reservoirs and the lower reaches of the Yellow River, has inevitably influenced the sediment distribution and coastal morphology of the Yellow River Estuary.Using coastline delineation and suspended sediment concentration(SSC) retrieval methods, this study investigated water and sediment changes,identified detailed inter-annual and intra-annual variations of the coastline and SSC in the normal period(NP: 1986-2001, before and after the flood season) and WSR period(WSRP: 2002-2013, before and after WSR). The results indicate that(1) the sedimentation in the low reaches of the Yellow River turned into erosion from 2002 onward;(2) the inter-annual coastline changes could be divided into an accretion stage(1986-1996), a slow erosion stage(1996-2002), and a slow accretion stage(2002-2013);(3) an intra-annual coastline extension occurred in the river mouth in most years of the WSRP; and(4) the mean intra-annual accretion area was 0.789 km^2 in the NP and 4.73 km2 in the WSRP,and the mean SSC increased from 238 mg/L to 293 mg/L in the NP and from 192 mg/L to 264 mg/L in the WSRP.

Impact of Water-Sediment Regulation on Variations of Amino Acids in the Middle-Lower Yellow River, China

In order to examine the impacts of water-sediment regulation on regional carbon cycling,we collected water,particulate and sediment samples from the middle-lower Yellow River in late June and early July,2015 and analyzed their specific amino acids(AA),DOC,POC,and bacteria abundance.Summarized by 14 specific AA,the total hydrolysable AA(THAA),particulate AA(PAA),and sediment AA(SAA)varied in ranges of 2.29-9.05μmol L^-1,5.22-22.96μmol L^-1,and 81.7-137.19μg g^-1 dry weight.After the regulation,dissolved free AA(DFAA)decreased by 29%while DCAA increased by 72%.These variations suggested that DFAA were further degraded,while DCAA molecules were further activated.Meanwhile,PAA increased almost 4 times as many as those before regulation,and SAA increased as well.After regulation,the amounts of bioactive amino acids(Asp,Glu and Gly)increased in THAA but decreased in PAA,with little changes in SAA.The ratios of Asp/Gly in different phases increased after regulation,indicating the AA contributions were promoted by calcareous organisms rather than by siliceous organisms.Multiple correlation analysis showed that PAA was primary representatives of AA and organic carbon,followed by DCAA and POC.Moreover,bacterial reproduction played a key role in shaping the AA compositions and properties,followed by the redox condition and acid-base balance.The results of this study provided a clear evidence for the effects of water-sediment regulation on regional biogeochemistry of organic carbon in the middle-lower Yellow River.

Using Rn-222 to Study Human-Regulated River Water-Sediment Input Event in the Estuary

The implementation of the water sediment regulation scheme(WSRS)is a typical example of artificially controlling land-source input.During WSRS,the water discharge of the Yellow River will increase significantly,and so will the input of terri-genous materials.In this study,we used a natural geochemical tracer 222Rn to quantify terrestrial inputs under the influence of the 2014 WSRS in the Yellow River Estuary.The results indicated that during WSRS the concentration of 222Rn in the estuary increased by about four times than in the period before WSRS.The high-level 222Rn plume disappeared quickly after WSRS,indicating that 222Rn has a very short‘memory effect’in the estuary.Based on the investigation conducted from 2015 to 2016,the concentration of 222Rn tended to be stable in the lower reaches of the Yellow River.During WSRS,the concentrations of 222Rn in the river water in-creased sharply at about 3–5 times greater than in the non-WSRS period.Based on the 222Rn mass balance model,the fluxes of 222Rn caused by submarine groundwater discharge(SGD)were estimated to be(3.5±1.7)×10^(3),(11±3.9)×10^(3),and(5.2±1.9)×10^(3)dpm m^(-2)d^(-1)in the periods before,during,and after WSRS,respectively.This finding indicated that SGD was the major source of 222Rn in the Yellow River Estuary,which can be significantly increased during WSRS.Furthermore,the SGD-associated nutrient fluxes were estimated to be 9.8×10^(3),2.5×102,and 1.1×10^(4)μmolm^(-2)d^(-1)for dissolved inorganic nitrogen,phosphorus,and silicon,respectively,during WSRS or about 2–40 times greater than during the non-WSRS period.

Response of the distributary channel of the Huanghe River estuary to water and sediment discharge regulation in 2007

The water and sediment discharge regulation （WSDR） project, which has been performed since 2002 before flood season every year, is of great significance to the river management in China. Until 2007, six experiments have been fulfilled to evaluate the effect of the project on the natural environment. To fill the gap of investigations, a study on flood and suspended sediment transportation and channel changing along the distributary channel of the Huanghe （Yellow） River was conducted during the WSDR project period in 2007. The lower channel was scoured rapidly and the channel became unobstructed gradually several days after the flood peak water was discharged from the Xiaolangdi Reservoir. Within four days after the flood peak at 3 000 m3/s entered the distributary, the channel in the river mouth area was eroded quickly. Both the mean values of area and depth of the main channel were tripled, and the maximum flood carrying capacity increased to 5 500 m3/s or more. Then, the river channel was silted anew in a very short time after completion of the WSDR. Favored by the WSDR project, the fiver status in April 2008 became better than that of the year before. The adjustment ranges of main channel parameters were about 30%, 10%, and 10% at sections C2, Q4, and Q7, respectively. The process of rapid erosion-deposition was more active 15 km away in the channel from the fiver mouth due to the marine influence. It is reasonable for discharging sediment at concentration peak from Xiaolangdi Reservoir at the end of the flood peak. As a result, the sediment peak reached the river mouth about two days later than that of the water current. In addition, the WSDR project has improved the development of the estuarine wetland. Wetland vegetation planted along the river banks restrained the water flow as a strainer and improved the main channel stability. It is suggested to draw water at mean rate of 150 m3/s from the Huanghe River during flood periods, because at the rate the water in the wetland would be stored and replenished in balance. Moreover, we believe that cropland on the river shoal of the lower Huanghe River should be replaced by wetland. These activities should achieve the Huanghe River management strategy of ＂To concentrate flow to scour sediment, stabilize the main channel, and regulate water and sediment＂.

Understanding the influencing factors and evolving trends of the Yellow River Water-Sediment Regulation System from a system perspective

Understanding the influencing factors and the evolving trends of the Water-Sediment Regulation System(WSRS)is vital for the protection and management of the Yellow River.Past studies on WSRS have been limited in focus and have not fully addressed the complete engineering control system of the basin.This study takes a holistic view,treating sediment management in the Yellow River as a dynamic and ever-evolving complex system.It merges concepts from system science,information theory,and dissipative structure with practical efforts in sediment engineering control.The key findings of this study are as follows:between 1990 and 2019,the average Yellow River Sediment Regulation Index(YSRI)was 55.99,with the lowest being 50.26 in 1990 and the highest being 61.48 in 2019;the result indicates that the WSRS activity decreased,yet it fluctuated,gradually approaching the critical threshold of a dissipative structure.

Rapid shifts of the river plume pathway off the Huanghe (Yellow) River mouth in response to water-sediment regulation scheme in 2005

Freshwater plume represents a key passage for the river to deliver sediment to the coastal ocean. A wa- ter-sediment regulation scheme was implemented for the Huanghe River in 2005; in order to examine the effect of such an activity on the river plume dynamics, three cruises were carried out off the Huanghe River mouth. The prelimi- nary results of the in-situ measurements suggested that the plume pathway shifted rapidly during the period of less than twenty days, which was confirmed by satellite remote sensing data in the same period. The rapid shifts were resulted from intensive interactions between river discharge and the vary- ing bathymetry in the river mouth area. A large amount of river sediment was delivered to the coastal region during this period and mostly deposited in the mouth bar area due to jet-flow deceleration, forming a cluster of mouth bars across the river mouth, which caused the rapid shifts of the plume pathway.

Model of water-sediment regulation in Yellow River and its effect

Water-sediment regulation of the Yellow River is to regulate and control the flow and sediment transport relationship of the lower reaches through reservoirs on the main streams and tributaries to create balance between water and sediment so that sediment transport capacity of the downstream channels can be maximized,shrinking of channels be contained,and medium flood channel be restored and maintained.Many years' research by the Yellow River Conservancy Commission(YRCC) reveals the water and sediment transport relationship that will prevent sedimentation at the downstream river channels.Based on this relationship and coming sediment and water conditions in the Yellow River basin,the YRCC,with maximized use of reservoirs on the main streams and tributaries,has developed three models of water-sediment regulation:single Xiaolangdi Reservoir-dominated regulation,space scale water-sediment match,and mainstream reservoirs joint operation.Ten water-sediment regulations based on these three models have resulted in an average drop of 1.5 m in the main channel of the downstream 800 km river and an increase of carrying capacity from 1800 to 4000 m3/s.Besides,the wetland ecosystems of estuarine delta has also been improved and restored significantly.

Equilibrium sediment transport in lower Yellow River during later sediment-retaining period of Xiaolangdi Reservoir

The Xiaolangdi Reservoir has entered the later sediment-retaining period, and new sediment transport phenomena and channel re-estab- lishing behaviors are appearing. A physical model test was used to forecast the scouring and silting trends of the lower Yellow River. Based on water and sediment data from the lower Yellow River during the period from 1960 to 2012, and using a statistical method, this paper analyzed the sediment transport in sediment-laden flows with different discharges and sediment concentrations in the lower Yellow River. The results show that rational water-sediment regulation is necessary to avoid silting in the later sediment-retaining period. The combination of 3 000 m^3/s 〈 Q 〈 4 000 m^3/s and 20 kg/m^3 〈 S 〈 60 kg/m^3 （where Q is the discharge and S is the sediment concentration） at the Huayuankou section is considered an optimal combination for equilibrium sediment transport in the lower Yellow River over a long period of time.

地形地貌变化对调水调沙期间黄河口沉积格局的影响

自2002年实施调水调沙以来,由于入海径流、沉积物的通量和组成发生变化,黄河现行河口三角洲叶瓣不断向海淤积造陆,水下三角洲坡度变陡。地形地貌变化对调水调沙期间入海泥沙沉积格局的影响成为黄河口研究的重要科学问题。本文基于Delft3D模型系统,利用岸线、水深和河流水沙数据构建三维水沙数值模型,对2002年、2008年、2014年和2019年调水调沙期间现行河口近岸海域泥沙的输运和沉积过程进行模拟。结果表明,随着水深、岸线的变化,黄河口近岸海域动力环境增强,泥沙的横向输运增强,纵向输运相应减弱;进而导致黄河入海泥沙堆积体的横向长度增加约30%,纵向长度减小约27%,厚度、形态也相应变化。本研究揭示了地形地貌变化条件下,黄河调水调沙期间入海泥沙在河口的沉积格局及动力机制,对深入理解黄河口近岸海域水动力-地貌耦合系统有重要参考价值。

黄河现行流路与启用刁口流路不同情景下调水调沙期间入海水沙扩散特征与影响因素

《黄河流域综合规划(2012—2030年)》中指出,规划期内仍主要利用清水沟流路行河,保持流路相对稳定,清水沟流路使用结束后,优先启用刁口备用流路。为探究黄河启用刁口流路后入海水沙扩散特征及其与现行流路的差异,本研究选取黄河水沙入海的主要时期——调水调沙期,通过FVCOM三维数值模式,模拟研究了黄河调水调沙期间经两条流路入海情况下的盐度、悬沙浓度及河口动力特征,对比发现(1)两条流路沿岸流系总体变化趋势一致,入海径流受地转偏向力影响整体向东偏转,局部流场存在差异,刁口流路入海时无明显环流;(2)两种流路下羽流和悬沙的扩散特征对调水调沙不同阶段的水沙变化存在一致性的响应;然而,受河口地形和岸线的影响,刁口流路情景下羽流和悬沙的扩散范围显著大于现行流路;(3)伴随着流路变化,三角洲不同区域的演化特征将产生快速响应:刁口流路启用后,现行河口三角洲将进入蚀退期,刁口三角洲叶瓣进入快速造陆期。此外,模型结果显示,由于刁口外较浅的水深和平缓的地貌特征,相同条件下刁口流路情景下三角洲的造陆速率在短期内可能高于现行流路。

2022年黄河调水调沙对下游有机物和营养盐年内变化的影响

2021年11月至2022年10月,在黄河下游泺口站进行了为期一年、每月一次的采样,测定了河水中溶解有机碳(Dissolved Organic Carbon,DOC)、有色溶解有机物(Chromophoric Dissolved Organic Matter,CDOM)、荧光溶解有机物(Fluorescent Dissolved Organic Matter,FDOM)、营养盐,以及悬浮颗粒态(Suspended Particulate Matter,SPM)中颗粒有机碳(Particulate Organic Carbon,POC)占比(POC占SPM的质量百分比,POC%)、δ^(13)C和δ^(15)N等生源要素相关指标。结果表明,调水调沙已经成为控制黄河下游多种生源要素在一年之中变化格局的关键因素,决定着其全年变化范围的上限和下限。在调水调沙的调水阶段,脉冲式激增的径流量通过稀释作用使得DOC浓度、CDOM浓度、FDOM中的类腐殖质组分含量,以及SPM中δ^(13)C和δ^(15)N达到全年的最低值,而CDOM光谱斜率(S_(275-295))达到最高值。在调水调沙的排沙阶段,上述指标则在相反方向上达到全年的极值。最近20年间,在调水调沙、流域生态环境保护、气候变化等一系列措施的影响下,黄河下游营养盐和DOC浓度呈现明显的下降趋势,而POC%的上升迹象也初步显现。黄河下游生源要素浓度、组成、性质、输出通量正经历着复杂而深刻的变化,将直接影响到黄河口的海洋生态环境。本研究有助于进一步理解在人类活动背景下大河生源要素的响应特征和反馈机制及其对邻近海洋生态环境的潜在影响。

黄河调水调沙对河口及邻近海域鱼卵、仔稚鱼群落结构的影响

为了解调水调沙(Water-Sediment Regulation Scheme,WSRS)对黄河口海域鱼卵、仔稚鱼的群落结构和时空分布格局的影响,分别于2017年(非调水调沙年)和2018年(调水调沙年)的6—7月在黄河口海域利用水平拖网开展了6个航次的鱼卵、仔稚鱼调查。运用聚类分析和冗余分析(RDA)等方法对该海域非调水调沙年和调水调沙年的鱼卵、仔稚鱼丰度和群落结构的空间分布及环境因子状况等进行了综合的分析比较,结果表明:6个航次调查共采获鱼卵6212粒,仔稚鱼431尾,隶属于8目12科14属,其中,河口定居性鱼类短吻红舌鳎(Cynoglossus joyeri)为控制黄河口及邻近海域夏季鱼类浮游生物群落演替格局的主要种类;鱼卵受环流和调水调沙的共同影响,其空间分布在各调查阶段有所不同,仔稚鱼则趋向于在河口近岸海域分布;河口东北部及东南部靠近莱州湾区域是黄河口及邻近海域鱼类浮游生物群落的主要聚集区;调水调沙年鱼卵、仔稚鱼的采获总量以及底层鱼类鱼卵的采获数量均明显高于非调水调沙年,调水调沙带来的丰富径流和泥沙有利于黄河口海域渔业资源的补充;冗余分析结果表明,海洋鱼类的群落结构与环境因子关系密切,研究区域鱼卵、仔稚鱼的群落结构与盐度、水温、水深及浮游生物密度等因素息息相关,环境条件影响着鱼类对栖息地的选择。黄河调水调沙输送的丰富入海淡水和泥沙与其邻近海域的海洋生态环境及海洋生物资源构成了密切的响应关系,随着我们对调水调沙实践经验的不断积累,建议应在今后的工作中进一步加强对调水调沙的目标、时间和频次优化等问题的关注。

黄河三角洲NDVI时空演化特征及其驱动因素

为了解黄河三角洲地区植被盖度的时空动态,在利用遥感资料分析归一化植被指数(NDVI)空间分布格局及其年际变化规律的基础上,进一步探讨了影响NDVI时空变化的自然和人为因素。结果显示,黄河三角洲地区2002、2006、2008、2013年10月的NDVI均值分别为-0.04、0.06、0.10、0.16,NDVI>0的区域面积分别约1253、1733、1742、2175km^2(分别占区域总面积的43.67%、60.01%、66.82%、81.77%)。在时间动态上,区域NDVI总体呈逐渐增加的良性发展态势,黄河入海口地区尤为突出;在空间格局上,NDVI可分为高植被覆盖区(NDVI>0.4)、中等植被覆盖区(NDVI为0.1—0.4)和稀疏植被覆盖区(NDVI<0.1),且按离海远近在区域内分别呈现斜"Y"、斑块和条带状。地形高度、地下水和土壤水盐条件(尤其是潜水氯离子浓度,二者之间R=0.737)等环境因素影响NDVI整体空间分布格局,区域降水和气温等气候条件造成NDVI年际动态变化,而黄河下游生态调度对过水区域特别是河口地区NDVI良性变化具有显著的促进作用。黄河三角洲地区应持续加强生态环境保护与修复,提高植被盖度及其综合效益。

基于多维调控方案的黄河流域水资源可承载程度评价

在黄河流域多维临界调控模型得到的水资源配置结果的研究基础上,从调控方案所实现的经济效果、社会效果和生态环境效果三个层次建立了评价黄河水资源可承载程度的指标体系,并构造了水资源可承载程度的模糊综合评价模型;最后应用该评价模型对黄河流域2010和2020水平年共27个调控方案进行了水资源可承载程度分析评价,可为黄河流域水资源可持续开发利用提供决策参考。

黄河口清水沟河道的冲淤过程与模拟

为揭示黄河口清水沟河道长时段的冲淤演变规律并建立其冲淤计算方法,分析了清水沟1976—2015年的时空冲淤演变过程,采用河床演变的滞后响应模型,考虑河口来水来沙及河道延伸与蚀退的影响,建立了清水沟累计冲淤量的计算方法。结果表明:1976—1980年改道初期清水沟改道点上游先冲后淤,改道点下游淤滩塑槽,淤积量随着下游河道展宽而增加,1980年后改道点上、下游河道冲淤过程趋于一致;受水沙条件等因素影响,1980—1986年清水沟主槽冲刷展宽,之后主槽淤积萎缩;1996年清八改汊和2002年小浪底水库"调水调沙"原型试验以来,河道转淤为冲,2002年后河道冲刷速率随时间指数衰减;河床演变的滞后响应模型可计算清水沟长时段的冲淤过程,该方法可为预测未来清水沟冲淤演变趋势提供科学参考。

新入海水沙情势下黄河口的地貌演变

近年来,受流域气候变化和强烈的人类活动干预,黄河入海水沙情势出现了新的变化,河口区地貌演变也随之改变。为了解新入海水沙情势下现行黄河口地貌演变特征,基于利津站水沙数据和现行河口实测水下地形资料,运用统计学方法进行分析研究。结果表明:黄河入海水沙情势由'水少沙多'向'枯水少沙'转变,入海泥沙持续减少,悬沙浓度降低,泥沙颗粒粗化;2002-2015年持续调水调沙的14年间入海泥沙共19.79亿t,其中有8.34亿m^3(13.09亿t)泥沙沉积在现行河口滨海区,而2016年由于水量极枯调水调沙首次中断,河口滨海区大面积蚀退,净蚀退量达0.72亿m^3(1.13亿t),现行河口2~5 m水深平均侵蚀厚度为0.38 m,对入海水沙锐减的响应最为突出;维持现行河口滨海区冲淤平衡的入海泥沙通量临界值为1.3亿t/a,黄河入海水沙情势的改变使河口地貌演变将出现新的态势。

镭、氡同位素示踪调水调沙对黄河口水体运移及营养盐分布特征的影响

为研究调水调沙影响下的镭、氡同位素和营养盐在黄河口的分布特征,于2013年7月调水调沙期间在黄河口及其邻近海域进行了多点的连续观测。研究发现:(1)黄河口海域镭、氡同位素分布呈现明显的"分区"现象,南北两区分别为"调水调沙影响非显著区域"和"调水调沙影响显著区域",北部海域镭、氡同位素浓度高值主要来源于陆源输入(包括河流输入和海底地下水排放);(2)调查期间,北部海域水体年龄为(2.9±1.6)d,南部海域水体年龄为(5.0±2.1)d;水龄随潮汐变化表现出涨潮时水龄增大、落潮时水龄减小的波动趋势;(3)北部海域溶解无机氮(DIN)和溶解硅(DSi)含量明显高于南部海域,而溶解无机磷(DIP)在两个区域的含量相差不大。