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1.
《中国科学:地球科学》2015,(7)
分析了黄河水体中悬浮颗粒物(SPM)、溶解硅(DSi)、生物硅(BSi)、植硅体和其他相关参数,旨在揭示自然过程与人为活动对黄河输送硅的影响.结果表明,黄河中溶解硅浓度自1986年以来明显下降;1986~2010年,约有34%的溶解硅因土壤侵蚀的减少而滞留在黄河流域.来源于高等植物的植硅体占河流生物硅的67.2%~96.3%,并以平滑棒形为主要形态.由于含沙量大,黄河生物硅浓度普遍高于世界其他河流,在近黄河口处的利津站位,BSi/(BSi+DSi),BSi/SPM比值分别为0.5和0.003,这表明黄河悬浮颗粒物携带的生物硅是河流输送硅的一个重要组成部分.黄河中相对较高的生物硅含量反映了黄河流域浑浊度与土壤侵蚀程度较高;源自黄土高原巨大的泥沙通量可能是导致黄河中生物硅含量较高的原因,这与世界河流系统生物硅通量随产沙模数增大而增加的趋势相一致.在黄河口外的渤海沉积物中的生物硅也主要由植硅体所构成,平滑棒形同样是其主要的形态.研究表明,由河流输送的生物硅主要由来源于表层土壤侵蚀的植硅体所构成,其也是近岸水域硅生物地球化学循环的重要部分. 相似文献
2.
长江流域水库"过滤器效应"对入海溶解硅通量的影响 总被引：3，自引：2，他引：1
根据1960-2000年间长江大通水文站记录的水、沙以及硅、氮、磷等数据,结合1954-2006年间长江流域库容大于108 m3的162座水库的库容、上游径流量、总磷等数据,利用Vollenweider模型分析了水库"过滤器效应"对入海溶解硅(DSi)通量的影响.结果表明:1)1990s相比1960s,长江入海DSi通量下降了约1.85×106 t/a,减少了大约25.3%;入海DSi通量的下降与流域径流波动、入海悬沙通量下降以及溶解无机氮通量的增加紧密相关.2)流域水库明显改变径流的自然过程,增加径流的滞留时间,流域90%以上的水库对上游径流的滞留时间超过0.05年,水库产生显著的DSi"生物过滤器"效应.模型计算显示流域大型水库对DSi的累计滞留量可达0.85×106 t/a,占年均入海DSi通量(1990-2000年)5.4×106 t的15.7%,是入海DSi通量减少量(1.85×106 t/a)的45.9%.3)根据保守估计,流域162座大型水库内泥沙累计淤积量达6.75×108 t/a,不仅使悬沙入海通量显著下降,而且造成大量颗粒吸附的外源和内源DSi颗粒沉淀,这对入海DSi通量减少也起到重要贡献.但目前对水库"泥沙过滤器"的滞留机理并不清楚,需要展开进一步的研究. 相似文献
3.
于特枯水情年对三峡水库溶解硅和长江干流自涪陵至河口段悬浮颗粒物、溶解硅、生物硅和叶绿素a浓度等进行调查.研究表明,在平水期和汛期末,长江干流水体溶解硅和生物硅浓度和通量在其上游受大坝"滞留"效应的影响呈现沿程降低的趋势,中、下游受"两湖"和汉江等的补充作用有明显升高.在枯水年,长江干流水体生物硅浓度占活性硅(溶解硅和生物硅之和)浓度的2%~5%,显著低于平水年的比例(13%),同时也低于世界河流的平均水平(16%).三峡水库在4-12月份减少溶解硅向下游的输送通量,而在1-3月份增加溶解硅的输送通量;水库在枯水年滞留了大约3%~6%的溶解硅.三峡水库内低的初级生产水平和高的生物硅再生速率是其难以对溶解硅形成有效滞留的主要因素.大坝下游会因清水下泄产生潜在的滞留效应,不过还需要更多的数据去量化. 相似文献
4.
江西柘林水库是长江中游的大型峡谷型旅游性水库,库容79.2×10~8m~3,长115 km.2015年4月在56 km的中心库区走航和定点测量了水库表层水体浮游藻类、叶绿素a(Chl.a)浓度与溶解无机氮(DIN)浓度、溶解无机磷(DIP)浓度、溶解硅(DSi)浓度、水温、浊度和溶解氧浓度等环境因子的分布特征.结果表明:1)水库属于中营养水体,表层主要浮游藻类(细胞丰度1000 cells/L)有34种,平均生物量为0.41 mg/L.主要优势藻类(优势度≥0.02)为硅藻和蓝藻,藻类组成与DIN浓度、DIP浓度、DSi浓度和水温等环境因子关系密切,4种因子对藻类结构的解释水平达60%以上.2)水库水体Chl.a浓度具有显著的次表层叶绿素最大值(SCM)现象,SCM层深度为3~8 m,厚度为2~7 m,SCM层占整个水体的25.2%~74.1%.SCM层的藻类对营养盐吸收消耗致使DIN、DIP和DSi浓度下降,同时藻类的产氧使溶解氧浓度增加.3)水库对DSi具有显著的生物过滤器效应,中、上层约有11%~12%的DSi被生物吸收利用,从上游至下游,累积约有21%的DSi被藻类吸收沉降于库底.4)人类氮、磷排放对水库生态和水质有严重影响,毗邻县城区域水体的Chl.a和DIP浓度分别是自然河段的2.9倍和3倍左右. 相似文献
5.
鄱阳湖夏季水热通量特征及环境要素影响分析 总被引：2，自引：2，他引：0
气候变化加速了全球水文循环过程,然而,气候变化如何影响水体蒸发及其水热通量交换仍然不清楚.基于涡度相关系统观测鄱阳湖水体水热通量过程,在小时和日尺度分析了水热通量的变化规律及其主要影响因子.研究表明,潜热通量日变化波动剧烈,大部分为正值,变化范围在-50~580 W/m2之间.而感热通量数值较小,变化范围在-50~50 W/m2之间.8月份潜热通量和感热通量均呈波动下降趋势,均值分别为167.4和15.9 W/m2.8月份日平均潜热通量和感热通量之和大于净辐射,这是由于这一时段储存在水体中的热量释放并补充潜热通量和感热通量.小时尺度上潜热通量日变化在相位上与净辐射无显著相关性,而与风速显著相关.在日尺度变化趋势上,8月份日平均潜热通量仍主要受到风速和水温的影响,感热通量则主要受到风速和饱和水汽压差的影响. 相似文献
6.
基于时间序列MODIS影像的鄱阳湖丰水期悬浮泥沙浓度反演及变化 总被引：2，自引：0，他引：2
悬浮泥沙浓度是描述水质的重要参数之一,获得其在空间和时间上的分布信息对于理解、管理和保护湖泊生态系统是必要的.此研究旨在建立基于中分辨率成像光谱仪(MODIS)影像的鄱阳湖悬浮泥沙浓度反演模型,并利用建立的模型反演2000-2007年鄱阳湖丰水期的悬浮泥沙浓度,分析其在时间和空间上的变化特征并对引起这些变化的原因进行讨论.研究结果揭示:MODIS Terra影像红波段与悬浮泥沙浓度具有显著的相关性(R2=0.92,s.e.=12.02mg/L,F=154.30,P<0.001),可以用于鄱阳湖丰水期悬浮泥沙浓度的反演;自2000-2007年间,鄱阳湖悬浮泥沙浓度呈明显的时间和空间分布特征,在南部水体悬浮泥沙浓度无明显变化,在北部呈增加趋势,而中部水体泥沙浓度波动较大;鄱阳湖北部的采砂活动是导致此区域悬浮泥沙浓度增加的主要原因,其与长江江水倒灌鄱阳湖共同作用引起鄱阳湖中部泥沙浓度的波动,抚河、信江和饶河输沙量的非显著变化也导致南部鄱阳湖水体悬浮泥沙浓度的非显著变化. 相似文献
7.
西藏纳木错及其入湖河流溶解有机碳和总氮浓度的季节变化 总被引：5，自引：1，他引：4
为深入理解纳木错湖水及入湖河流中溶解有机碳（DOC）和总氮（TN）浓度的季节变化特征及其影响因素，于2012-2013年不同季节对纳木错2个站点及流域内21条主要入湖河流进行采样及分析，采用统计学方法初步探讨纳木错水体和21条河流DOC和TN浓度季节变化特征.结果表明，河流DOC平均浓度范围为0.763~1.537 mg/L，TN平均浓度范围为0.179~0.387 mg/L.21条入湖河流DOC浓度在春末夏初和夏季达到高值，冬季为低值，TN浓度季节变化趋势大体上与DOC浓度相反.湖泊水体DOC和TN浓度范围分别为2.42~8.08和0.237~0.517 mg/L，明显分别高于河水中的浓度.湖泊DOC浓度季节变化趋势与河流一致，而TN浓度无明显的季节性变化.河水DOC浓度的季节变化和空间差异受控于河流的补给方式，湖水DOC浓度受湖泊内部藻类等水生植物活动和河流外源输入的影响.DOC等有机质的分解是影响纳木错流域湖水和河水TN浓度的重要原因. 相似文献
8.
呼伦湖主要入湖河流克鲁伦河丰水期污染物通量(2010-2014) 总被引：4，自引：3，他引：1
为控制呼伦湖的水体恶化趋势,利用2010-2014年的水质监测数据首次对呼伦湖的主要入湖河流——克鲁伦河丰水期(6-8月)氨氮、总氮、总磷和化学需氧量等污染物的入湖通量进行详细研究.采用单因子指数法对水质进行评价,通过等标污染负荷确定入湖口的首要污染物,利用相关性分析研究水质、水量、污染物通量三者之间的相互关系.结果表明:克鲁伦河入湖口水体受总氮与化学需氧量污染较为严重,均处于V类或劣V类水平,总磷浓度整体处于Ⅲ~Ⅳ类水平.污染物入湖通量有逐年递增之势,2014年稍有下降,总氮的等标污染负荷最高,为入湖口的主要污染物.入湖口水质与水量呈现出一定的正相关关系,水量是影响污染物入湖通量的关键因子,而入湖水质则是影响入湖通量的主要影响因子.控制总氮及化学需氧量的入湖通量是当前的首要任务,合理控制放牧、将村镇的污废水处理后达标排放是减轻河湖水体污染的当务之急. 相似文献
9.
分析湖泊中磷浓度的变化特征,揭示其变化的驱动机制,是有效实施湖泊水体磷浓度控制的前提.本文整理分析了太湖70年来(1949 2020年)水体磷浓度监测历史资料,对比了太湖不同湖区、不同时间尺度水体磷浓度的差异性及波动性,发现影响太湖磷浓度变化的原因既有人为的因素,也有自然的因素.无论是污染较轻的1950年,还是污染负荷相对较重的近30年,太湖水体磷浓度一直存在较大时空差异性.暴雨引发入湖河流携带磷污染的扩散、风浪扰动引起的内源释放及蓝藻水华期间藻类生物量的大幅时空变化,都加剧了太湖水体磷浓度的不稳定性.近20年的太湖水污染治理对磷浓度的时空分布影响明显,1998年的太湖水污染治理"零点行动",2007年以来的水利调度等系列水污染治理工程,以及2017年以来的藻情变化等,都对太湖水体磷浓度的时空格局产生了影响.然而,高强度治理投入下太湖水体磷浓度依然偏高,其原因与流域建设用地比例增加、人口增加、耕地种植结构变化等外源负荷因素发生变化有关,也与湖体沉水植被退化、出入流结构发生变化、气候变化引发的蓝藻水华扩张等内源强度及水体表观磷浓度决定因素的生态环境变化有关.近70年来太湖水体磷浓度的变化过程对类似大型浅水湖泊的磷控制策略具有启示意义:大型浅水湖泊存在磷浓度较大波动的自然属性,在水环境保护目标考核中应充分考虑其不确定性,制定切实可行的控制目标;在控制策略上应将外源负荷控制放在首位,在流域污水处理厂深度除磷及流域土地利用调整等方面采取措施,实现入湖磷负荷的大幅削减,同时实施湖体生态修复与食物链调控措施,才能逐步实现湖泊水体磷浓度的控制目标. 相似文献
10.
广东新丰江水库表层水体CO2分压及其影响因素 总被引：2，自引：1，他引：1
于2012年7月和2013年1月定点采集新丰江水库表层水样,测定水样的理化及生物学参数,计算水体中二氧化碳分压(p(CO_2))大小并分析其时空变化,探讨新丰江水库p(CO_2)的影响因素及其CO_2源/汇机制.结果表明:丰水期p(CO_2)变化范围为16~3545μatm,均值为999μatm,从水库上游到坝前p(CO_2)逐渐升高;枯水期p(CO_2)变化范围为399~1355μatm,均值为756μatm,从水库上游到坝前p(CO_2)呈下降趋势.丰水期p(CO_2)受温度影响较小,与营养盐(NO-3、DSi)浓度呈正相关,与叶绿素a(Chl.a)、溶解有机碳(DOC)浓度呈负相关,与溶解无机碳(DIC)浓度没有明显相关性;枯水期p(CO_2)受温度影响也较小,受碳酸盐体系的影响,与NO-3、DSi、Chl.a、DIC浓度呈正相关,与DOC浓度没有明显相关性.新丰江水库相对于大气来说是一个通量值偏低的CO_2源. 相似文献
11.
基于黄河上、中和下游的径流及气候资料，对径流的年代际变化规律及与气候变化的关系进行了分析.结果表明：黄河流域的径流均存在显著的年代际变化趋势，径流的显著特征是从20世纪80年代开始的减少趋势，但并未达到历史的最低，径流减少的趋势在下游比上游更显著，而这种变化趋势与流域的气候变化趋势基本一致，说明在年代际尺度上，径流的变化主要受气候的控制；在不同季节，这种关系有明显差异，如在冬季两者的变化趋势有较大差异.分析还发现，近年来流域地表的干化是流域径流减少的原因，气温的升高更加剧了流域地表干化. 相似文献
12.
Streamflow trends and climate linkages in the source region of the Yellow River,China 总被引：1，自引：0，他引：1
Much of the discussion on hydrological trends and variability in the source region of the Yellow River centres on the mean values of the mainstream flows. Changes in hydrological extremes in the mainstream as well as in the tributary flows are largely unexplored. Although decreasing water availability has been noted, the nature of those changes is less explored. This article investigates trends and variability in the hydrological regimes (both mean values and extreme events) and their links with the local climate in the source region of the Yellow River over the last 50 years (1959–2008). This large catchment is relatively undisturbed by anthropogenic influences such as abstraction and impoundments, enabling the characterization of widely natural, climate‐driven trends. A total of 27 hydrological variables were used as indicators for the analysis. Streamflow records from six major headwater catchments and climatic data from seven stations were studied. The trend results vary considerably from one river basin to another, and become more accentuated with longer time period. Overall, the source region of the Yellow River is characterized by an overall tendency towards decreasing water availability. Noteworthy are strong decreasing trends in the winter (dry season) monthly flows of January to March and September as well as in annual mean flow, annual 1‐, 3‐, 7‐, 30‐ and 90‐day maxima and minima flows for Maqu and Tangnag catchments over the period 1959–2008. The hydrological variables studied are closely related to precipitation in the wet season (June, July, August and September), indicating that the widespread decrease in wet season precipitation is expected to be associated with significant decrease in streamflow. To conclude, decreasing precipitation, particularly in the wet season, along with increasing temperature can be associated with pronounced decrease in water resources, posing a significant challenge to downstream water uses. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
13.
In this paper, the changes in sediment transport over 51 years from 1955 to 2006 in the Kuye River in the Loess Plateau in China are assessed. Key factors affecting sediment yield and sediment transport, such as precipitation depth, discharge, and human activities are studied. To investigate the changes in sediment yield in this watershed, a trend analysis on sediment concentration, precipitation depth, and discharge is conducted. Precipitation depths at 2 Climate Stations （CSs）, as well as discharge and sediment transport at 3 Gauging Stations （GSs） are used to assess the features of sediment transport in the Kuye River. The rtmoff modulus （defined as the annual average discharge per unit area, L/（s·km^2）） and the sediment transport modulus （defined as the annual suspended sediment transport per unit area, t/（yr km^2）） are introduced in this study to assess the changes in runoff and sediment yield for this watershed. The results show that the highest average monthly discharge during the study period in the Kuye River is 66.23 m^3/s in August with an average monthly sediment concentration of 88.9 kg/m^3. However, the highest average monthly sediment concentration during the study period in the Kuye River is 125.34 kg/m^3 and occurs in July, which has an average discharge of 42.6 m^3/s that is much less than the average monthly discharge in August. It is found that both the runoff modulus and sediment transport modulus at Wenjiachuan GS on the Kuye River has a clear downward trend. During the summer season from July to August, the sediment transport modulus at Wenjiachuan GS is much higher than those at Toudaoguai and Longmen GSs on the Yellow River. The easily erodible loess in the Kuye River watershed and the sparse vegetation are responsible for the extremely high sediment yield from the Kuye River watershed. The analyses of the grain size distribution of suspended load in the Kuye River are presented. The average monthly median grain size of suspended load in the Kuye River is largest in February and then decreases until June. In July, the average monthly median grain size of suspended load approaches another peak and decreases until September. Then, the median grain size of suspended load starts to increase until February of the following year. However, the average monthly median grain size of suspended load in the Yellow River at Toudaoguai and Longmen GSs is the smallest between early summer and late fall The median grain size in the Yellow River starts to increase in November and approaches the largest size in January. 相似文献
14.
Dejiang Fan Hongyan QiXiaoxia Sun Yong LiuZuosheng Yang 《Continental Shelf Research》2011,31(2):129-137
Annual sedimentary layers in core A from the Yangtze River (Changjiang) subaqueous delta were identified based on high-resolution biogenic silica (BSi) and grain-size records. The contents of BSi, the sediment grain-size and the sensitive grain-size fractions of <13.14 μm and 13.14-250 μm illustrated steady coincident fluctuations with the depth profile of core A. These fluctuations were inferred to reflect seasonal changes in physical and biological processes. For example, variations in the content of BSi likely represent changes in primary production in flood versus dry seasons. It in flood seasons was several times higher than that in dry seasons. The amounts of <13.14 and 13.14-250 μm fractions were complimentary to each other and co-varied with the BSi amount. Therefore, the BSi, grain-size and sensitive fractions can be used as proxies for the annual sedimentation. From 1992 to 2005, the estimated sedimentary rate based on the annual layer varied from 1.0 to 3.5 cm/a (mean of 2.07 cm/a), and these values varies with the annual sediment discharge from the Yangtze River to the sea. The significant seasonal variations in the water discharge, sediment load, ocean hydrodynamics and primary production, which are common in the area affected by the East Asian monsoon, are likely responsible for the formation of the annual sedimentary lamination. 相似文献
15.
Data on sediment flux at three hydrologic stations from the 1950s to 2006 are utilized to study the decadal,annual,and monthly variations in suspended sediment load delivered from the Pearl River to the ocean.Results show that variations in sediment flux from three main tributaries,including the West River,the North River and the East River,are spatially non-uniform.Since nearly 90%of the suspended sediment load comes from the West River,its variation has dominated the overall tendency of sediment flux in the entire Pearl River.Although a significant decreasing trend exists in the annual variation of the total sediment flux,the decadal change can be divided into an increasing phase and a decreasing phase,with the turning point between the two phases in the late 1980s.From the 1950s to the 1980s,the average annual river sediment flux increased by 30.43%.However,sediment flux has decreased significantly since the 1990s,with the average sediment flux being 38.60%less in the 2000s than that in the 1950s.The current sediment flux is also 52.93%less than its peak in the 1980s. The monthly variation pattern of the suspended sediment load transport to the sea is more interesting. For the West River,all months show a decreasing trend,and for most months the reduction values are significant.However,for the East River the sediment load shows a decrease trend in the dry season and an increase trend in the wet season.The method of regression analysis was used to study the influence of precipitation in the variation on the sediment flux.It was found that the climate change is not the main driving force behind the variation in suspended sediment load.Before the 1990s, intensive land use destroyed the vulnerable ecosystem of the upper Pearl River,and speeded up the process of rocky desertification.Consequently,aggravated soil erosion caused an increase in suspended sediment load.However,sediment retention within reservoirs had begun to play a dominant role after the massive construction of large dams after 1990,and resulted in a decrease in the suspended sediment load delivered to the ocean. 相似文献
16.
磷(P)是长江流域备受关注的污染物。乌江是长江八大支流之一,位于三峡水库近库尾江段。武隆断面是乌江入长江控制断面。对1998—2019时期武隆断面径流量、悬浮泥沙浓度(SS)与输沙量、磷浓度与通量(包括总磷(TP)、溶解态磷(DP)和颗粒态磷(PP))年际变化及季节特征进行研究,并基于河流基流分割原理对磷的来源进行了解析。结果表明,(1)1998—2019年,乌江武隆断面径流量在一定幅度内上下波动,而悬浮泥沙浓度和输沙量下降剧烈。(2)22年来,乌江TP和DP浓度与通量总体上呈先升高后下降的趋势,2009—2013年为磷污染峰值期,TP和DP浓度与通量远高于其它时期。(3)2007年是一个重要的时间节点,该节点前,TP的赋存形态以颗粒态为主,颗粒态磷在总磷中的占比均值为65%;该节点后,TP的赋存形态转变为以溶解态为主,颗粒态磷占比均值下降为16%,相应地,溶解态磷占比由35%上升为84%。水沙条件改变是磷形态发生显著变化的主要驱动力,磷污染程度亦是磷形态变化的重要影响因素。(4)磷通量在年内的季节分布发生了显著变化,丰水期磷通量减少,枯水期磷通量增加。(5)1998—2012、2009—2013和2014—2019年3个时期点源负荷占比分别为23.5%、36.8%和62.1%,呈增加趋势。(6)建议制定适宜的总磷控制目标,结合目前所存在的磷污染风险点,进一步强化监管,侧重源头治理。 相似文献
17.
Based on field data of river discharge, tide, tidal bore, and riverbed topography, the characteristics of river discharge, the effect of river discharge on riverbed erosion and sedimentation, and the feedback effect of riverbed erosion and sedimentation on the tide and tidal bore in the Qiantang River are analyzed. The results show that the inter-annual and seasonal variation of river discharge in the Qiantang River is noticeable, while the seasonal distribution of river discharge tends to be un... 相似文献
18.
Thi Phuong Quynh Le Viet Nga Dao Emma Rochelle‐Newall Josette Garnier XiXi Lu Gilles Billen Thi Thuy Duong Cuong Tu Ho Henri Etcheber Thi Mai Huong Nguyen Thi Bich Ngoc Nguyen Bich Thuy Nguyen Nhu Da Le Quoc Long Pham 《地球表面变化过程与地形》2017,42(9):1329-1341
Riverine transport of organic carbon from terrestrial ecosystems to the oceans plays an important role in the global carbon cycle. The Red River is located in Southeast Asia where river discharge, sediment loads and fluxes of elements (carbon, nitrogen and phosphorus) associated with suspended solids have been dramatically altered over past decades as a result of reservoir impoundment and land use, population, and climate change. Dissolved organic carbon (DOC) and particulate organic carbon (POC) concentrations were measured monthly at four stations of the Red River system from January 2008 to December 2010. The results reveal that POC changed synchronically with total suspended solids (TSS) concentration and with the river discharge, whereas no clear trend was observed for DOC concentration. The mean value of total organic carbon (TOC = DOC + POC) flux in the delta of the Red River was 31.5 × 1013 ± 4.0 × 1013 MgC.yr?1 (range 27.9–35.8 × 1013 MgC.yr?1 which leads to a specific TOC flux of 2012 ± 255 kgC.km?2.yr?1 during this 2008–2010 period. About 80% of the TOC flux was transferred to the estuary during the rainy season as a consequence of the higher river water discharge. The high mean value of the POC:Chl‐a ratio (1585 ± 870 mgC.mgChl‐a?1) and the moderate C:N ratio (7.3 ± 0.1) in the water column system suggest that organic carbon in the Red River system is mainly derived from erosion and soil leaching in the basin. The effect of two new dam impoundments in the Red River was also observable with lower TOC fluxes in 2010 compared with 2008. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
19.
《国际泥沙研究》2016,(4):351-359
Functional no-flow is a topic of considerable interest in the research and management of the Yellow River. The operation of the Xiaolangdi Reservoir has been a source of concern regarding hydraulic characteristics and hydro-environmental responses. However, the impacts of the reservoir on functional no-flow events have not been reported to date. Using a complete set of daily hydrological data from four key hydrological stations for the past six decades and at three different temporal scales (year, wet season and dry season), the differences in incoming water and functional no-flow events have been compared before and after the Xiaolangdi Reservoir began operation, using two sets of critical runoff values that were summarized from previous studies. The results indicate that the frequency of functional no-flow events has decreased since the Xiaolangdi Reservoir began to operate, based on critical runoff or dis-charge values defined by long term hydrological records, and the frequency decreased more when the critical values defining the new situation were used. However, functional no-flow events still occurred in the Lower Yellow River, especially in the lower reach during the wet season. The degree of severity of the functional no-flow events and the magnitude and variation of daily discharge are strongly linearly related before and after the reservoir began operation, regardless of which set of critical values were used to identify the functional no-flow events. 相似文献