A distributed non-point source pollution model: calibration and validation in the Yellow River Basin

The applicability of a non-point source pollution model—SWAT(soil and water assessment tools) in a large river basin with high sediment runoff modulus(770 t/km2 in the Yellow River) was examined. The basic database, which includes DEM, soil and landuse map, weather data, and land management data, was established for the study area using GIS. A two-stage “Brute Force' optimization method was used to calibrate the parameters with the observed monthly flow and sediment data from 1992 to 1997. In the process of calibration automated digital filter technique was used to separate direct runoff and base flow. The direct runoff was firstly calibrated, and the base flow, then the total runoff was matched. The sediment yield was calibrated to match well. Keeping input parameters set during the calibration process unchanged, the model was validated with 1998—1999's observed monthly flow and sediment. The evaluation coefficients for simulated and observed flow and sediment showed that SWAT was successfully applied in the study area: relative error was within 20%, coefficient of determination and Nash-Suttcliffe simulation efficiency were all equal to or above 0.70 during calibration and validation period.

Methodology to determine regional water demand for instream flow and its application in the Yellow River Basin

In order to realistically reflect the difference between regional water demand for instream flow and river ecological water demand as well as to resolve the problem that water demand may be counted repeatedly, a concept of regional water demand for minimum instream flow have been developed. The concept was used in the process of determining river functions and calculating ecological water demand for a river. The Yellow River watershed was used to validate the calculation methodology for regional water demand. CaIculation results indicate that there are significant differences in water demands among the different regions. The regional water demand at the downstream of the Yellow River is the largest about 14.893 × 10^9 m^3/a. The regional water demand of upstream, Lanzhou-Hekou section is the smallest about -5.012 × 10^9 m^3/a. The total ecological water demand of the Yellow River Basin is 23.06 × 10^9 m^3/a, about the 39% of surface water resources of the water resources should not exceed 61% in the Yellow River Basin. Yellow River Basin. That means the maximum available surface The regional river ecological water demands at the Lower Section of the Yellow River and Longyangxia-Lanzhou Section exceed the surface water resources produced in its region and need to be supplemented from other regions through the water rational planning of watershed water resources. These results provides technical basis for rational plan of water resources of the Yellow River Basin.

Impact of an artificial chute cutoff on the river morphology and flow structure in Sipaikou area of the Upper Yellow River

Artificial chute cutoff can fundamentally eliminate the threat of flood caused by the meandering river,but it significantly changes its morphodynamic characteristics.Channel adjustments after cutoff are rapid,which makes it difficult to study the interaction between river morphology and flow structure only through field measurement.However,numerical simulations can provide insights into the hydrodynamic characteristics after artificial chute cutoffs.In this study,both field measurement and numerical simulation are employed to investigate the flow structure and bed morphology caused by an artificial chute cutoff in Sipaikou area of the Upper Yellow River in 2018.The measured hydrological data provide boundary conditions and initial values for the numerical model.The field measurement results reveal that the concave bank of the study area is severely scoured up to 270 m after the artificial cutoff,and a 20 m deep scour hole and a 2.26 km long pool are formed at the entrance and near the left bank of the chute channel.The numerical simulation results of velocity at typical cross-sections are in good agreement with the measurement results.Flow separation and stagnation zones are observed near the right bank during the low flow conditions(discharge of at least 902 m^(3)/s),but this phenomenon is not seen during larger flow conditions(discharge exceeds 2000 m^(3)/s).Interestingly,flow recirculation zones are also found near the left and right banks of the scour hole.Further,a long flux belt is formed at the scour hole and the pool.Consequently,the impact of the bed topography on the hydrodynamic characteristics is relatively prominent when the discharge is small,while the impact on the river banks and river bed is more noticeable when the water discharge is large.In addition,high shear stress is observed near the left bank at the downstream of the studied area,which indicates that the left bank at the downstream is still being scoured.These results suggest that bank protection measures along the left bank are required to maintain the effectiveness of the artificial chute cutoff.

The relationship between ENSO cycle and high and low-flow in the upper Yellow River

Firstly, the hydrological and meteorological features of the upper reaches of the Yellow River above Tangnag are analyzed based on observation data, and effects of EI Nino and La Ni na events on the high and low flow in the upper Yellow River are discussed. The results show El Nino and La Nina events possess consanguineous relationship wi th runoff in the upper Yellow River. As a whole, the probability of low fl ow occurrence in the upper Yellow River is relatively great along wit h the occurrence of El Nino event. Moreover, the flood in the upper Yellow River occurs frequently with the occurrence of La Nina event. Besides, the results also show dissimilarity of El Nino event occurri ng time exerts greater impact on high flow and low flow in the uppe r Yellow River, that is, the probability of drought will be greater in the sam e year if El Nino event occurs in spring, the high-flow may happen in this y ear if El Nino occurs in summer or autumn; the longer the continuous period of El Nino is, the lower the runoff in the upper Yellow River is.

Numerical simulations of flow and sediment transport within the Ning-Meng reach of the Yellow River,northern China

Effective management of a river reach requires a sound understanding of flow and sediment transport generated by varying natural and artificial runoff conditions. Flow and sediment transport within the Ning-Meng reach of the Yellow River（NMRYR）, northern China are controlled by a complex set of factors/processes, mainly including four sets of factors：（1） aeolian sediments from deserts bordering the main stream;（2） inflow of water and sediment from numerous tributaries;（3） impoundment of water by reservoir/hydro-junction; and（4） complex diversion and return of irrigation water. In this study, the 1-D flow ＆ sediment transport model developed by the Yellow River Institute of Hydraulic Research was used to simulate the flow and sediment transport within the NMRYR from 2001 to 2012. All four sets of factors that primarily control the flow and sediment transport mentioned above were considered in this model. Compared to the measured data collected from the hydrological stations along the NMRYR, the simulated flow and sediment transport values were generally acceptable, with relative mean deviation between measured and simulated values of 〈15%. However, simulated sediment concentration and siltation values within two sub-reaches（i.e., Qingtongxia Reservoir to Bayan Gol Hydrological Station and Bayan Gol Hydrological Station to Toudaoguai Hydrological Station） for some periods exhibited relatively large errors（the relative mean deviations between measured and simulated values of 18% and 25%, respectively）. These errors are presumably related to the inability to accurately determine the quantity of aeolian sediment influx to the river reach and the inflow of water from the ten ephemeral tributaries. This study may provide some valuable insights into the numerical simulations of flow and sediment transport in large watersheds and also provide a useful model for the effective management of the NMRYR.

Formation Mechanisms and Geomorphic Evolution of the Erlian Mudflow Fans, Eastern Guide Basin of the Upper Reaches of Yellow River

Several argillaceous platforms lie along the Yellow River（YR） of the eastern Guide Basin, northeastern Tibetan Plateau, and their compositions, formation processes, and geomorphic evolution remain debated. Using field survey data, sample testing, and high-resolution remote sensing images, the evolution of the Erlian mudflow fans are analyzed. The data show significant differences between fans on either side of the YR. On the right bank, fans are dilute debris flows consisting of sand and gravel. On the left bank, fans are viscosity mudflows consisting of red clay. The composition and formation processes of the left bank platforms indicate a rainfall-induced pluvial landscape. Fan evolution can be divided into two stages： early-stage fans pre-date 16 ka B.P., and formed during the last deglaciation; late-stage fans post-date 8 ka B.P.. Both stages were induced by climate change. The data indicate that during the Last Glacial Maximum, the northeastern Tibetan Plateau experienced a cold and humid climate characterized by high rainfall. From 16–8 ka, the YR cut through the Erlian early mudflow fan, resulting in extensive erosion. Since 8 ka, the river channel has migrated south by at least 1.25 km, and late stage mudflow fan formation has occurred.

The characteristics of dike-break flood in different scenarios of the lower Yellow River based on numerical simulations

The lower Yellow River still faces the threat of flood due to the unusual precipitation caused by global environmental change, river channel sedimentation, hidden danger in the dike and unfavorable river regime of ＂hanging river＂. According to the characteristics of the dike-break flood of the Yellow River, this paper has simulated, in six different scenarios, the dike-break flood routing by inputting the terrain data, typical historical flood data and land use data of study area to two-dimensional unsteady flow model. The results show that： firstly, the routing process of flood will occupy other rivers on the way and return to the rivers after reaching the lower reaches; secondly, in the same river reach, flood inundating area of north band is bigger than that at corresponding location of south bank under the same historical flood; thirdly, it is different in the degree of flood inundation in different regions due to different geographical locations in flood plain; fourthly, the area of mainstream where flood is deep and flow velocity is quick is relatively smaller, but the area of non-mainstream, where flood is shallow and flow velocity is slow, is relatively big; and finally, the possible influenced area of the dike-break flood is 141,948 km^2.

Critical effects on the photosynthetic efficiency and stem sap flow of poplar in the Yellow River Delta in response to soil water

To explore the critical relationships of photosynthetic efficiency and stem sap flow to soil moisture,two-year-old poplar saplings were selected and a packaged stem sap flow gauge,based on the stem-heat balance method,and a CIRAS-2 portable photosynthesis system were used.The results show that photosynthetic rates(P_(n)),transpiration rates(T_(r)),instantaneous water use efficiency(WUE)and the stem sap flow increased initially and then decreased with decreasing soil water,but their critical values were different.The turning point of relative soil water content(W_(r))from stomatal limitation to nonstomatal limitation of P_(n)was 42%,and the water compensation point of P_(n)was 13%.Water saturation points of P_(n)and T_(r)were 64%and 56%,respectively,and the WUE was 71%.With increasing soil water,the apparent quantum yield(AQY),light saturation point(LSP)and maximum net photosynthetic rate(P_(n)max)increased first and then decreased,while the light compensation point(LCP)decreased first and then increased.When W_(r)was 64%,LCP reached a lower value of 30.7µmol m^(-2)s^(-1),and AQY a higher value of 0.044,indicating that poplar had a strong ability to utilize weak light.When W_(r)was 74%,LSP reached its highest point at 1138.3µmol·m^(-2)s^(-1),indicating that poplar had the widest light ecological amplitude and the highest light utilization efficiency.Stem sap flow and daily sap flow reached the highest value(1679.7 g d^(-1))at W_(r)values of 56%and 64%,respectively,and then declined with increasing or decreasing W_(r),indicating that soil moisture significantly affected the transpiration water-consumption of poplar.Soil water was divided into six threshold grades by critical values to maintain photosynthetic efficiency at different levels,and a W_(r)of 64-71%was classified to be at the level of high productivity and high efficiency.In this range,poplar had high photosynthetic capacity and efficient physiological characteristics for water consumption.The saplings had characteristics of water tolerance and were not drought resistant.Full attention should be given to the soil water environment in the Yellow River Delta when planting Populus.

Effects of Southward Flow of Yellow River on Eco-environment of Xu-Huai River Basin

Based on the historical records,the flood disasters in Xu-Huai River Basin caused by southward flow of Yellow River were studied,while its effects on Xu-Huai regional economic,transportation and eco-environment were also highlighted,and finally historical natural disasters were presented in this study.

Investigation on Water Pollution of Four Rivers in Coastal Wetland of Yellow River Estuary

[Objective] The study aimed at analysing water pollution of four rivers in coastal wetland of Yellow River estuary. [Method] Taking four seriously polluted rivers (Guangli River, Shenxian Ditch, Tiao River and Chao River) in coastal wetland of Yellow River estuary as study objects, water samples were collected from the four rivers in May (dry period), August (wet period) and November (normal period) in 2009 and 2010 respectively, then pollution indices like nutritive salts, COD, chlorophyll-a, petroleum, etc. were measured. Afterwards, the status quo of water pollution was assessed based on Nemero index and comprehensive trophic level index (TLI), so as to find out the integral status quo of water quality of wetland rivers and damages to aquatic ecological environment. [Result] On the whole, water pollution of four rivers in coastal wetland of Yellow River estuary was serious, in the eutrophication state, and the main pollutants were TN, TP, NH+4-N and petroleum. In addition, excessive N and P in the four rivers resulted in water eutrophication of Bohai Bay, so further leading to ride tide, which destroyed the coastal ecological environment of Bohai Sea. Moreover, compared with historical data, water pollution by nitrogen and phosphorus became more serious, while there was no obvious aggravation in the water pollution by petroleum. In a word, water pollution wasn’t optimistic on the whole. [Conclusion] The research could provide theoretical bases for the protection and utilization of river water in coastal wetland of Yellow River estuary and its coastal sea area.

Surface flow constructed wetland with composite plant bed for pretreatment of micro-polluted Yellow River raw water in China

In order to investigate the feasibility of pretreating the micro-polluted Yellow River raw water by constructed wetland, an experiment was conducted using a surface flow constructed wetland with composite plant bed. The contamination removal efficiency and their trends in the wetland treatment system were studied under different hydraulic loading rates(HLR). The contamination removal efficiencies were compared according to the seasonal change under optimum HLR. The result shows that in the same season, under different hydraulic loadings ranging from 2 to 6 m3/(m2·d) at the same period, the best HLR is 4 m3/(m2·d) in the experimental system. The average removal rates of COD, TN, ammoniacal nitrogen(NH4+-N), and TP in the constructed wetland are 38.37%, 45.97%, 39.86% and 41.69%, respectively. According to China Standard for Surface Water Resources (GB3838-2002), mean effluent of COD, TN, NH4+-N and TP can nearly reach Grade Ⅲ, GradeⅤ, GradeⅠand GradeⅠ, respectively. Furthermore, treatment efficiency of the system in summer is obvious higher than that in other seasons. The expenditure of constructing the constructed wetland with the average treating capacity of 176 m3/d and lifetime of 20 years is 17075.00 RMB. The average disposal cost is summed up to 0.17 RMB/m3, which shows that the pretreatment of the micro-polluted Yellow River raw water by constructed wetland is feasible.

基于River 2D模型的黄河花园口河段生态流量研究

针对目前生态流量研究方法难以充分考虑鱼类栖息地等生境因素的问题,以黄河花园口鲤鱼核心保护区为研究区域,选取黄河鲤鱼为研究物种,基于耦合水动力学模型和栖息地模型的River 2D模型确定黄河鲤鱼的生态流量,将水深和流速作为鱼类生存保护的限定性因子,采用栖息地模型模拟不同流量下对应的黄河鲤鱼的适宜栖息地面积。计算结果表明:花园口河段鲤鱼产卵期的最小生态流量为230 m^(3)/s,生长期的最小生态流量为430 m^(3)/s,越冬期的最小生态流量为150 m^(3)/s。计算结果可以为花园口核心鱼类保护区的鱼类保护以及黄河小浪底水库的生态调度提供参考。

Optimization of water-urban-agricultural-ecological land use pattern:A case study of Guanzhong Basin in the southern Loess Plateau of Shaanxi Province,China

Extensive land use will cause many environmental problems.It is an urgent task to improve land use efficiency and optimize land use patterns.In recent years,due to the flow decrease,the Guanzhong Basin in Shaanxi Province is confronted with the problem of insufficient water resources reserve.Based on the Coupled Ground-Water and Surface-Water Flow Model(GSFLOW),this paper evaluates the response of water resources in the basin to changes in land use patterns,optimizes the land use pattern,improves the ecological and economic benefits,and the efficiency of various spatial development,providing a reference for ecological protection and high-quality development of the Yellow River Basin.The research shows that the land use pattern in the Guanzhong Basin should be further optimized.Under the condition of considering ecological and economic development,the percentage change of the optimum area of farmland,forest,grassland,water area,and urban area compared with the current land use area ratio is+2.3,+2.4,-6.1,+0.2,and+1.6,respectively.The economic and ecological value of land increases by14.1%and 3.1%,respectively,and the number of water resources can increase by 2.5%.

黄河下游典型悬河段地表水-地下水对湿地形成条件影响

对比分析黄河下游径流及河道变迁特征、不同时期地下水流场特征,结合遥感解译手段解析地下水和地表水对沿黄湿地条件的影响,为该区湿地生态修复提供理论依据。结果表明:(1)黄河下游典型悬河段人工湿地面积增幅较多,自然湿地仍呈萎缩趋势,滩涂湿地破碎度上升,生态环境稳定性较差。(2)地表水流量和水位整体呈现逐年降低的趋势,且河道的游荡摆动依然明显,直接影响了河流滩涂湿地面积及其稳定性。(3)研究区浅层地下水位十余年最大下降5 m、二十余年最大下降9 m。浅层地下水的持续下降导致北岸堤外湿地面积减少;南岸堤外因引黄水和退水侧渗形成新的背河洼地,湿地面积呈增长趋势,生态环境稳定性相对较好。地表水和地下水连通性较好,较低的地下水位将会削弱河道径流的作用,对沿黄湿地整体发展不利。(4)减少地下水的开采,确保引黄水量充足,对黄河大堤外背河洼地部位湿地的发展有利。

黄河流经省域国家级自然保护区管理成效评估

开展自然保护区管理成效评估是实现保护管理目标的有效途径,但我国现有管理评估多集中于单一、同类型、同省域内的自然保护区,对中大型尺度多类型自然保护区管理成效的评估较少。黄河流经省域分布着许多国家重点生态功能区,国家级自然保护区作为生态屏障的重要基础,在维持区域生态安全方面具有突出作用。为促进区域生态保护和高质量发展,本文通过构建5类共26项的管理成效评估指标体系,采用基于证据的专家打分法,评估了黄河流经省域内82处国家级自然保护区2016—2020年间的管理成效,在识别影响管理成效关键因素的基础上提出了针对性的对策建议。结果表明:①2016年以来,黄河流经省域82处国家级自然保护区管理成效总体较好,优秀率达26.83%,良好率达64.63%,主要体现在管理主体、本底调查、保护对象等指标的平均得分较高。②Spearman相关分析表明,管理级别越高、建立越早,公共服务、规章制度、经费保障等方面越完善的保护区管理成效越好;此外,基础设施与日常巡护,科研监测与科普宣教、信息化建设,社区关系与生态修复、保护对象指标间存在显著正相关;③管理成效的短板主要体现在人才建设、综合执法、社区发展、人类干扰等方面,建议有关单位在人才队伍、行政执法、生态补偿等方面加以完善,以提升管理效果。

12种水生植物对农田退水氮磷的去除效果

【目的】探究不同水生植物对农田退水氮磷污染物的去除效果,为利用水生植物修复和防治水体污染提供科学依据。【方法】采用水培试验测定12种水生植物茎叶和根的生物量、氮磷含量、氮磷吸收量以及对水体氮磷的去除率,运用筛选指标的平均隶属函数值对12种水生植物去除氮磷能力进行聚类分析。【结果】挺水植物中,水葱、芦苇、香蒲净增生物量较高;芦苇氮吸收量最高达到201.22 mg·m^(-2),香蒲磷吸收量最高达到26.64 mg·m^(-2);芦苇对氨氮、硝氮、总氮、总磷去除率最高,分别达到98.56%、78.93%、80.22%、81.36%。浮水植物中,凤眼莲净增生物量最高;凤眼莲氮吸收量最高达到156.14 mg·m^(-2),睡莲磷吸收量最高达到23.48 mg·m^(-2);凤眼莲对氨氮、硝氮、总氮、总磷去除率最高,分别达到95.63%、76.01%、71.66%、80.58%。沉水植物中,狐尾藻净增生物量最高;狐尾藻氮吸收量最高达到230.75 mg·m^(-2),苦草磷吸收量最高达到26.11 mg·m^(-2);狐尾藻对氨氮、总氮去除率最高,分别达到97.94%、84.93%;苦草对硝氮、总磷去除率最高,分别达到76.32%、79.09%。芦苇、水葱、睡莲主要通过根吸收累积氮磷,其他9种水生植物主要通过茎叶吸收氮磷从而增加生物量去除水体氮磷。水体氮磷去除率与植物氮磷吸收量呈极显著正相关。芦苇、香蒲、狐尾藻为高效净化植物,苦草、水葱、凤眼莲、睡莲、千屈菜为较高效净化植物。【结论】挺水植物芦苇、香蒲、水葱、千屈菜,浮水植物睡莲和沉水植物狐尾藻、苦草对宁夏引黄灌区农田退水氮磷污染物去除效果较好。

基于数值模拟的黄河中游典型流域基流分割研究

基流作为河川径流中相对稳定的一种组分,同时也是干旱半干旱地区枯水期径流的主要来源,对流域的水资源优化配置及生态环境的维护有着十分关键的意义。基流分割结果的准确性对于预测流域水文过程以及探究基流变化规律有很大的影响。汾河作为黄河中游重要支流,关系着整个中游地区的经济发展,研究汾河的基流变化能有效表征黄河中游基流的变化机制,因此,选取适宜的分割方法显得尤为重要。基流分割方法众多,数值模拟法凭借其客观性、可重复性和易操作性等特点,且可对长系列冗长繁琐数据进行高效便捷处理,因此在实际应用中受到广泛认可。基于黄河中游汾河静乐水文站2006-2014年日径流资料,采用8种常用的数值模拟方法进行基流分割计算,分析径流年内、年际变化特征,从基流指数的不稳定系数、标准差和变异系数3个角度分析其特征,并分析年基流指数的相关性,比较典型年的基流过程与径流过程,选用Nash-Sutcliffe效率系数、平均相对误差和相关系数这3个指标来进行基流分割结果的有效性检验。结果表明:Chapman滤波法、Chapman-Maxwell滤波法和Eckhardt滤波法是静乐水文站控制流域较为适宜的基流分割方法,计算所得的BFI值分别为0.491、0.495、0.496。研究结果为黄河中游基流分割和基流变化规律等研究提供技术支持,为黄河中游水资源合理利用和更好地建设当地生态环境提供科学依据。

小浪底水库运行下花园口河段黄河鲤生态流量研究

【目的】大坝和水库等水利工程的修建在带来防洪减灾效益的同时,也给所在区域的水生生物栖息繁衍带来了一定影响,诊断关键水生生物的生态流量对大坝下游的生态环境修复工作具有重要意义。【方法】以黄河下游花园口河段为例,探讨了小浪底水库运行下不同流量情景下的黄河鲤栖息地质量情况,并由此推求黄河鲤的生态流量。基于栖息地模拟法,通过构建耦合栖息地适宜度模型的二维水动力模型,分析了黄河鲤鱼苗期、亲鱼期的栖息地适宜度指数空间分布,分别建立了黄河鲤两个生命阶段流量与栖息地加权可用面积关系曲线。【结果】结果表明:随着模拟流量的增大,黄河鲤不同生命阶段的栖息地适宜度指数空间分布及栖息地加权可用面积呈现先增加,达到峰值后逐渐减小的变化规律。【结论】黄河下游花园口河段的最小生态流量为1 150 m~3/s,适宜生态流量为1 450 m~3/s,最适宜生态流量为3 000 m~3/s,研究成果加深了对大流量情景下黄河鲤栖息地质量的认识,对黄河下游生态保护与修复具有重要意义。

汛期与非汛期水沙条件对黄河下游不同河段过流能力的影响

20世纪80年代以来黄河下游水沙输移特性显著改变,下游河道经历强来沙作用下的持续淤积与小浪底水库调控下的持续冲刷过程。基于黄河下游1986—2020年实测水沙数据与固定断面地形,计算了河段尺度的平滩流量,量化了汛期与非汛期水沙过程对各河段过流能力的相对贡献。结果表明:①小浪底枢纽运行前水流冲刷强度随时间减弱,下游河道呈汛期淤积、非汛期冲刷的整体淤积态势,平滩流量持续减小,最小过流能力小于2000 m^(3)/s。②小浪底枢纽运行后水流冲刷强度显著增大,尤其在非汛期,对河床冲刷产生重要影响;各河段过流能力显著恢复,其中游荡段恢复最为迅速。③各河段平滩流量与前5 a汛期、非汛期平均水流冲刷强度呈良好的幂律关系,该关系能较好地反映汛期与非汛期累积水沙过程对过流能力的综合影响。④小浪底枢纽运行后,非汛期水沙条件对平滩流量的贡献率增大,尤其是对游荡段具有重要影响(占比53%),对过渡段与弯曲段贡献则较小(占比不到20%)。