Evaluation of dynamic characteristics of silt in Yellow River Flood Field after freeze-thaw cycles

Frothing is a main disease of highways in Yellow River Flood Field, due to the loss of dynamic strength of roadbed soils under the couple effects of temperature, salt, and vehicle traffic load. This is strongly linked to the dynamic characteristics of silt in this region. To analyze these couple effects on the dynamic characteristics of silt, a series of tests(i.e., freeze-thaw cycling tests, vibration triaxial tests and ultrasonic wave velocity tests) were conducted and two kinds of silt(i.e., salt-free and 3%-salt silt) were designed. The results indicate that the dynamic shear strength and dynamic modulus decrease with increasing freeze-thaw cycles, while the damping ratio simultaneously increases. Furthermore, compared to salt-free silt, the decrement of dynamic shear strength and dynamic modulus of silt with 3% salt is more significant, but the damping ratio of 3%-salt silt is larger. In ultrasonic wave velocity tests, ultrasonic wave velocity of frozen soil specimens decreases as the number of freeze-thaw cycles increases. Based on the results of ultrasonic wave velocity tests, a preliminary model is proposed to evaluate damage of silt through field measurement ultrasonic data. The study could provide a theoretical basis for the treatment of silty soil highway.

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.

Yellow River Valley flood and drought disaster：spatial－temporal distribution prediction and early－warning

By means of analysing the historical data of flood-drought grade series in the past 2000 years(A.D.0-1900),especially in the last 5000 years (1470-1900) , this paper revealed the spatial-temporaldistribution features of severe flood and drought in Yellow River Valley. Statistical methods of varianceanalysis, probability transition and the principles of scale correspondence were employed tocomprehensively predicate 90's tendency of severe flood and drought in the Yellow River Valley. In addi-tion, this paper pointed out the possible breaching dikes, sectors and the flooding ranges by future's se-vere flood, meanwhile estimating the associated economic losses and impact to environment.

Natural Disasters of the Lower Reaches of Yellow River during the Longshan Period——The Natural Background of Dayu's Flood Control

It is very important to study the archaeological culture and origin of civilization in ancient China.The changes of the channels in the lower reaches of the Yellow River in the prehistoric period are part of the natural environmental background of the development of the ancient civilization in that area to be explored.This paper presents a series of legends,indications,scientific evidence,and macroscopic geographical background information of the evolution in the lower reaches of the Yellow River during the Longshan period.At first the river flowed from Northern Henan and Hebei to southwestern Shandong Province and Northern Anhui–Jiangsu provinces,and the mainstream of the Yellow River changed from the southeast to return to the north and flowed into the Bohai Sea in the late Longshan Period.During this period,floods were frequent.Various ethnic groups in the northern China plains suffered natural disasters and made great migrations which also contributed to the ethnic exchanges and integration.The people of the Central Plains made more dynamic adjustments in the relationship between mankind and the land by primitively escaping from the water and self–defensively controlling the rivers then to maintaining the local ecological environment by large–scale flood control measures,which promoted the settlement of Shandong,Henan,Jiangsu and Anhui provinces,the urban cultural development,and social evolution.Based on these events,the culture symbol of Dayu's Flood Control could be formed.

Flood Risk Forecasting and Early Warning Technology for Medium and Small Rivers in the Yellow River Basin Induced by Heavy Rain

The Yellow River Basin is one of the important sand-producing and sediment-transporting areas in China,and one of the three most important sand-producing areas in the world.The amount of sand and dust days in the“Three Norths”(Dongbei,Xibei,and Huabei)area has increased,and regional sand and dust storms have occurred frequently.There are generally more serious hidden danger points of debris flow geological disasters in small and medium-sized river basins.The technical achievements of flood risk forecasting and early warning for medium and small rivers in the Yellow River Basin based on rainstorm-induced floods are important technical supports for flood forecasting and early warning for medium and small rivers.Based on this,a case study was carried out on the problems such as the weak forecasting and early warning ability of flood disasters induced by heavy rain and the low accuracy of flood disaster loss assessment in the flood disasters of medium and small rivers,for the reference of relevant personnel.

基于D-S证据理论改进AHP-熵权的流域洪涝灾害评估研究

考虑致灾因子危险性、孕灾环境敏感性以及承灾体易损性,选取指标构建小清河流域洪涝灾害风险评估指标体系,提出一种基于D-S证据理论的改进AHP-熵权法计算指标权重,求取洪涝灾害风险指数,运用自然断点分级法确定洪涝灾害风险等级,分析小清河流域洪涝灾害风险空间分布情况。结果表明:小清河流域洪涝灾害风险总体上表现出南低北高的趋势,其中高风险区和较高风险区分别占流域面积的8.7%和14.3%,主要分布在小清河干流以及主要支流两岸。所得评估结果同“利奇马”台风发生期间实际洪灾风险分布情况一致,对比证明基于D-S证据理论的改进AHP-熵权法优于AHP和熵权法,可为小清河流域防洪减灾决策提供依据。

Changes in sediment discharge in a sediment-rich region of the Yellow River from 1955 to 2010: implications for further soil erosion control

The well-documented decrease in the discharge of sediment into the Yellow River has attracted considerable attention in recent years. The present study analyzed the spatial and temporal variation of sediment yield based on data from 46 hydrological stations in the sediment-rich region of the Yellow River from 1955 to 2010. The results showed that since 1970 sediment yield in the region has clearly decreased at different rates in the 45 sub-areas controlled by hydrological stations. The decrease in sediment yield was closely related to the intensity and extent of soil erosion control measures and rainstorms that occurred in different periods and sub-areas. The average sediment delivery modulus（SDM） in the study area decreased from 7,767.4 t/（km^2·a） in 1951–1969 to 980.5 t/（km^2·a） in 2000–2010. Our study suggested that 65.5% of the study area with the SDM below 1,000 t/（km^2·a） is still necessary to control soil deterioration caused by erosion, and soil erosion control measures should be further strengthened in the areas with the SDM above 1,000 t/（km^2·a）.

The Effects of Natural Capital Protection on Pastoralist's Livelihood and Management Implication in the Source Region of the Yellow River, China

The interaction among different livelihood capitals is a key to generate a deeper understanding of the livelihood sustainability.In this paper,we use net income per capita(economic capital),meat and milk production per capita(physical capital),and areas of fenced pasture,livestock shelter,grassland rodent control and planted grassland(physical capital) as proxy indicators of livelihood promotion,livelihood provision,and livelihood protection respectively.By developing a correlation model between pastoralists' livelihood protection and improvement,we found that(1) there is a statistically significant correlation between the pastoralists' livelihood protection and promotion;(2) based on the maximum effect of pastoralists' livelihood promotion and provision,there is a benchmark in the effect of the intervention intensity of livelihood capital(grassland resource protection) on livelihood improvement;(3) on basis of two indicators,i.e.net income per capita and meat production per capita,the reasonable scales of fenced pasture,livestock shelter and planted grassland are less than 843,860 and 46 thousand hectares(hm2) per year respectively.With the marginal effect of livelihood protection,moderately decreased areas of fenced pasture and planted grassland,and increased area of livestock shelter is a critical to ensure pastoralist's livelihood sustainability.

Numerical modeling of flow in continuous bends from Daliushu to Shapotou in Yellow River

The upper reach of the Yellow River from Daliushu to Shapotou consists of five bends and has complex topography. A two-dimensional Re-Normalisation Group （RNG） k-ε model was developed to simulate the flow in the reach. In order to take the circulation currents in the bends into account, the momentum equations were improved by adding an additional source term. Comparison of the numerical simulation with field measurements indicates that the improved two-dimensional depth-averaged RNG k-e model can improve the accuracy of the numerical simulation. A rapid adaptive algorithm was constructed, which can automatically adjust Manning＇s roughness coefficient in different parts of the study river reach. As a result, not only can the trial computation time be significantly shortened, but the accuracy of the numerical simulation can also be greatly improved. Comparison of the simulated and measured water surface slopes for four typical cases shows that the longitudinal and transverse slopes of the water surface increase with the average velocity upstream. In addition, comparison was made between the positions of the talweg and the main streamline, which coincide for most of the study river reach. However, deviations between the positions of the talweg and the main streamline were found at the junction of two bends, at the position where the river width suddenly decreases or increases.

Properties of Alkali-activated Yellow River Sediment-slag Composite Material

In order to consume the Yellow River sediment as much as possible and improve the longterm stability of the Yellow River, Yellow River sediment was utilized as the main raw material to produce a composite material. Ca(OH)_2 was used as alkali-activator to activate the active SiO_2 and Al_2O_3 compositions in Yellow River sediment. 10 wt% slag was added into the mixture to further improve the strength of the composites. The effect of activity rate of the Yellow River sediment and dosage of Ca(OH) _2 on the compressive strength of the Yellow River sediment-slag composite material at different curing ages was researched. XRD, SEM/EDS, light microscope and FTIR were used to further explore the products and the microstructure of the composite material. Results showed that the active ratio of sediment had a great influence on the compressive strength of specimen. In addition, the compressive strength of specimen increased with the increase of Ca(OH)_2dosage and curing age. When the dosage of Ca(OH)_2 was more than 5 wt% as well as the curing age reached 90 days, the compressive strength of the composite material could meet the engineering requirement. In the alkali-activated process, the main product was hydrated calcium silicate(C-S-H) gel, which filled up the gaps among the sediment particles and decreased the porosity of the specimen. Moreover, the CaCO_3 produced by the carbonization of the C-S-H gel and excess Ca(OH)_2 also played a role on the strength.

Flood and Waterlogging Disaster Damage Evaluation in Middle-Lower Yangtze River by 3S technology

The evaluation method, model and process for the flood and waterlogging disaster condition by GIS,RS and GPS technology and the method for setting up disaster condition database, dyke database and historical disaster damage database are presented. An index of flood damage degree(FDD) used to evaluate the relative degree of disaster loss and divide flood and waterlogging area is suggested. The value of flood damage degree can be calculated as follows :taking the various disaster losses of sample area in a base year as standard value and computing the ratios of various disaster loss values in different areas and years to the standard flood disaster loss values, then summing up the weighted ratios. The computed results are the value of flood damage degree in the every year. The macroscopic flood disaster distribution can be evaluated by the values of flood loss degree.

基于DRAINMOD-S和-NⅡ模型的黄河三角洲盐碱地玉米施氮策略

玉米是黄河三角洲(简称黄三角)滨海盐碱区主要粮食作物之一,氮肥合理施用对于促进该地区玉米产量提升、养分资源高效利用以及生态环境改善至关重要。为了明确该地区玉米的适宜施氮量和施氮制度,该研究基于2 a(2019—2020年)玉米栽培田间滴灌施肥试验,校验和评估DRAINMOD-S和DRAINMOD-NⅡ模型在该地区的适用性和可靠性,从而确定田间排水沟/管间距和建立玉米适宜施氮量估算模型与施氮制度。结果表明:1)DRAINMOD-S和-NⅡ模型可较准确地模拟黄三角滨海盐碱农田地下水埋深、土壤含盐量和硝态氮含量分布的动态变化,其模拟值与实测值之间的决定系数R2均大于0.80,标准化均方根误差(normalized root mean squared error,NRMSE)均低于25%;2)通过分析排水间距与土壤渍水和盐分胁迫减产效应间的关系,推荐该地区排水间距可设为17 m;3)在兼顾作物氮素需求(即吸氮量满足玉米自身需求)、土壤持续供氮能力(收获后土壤无机氮储量与播种时大抵相近)及养分淋失风险可控(氮淋失量尽量小)等目标的前提下,基于数值模拟确定了不同气候和初始土壤无机氮含量条件下的玉米适宜施氮量,并建立了其与主要环境变量如降雨量、降雨强度和初始土壤无机氮含量之间的定量关系(R^(2)=0.70,P<0.01);4)评估了典型枯水年、平水年、丰水年施肥1~3次下不同施肥时期组合的影响,表明不同水文年里都可选择在玉米拔节期-抽雄期(或拔节期-抽雄期-灌浆期)追施氮肥2(3)次。研究结果可为黄河三角洲滨海盐碱农田玉米氮素管理提供参考。

Studies on the Evolutionary Laws and Maintaining Mechanism of Renewability of the Yellow River's Water Resources

The Yellow River has a vast catchment area and historically it is the mother river of the Chinese nation. Now it serves as one of the main theatres for the on-going national campaign to develop China's western hinterland.……

基于GIS与DRASTIC模型的苏北黄泛平原典型区域地下水脆弱性评价

苏北黄泛平原地势平坦,浅部地层结构松散,地下水易受地表环境影响。为此,本文以南部的淮安市区为研究对象,选取影响研究区地下水脆弱性的7个主要指标,建立DRASTC脆弱性评价模型,利用GIS软件的空间分析功能,绘制出各指标分级图,而后进行各指标的加权叠加分析,得到脆弱性评价综合指数。评价结果表明区内地下水整体较脆弱,以苏北灌溉总渠为界,以北区域多为地下水脆弱性较高分区,总渠以南的洪泽区、施河-马甸-朱桥-博里一带为脆弱性中等分区。评价结果可为地下水污染防治、国土空间规划等工作提供科学的基础支持。

GRU-Transformer洪水预报模型构建与应用

洪水预报是黄河中游地区防洪减灾重要的非工程措施之一。研究通过耦合门控制循环单元(Gate Recurrent Unit,GRU)和Transformer机器学习模型,构建GRU-Transformer洪水预报模型,对黄河中游地区典型流域进行降雨径流模拟预测。同时将预报结果与ANN(Artificial Neural Network)、WOA-GRU(Whale Optimization Algorithm Gate Recurrent Unit)神经网络洪水预报模型的预报结果对比分析,着重探索如何将Transformer模型更好地应用于洪水预报领域,旨在提高黄河中游地区洪水预报精度。采用故县水库控制流域1990-2016年49场历史观测洪水数据,以24个站点实测降雨量及出口断面流量作为输入,不同预见期下的洪水过程作为输出,率定期为39场次,验证期为10场次。研究结果表明:GRU-Transformer模型在洪水预报种具有较好的适用性,在预见期1~6 h洪水预报中,GRU-Transformer预报精度较高,校准期和验证期的NSE均大于0.85,且预报精度在相同预见期下优于WOA-GRU和ANN模型,但预报精度会随着预见期增大而出现一定程度的下降;GRU-Transformer模型较稳定地更好预测洪峰,且在较小流量洪水过程预报时及洪水退水阶段模拟效果表现出优异效果,但随预见期增加出现低估洪峰现象;GRU-Transformer模型比WOA-GRU和ANN模型具有更好的鲁棒性,随洪水预见期增大,其预报精度呈缓慢下降,降低的最慢。因此,GRU-Transformer模型可以作为较好的洪水预报方法之一,相关成果为流域防洪安全提供了新的预报方法及科学决策依据。

龙羊峡水库后汛期入库径流特征及可蓄水量分析

以1956—2022年唐乃亥水文站实测水文数据为基础,采用数理统计方法,重点分析黄河源区后汛期径流特征,并结合龙羊峡水库满负荷发电流量,对龙羊峡水库在后汛期可蓄水量进行不同情景的分析讨论。研究表明:1)唐乃亥水文站后汛期径流量年际变化较大,丰枯不均,以正常偏枯为主,多年平均后汛期径流量占汛期径流量的29.1%;2)唐乃亥水文站后汛期日平均流量在1000 m^(3)/s以上的径流量平均为8.96亿m^(3),年际变化极大,以1000 m^(3)/s发电流量运用,龙羊峡水库蓄至正常蓄水位的保证率仅为10%,多数年份汛期结束后水位无法达到正常蓄水位2600 m。建议根据后期来水,适时调整进入后汛期的时机,优化和调整龙羊峡水库年度调度方案,为高效合理利用黄河源区后汛期水资源奠定基础。

黄河下游花园口至孙口河段高效输沙洪水阈值研究

河流能量耗散率变化反映了河道水沙输移能力以及河床形态的调整规律。本文研究区域为黄河下游花园口至孙口河段,从能量耗散角度出发,结合对实测资料的统计分析,探究了河流边界阻力能耗率与来水来沙、断面形态以及河床稳定性之间的定量关系,并基于边界阻力能耗率与河床稳定性双重指标,确定了花园口至孙口河段的高效输沙洪水阈值。研究结果表明:流量是影响边界阻力能耗率的主要因素,并与边界阻力能耗率的幂次呈线性相关;随着流量增大到2000 m^(3)/s以上,边界阻力能耗率随含沙量增加呈先减弱后增强的趋势。大流量条件下边界阻力能耗率与宽深比呈负相关关系,花园口与夹河滩断面形态复杂,相关性较弱;相比之下高村与孙口断面形态简单,相关性增强。非恒定水沙条件下的河床大多处于失稳状态,在综合考虑河床形态稳定及边界阻力能耗率最低的前提下,计算得出花园口至孙口河段的洪水高效输沙临界流量约为1500 m^(3)/s,含沙量约为23 kg/m^(3)。

干旱区与湿润区旱涝急转演变特征对比研究

以长江、黄河和淮河流域为研究对象,基于标准化旱涝急转指数,利用趋势分析、变点检验、小波分析、随机森林等方法探究典型干旱区与湿润区旱涝急转演变特征及其驱动因子。结果表明:湿润和半湿润区是极端旱涝急转事件的高频发生区,干旱区是极端旱转涝事件的高频发生区;干旱区的突变发生在1998年,湿润区的突变在1978年,未来干旱区更易发生旱转涝事件,湿润区则相反;气象因子在湿润区对旱涝急转的贡献度更大,大气环流对干旱区的影响突出,旱涝急转与不同驱动因子间存在非线性关系。

黄河下游花园口以上河道滞沙指标研究

水沙搭配关系是影响黄河下游河道冲淤调整的重要因素,局部河段滞沙则是改善下游水沙关系的有效手段之一。小浪底水库运用后,河槽沿程冲刷不均衡,河床粗化,细沙补给不足,输沙效率明显降低。分析黄河下游河道冲淤特性及水沙演进规律,建立不同类型洪水滞沙河段(花园口以上河段)与排洪瓶颈河段(高村—艾山河段)的冲淤关系。基于滞沙对河道行洪和稳定性的影响,以排洪瓶颈河段不淤积为约束,提出洪水滞沙的水沙优化配置指标。中泥沙洪水滞沙指标为:洪水平均流量为1800~3700 m^(3)/s,平均含沙量为66~235 kg/m^(3)。