Evaluation of the water conservation function in the Ili River Delta of Central Asia based on the InVEST model

The Ili River Delta(IRD)is an ecological security barrier for the Lake Balkhash and an important water conservation area in Central Asia.In this study,we selected the IRD as a typical research area,and simulated the water yield and water conservation from 1975 to 2020 using the water yield module of the Integrated Valuation of Ecosystem Services and Tradeoffs(InVEST)model.We further analyzed the temporal and spatial variations in the water yield and water conservation in the IRD from 1975 to 2020,and investigated the main driving factors(precipitation,potential evapotranspiration,land use/land cover change,and inflow from the Ili River)of the water conservation variation based on the linear regression,piecewise linear regression,and Pearson's correlation coefficient analyses.The results indicated that from 1975 to 2020,the water yield and water conservation in the IRD showed a decreasing trend,and the spatial distribution pattern was"high in the east and low in the west";overall,the water conservation of all land use types decreased slightly.The water conservation volume of grassland was the most reduced,although the area of grassland increased owing to the increased inflow from the Ili River.At the same time,the increased inflow has led to the expansion of wetland areas,the improvement of vegetation growth,and the increase of regional evapotranspiration,thus resulting in an overall reduction in the water conservation.The water conservation depth and precipitation had similar spatial distribution patterns;the change in climate factors was the main reason for the decline in the water conservation function in the delta.The reservoir in the upper reaches of the IRD regulated runoff into the Lake Balkhash,promoted vegetation restoration,and had a positive effect on the water conservation;however,this positive effect cannot offset the negative effect of enhanced evapotranspiration.These results provide a reference for the rational allocation of water resources and ecosystem protection in the IRD.

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%.

Unraveling the mechanisms underlying lake expansion from 2001 to 2020 and its impact on the ecological environment in a typical alpine basin on the Tibetan Plateau

Yanhu Lake basin(YHB)is a typical alpine lake on the northeastern Tibetan Plateau(TP).Its continuous expansion in recent years poses serious threats to downstream major projects.As a result,studies of the mechanisms underlying lake expansion are urgently needed.The elasticity method within the Budyko framework was used to calculate the water balance in the Yanhu Lake basin(YHB)and the neighboring Tuotuo River basin(TRB).Results show intensification of hydrological cycles and positive trends in the lake area,river runoff,precipitation,and potential evapotranspiration.Lake expansion was significant between 2001 and 2020 and accelerated between 2015 and 2020.Precipitation increase was the key factor underlying the hydrological changes,followed by glacier meltwater and groundwater.The overflow of Yanhu Lake was inevitable because it was connected to three other lakes and the water balance of all four lakes was positive.The high salinity lake water diverted downstream will greatly impact the water quality of the source area of the Yangtze River and the stability of the permafrost base of the traffic corridor.

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.

Maintaining healthy rivers and lakes through water diversion from Yangtze River to Taihu Lake in Taihu Basin

On the basis of the Taihu water resources assessment, an analysis of the importance and rationality of the water diversion from the Yangtz,e River to Taihu Lake in solving the water problem and establishing a harmonious eco-environment in the Taihu Basin is performed. The water quantity and water quality conjunctive dispatching ＇decisi＂ofi-makifig support system, which ensures flood control, water supply and eco-aimed dispatching, is built by combining the water diversion with flood control dispatching and strengthening water resources monitoring and forecasting. With the practice and effect assessment, measures such as setting the -integrated basin management format, further developing water diversion and improving the hydraulic engineering projects system and water monitoring system are proposed in order to maintain healthy rivers and guarantee the development of the economy and society in the Taihu Basin.

Morphological Characteristics of Cambodia Mekong Delta and Tonle Sap Lake and Its Response to River-Lake Water Exchange Pattern

Tonle Sap Lake is the largest river-connected lake, buffer area and ecological zone of Mekong River, which plays a huge role in dispelling flood peak and compensating water, and the conservation of biological diversity. The river-lake relationship between Mekong River and Tonle Sap Lake is unique and has always been a major focus in the international community. The land terrain and under-water topography were used to analyze the morphological characteristics of Cambodia Mekong Delta and Tonle Sap Lake. Long series of hydrological data of river-lake controlling stations were used to analyze the water level variation characteristics and water volume exchange pattern between Mekong River and Tonle Sap Lake, and the response relationship to river-lake morphological characteristics were also researched. The results show that: Cambodia Mekong Delta and Tonle Sap Lake Area is low-lying and flat with gentle channel gradient and water surface gradient, making the relationship between water level and area (or volume) smooth. The channel storage capacity of Mekong River and Tonle Sap River is not enough compared to the inflow, so vast flooding plain is extremely prone to be inundated, making the flood relationships between the left and right banks become very complicated. Tonle Sap Lake is a seasonal freshwater lake with water flowing in and flowing out, and the timing and intensity of water exchange with Mekong River are closely related to the water flow resistance at the exit section of Tonle Sap Lake and the cross-sectional area of Tonle Sap River, which can be reflected by the river-lake water level difference and the water level of Tonle Sap River. Affected by the river-lake morphological characteristics, the water exchange intensity between Mekong River and Tonle Sap Lake is great. Tonle Sap Lake not only stores 14.4% of flood volume (39.7 billion m3) from the Mekong River every year, but also supplies 29.7% of dry water (69.4 billion m3) to the Mekong River. Influenced by the adjustment of the floodplain, the water level fluctuation of Mekong River and Tonle Sap Lake is slow, and the rising and droop rates of water level are positively correlated with the floodplain storage area. The research results will help to understand the relationship mechanism between Mekong River and Tonle Sap Lake and provide a scientific basis for the comprehensive governance of Cambodia Mekong Delta and Tonle Sap Lake Area.

Evaluation on Current Situation of the Water Ecology of the Main Rivers and Lakes in the Liaohe River Basin

In this paper,15 rivers and 10 lake reservoirs in the Liaohe River basin were taken as research objects. Based on six indexes: satisfaction situation of ecological water demand,standard-reaching rate of water quality in water function area,eutrophication index of lakes and reservoirs,longitudinal connectivity of rivers,reserve rate of important wetlands and status of important aquatic habitat,water ecological conditions of main rivers and lakes in the basin were evaluated. The results showed that the rivers with better ecology were mainly distributed in east mountainous area of Liaoning,such as the upper reaches of the Hunhe River and the Taizi River;the problems of water pollution,ecological water shortage and habitat shrinkage were widespread in the Liaohe River basin,and the situation of water ecological security in the Liaohe River basin still faced great pressure.

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.

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.

Relationship between Land Cover Changes with Water Quantity in Lake Victoria—A Case Study of Mara River Basin in Tanzania

LV(Lake Victoria)is valuable to the East African sub region and Africa in general,sources of water for LV are from its catchment areas and tributaries e.g.Kagera and Mara Rivers on Tanzania part.Apparently,catchment areas in proximities of LV and on MR(Mara River),indeed on MRB(Mara River Basin)in particular,are experiencing increased anthropogenic activities such as mining,fishing,settlements,agriculture etc.,which lead to increased water usage,land degradation and environmental pollution.Such activities threaten the sustainability of the environment surrounding MRB and impliedly LV and its ecosystem.The level of water in LV is reported to be declining threatening its extinction.This paper is reporting on a study undertaken to establish the relationship between land cover changes with ground water discharge from specifically MRB into LV over the period of 24 years,i.e.1986 to 2010.Methodology used is assessment of vegetation changes by using remote sensing through analysis of TM(Thematic Mapper)Landsat Images of 1986,1994,2002 and 2010 ETM(Enhanced Thematic Mapper)Landsat images,from which respective land cover change maps were generated and compared with ground water levels from MRB.Results indicates that there is a significant decline of land cover and ground water flowing into LV from MRB,and that there is positive correlation between land cover changes and the quantity of ground water flowing from MRB to LV.This phenomenon is common to all tributaries of LV,thus leading to decline of water in LV.It is recommended that relevant government institutions should endeavor formulating policies to control excessive use of wetlands and drylands in the proximity of LV and MRB in particular,such that the flow of water to LV may be sustained.

Climate Change Impact to the Water Resources of Eastern Caucasus （Kura Basin） Rivers and Ways of Its Mitigation

This article is about assessment of climate change impact to water resources of Eastern Caucasus rivers for different period in the past and expected future trends by use of different sceneries. According to the results of assessment increase of air temperature in last 30 years for about 0.5-1.0 degree Celsius lead to reduction of flow by 5%. In regions where in addition to rising of temperature also precipitations are reduced this figure makes 10%. According to climate sceneries increase of air temperature in the future for 4.0-4.5 degree Celsius may lead to reduction of water resources for 30%. Different measures of adaptation have been identified in the article to combat water scarcity linked to impact of climate change.

Ecosystem Service Flow Insights into Horizontal Ecological Compensation Standards for Water Resource: A Case Study in Dongjiang Lake Basin, China

Water supply services(WSSs) are critical for the regional water balance and water circulation, but relevant studies have not established the relationship between WSSs and human well-being. This research identifies the scope of areas that benefit from WSSs from an ecosystem service flow perspective. Moreover, the path and quantity of the flow of WSSs are simulated to provide a scientific theoretical basis for ecosystem service management and ecological compensation. The Dongjiang Lake Basin is a national priority river basin in China where ecological compensation pilot programmes concerning water resources are top priorities. Dongjiang Lake Basin experienced an increase and then a decrease in the overall supply of water, with an average net water supply of 1096–1500 mm for the years 1995, 2000, 2005 and 2010. The water demand increased each year in service beneficiary areas(SBAs), varying from 387 to 580 mm. Overall, Dongjiang Lake Basin met the net water demands of the actual SBAs in the lower reaches, but a gap in the water supply and demand emerged gradually. This research provides an understanding of the functional mechanisms for the provision, demand and flow of WSSs and provides a scientific theoretical basis for ecosystem service management and ecological compensation.

Characteristics and Effects of Inorganic Nitrogen in East Water-source and Inflow Rivers of Chaohu Lake

[Objective] To study the characteristics and effects of inorganic nitrogen in east water-source and inflow rivers of Chaohu Lake. [Method] The speciation and distribution characteristics of dissolvable inorganic nitrogen （DIN） in east water-source and inflow rivers of Chaohu Lake were investigated, and their effects on water qual- ity were examined. [Result] The concentrations of NH3-N and NO2--N were the high in flood season, and low in non-flood season, while the concentration of NO3--N pre- sented the opposite trend; the concentration of NO3--N was the highest in Shuangqiao estuary, where the pollution was the worst. DIN in Zhegao estuary and Xiaozhegao estuary was mainly caused by domestic sewage and industrial wastewaters; surface runoff and pollution from ships contribute the most to the DIN content in Shuangqiao estuary. [Conclusion] This study provided basic data and theoretical basis for the control and management of eutrophication in Chaohu Lake.

Relationship Between Changes of River-lake Networks and Water Levels in Typical Regions of Taihu Lake Basin,China

The typical regions of the Taihu Lake Basin,China,were selected to analyze the variation characteristics of river-lake networks under intensive human activities.The characteristics of the fractal dimension of river networks and lakes for different periods were investigated and the influences of river system evolution on water level changes were further explored through the comparison of their fractal characters.The results are as follows:1) River network development of the study area is becoming more monotonous and more simple;the number of lakes is reducing significantly,and the water surface ratio has dropped significantly since the 1980s.2) The box dimension of the river networks in all the cities of the study area decreased slowly from the 1960s to the 1980s,while the decrease was significant from the 1980s to the 2000s.The variations of lake correlation dimension are similar to those of the river network box dimensions.This is unfavorable for the storage capacity of the river networks and lakes.3) The Hurst exponents of water levels were all between 0.5 and 1.0 from the 1960s to the 1980s,while decreased in the 2000s,indicating the decline in persistence and increase in the complexity of water level series.The paper draws a conclusion that the relationship between the fractal dimension of river-lake networks and the Hurst exponents of the water level series can reveal the impacts of river system changes on flood disasters to some extent:the disappearance of river networks and lakes will increase the possibility of flood occurrence.

Rare earth elements in tropical surface water,soil and sediments of the Terengganu River Basin,Malaysia

The 14 stable rare earth element(REE) concentrations and distribution patterns were investigated for surface waters(n=51),soils(n=52) and sediments(n=42) from the tropical Terengganu River basin,Malaysia.The chondrite normalized REE patterns of soils developed on four geological units showed enrichment of LREE,a pronounced negative Eu,and depletion of HREE with an enrichment order granite>>metasedimentary>alluvium>volcanic.The REE patterns in sediments reflected the soil REE patterns with an ove...

Water Quality Assessment of the River Nile System:An Overview

Objectives The main objective of the present article is to assess and evaluate the characteristics of the Nile water system , and identify the major sources of pollution and its environmental and health consequences. The article is also aimed to highlight the importance of water management via re-use and recycle of treated effluents for industrial purpose and for cultivation of desert land. Method An intensive effort was made by the authors to collect, assess and compile the available data about the River Nile. Physico-chemical analyses were conducted to check the validity of the collected data. For the determination of micro-pollutants, Gas Chromatography (GC) and High Performance Liquid Chromatography (HPLC) were used. Heavy metals were also determined to investigate the level of industrial pollution in the river system. Results The available data revealed that the river receives a large quantity of industrial, agriculture and domestic wastewater. It is worth mentioning that the river is still able to recover in virtually all the locations, with very little exception. This is due to the high dilution ratio. The collected data confirmed the presence of high concentrations of chromium and manganese in all sediment samples. The residues of organo-chlorine insecticides were detected in virtually all locations. However, the levels of such residues are usually below the limit set by the WHO for use as drinking water. The most polluted lakes are Lake Maryut and Lake Manzala. Groundwater pollution is closely related to adjacent (polluted) surface waters. High concentrations of nutrients, E.coli, sulfur, heavy metals, etc. have been observed in the shallow groundwater, largely surpassing WHO standards for drinking water use. Conclusion A regular and continuous monitoring scheme shall be developed for the River Nile system. The environmental law shall be enforced to prohibit the discharge of wastewater (agricultural, domestic or industrial) to River Nile system.

Water quantity-quality combined evaluation method for rivers＇ water requirements of the instream environment in dualistic water cycle： A case study of Liaohe River Basin

In this article the meaning of the quantity and quality of environmental flows of river in dualistic water cycle is discussed, and compared with the meaning of unitary water cycle. Based on the analysis of the relationship between environmental flows of river requirements, the efficiency of water resource usage, the consumption coefficient, and the concentration of waste water elimination, the water quantity and water quality calculation method of the environmental flows of river requirements in dualistic water cycle is developed, and the criteria for environmental flows of river requirements are established, and therefore the water quantity-quality combined evaluation of natural river flows requirements are realized Taking the Liaohe River as a model, the environmental flows of river requirements for Xiliao River, Dongliao River, mainstream Liaohe River, Huntai River and northeast rivers along the coasts of the Yellow and Bohai seas in unitary water cycle are calculated, each taking up 39.3%, 63.0%, 43.9%, 43.3% and 43.5% of runoff respectively. Evaluated according to Tennant recommended flow, the results show that： except Xiliao River is ＂median＂, the rest are all upon ＂good＂, the Dongliao River is even ＂very good＂. The corresponding results in dualistic water cycle are that, the proportion of natural flows for each river is 57.5%, 74.1%, 60.8%, 60.3% and 60.4%; while the combined evaluation results show that： considering ＂quantity＂, except Xiliao River, the rest rivers can all achieve the ＂quantity＂ criteria of the en- vironmental flows of river requirements, but if considering the aspect of ＂quality＂, only Dongliao River can reach the ＂quality＂ standard. By water quantity-quality combined evaluation method, only Dongliao River can achieve the criteria. So the water quality is the main factor that determines whether the environmental flows can meet the river ecosystem demands.

Variation of Floods Characteristics and Their Responses to Climate and Human Activities in Poyang Lake, China

The Poyang Lake is one of the most frequently flooded areas in China. Understanding the changing characteristics of floods as well as the affecting factors is an important prerequisite of flood disaster prevention and mitigation. The present study identified the characteristics variations of historical floods in the Poyang Lake and their tendencies based on the Mann-Kendall(M-K) test, and also investigated the related affecting factors, both from climate and human activities. The results revealed that the highest flood stages, duration as well as hazard coefficient of floods showed a long-term increasing linear trend during the last 60 years with the M-K statistic of 1.49, 1.60 and 1.50, respectively. And, a slightly increasing linear trend in the timing of the highest stages indicated the floods occurred later and later during the last six decades. The rainfall during the flood season and subsequent discharges of the Changjiang(Yangtze) River and runoff from the Poyang Lake Basin were mainly responsible for the severe flood situation in the Poyang Lake in the 1990 s. In addition, the intensive human activities, including land reclamation and levee construction, also played a supplementary role in increasing severity of major floods. While, the fewer floods in the Poyang Lake after 2000 can be attributed to not only the less rainfall over the Poyang Lake Basin and low discharges of the Changjiang River during flood periods, but also the stronger influences of human activity which increased the floodwater storage of the Poyang Lake than before.

Effect of Froude similitude deviation on curved channel simulations: A case study in the Middle Yangtze River

Froude similitude and friction similitude are the two crucial similarity conditions that are often used in physical-scale modeling of rivers.However,models often deviate from Froude similitude when dealing with real-world situations.This study developed several fixed-bed river models with various curvatures to determine the effect of Froude similitude deviation on curved channel modeling.Models were constructed according to the characteristics of the Middle Yangtze River.Differences in longitudinal slope,transverse slope,and main stream line location were measured by varying Froude similitude deviation.The deviations of longitudinal slope and velocity were negligible because friction similitude was accounted for.The transverse slope varied significantly with the Froude similitude deviation,and the main stream line varied with the curvature and Froude similitude deviation.Formulae were derived to estimate the slope deviation.These analyses helped to clarify the feasibility of the method of Froude similitude deviation for curved channels.

Sediment transport following water transfer from Yangtze River to Taihu Basin

To meet the increasing ：need of fresh water and to improve the water quality of Taihu Lake, water transfer from the Yangtze River was initiated in 2002. This study was performed to investigate the sediment distribution along the river course following water transfer. A rainfall-runoff model was first built to calculate the runoff of the Taihu Basin in 2003. Then, the flow patterns of river networks were simulated using a one-dimensional river network hydrodynamic model. Based on the boundary conditions of the flow in tributaries of the Wangyu River and the water level in Taihu Lake, a one-dimensional hydrodynamic and sediment transport numerical model of the Wangyu River was built to analyze the influences of the inflow rate of the water transfer and the suspended sediment concentration （SSC） of inflow on the sediment transport. The results show that the water transfer inflow rate and SSC of inflow have significant effects on the sediment distribution. The higher the inflow rate or SSC of inflow is, the higher the SSC value is at certain cross-sections along the ：river course of water transfer. Higher inflow rate and SSC of inflow contribute to higher sediment deposition per kilometer and sediment thickness. It is also concluded that a sharp decrease of the inflow velocity at the entrance of the Wangyu River on the river course of water transfer induces intense sedimentation at the cross-section near the Changshu hydro-junction. With an increasing distance from the Changshu hydro-junction, the sediment deposition and sedimentation thickness decrease gradually along the river course.