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.

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.

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.

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.

Morphological Difference and Karyotype of Pelteobagrus fulvidraco in Dongting Lake Water System

[Objective] The research aimed to study the morphological characteristics and karyotype of Pelteobagrus fulvidraco in Dongting Lake water system.[Method] By using the conventional biological morphometry,PHA and colchicine injection method in vivo,the morphological characteristics and karyotype of P.fulvidraco in Yuanshui River and Lishui River of Dongting Lake were analyzed.[Result] In three ratio traits including standard length/head length,standard length/caudal peduncle depth,head length/snout length,P.fulvidraco of Yuanshui River and Lishui River had significant differences（P0.05）.However,the number and karyotype of their chromosomes were same.The chromosome number was 2n = 52,and the karyotype formula was 20M＋12SM＋10ST＋10T.The number of chromosome arm was 84.[Conclusion] The research result had certain theoretical guidance significance for the protection and utilization of wild P.resource in Dongting Lake water system.

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.

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.

Formation and water environmental evolution of the Nansihu Lake

Through high-resolution research of sedimental chronology and the sediment environmental indexes, such as graininess, minerals, magnetic parameters, pigment content, organic carbon and chronology in Ds-core and Ws-core in Nansihu Lake, the authors analyze the formation cause of the Nansihu Lake and its water environmental changes. Historical documents are also analyzed here in order to reach the conclusion. Researches indicate that the Nansihu Lake came into being about 2500 aBP and its evolution succession can be divided into four stages. In this evolution process, several scattered lakes merge into one large lake in the east of China. This process is distinctively affected by the overflow of the Yellow River, the excavation of the Grand Canal and other human activities.

Characteristics of Salt Water Movement in Iwaki River Estuary, Japan

The present study aims to investigate the characteristics of the motion of salt water and to show the temporal fluctuation of the vertical salinity distribution in Lake Jusan located in the estuary of Iwaki River in Aomori Prefecture, Japan. The Lake Jusan is the best productive water area of the shellfish, corbicula, in Japan in 2013. Then, the lake is very important in Aomori Prefecture as corbicula＇s home. The change of the brackish environment influences the ecology of the corbicula shellfish, then, the shellfish harvest changes every year. Now, it is important to make clear the characteristics of the motion of salt water in the lake. In the present study, observations for the motion of the salt water going up to the lake and going down from the lake to the sea were carried out from June to September in 2015. The present study investigates the time change of the salinity distribution in a perpendicular direction and shows that the movement of the saltwater in the lake can be generated well by the theory given by Sasaki et al., 2009.

Elevation of basal lacustrine sediments along the mid-lower reaches of the Yangtze River and its implications for the reconstruction of Holocene water levels

The middle and lower reaches of the Yangtze River,a primary region for freshwater lakes in China,have undergone significant transformations throughout the Holocene.These changes,driven by factors such as sea-level rise,climate change,and human activities,have led to the progressive elevation of water levels in this area.As a result,a floodplain has emerged,characterized by the formation of numerous shallow lakes along the river course.However,the pattern of water-level changes in the main channel of the Yangtze River during the Holocene remains unclear.This gap in knowledge poses challenges for understanding sediment transport dynamics,the interactions between the river and its adjacent lakes,and the prevention and control of flood disasters in the Yangtze River basin.To shed light on these issues,our study compiled data on the surface elevation and water depth of 81 lakes in the mid-lower reaches of the Yangtze River basin.Additionally,we analyzed historical water-level records from the 1900s to the 1970s at eight gauging stations from Shashi to Jiangyin along the river’s main stream.Our findings reveal that,particularly along the Jingjiang section,the basal elevation of most lakes is lower than the Yangtze River’s water level during the dry season.Conversely,the water level of the main stream exceeds that of both the floodplain and the lakes enclosed by the Jingjiang embankment.In the tidal reach,especially within the Taihu Lake basin,the basal elevation of lakes typically falls below sea level.Meanwhile,lakes located along the section from Chenglingji to Wuhu exhibit basal elevations that correspond with the Yangtze River’s annual average and dry season water levels.Given the widespread presence of lakes along the middle and lower reaches of the Yangtze River,our study introduces a new proxy for reconstructing the mean water level of the mid-lower Yangtze River in the Holocene.By analyzing sediments from Nanyi Lake and Chenyao Lake in the lower Yangtze River,we attempted to reconstruct the water level of the Yangtze River’s main channel since 8 ka BP.

Analysis of the distribution characteristics of ^(226)Ra and ^(228)Ra and their sources in the western part of Qinghai Lake

The ^226Ra and ^228Ra activities of Qinghai Lake surface water, groundwater, river water, suspended particles, and bottom sediments were measured in a gamma-ray spectrometer. The sources of ^226Ra and ^228Ra were discussed according to their distribution characteristics. ^226Ra and ^228Ra activities （dpm/（100 L）） ranged from 14.13±0.22 to 19.22±0.42 and 17.724-0.66 to 30.96：kl.47 in the surface water of the North Bay, respectively, and from 7.88±0.24 to 33.80±0.47 and 15.73±0.74 to 57.31±1.44, respectively, in the South Bay. The surface water near the estuary had a lower salinity and had a higher concentration of radium isotopes than the samples collected further away. The farther offshore the sample, the higher the salinity was, and the lower the radium isotope activity. The distribution of radium activities in the western part of Qinghai Lake is controlled by several factors, including Buha River runoff, desorption from suspended particles derived from the river, groundwater discharge, and a small amount of diffusion from the sediment.

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.

Water quality of Kaptai reservoir in Chittagong Hill Tracts of Bangladesh

A study was conducted in Kaptai reservoir, one of the largest man-made freshwater lakes of South-east Asia, to determine present status of water quality and its suitability for fishing and other uses. Water samplings were from middle part of the reservoir at 0.2 and 0.8 fractional depths at five different locations from upstream to downstream viz. Burburichara, Maichchari, Subolong, Basanthakum, and Rangamati. Water analyses show that concentrations of NO3-N, K＋ and total P, and suspended solid at all the sampling stations were beyond the recommended values for fish culture. Concentrations of Na^＋, Ca^2＋, Mg^2＋, SO4^2-, Cl^-, total dissolved solid （TDS）, dissolved oxygen （DO） and chemical oxygen demand （COD） were within the standards for aquaculture. Concentrations of NO3-N, SO4^2-, K＋ and total P showed no definite trend with depths, locations as well as rainy and dry seasons. Water pH, conductivity, Na^＋ and HCO3- contents were lower in rainy season, and DO and COD higher at almost all the locations in both the depths, compared with dry season. Total solids and concentrations of TDS, DO, COD, Ca^2＋, Mg^2＋ and Na^＋ were higher in upstream and decreased gradually towards downstream in the reservoir. Concentrations of DO and Ca2＋ and pH were higher and Mg2＋ less at 0.2-fractional depth than those at 0.8-fractional depth at almost all the locations. The reservoir is in mesotrophic condition containing high concentration of NO3-N and total P, in alarming status with the presence of excessive suspended solids from urban pollution around the town. It is necessary to adopt measures for protecting water quality in the reservoir due to such deteriorations.

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.

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.

The closed Lake Issyk-Kul as an indicator of global warming in Tien-Shan

Lake Issyk-Kul is the seventh deepest lake in the world situated inCentral Asiain theTien-ShanMountainsat the elevation of 1607 m above sea level. This area belongs toKyrgyzstan. From 1927 to 1997 the water level decreased by 3.4 m, and increased by 0.93 m from 1997 to 2011. The article analyzes the impact of the global warming on the Lake Issyk-Kul thermal regime and the components of its water balance: river discharge, precipitation, evaporation and lake level variations. It shows that the global warming has entailed the increase of the Lake Issyk-Kul water temperature down to the maximum depths, and river discharge increase due to the glaciers melting and the evaporation from the lake surface. The air temperature increase of 1 ℃ results in river discharge increas and lake level rise of 44 mm/year and surface evaporation increase of 88 mm/year. TheLakeIssyk-Kullevel increase after 1997, which takes place in the situation of global warming, was caused by the activation of the West air masses transport and increase of precipitation in autumn.

国家水网构建与生态安全保障辩证关系探析

国家水网建设和水生态安全保障是当前和今后一个时期水利行业的核心工作,准确认识两者的辩证关系,对于促进水利高质量发展、为中国式现代化提供高标准水安全保障具有重要意义。从国家水网建设与我国生态安全总体格局、北方生态屏障区保护修复、缺水地区河湖生态环境复苏、地下水超采区治理恢复、河湖水质改善、重要湿地及其生物多样性保护等六个方面的关系阐述了国家水网对于保障国家生态安全的重要作用。科学解析了国家水网规划、建设与运行对生态安全保障可能带来的影响,提出协同推进国家水网建设与生态安全保障的措施建议:优化国家生态安全保障整体格局,明晰重点区域生态安全保障水资源需求;在国家水网框架内,开展国家水生态网整体规划与建设;维护和发挥地下水应急储备水源功能,构建立体国家水网;加强水网内部源头减排与属地治理,建设清洁水网;发挥国家战略储备水源区作用,降低集中调水对长江流域的影响;加强水工程全生命期绿色技术研发与应用。