Changes in Hydrochemical Characteristics of Water Bodies in the Southern Aral Region

Based on the hydrochemical characteristics of water bodies in the northwestern part of the southern Aral Sea region, limnic ecosystems are shown to be liable to anthropogenic changes. The dynamics of the salinity, ionic composition, oxygen content of water, and nutrients under human impact on water bodies of the southern Aral Sea region are shown.     

Natural Tritium as an Indicator of Changes in the Vertical Structure of Caspian Sea Water Mass with Sea Level Variations

Analysis of changes in the vertical distribution of tritium in the Caspian Sea water mass in 1994–1996 led to a conclusion that the sea level fall that started in 1996 was accompanied by a rearrangement of the water mass steady hydrological structure characteristic of the high sea-level stand.__________Translated from Vodnye Resursy, Vol. 32, No. 4, 2005, pp. 406–409.Original Russian Text Copyright © 2005 by Brezgunov, Ferronskii.     

The Baltic Sea Experiment BALTEX: A brief overview and some selected results of the authors

The mechanisms responsible for the transfer of energy and water within the climate system are under worldwide investigation within the framework of the Global Energy and Water Cycle Experiment (GEWEX) to improve the predictability of natural and man-made climate changes at short and long ranges and their impact on water resources. Five continental-scale experiments have been established within GEWEX to enable a more complete coupling between atmospheric and hydrological models. One of them is the Baltic Sea Experiment (BALTEX).In this paper, the goals and structure of BALTEX are outlined. A short overview of measuring and modelling strategies is given. Atmospheric and hydrological model results of the authors only are presented. These include also the validation of precipitation using station measurements as well as validation of modelled cloud cover with cloud estimates from satellite data. Furthermore, results of a large-scale grid based hydrological model to be coupled to atmospheric models are presented.This research has never been possible without the contribution of research groups and operational institutions from all 10 member countries. We concentrate here on results obtained at the GKSS research center.     

Modelling the hydrologic effects of dynamic land‐use change using a distributed hydrologic model and a spatial land‐use allocation model

This study develops a novel approach for modelling and examining the impacts of time–space land‐use changes on hydrological components. The approach uses an empirical land‐use change allocation model (CLUE‐s) and a distributed hydrological model (DHSVM) to examine various land‐use change scenarios in the Wu‐Tu watershed in northern Taiwan. The study also uses a generalized likelihood uncertainty estimation approach to quantify the parameter uncertainty of the distributed hydrological model. The results indicate that various land‐use policies—such as no change, dynamic change and simultaneous change—have different levels of impact on simulating the spatial distributions of hydrological components in the watershed study. Peak flow rates under simultaneous and dynamic land‐use changes are 5·71% and 2·77%, respectively, greater than the rate under the no land‐use change scenario. Using dynamic land‐use changes to assess the effect of land‐use changes on hydrological components is more practical and feasible than using simultaneous land‐use change and no land‐use change scenarios. Furthermore, land‐use change is a spatial dynamic process that can lead to significant changes in the distributions of ground water and soil moisture. The spatial distributions of land‐use changes influence hydrological processes, such as the ground water level of whole areas, particularly in the downstream watershed. Copyright © 2010 John Wiley & Sons, Ltd.     

Changes in the Lena River runoff during the Holocene

The spatial and temporal changes in the Lena River runoff over the last 9 thousand years are reconstructed through studying the freshwater microfossils in sediment cores obtained from the Laptev Sea inner shelf immediately adjacent to the Lena delta and subject to the freshening effect of river water inflowing the sea through the main arms of the delta (the Trofimovskaya, Bykovskaya, and Tumatskaya arms), the sediments having been thoroughly AMS ¹⁴C dated. The freshwater species of diatoms (predominantly the river ones) and green algae that enter the shelf with river water served as indicators of river runoff. The reconstruction of paleosalinity of the sea surface water in the regions under study is based on the relationships (established earlier) between the distribution of freshwater diatoms in the surface layers of sediments in the Arctic seas and the gradients of water salinity in summer. Data on variations in the composition of aquatic microfossil associations in sediments and the reconstructed paleosalinity in the regions of the eastern and western paleovalleys of the Lena River are used to determine the main paleohydrologic events that controlled the variations in the Lena runoff into the shelf zone of the Laptev Sea during the Holocene.     

Hydrological processes in the Amur Liman

Data collected in 2005–2009 are analyzed to study the main features of hydrological processes in the main part of the Amur estuary—the Amur Liman. Data on the morphological structure of the liman and the surge and tidal phenomena are analyzed. The variability of salinity field in different phases of river hydrological cycle is studied. Wind currents are shown to have an appreciable effect on the water exchange and river runoff distribution between the seas of Japan and Okhotsk in the ice-free season. In summer, the Amur runoff enters the Sea of Okhotsk. The main features of the structure of liman water in summer are identified. The northern part of the estuary is freshened by river runoff and partially mixed; it has a two-layer structure. A salt wedge forms at the northern exit from the liman into the Sea of Okhotsk, and strong water stratification is observed there.     

The Effect of the Long-Term Variations in Climate Conditions on the Hydrological Structure and Ecology of the Black Sea

A scale of the atmospheric thermal conditions is elaborated, and the statistical distribution of the air temperature deviations from the norm is assessed. The cause of formation of the extreme atmospheric thermal conditions is found. Parameters of the winter hydrological structure are calculated, and their correlation with climatic conditions is shown. For the first time, the dynamic factor affecting the Black Sea hydrological structure is established, and its effect is shown.     

Present-Day Estimates of the Hydrological Conditions for the Formation of Biological Production in the Sea of Azov

The main feature of the present-day hydrological conditions governing the formation of biological production in the Sea of Azov is shown to be the appreciable freshening of seawater, which is due, first of all, to climate changes. It is established that the freshening of seawater can benefit most for the reproduction of fish resources in the Sea of Azov only if the river runoff withdrawals are reduced step by step down to 5 km³/year (14% of the norm), the annual runoff is maintained at 35–36 km³, and the spring runoff is restored to 18.5 km³.     

Changes in Moskva R. runoff under anthropogenic impacts

An algorithm has been proposed for assessing the hydrological role of the main anthropogenic factors governing the formation of Moskva R. runoff both separately and in total. The effect of landscape transformations, hydroengineering structures, and water use on the runoff in the Moskva R. basin has been analyzed for characteristic periods in the recent 150 years (the middle XIX century, the early XX century, 1960–1980, and the first decade of the XXI century, the period of calculation of the average long-term runoff). The main hydrological effect of urbanization in the Moskva R. basin on river runoff formation in recent decades has been demonstrated. The shares of the anthropogenic and climatic factors in the overall changes in Moskva R. runoff in the early XXI century have been evaluated.     

Changes in the long-term hydrological regimes and the impacts of human activities in the main Wei River,China

ABSTRACT

Under the combined influence of climate changes and human activities, the hydrological regime of the Wei River shows remarkable variations which have caused many issues in the Wei River in recent decades, such as a lack of freshwater, water pollution, disastrous flooding and channel sedimentation. Hence, hydrological regime changes and potential human-induced impacts have been drawing increasing attention from local government and hydrologists. This study investigates hydrological regime changes in the natural and measured runoff series at four hydrological stations on the main Wei River and quantifies features of their long-term change by analysing their historical annual and seasonal runoff data using several approaches, i.e., continuous wavelet transform, cross-wavelet, wavelet coherence, trend-free pre-whitening Mann-Kendall test and detrended fluctuation analysis. By contrasting two different analysis results between natural and measured river runoff series, the impacts of human activities on the long-term hydrological regime were investigated via the changes of spatio-temporal distribution in dominant periods, the trends and long-range memory of river runoff. The results show : (a) that periodic properties of the streamflow changes are the result of climate, referring to precipitation changes in particular, while human activities play a minor role; (b) a significant decreasing trend can be observed in the natural streamflow series along the entire main stream of the Wei River and the more serious decrease emerging in measured flow should result from human-induced influences in recent decades; and (c) continuous decreasing streamflow in the Wei River will trigger serious shortages of freshwater in the future, which may challenge the sustainability and safety of water resources development in the river basin, and should be paid great attention before 2020.

Editor Z.W. Kundzewicz; Associate editor K. Hamed     

Effect of Present-Day Climate Changes and Agricultural Activities on Spring Overland Runoff in Forest-Steppe and Steppe Regions of the Russian Plain

Space and time analysis of the formation of spring overland runoff in forest-steppe and steppe regions of the Russian Plain has been carried out. It has been shown that, in addition to zonal climate conditions, its distribution over the area is largely determined by the agricultural load on river catchment areas, primarily, the structure of agricultural lands—the proportions of areas under winter tillage and consolidated tillage. The character of overland runoff response to present-day climate changes and agricultural activity has been identified, and quantitative estimates have been given to the manifold hydrological role of these factors.     

Hydrological alterations from water infrastructure development in the Mekong floodplains

The Mekong floodplains, which encompasses the region from Kratie Township in Central Cambodia to the Vietnamese East Sea, is a region of globally renown agricultural productivity and biodiversity. The construction of 135 dams across the Mekong basin and the development of delta‐based flood prevention systems have caused public concern given possible threats on the stability of agricultural and ecological systems in the floodplains. Mekong dams store water upstream and regulate flow seasonality, while in situ flood prevention systems re‐distribute water retention capacity in the floodplains. The main aim of this paper is to evaluate possible impacts of the recent development of both hydropower dams and flood prevention systems on hydrological regimes in the Mekong floodplains. An analysis of measured daily and hourly water level data for key stations in the Mekong floodplains from Kratie to the river mouth in Vietnam was conducted. Hydropower dam information was obtained from the hydropower database managed by the Mekong River Commission, and the MODIS satellite imagery was used to detect changes in flooding extent related to the operation of flood prevention systems in the Vietnam Mekong Delta. Results indicate that the upper part of the floodplains, the Cambodian floodplains, may buffer upstream dam impacts to the Vietnam Mekong Delta. Flood prevention up to date has had the greatest effect on the natural hydrological regime of the Mekong floodplains, evidenced by a significant increase of water level rise and fall rates in the upper delta and causing water levels in the middle delta to increase. The development of flood prevention systems has also effected spatial distribution of flooding as indicated via a time series analysis of satellite imagery. While this development leads to increase localized agricultural productivity, our historical data analysis indicates that development of one region detrimentally affects other regions within the delta, which could increase the risk of future conflicts among regions, economic sectors and the ecological value of these important floodplains. Copyright © 2016 John Wiley & Sons, Ltd.     

Changes in water availability in the Upper Blue Nile basin under the representative concentration pathways scenario

Climatic and hydrological changes will likely be intensified in the Upper Blue Nile (UBN) basin by the effects of global warming. The extent of such effects for representative concentration pathways (RCP) climate scenarios is unknown. We evaluated projected changes in rainfall and evapotranspiration and related impacts on water availability in the UBN under the RCP4.5 scenario. We used dynamically downscaled outputs from six global circulation models (GCMs) with unprecedented spatial resolution for the UBN. Systematic errors of these outputs were corrected and followed by runoff modelling by the HBV (Hydrologiska ByrånsVattenbalansavdelning) model, which was successfully validated for 17 catchments. Results show that the UBN annual rainfall amount will change by ?2.8 to 2.7% with a likely increase in annual potential evapotranspiration (in 2041–2070) for the RCP4.5 scenario. These changes are season dependent and will result in a likely decline in streamflow and an increase in soil moisture deficit in the basin.     

变化环境下珠江流域洪水频率变化特征、成因及影响(1951-2010年)

气候变化和人类活动导致珠江流域水文变化,变化前后洪水频率分布显著不同.运用滑动秩和(Mann-Whitney U test)结合Brown-Forsythe、滑动T、有序聚类和Mann-Kendall检验法,并用累积距平曲线法获取年最大流量序列详细信息,综合确定样本最佳变化节点,并对水文变化成因做了系统分析.在此基础上,对整体序列、变化前后序列用线性矩法推求广义极值分布参数以及不同重现期设计流量.结果表明:(1)西江大部以及北江流域最佳变化节点在1991年左右;东江流域最佳变化节点与该流域内3大控制性水库建成时间基本吻合;(2)变化后,西江、北江年最大流量持续增加,洪峰强度增大,尤其是西江干流年最大流量显著增加;东江流域年最大流量显著减小,洪峰强度降低;(3)变化后,西江与北江洪水风险增加,尤其是下游珠三角地区本身受人类活动显著影响,加之西江与北江持续增加的洪水强度,珠三角地区发生洪水的强度及频次加剧,而东江洪水风险减小.此研究对于珠江流域在变化环境下的洪水风险评估与防洪抗灾具有重要意义.     

Many-year variations of the average salinity of the Sea of Azov

A brief review of studies of the hydrological regime of the Sea of Azov and approaches to assessing the average salinity—a key indicator of the state of its ecosystem is given. A database of salinity measurements at 47409 oceanographic stations over hundred years (from 1913 to 2014) were used to evaluate the sea-averaged mean annual salinity. The obtained values of the average salinity were found to differ from those published before because of the different approaches used to its calculation and different volumes of data involved. The difference was most significant for Taganrog Bay because of the high variability of its hydrological regime. Anomalies of the average salinity over period 1922–2014 were constructed, and the start of one more period of salinity increase in the Sea of Azov was recognized.     

Regime of water balance components of the Caspian Sea

The results of studying the hydrological regime of the Caspian Sea and its basin climate in observation period 1945–2010 are generalized. The results of analysis of the regime of precipitation, air temperature in the Caspian Sea basin and its level, as well as Volga runoff in periods of Caspian Sea level rise and drop are given. The conformity in variations of the trends in Caspian Sea level its basin climate is demonstrated, and the direction of further studies is substantiated.     

Water balance estimation under the challenge of data scarcity in a hyperarid to Mediterranean region

Water budget analyses are important for the evaluation of the water resources in semiarid and arid regions. The lack of observed data is the major obstacle for hydrological modelling in arid regions. The aim of this study is the analysis and calculation of the natural water resources of the Western Dead Sea subsurface catchment, one which is highly sensitive to rainfall resulting in highly variable temporal and spatial groundwater recharge. We focus on the subsurface catchment and subsequently apply the findings to a large‐scale groundwater flow model to estimate the groundwater discharge to the Dead Sea. We apply a semidistributed hydrological model (J2000g), originally developed for the Mediterranean, to the hyperarid region of the Western Dead Sea catchment, where runoff data and meteorological records are sparsely available. The challenge is to simulate the water budget, where the localized nature of extreme rainstorms together with sparse runoff data results in few observed runoff and recharge events. To overcome the scarcity of climate input data, we enhance the database with mean monthly rainfall data. The rainfall data of 2 satellites are shown to be unsuitable to fill the missing rainfall data due to underrepresentation of the steep hydrological gradient and temporal resolution. Hydrological models need to be calibrated against measured values; hence, the absence of adequate data can be problematic. Therefore, our calibration approach is based on a nested strategy of diverse observations. We calculate a direct surface runoff of the Western Dead Sea surface area (1,801 km²) of 3.4 mm/a and an average recharge (36.7 mm/a) for the 3,816 km² subsurface drainage basin of the Cretaceous aquifer system.     

The effect of water abundance in a territory on the population health

The paper presents the results of analysis of present-day scientific data on the dynamics of global hydroclimatic processes (with the establishment of long-term variations in the global water exchange processes) and the features of water abundance in territories under the effect of various natural and anthropogenic factors. Possible transformations of the hydrogeological situation under global climate changes are considered. The basic principles of the concept regarding the assessment of the effect of global hydroclimatic changes on the population health are presented. Medical-environmental data on the consequences of water-triggered environmental crises, taken as analogous natural models, are analyzed. The processes and regularities in the development of human pathology under the conditions of higher and lower water abundance in a territory are identified. The succession, time stages, and phases of the development of infection, parasitic, noninfectious pathologies are determined. Cause-and-effect relationships were established between the observed pathology and the effect of a complex of changing natural, anthropogenic, and social-environmental factors. Methodological approaches to the assessment of medical-environmental consequences of distinct changes in the water abundance in the territories are described. The possible use of subsurface water sources as a reserve of domestic water supply under emergencies are considered.     

The water balance of the Dead Sea: an integrated approach

The Dead Sea is the lowest spot on Earth. It is a closed saline lake located in the middle of the Jordan Rift Valley between Lake Tiberias and the Red Sea. Its major tributaries are the Jordan River itself and the Dead Sea side wadis. The Dead Sea has a unique ecosystem and its water has curative, industrial and recreational significance. The level of the Dead Sea has been continuously falling since the early 1930s at an average rate of 0·7 m per year. The water level, as of February 1998, is about 410·9 m below mean sea level. In this paper, a water balance model is developed for the Dead Sea by considering different hydrological components of this water balance, including precipitation, runoff, evaporation and groundwater flow. This model is calibrated based on historical levels of the Dead Sea. Different scenarios are investigated, including the proposed Dead Sea–Red Sea Canal. This project is supposed to halt the shrinking of the Dead Sea and restore it to pre‐1950 levels in the next century. Copyright © 2000 John Wiley & Sons, Ltd.     

Changes of anisotropy of the magnetic susceptibility of rocks induced by a magnetic field

Summary The changes of the anisotropy of magnetic susceptibility of igneous rocks, induced by a magnetic field, are studied. It is proved that changes in the degree of anisotropy of susceptibility and of the orientation of the susceptibility ellispoid of specimens occur due to the configuration of the domain structure under the effect of the magnetic field. The influence of this effect on the total anisotropy of rocks depends on the degree of anisotropy due to the shape factor and on the stability of the domain structure. A model concept is presented, explaining the qualitatively different pattern of the changes of the anisotropy of susceptibility under the effect of the magnetic field in various directions of the specimens.