Annual drought flow and groundwater storage trends in the eastern half of the United States during the past two-third century

Low flow drainage from a river system, in the absence of precipitation or snowmelt, derives directly from the water stored in the upstream aquifers in the basin; therefore, observations of the trends of the annual lowest flows can serve to deduce quantitative estimates of the evolution of the basin-scale groundwater storage over the period of the streamflow record. Application of this method has allowed for the first time to determine the magnitudes of the trends in groundwater storage over the past two-third century in some 41 large prototypical basins in the United States east of the Rocky Mountains. It was found that during the period 1940–2007 groundwater storage has generally been increasing in most areas; these positive trends were especially pronounced in the Ohio and Upper Mississippi Water Resources Regions, but they were weaker in most other regions. Notable exceptions are the northern New England and especially the South Atlantic-Gulf regions, which saw prolonged declines in groundwater levels over this nearly 70-year long period. These observed long-term trends are generally in agreement with previous studies regarding trends of other components of the water cycle, such as precipitation, total runoff, and terrestrial evaporation. Over the most recent 20 years, from 1988 through 2007, except for the Ohio and the Souris-Red-Rainy regions, most regions have experienced declining average groundwater levels to varying degrees, with maximal values of the order of ?0.2 mm a^?1.     

黄河流域城镇化对地下水的影响分析

黄河流域是我国重要的生态屏障,也是我国粮食作物的主要产区。近年来,随着城镇化的发展,当地水资源分配出现了显著变化。因此,厘清黄河流域城镇化作用下水循环的改变对制定黄河流域城镇化政策具有重要意义。本文利用资源环境科学与数据中心的黄河流域下垫面数据、世界人口数据集的人口密度和Gravity Recovery and Climate Experiment (Grace)的Center for Space Research (CSR)陆地总水储量格点数据,开展了黄河流域城镇化过程中地下水的变化特征分析工作。结果表明：黄河流域城镇化程度具有显著的空间差异,下游存在明显的城镇化加剧现象;全域人口密度整体呈上升趋势,其中下游的人口增长趋势最大;黄河流域的地下水呈下降趋势,以下游的地下水下降最为显著。通过对比黄河流域新增城镇、不变城镇和消失城镇的地下水变化差异,发现地下水下降幅度最小出现在消失城镇,新增城镇的地下水下降幅度小于不变城镇的区域。因此,黄河流域城镇化对地下水的减少具有显著的作用,新增城镇地下水并没有出现显著下降的结果也说明近年来城镇化后的地下水保护政策取得的效果良好。     

Investigation of surges in marine estuaries (A case study for the Don River mouth)

Upsurges and downsurges in the Don River mouth are investigated using the observational data of the standard hydrometeorological network. The characteristics ofsurges are determined, andthe catalog of maximum annual dangerous surges is compiled for the observation points in the estuarine offshore zone and mouth reach of the Don River from the beginning of observations till 2014. The series of the maximum annual upsurges and downsurges at marine gaging stations in the Taganrog Bay are formed and statistically processed. The distribution of surges along the Taganrog Bay is analyzed. Catastrophic surges which cause adverse and severe events are identified as well as the qualitative and quaniiiaiive patterns of surge peneiraiion to the Don River mouth. The coefficients of upsurges and downsurges, the intensity of their attenuation, and water levels with the probability of 0.1, 1, and 50% at different river runoff are calculated at all gaging stations in the Don estuary for specific upsurges and downsurges. The results of test computations of surges for the specific point in the Taganrog Bay for 2013-2015 based on the numerical hydrodynamic model of the Sea of Azov are compared with observational data. The possibility was revealed of forecasting downsurges and upsurges based on synoptic conditions over the Sea of Azov with the lead time of three days using hydrodynamic models that allowed developing the prediction scheme of surge transformation calculation.     

Climate Change and Water Resources in Britain

This paper explores the potential implications of climate change for the use and management of water resources in Britain. It is based on a review of simulations of changes in river flows, groundwater recharge and river water quality. These simulations imply, under feasible climate change scenarios, that annual, winter and summer runoff will decrease in southern Britain, groundwater recharge will be reduced and that water quality – as characterised by nitrate concentrations and dissolved oxygen contents – will deteriorate. In northern Britain, river flows are likely to increase throughout the year, particularly in winter. Climate change may lead to increased demands for water, over and above that increase which is forecast for non-climatic reasons, primarily due to increased use for garden watering. These increased pressures on the water resource base will impact not only upon the reliability of water supplies, but also upon navigation, aquatic ecosystems, recreation and power generation, and will have implications for water quality management. Flood risk is likely to increase, implying a reduction in standards of flood protection. The paper discusses adaptation options.     

多年平均年降水量的面积分布律

通过对全国，新疆，天山乌鲁木齐河流域三种不同区域多年平均年降水量的计算分析发现，在这三种区域里，多年平均年降水量与其占有的面积之间丰同一种函数关系－我指分布函数关系。这一关系式的得出，有助于（１）定量地描述某一气候区的降水气候状况。并且，这种对问题的提法既不太粗，也不太细，而是只提降水量为某一值的区域占有多大的比例；（３）根据河水径流深估计无雨量站区域的多年降水量和计算水文气象学中的一些参数。     

利用环境同位素技术研究沈阳浑河与地下水的水力联系

查明地下水与河水之间的水力联系,是研究浑河污染水体对地下水环境影响的前提。采用环境同位素技术研究浑河沿岸地下水演化规律,沿浑河冲洪积扇地下水流动方向取地下水样13个、河水样3个。结果表明:通过对水样进行D(氘)、18O分析,查明了浑河与地下水之间的水力联系,确定了河水对地下水的补给宽度,定量计算了河水对沿岸地下水的贡献比例。从浑河的上游至下游,河水对地下水的贡献比例由大变小,平均约为50%;河水对地下水强补给带位于浑河以南约1 km的范围内,二者的水力联系密切。     

基于SWAT模型分析淮河流域中上游水量平衡要素对气候变化的响应

本研究在对SWAT模型进行参数化的基础上,采用淮河干流吴家渡和鲁台子水文控制站1971-1990年和1991-2014年的月径流观测数据对SWAT模型进行了率定和验证。模拟效果评估结果显示：不论是率定期还是验证期,Nash-Sutcliffe系数Ens和确定系数R2均>0.8,相对误差Re<1%,模型能够较好地再现月尺度的降雨-径流过程。淮河中上游年径流深线性变化趋势不明显,但子流域空间差异显著,径流深上游及南部呈线性减小趋势,其他子流域呈增大趋势。从年水量平衡要素来看,蒸散量和渗漏量对水量平衡贡献最大。主成分分析表明,平均气温、降水量及蒸散量是淮河中上游水文要素变化的关键因子。剔除人为因素的影响,1971-2014年淮河中上游地区水资源量呈减少趋势,这可能是年平均气温升高、年降 水量略有减少以及年蒸散量减少综合作用的结果。本文研究成果可为淮河中上游水资源管理和相关政策的制定提供技术支撑。     

Assessment of concentration of radionuclides in river water and bottom sediments

The results of modeling of ^{89, 90}Sr, ¹³⁷Cs, and ^{239, 240}Pu migration in the Techa River are compared with observed data. It is shown that taking into account of the process of mass exchange between the main stream of a river and underflow is important for adequate modeling of migration and accumulation of radiative substances in a river. It is difficult to obtain results of modeling corresponding to the observed data if the process is neglected. Taking into account the mass exchange is especially important in developing models for long enough rivers that were polluted by radionuclides during long time. Authors believe that, in future, the considered aspects of modeling radioactive substances in rivers can be generalized on chemical polluting substances with similar physical and chemical properties, for example, heavy metals, phenols, etc.     

黑河实验区1987—1988年度宏观水平衡的初步研究

本文首先主要按水分条件对实验区内的土地进行了分类,然后又对1987—1988年度实验区的绿洲部分进行宏观的水平衡分析。分析表明,在张掖、临泽及高台绿洲带内年总散发量为585.3mm,接近于北京地区年降水量为625mm的生态环境。在该绿洲带内灌耕地的净耗水量平均为358.3m~3/亩,可作为绿洲地区合理用水的参考标准。     

Variations in climatic and hydrological parameters in the Selenga River basin in the Russian Federation

The variations in average annual surface air temperature, precipitation, and runoff in the Selenga River basin (within Russia) are analyzed. It is demonstrated that the considerable increase in average annual temperature of surface air layers occurred in the 1980s-1990s. The decrease in peak water discharge in the rivers and the increase in the frequency of low-water periods were revealed in the forest-steppe and steppe zones of the Selenga River basin in 2001-2010. In the southwestern mountain regions (the Dzhida River basin) the river runoff increased during that period.     

气候变化和人类活动对中国东部季风区水循环影响的检测和归因

水文循环过程受气候变化与人类活动的共同作用,区分气候内部自然变率与人类活动作用于水循环贡献对于增加气候变化的理解非常重要。本研究利用近期发展的考虑地下水取用水与灌溉影响的全球陆气耦合模式进行数值模拟,基于最优指纹法分析探讨中国东部季风区黄河、淮河、海河、珠江、长江、松花江流域水循环变化(地表温度、降水、径流、蒸散发)及归因。结果表明:大部分流域的地表温度年际变化在1965~2005年间检测到包括温室气体气溶胶人为排放、臭氧与土地利用变化产生的外强迫效应,显示在长期对于地表温度起主要作用的可能为上述强迫;1965~2005年降水年际变化仅在淮河及长江下游检测到上述强迫效应,且在长江下游效应占主导。在1965~1984年间,地表温度的年际变化在海河流域检测到由于地下水取水灌溉产生的外强迫效应,并且该效应占主导。在1982~2005年径流年际变化中,在淮河、长江下游及黄河下游处检测到了由于温室气体排放、气溶胶人为排放、臭氧变化及土地利用变化等产生的外强迫效应但无法有效分离,显示该信号在这些地区可能不为主导效应;1982~2005年间的蒸散发年际变化在珠江、长江下游同样检测到了上述强迫效应,并且该效应在长江下游占主导效应。     

博斯腾湖流域气候变化对开都河径流量的影响

利用线性回归分析法、突变检验法等分析博斯腾湖流域1980～2018年的年均气温、年降水量、年蒸发量等气候因子变化趋势和突变现象及其对开都河径流量的影响.结果表明:1980～2018年博斯腾湖流域年均气温呈波动中上升趋势,其变化速率为0.15℃(10a)-1,年降水量则以0.765mm(10a)-1的速率增加,而年蒸发量...     

Assessing streamflow sensitivity to variations in glacier mass balance

We examine long-term streamflow and mass balance data from two Alaskan glaciers located in climatically distinct basins: Gulkana Glacier, a continental glacier located in the Alaska Range, and Wolverine Glacier, a maritime glacier located in the Kenai Mountains. Over the 1966–2011 study interval, both glaciers lost mass, primarily as a result of summer warming, and streamflow increased in both basins. We estimate total glacier runoff via summer mass balance and quantify the fraction of runoff related to annual mass imbalances. In both climates, annual (net) mass balance contributes, on average, less than 20 % of total streamflow, substantially less than the fraction related to summer mass loss (>50 %), which occurs even in years of glacier growth. The streamflow fraction related to changes in annual balance increased significantly only in the continental environment. In the maritime climate, where deep winter snowpacks and frequent rain events drive consistently high runoff, the magnitude of this streamflow fraction was small and highly variable, precluding detection of any existing trend. Furthermore, our findings suggest that glacier mass change is likely to impact total basin water yield, timing of runoff and water quality in the continental environment. However, the impacts of maritime glacier change appear more likely to be limited to water quality and runoff timing.     

Chemical runoff of the Selenga River under conditions of low water content

Changes in chemical runoff of the main tributary of Lake Baikal, the Selenga River, observed since the mid-1990s, and determinant factors of these changes are under consideration. The estimates derived are indicative of a 20–40% reduction in the annual removal of dissolved substances because of a decrease in the water runoff of the river due to climate oscillations. The decreased inflow to Lake Baikal of mineral substances, especially silicon, nitrogen, and phosphorus, can lead to disturbance of production processes in Lake Baikal.     

CLIMATE CHANGE HYDROLOGY AND WATER RESOURCES IMPACT AND ADAPTATION FOR SELECTED RIVER BASINS IN THE CZECH REPUBLIC

The Czech Republic has a northern hemisphere Atlantic-continental type of moderate climate. Mean annual temperature ranges between 1.0 and 9.4 °C (between 8.8 and 18.5 °C in summer and between –6.8 and 0.2 °C in winter). Annual precipitation ranges between 450 mm in dry regions and 1300 mm in mountainous regions of the country. With its 2000 m³ per capita fresh water availability, the Czech Republic is slightly below average. Occasional water shortages do not usually result from general unavailability of water resources but rather from time or space variability of water supply/demand and high degree of water resources exploitation. To study potential impacts of climate change on hydrological system and water resources, four river basins have been selected in the territory of the Czech Republic: the Elbe River at Decin (50761.7 km²), the Zelivka River at Soutice (1188.6 km²), the Upa River at Ceska Skalice (460.7 km²) and the Metuje River at Marsov n. M. (93.9 km²). To simulate potential changes in runoff, three hydrological models have been applied using incremental and GCM (GISS, GFDL and CCCM) scenarios: the BILAN water balance model, the SACRAMENTO (SAC-SMA) conceptual model and the CLIRUN water balance model. The paper reviews methods applied in the study, results of the assessments and concludes with suggestions for possible general adaptation policy options where the preference is for nonstructural measures such as water conservation, efficient water demand management and protection of water resources.     

The impact of climate change on the river rhine: A scenario study

This paper concerns the impact of human-induced global climate change on the River Rhine discharge. For this purpose a model for climate assessment, named ESCAPE, is coupled to a water balance model, named RHINEFLOW. From climate scenarios, changes in regional annual water availability and seasonal discharge in the River Rhine Basin are estimated. The climate scenarios are based on greenhouse gases emissions scenarios. An assessment is made for best guess seasonal discharge changes and for changes in frequencies of low and high discharges in the downstream reaches of the river. In addition, a quantitative estimation of the uncertainties associated with this guess is arrived at.The results show that the extent and range of uncertainty is large with respect to the best guess changes. The uncertainty range is 2–3 times larger for the Business-as-Usual than for the Accelerated Policies scenarios. This large range stems from the doubtful precipitation simulations from the present General Circulation Models. This scenario study showed the precipitation scenarios to be the key-elements within the present range of reliable climate change scenarios.For the River Rhine best guess changes for annual water availability are small according to both scenarios. The river changes from a present combined snow-melt-rain fed river to an almost entirely rain fed river. The difference between present-day large average discharge in winter and the small average discharge in autumn should increase for all scenarios. This trend is largest in the Alpine part of the basin. Here, winter discharges should increase even for scenarios forecasting annual precipitation decreases. Summer discharge should decrease. Best guess scenarios should lead to increased frequencies of both low and high flow events in the downstream (Dutch) part of the river. The results indicate changes could be larger than presently assumed in worst case scenarios used by the Dutch water management authorities.     

Probabilistic characterization of hydrological droughts

It is proposed to use the joint distribution of probabilities of minimum water discharges and the river runoff depth to characterize the severity and danger of durable low-flow periods. The copula theory is used to construct this distribution that enables to take account of differences in the types of one-dimensional probability distributions of initial variables and of the correlation between them. The studies were carried out for the vegetation periods using the data of the runoff depth measurements in Georghiu-Dej on the Don River in 1895–1980 and in Kirov on the Vyatka River in 1878–1980. The selection of copulas was based on comparing empirical and theoretical joint distributions of low-flow characteristics. It is demonstrated that the best results for the approximation of the joint probability distribution of low-flow characteristics are obtained from the Frank copula. Plotted are the dependences of low-flow frequency on the specified values of corresponding minimum water discharges and the river runoff depth during vegetation periods. Estimated are the probability and frequency of some most severe lowflow periods observed on the Don and Vyatka rivers.     

A new approach to the automatic computation of partial volumes of river runoff with various degrees of pollution (a case study for the Selenga River)

Proposed are the methods and software package that enable estimating automatically the degree of the pollution of annual and long-term river runoff at the joint processing of large volumes of standard (routine) hydrological and hydrochemical information. As a result of computations, the individual quality certificate of river runoff was created for the part of the river under study. Computation methods include regulations concerning the parameters that connect the water runoff volume with water quality; the parameters that may connect the computation of the pollution degree using RD 52.24.643-2002 adapted for the partial volumes of the annual runoff according to these methods, with the subsequent classification of the pollution degree. The computation technique was worked out and used for the first time. The informativeness of estimates is demonstrated for one of the discharge section lines of the Selenga River.     

Tide,Wind, and River Forcing of the Surface Currents in the Fraser River Plume

A long-term record of surface currents from a high-frequency radar system, along with near-surface hydrographic transects, moored current meter records, and satellite imagery, are analyzed to determine the relative importance of river discharge, wind, and tides in driving the surface flow in the Fraser River plume. The observations show a great deal of oceanographic and instrumental variability. However, averaged quantities yielded robust results. The effect of river flow, which determines buoyancy and inertia near the river mouth, was found by taking a long-term average. The resulting flow field was dominated by a jet with two asymmetric gyres; the anticyclonic gyre to the north had flow speeds consistent with geostrophy. The mean flow speed near the river mouth was 14.3?cm?s^–1, while the flow further afield was 5?cm?s^–1 or less. Wind stress and surface currents were highly coherent in the subtidal frequency band. Northwesterly winds drive a surface flow to the southeast at speeds of nearly 30?cm?s^–1. Southeasterly winds drive a surface flow to the northwest at speeds reaching 20?cm?s^–1; however, there is more spatial variability in speed and direction relative to the northwesterly wind case. A harmonic analysis was used to extract the tidally driven flows. Ellipse parameters for the major tidal constituents varied considerably in both alignment and aspect ratio over the radar domain, in direct contrast to a barotropic model which predicted rectilinear flow along the Strait of Georgia. This is a result of water filling and draining the shallow mud flats north of the Fraser's main channel. The M₂ velocities at the surface were also weaker than their barotropic counterparts. However, the shallow water constituent MK₃ was enhanced at the surface and nearly as strong as the mean flow, implying that non-linear interactions are important to surface dynamics.