Impacts of future climatic and land cover changes on the hydrological regime of the Madeira River basin

Brazilian strategic interest in the Madeira River basin, one of the most important of the southern Amazon tributaries, includes the development of hydropower to satisfy the country’s growing energy needs and new waterways to boost regional trade and economic development. Because of evidences that climate change impacts the hydrological regime of rivers, the aim of this study was to assess how global climate change and regional land cover change caused by deforestation could affect the river’s hydrological regime. To achieve this goal, we calibrated a large-scale hydrological model for the period from 1970–1990 and analyzed the ability of the model to simulate the present hydrological regime when climate model simulations were used as input. Climate change projections produced by climate models were used in the hydrological model to generate scenarios with and without regional land-use and land-cover changes induced by forest conversion to pasture for the period from 2011–2099. Although results show variability among models, consensus scenarios indicated a decrease in the low-flow regime. When the simulations included forest conversion to pasture, climate change impacts on low flows were reduced in the upper basin, while, in the lower basin, discharges were affected along the whole year due to the more vigorous land-use conversion in the Brazilian region of the basin.     

River discharge and freshwater runoff to the Barents Sea under present and future climate conditions

River discharge forms a major freshwater input into the Arctic Ocean, and as such it has the potential to influence the oceanic circulation. As the hydrology of Arctic river basins is dominated by cryospheric processes such as snow accumulation and snowmelt, it may also be highly sensitive to a change in climate. Estimating the water balance of these river basins is therefore important, but it is complicated by the sparseness of observations and the large uncertainties related to the measurement of snowfalls. This study aims at simulating the water balance of the Barents Sea drainage basin in Northern Europe under present and future climate conditions. We used a regional climate model to drive a large-scale hydrological model of the area. Using simulated precipitation derived from a climate model led to an overestimation of the annual discharge in most river basins, but not in all. Under the B2 scenario of climate change, the model simulated a 25% increase in freshwater runoff, which is proportionally larger than the projected precipitation increase. As the snow season is 30–50 day shorter, the spring discharge peak is shifted by about 2–3 weeks, but the hydrological regime of the rivers remains dominated by snowmelt.     

Hydrological Regime of the Lower Volga River under Modern Conditions

The regularities of changes in the parameters of the hydrological regime of the Lower Volga are considered using data of routine observations at gaging stations and data of field studies carried out by the specialists of Zubov State Oceanographic Institute in 2006–2017. The main modern trends are revealed for runoff and water level, water temperature, and ice phenomena as well as for the duration of flooding of the Volga-Akhtuba floodplain during the spring flood. The parameters are compared for natural and regulated Volga River runoff conditions. It is shown that considerable variation in the duration of flooding of floodplains, in water temperature, and heat flow during the spring flood under modern conditions is caused both by runoff operation and by increase in the anthropogenic load on the area of the Volga-Akhtuba floodplain in the recent decades.     

Simulating the hydrological response to predicted climate change on a watershed in southern Alberta, Canada

The current body of research in western North America indicates that water resources in southern Alberta are vulnerable to climate change impacts. The objective of this research was to parameterize and verify the ACRU agro-hydrological modeling system for a small watershed in southern Alberta and subsequently simulate the change in future hydrological responses over 30-year simulation periods. The ACRU model successfully simulated monthly streamflow volumes (r ²?=?0.78), based on daily simulations over 27 years. The delta downscaling technique was used to perturb the 1961?C1990 baseline climate record from a range of global climate model (GCM) projections to provide the input for future hydrological simulations. Five future hydrological regimes were compared to the 1961?C1990 baseline conditions to determine the average net effect of change scenarios on the hydrological regime of the Beaver Creek watershed over three 30-year time periods (starting in 2010, 2040 and 2070). The annual projections of a warmer and mostly wetter climate in this region resulted in a shift of the seasonal streamflow distribution with an increase in winter and spring streamflow volumes and a reduction of summer and fall streamflow volumes over all time periods, relative to the baseline conditions (1961?C1990), for four of the five scenarios. Simulations of actual evapotranspiration and mean annual runoff showed a slight increase, which was attributed to warmer winters, resulting in more winter runoff and snowmelt events.     

Global Warming and the Summertime Evapotranspiration Regime of the Alpine Region

Changes of the summer evapotranspiration regime under increased levels of atmospheric greenhouse gases are discussed for three Alpine river basins on the basis of a new set of simulations carried out with a high-resolution hydrological model. The climate change signal was inferred from the output of two simulations with a state-of-the-art global climate model (GCM), a reference run valid for 1961–1990 and a time-slice simulation valid for 2071–2100 under forcing from the A2 IPCC emission scenario. In this particular GCM experiment and with respect to the Alpine region summer temperature was found to increase by 3 to 4 ^∘C, whereas precipitation was found to decrease by 10 to 20%. Global radiation and water vapor pressure deficit were found to increase by about 5% and 2 hPa, respectively. On this background, an overall increase of potential evapotranspiration of about 20% relative to the baseline was predicted by the hydrological model, with important variations between but also within individual basins. The results of the hydrological simulations also revealed a reduction in the evapotranspiration efficiency that depends on altitude. Accordingly, actual evapotranspiration was found to increase at high altitudes and to the south of the Alps, but to decrease in low elevation areas of the northern forelands and in the inner-Alpine domain. Such a differentiation does not appear in the GCM scenario, which predicts an overall increase in evapotranspiration over the Alps. This underlines the importance of detailed simulations for the quantitative assessment of the regional impact of climate change on the hydrological cycle.     

The Kolyma River mouth area under present conditions of anthropogenic impact

The variability is under consideration of the hydrological and ecological state of the water environment of the Kolyma River mouth area. Its hydrological regime and variability of the component composition of the water environment are described. The anthropogenic load is estimated of the inflow of dissolved chemical substances to the Kolyma River mouth area. The hydrobiocenosis structure is studied from qualitative and quantitative indicators of the level of the phyto- and zooplankton development in the mouth area. The hydrobiocenosis state and structure indicate that the ecosystem of the Kolyma River mouth area is functioning under conditions of moderate pollution of the water environment and the depression effect of the biocenosis development is periodically pronounced.     

南渡江流域暴雨洪涝致灾临界面雨量的确定

基于海南省南渡江流域龙塘水文站1976—1987年和2009—2010年的逐日气象水文资料,采用HBV-D水文模型,通过对模型参数率定和验证,确定了适合南渡江流域的HBV-D水文模型最优化参数。结果表明:该模型在1976—1981年率定期、1982—1987年验证期和2009—2010年验证期的Nash-Sutcliffe效率系数分别为0.891,0.831,0.953,相关系数分别为0.944,0.912,0.977,达到了0.01显著性水平。通过建立的南渡江流域HBV-D水文模型进行模型反演,确定了不同前期水位 (7 m,8 m,9 m,10 m,11 m) 的面雨量和水位关系,根据龙塘水文站的警戒水位、10年重现期水位、30年重现期水位、50年重现期水位作为不同等级预警的临界判别条件,最终确定了不同前期水位的致灾临界面雨量指标。     

未来气候变化对黄河流域水文过程的影响

使用NASA/NCAR有限区域大气环流模型FvGCM结果驱动高分辨率区域气候模式RegCM3 (20 km),进行1961～1990年当代气候模拟(控制试验)和2071～2100年IPCC A2排放情景下未来气候模拟(A2情景模拟试验)。将RegCM3径流模拟结果同大尺度汇流模型LRM [分辨率0.25°(纬度)×0.25°(经度)]相连接,模拟预估未来气候变化对我国黄河流域水文过程的影响。结果表明:相对于当代气候,未来黄河流域呈现气温升高、降水增加(夏季7～8月降水减少)和蒸发增大的趋势,且空间分布极不均匀,造成河川径流在5～10月减少,加剧流域夏季的水资源短缺;未来气温升高使得融雪径流增加,可能导致更早和更大的春季径流,使径流过程发生季节性迁移,引起黄河流域水资源年内分配发生变化。     

基于陆面水文耦合模式CLHMS的淮河流域水文过程的模拟评估及其不确定性分析

利用最新的CFSR(Climate Forecast System Reanalysis)再分析及观测的降水和地表气温资料驱动陆面水文耦合模式CLHMS(Coupled Land surface and Hydrologic Model System),对淮河流域1980~2003年共24年的水文水循环过程进行了模拟,系统评估了CLHMS对淮河流域水文过程的模拟能力及其不确定性。分析结果表明,CLHMS模式对淮河流域水文过程具有良好的模拟能力,模式尤其对湿润年份流域的水量平衡以及河道流量的季节、年际变化具有很强的模拟能力,而对降水偏少的干旱年份,模式模拟的河道流量通常会高于观测实况,与实况间存在着一定的偏差,而这也是导致CLHMS对流域水文过程模拟能力存在显著年代际差异的主要原因。基于三组不同降水强迫的流域水文过程模拟结果比较表明,降水驱动资料准确与否是陆面水文模拟最主要的不确定性来源之一,正是由于CFSR再分析降水与观测降水之间存在较大的差异,从而导致CFSR降水驱动下模式模拟的淮河流域河道流量与观测存在较大的偏差,其模拟性能相对较差。进一步分析还表明,可以保持较强降水日变化的时间解集方法,也是保证合理模拟流域水文过程的重要因素。     

Changes in Water Resources under Conditions of Climate Warming and Their Impact on Water Inflow to Russian Large Reservoirs

Changes are considered in the runoff regime of Russian rivers and in the water inflow to reservoirs as a result of the climate warming observed in the country since the second half of the 1970s. Based on the analysis of long–term observational data on water inflow to 41 large reservoirs with the volume of 10 x 10⁶ m³, it is shown that considerable changes in its intraannual distribution have occurred in the recent decades. These changes are characterized, in particular, by the inflow increase during the cold season and by the runoff variability increasing in winter and summer–autumn seasons. The growth of the number of severe hydrological events, especially of flash floods induced by rainfalls, has been registered in the recent decades. Potential future changes in water inflow to reservoirs are considered in accordance with the scenarios of further climate warming. It is justified that rules of using water resources of reservoirs should be corrected taking into account the observed changes in the river water inflow regime.     

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.     

沙澧河流域致洪预警系统设计与应用

沙澧河流域致洪预警系统基于中小河流致洪预警气象服务需求,以气象与水文相结合,应用地理信息(GIS)先进技术,利用气象常规数据、地面自动雨量站资料、数值模式、卫星雷达资料及水文雨量、水位数据等资料,运用动力学诊断和统计分析、多元线性回归方法、模式输出法、相似预报等方法,输出暴雨和水位增量预报模型。该系统通过C/C++语言编程,集气象水文信息显示分析、数据库、预报模型和用户界面于一体,建立了涵盖流域暴雨预报、水位增量监测预测、洪涝灾害预警服务等多功能的可视化业务技术平台。在本地基层台站首次将气象和水文两个学科结合,建立降水、水文和洪涝数据库;首次对沙澧河流域进行暴雨形势分型,并建立流域暴雨预报模型;首次建立沙澧河流域五大水库水位增量预报模型。自系统运行以来,成功对沙澧河流域出现的几次致洪暴雨进行了预警,服务效果明显。     

Variations of the water regime of bogs of northern and northwestern Russia under influence of climatic factors

A considerable variation of hydrological regime of oligotrophic bogs of northern and northwestern Russia takes place during all phases of hydrological year under influence of climatic changes of recent decades. The mechanism and factors of climate changes influencing the regime of bog water level and the runoff from bog massifs are revealed. It is demonstrated that the change in the hydrological regime influences the stability of ecosystems of oligotrophic bog massifs.     

基于HBV模型的太子河流域致洪临界雨量的确定

以太子河流域为研究区域,基于流域内的气象水文数据、数字高程模型及土地利用等资料,采用HBV水文模型对流域的水文过程进行模拟,通过对模型参数的率定与验证,评估了HBV模型在该流域径流模拟的适用性,确定了适合太子河流域的最优化参数,结合水位-流量关系曲线,推算太子河流域不同等级洪水致洪临界雨量。结果表明: HBV模型对太子河流域的径流模拟效果较好,率定期与验证期Nash效率系数与确定性系数均超过0.60,模型中积雪和融雪模块(CFR)、土壤含水量计算模块(BETA)与响应模块(KUZ2、UZ1、PERC)中的这些参数最为敏感,模型基本模拟出了洪水对降水的响应过程。通过建立的HBV水文模型,结合小林子水文站的水位-流量关系曲线,以警戒水位、保证水位作为不同等级洪水的判别条件,推算得到了不同起始水位下太子河流域动态临界雨量指标,临界雨量随起始水位的升高而有所减小。     

Long-term variability of sea surface temperature in the coastal zone of northeastern part of the black sea in spring and autumn

Within the frameworks of the presented model, the beginning of the spring and autumn hydrological seasons depends on the temperature regime of air flows in the region under investigation. As compared with the standard procedure of season determination, this model is more flexible in taking account of the probabilistic nature of the time of the beginning of hydrological seasons and variations of their duration. It ensures a higher reliability of estimates of thermal surface water properties and analysis of their evolution within the seasons and annual cycles. A considerable irregularity in the time of the beginning of spring and autumn seasons and a possibility of significant fluctuations of their duration changes the estimation of thermal surface water conditions so considerably that the initial (calendar) model can be no longer considered as the source of reliable information.     

Hydrological Studies of Lake Outbursts in the Antarctic Oases

The results of a detailed hydrological study of the Larsemann Hills Oases (East Antarctica) during field seasons of 2017 to 2019 are presented. The study investigates a variety of lakes’ hydrological regime and the characteristics of outburst floods resulting from the lakes’ water flowing through tunnels in the snow-ice dams. The hydrographs calculated by the mathematical modeling do not generally contradict the physical essence of the process of outburst flood formation.

     

Hydrological effects of the increased CO2 and climate change in the Upper Mississippi River Basin using a modified SWAT

Increased atmospheric CO₂ concentration and climate change may significantly impact the hydrological and meteorological processes of a watershed system. Quantifying and understanding hydrological responses to elevated ambient CO₂ and climate change is, therefore, critical for formulating adaptive strategies for an appropriate management of water resources. In this study, the Soil and Water Assessment Tool (SWAT) model was applied to assess the effects of increased CO₂ concentration and climate change in the Upper Mississippi River Basin (UMRB). The standard SWAT model was modified to represent more mechanistic vegetation type specific responses of stomatal conductance reduction and leaf area increase to elevated CO₂ based on physiological studies. For estimating the historical impacts of increased CO₂ in the recent past decades, the incremental (i.e., dynamic) rises of CO₂ concentration at a monthly time-scale were also introduced into the model. Our study results indicated that about 1–4% of the streamflow in the UMRB during 1986 through 2008 could be attributed to the elevated CO₂ concentration. In addition to evaluating a range of future climate sensitivity scenarios, the climate projections by four General Circulation Models (GCMs) under different greenhouse gas emission scenarios were used to predict the hydrological effects in the late twenty-first century (2071–2100). Our simulations demonstrated that the water yield would increase in spring and substantially decrease in summer, while soil moisture would rise in spring and decline in summer. Such an uneven distribution of water with higher variability compared to the baseline level (1961–1990) may cause an increased risk of both flooding and drought events in the basin.     

Validation of A One-Dimensional Snow-Land Surface Model at the Sleepers River Watershed

A one-dimensional land surface model, based on conservations of heat and water substance inside the soil and snow, is presented. To validate the model, a stand-alone experiment is carried out with five years of meteorological and hydrological observations collected from the NOAA-ARS Cooperative Snow Research Project (1966–1974) at the Sleepers River watershed in Danville, Vermont, U.S.A. The numerical results show that the model is capable of reproducing the observed soil temperature at different depths during the winter as well as a rapid increase of soil temperature after snow melts in the spring. The model also simulates the density, temperature, thickness, and equivalent water depth of snow reasonably well. The numerical results are sensitive to the fresh snow density and the soil properties used in the model, which affect the heat exchange between the snowpack and the soil.     

Changes of atmospheric water vapor budget in the Pearl River basin and possible implications for hydrological cycle

In this study, we thoroughly analyzed abrupt behaviors, trends, and periodicity properties of water vapor flux and moisture budget entering and exiting the four edges of the Pearl River basin based on the NCAR/NCEP reanalysis dataset by using the continuous wavelet transform and the simple two-phase linear regression technique. Possible implications for hydrological cycle and water resource management of these changes are also discussed. The results indicate that: (1) the water vapor propagating through the four edges of the Pearl River basin is decreasing, and it is particularly true for the changes of the water vapor flux exiting from the north edge of the study river basin. The transition point from increase to decrease occurs in the early 1960s; (2) The wavelet transform spectra indicate that the monthly water vapor flux through the north edge decreases and this decrease is mainly reflected by intermittent distribution of the wavelet power spectra after early 1980s. The periodicity properties of the water vapor flux through the north edge imply that the northward propagation of water vapor flux decreases after the 1980s; (3) close relations between water vapor flux, precipitation and streamflow implies that the altered hydrological cycle in the Pearl River basin is mainly manifested by seasonal shifts of water vapor flux after early 1960s. One of the direct consequences of these changes of water vapor flux is the seasonal transition of wet and dry conditions across the Pearl River basin. Regional responses of hydrological cycle to climate variation/change could be different from one river basin to another. Hydrological responses of the Pearl River basin to the global warming are mainly demonstrated by seasonal shifts of precipitation changes: winter comes to be wetter and summer tends to be dryer. The finding of the seasonal transition of precipitation in the Pearl River basin is of great scientific and practical merits in basin scale water resource management in the Pearl River basin under the changing climate and global warming in particular.