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Snowdrifts on lake ice provide vital breeding habitats for the endangered Saimaa ringed seal. In this study, a lake ice model of Watershed Simulation and Forecasting System (WSFS-Ice) was developed for improved estimation of ice and snow conditions in Lake Saimaa during the pupping season of the Saimaa ringed seal. The WSFS-Ice model is based on energy balance, enabling reliable estimation of the ice cover evolution in current and future climate. In addition, a simple snowdrift model was used to simulate formation of snowdrifts, which are essential for the seals breeding success in Lake Saimaa. The model was calibrated against ice thickness, ice type and snow depth measurements. According to our results based on climate scenarios with intermediate representative concentration pathway (RCP4.5), the breeding habitat of the Saimaa ringed seal is significantly deteriorating during the twenty-first century. The mean depth of the snowdrifts is projected to decrease approximately to half from the 1981–2010 to 2070–99 period and at the same time the ice-covered period is reduced by one and a half months. During the mildest winters the ice cover is projected to melt even before the pupping season has ended. The results highlight the importance of climate change mitigation and active conservation measures to enhance seal population growth, enabling it to survive in a changing climate. [ABSTRACT FROM AUTHOR]

In this study, HSPF (Hydrologic Simulation Program-FORTRAN) was used to analyze the potential impact of climate change on the streamflow of four major river basins in Ethiopia: Awash, Baro, Genale, and Tekeze. The calibrated and validated HSPF model was forced with daily climate data of 10 CMIP5 (Coupled Model Intercomparison Project phase 5) Global Climate Models (GCMs) for the 1971-2000 control period and the RCP4.5 and RCP8.5 climate projections of 2041-2070 (2050s) and 2071-2100 (2080s). The ensemble median of these 10 GCMs projects the temperature in the four study areas to increase by about 2.3 °C (3.3 °C) in 2050s (2080s), whereas the mean annual precipitation is projected to increase by about 6% (9%) in 2050s (2080s). This results in about 3% (6%) increase in the projected annual streamflow in Awash, Baro, and Tekeze rivers whereas the annual streamflow of Genale river is projected to increase by about 18% (33%) in the 2050s (2080s). However, such projected increase in the mean annual streamflow due to increasing precipitation over Ethiopia contradicts the decreasing trends in mean annual precipitation observed in recent decades. Regional climate models of high resolutions could provide more realistic climate projections for Ethiopia's complex topography, thus reducing the uncertainties in future streamflow projections. [ABSTRACT FROM AUTHOR]

The river ice regime is considered a sensitive indicator of climate change and within this study long term changes (in case of River Daugava starting from 1530, but for other studied rivers starting from first half of twentieth century) river ice regimes in the Baltic region have been studied. The ice cover duration on the rivers (17 rivers) in the Baltic countries and Belarus has decreased during the recent decades. In addition to this, long term observational records of ice break on the rivers of the studied region exhibit a pattern of periodic changes in the intensity of ice regime. Both the ice regime and the seasonal river discharge are shown to be strongly influenced by large-scale atmospheric circulation processes over North Atlantic that manifests through close correlation with North Atlantic Oscillation index. [ABSTRACT FROM AUTHOR]

This study examines the climatic drivers of ice-off dates for lakes and rivers across the Northern Hemisphere. Most lakes and rivers have trended toward earlier ice-off dates over the last century, as would be expected from long-term climate change. However, we also identify modes of climate variability that significantly impact the short-term behavior of ice-off time series. In particular, the North Atlantic Oscillation (NAO), Pacific-North American Pattern (PNA), and to a lesser degree the El Niño-Southern Oscillation (ENSO) explain a substantial fraction of the interannual variance in melt dates, while the Pacific Decadal Oscillation (PDO) and Atlantic Multidecadal Oscillation (AMO) generally do not. Furthermore, the spatial pattern of the early or late ice-off dates associated with the NAO, PNA, and ENSO matches a priori expectations due to the known surface temperature patterns associated with these oscillations. In all regions, the strongest correlation to ice-off is with one of the high-frequency modes—the NAO or PNA, suggesting that short-term weather variations play a stronger role than lower-frequency climate variability (ENSO, PDO, AMO) in driving ice-off. [ABSTRACT FROM AUTHOR]

Climate change in the future would have implications for river discharges in Bangladesh. In this article, possible changes in the magnitude, extent and depth of floods of the Ganges, Brahmaputra and Meghna (GBM) rivers in Bangladesh were assessed using a sequence of empirical models and the MIKE11-GIS hydrodynamic model. Climate change scenarios were constructed from the results of four General Circulation Models (GCMs) – CSIRO9, UKTR, GFDL and LLNL, which demonstrate a range of uncertainties. Changes in magnitude, depth and extent of flood discharge vary considerably between the GCMs. Future changes in the peak discharge of the Ganges River are expected to be higher than those for the Brahmaputra River. Peak discharge of the Meghna River may also increase considerably. As a result, significant changes in the spatial extent and depths of inundation in Bangladesh may occur. Faster changes in inundation are expected at low temperature increases than of higher temperature changes. Changes in land inundation categories may introduce substantial changes in rice agriculture and cropping patterns in Bangladesh. Reduction of increased flood hazard due to climate change requires strengthening of flood management policies and adaptation measures in Bangladesh. [ABSTRACT FROM AUTHOR]

Civilization can be at least partially determined by climatic constraints upon net primary productivity and heat dissipation from the human body (Kleidon ). I discuss how these “metabolic” limitations were historically overcome: first, because large rivers in dry regions provided water to ancient civilizations; second, because fossil fuel energy servants working externally to muscle-limited bodies have produced economic well-being in a number of world areas. [ABSTRACT FROM AUTHOR]

Discusses the effects of climate change scenarios in the increase in frequency and magnitude of flooding events in rivers in Britain. Rainfall-runoff model; Climate change; Effect of changes in rainfall patterns; Land use change.

The transboundary Sesan and Srepok sub-basins (2S) are the “hot-spot” areas for reservoir development in the Lower Mekong region, with 12 reservoirs built in the Vietnam territory. This study examines the impacts of reservoir operations in Vietnam and projected climate change on the downstream hydrologic regime of the 2S Rivers by jointly applying the Soil Water Assessment Tool (SWAT) and Water Evaluation and Planning (WEAP) models. Different scenarios of reservoir operation are considered and simulated to assess their impact on annual, seasonal, and monthly flow regimes under maximum hydropower capacity generation with and without taking into account the minimum flow requirement downstream near the Vietnam border with Cambodia. The precipitation and temperature projections from the high-resolution regional climate model HadGEM3-RA under two Representative Concentration Pathways, 4.5 and 8.5, of HadGEM2-AO are used as future climate change scenarios for the impact assessment. The study results show that reservoir operation leads to an increase in the dry season stream flows and a decrease in the wet season stream flows. The monthly flow regime exhibits considerable changes for both the Sesan and Srepok Rivers but with different magnitudes and patterns of increase and decrease. Climate change is likely to induce considerable changes in stream flows, though these changes are comparatively lower than those caused by reservoir operation. Climate change is likely to have both counterbalancing and reinforcing effects over the impact of reservoir operation, reducing changes during dry season but increasing changes in most of the other months. [ABSTRACT FROM AUTHOR]

Lakes sensitively respond to global and regional climate change, especially in arid areas. Using Moderate Resolution Imaging Spectroradiometer (MODIS) daily snow products, the lake ice phenology of 23 lakes in the Xinjiang Uygur Autonomous Region of China from 2001 to 2018 was extracted based on thresholds of ice/water pixel numbers, and their change trends over 18 years were calculated. The results of MODIS-derived lake ice phenology showed consistent variations with existing ice phenology data sets derived from passive microwave data. Generally, lakes in Xinjiang begin to freeze from October to December every year, and their ice cover periods end from March to June. The average ice cover duration for the 23 lakes is 167 days, of which 16 lakes have an average shortening rate of − 1.08 days/year and seven lakes have an average extending rate of 1.18 days/year. The majority of lakes experienced later freeze-up (17 lakes) and earlier break-up (18 lakes) from 2001 to 2018. Lake ice phenology is affected by both climatic factors and lake physicochemical characteristics, in which freeze-up dates are more easily affected by lake-specific factors such as lake area (r = 0.535), while climatic factors especially water surface temperature have greater impacts on lake break-up dates (r = − 0.874). Compared to air temperature, water surface temperature changes have a more direct influence on the variations in lake ice phenology, 1° increase in water surface temperature may cause the ice cover duration to decrease by 12 days, while precipitation changes have almost no effect on the lakes in Xinjiang. In some cases, lake changes such as changes to the area and mineralization may also have dominant impacts on lake ice phenology. [ABSTRACT FROM AUTHOR]

Importance of evaluation of global hydrological models (gHMs) before doing climate impact assessment was underlined in several studies. The main objective of this study is to evaluate the performance of six gHMs in simulating observed discharge for a set of 57 large catchments applying common metrics with thresholds for the monthly and seasonal dynamics and summarize them estimating an aggregated index of model performance for each model in each basin. One model showed a good performance, and other five showed a weak or poor performance in most of the basins. In 15 catchments, evaluation results of all models were poor. The model evaluation was supplemented by climate impact assessment for a subset of 12 representative catchments using (1) usual ensemble mean approach and (2) weighted mean approach based on model performance, and the outcomes were compared. The comparison of impacts in terms of mean monthly and mean annual discharges using two approaches has shown that in four basins, differences were negligible or small, and in eight catchments, differences in mean monthly, mean annual discharge or both were moderate to large. The spreads were notably decreased in most cases when the second method was applied. It can be concluded that for improving credibility of projections, the model evaluation and application of the weighted mean approach could be recommended, especially if the mean monthly (seasonal) impacts are of interest, whereas the ensemble mean approach could be applied for projecting the mean annual changes. The calibration of gHMs could improve their performance and, consequently, the credibility of projections. [ABSTRACT FROM AUTHOR]

Spring snowmelt is the most important contribution of many rivers in western North America. If climate changes, this contribution may change. A shift in the timing of springtime snowmelt towards earlier in the year already is observed during 1948–2000 in many western rivers. Streamflow timing changes for the 1995–2099 period are projected using regression relations between observed streamflow-timing responses in each river, measured by the temporal centroid of streamflow (CT) each year, and local temperature (TI) and precipitation (PI) indices. Under 21st century warming trends predicted by the Parallel Climate Model (PCM) under business-as-usual greenhouse-gas emissions, streamflow timing trends across much of western North America suggest even earlier springtime snowmelt than observed to date. Projected CT changes are consistent with observed rates and directions of change during the past five decades, and are strongest in the Pacific Northwest, Sierra Nevada, and Rocky Mountains, where many rivers eventually run 30–40 days earlier. The modest PI changes projected by PCM yield minimal CT changes. The responses of CT to the simultaneous effects of projected TI and PI trends are dominated by the TI changes. Regression-based CT projections agree with those from physically-based simulations of rivers in the Pacific Northwest and Sierra Nevada. [ABSTRACT FROM AUTHOR]

The ECOlogical Model for Applied Geophysics (ECOMAG) and the HYdrological Predictions for the Environment (HYPE) process-based hydrological models were set up to assess possible impacts of climate change on the hydrological regime of two pan-Arctic great drainage basins of the Lena and the Mackenzie Rivers. We firstly assessed the reliability of the hydrological models to reproduce the historical streamflow series and analyzed the hydrological projections driven by the climate change scenarios. The impacts were assessed for three 30-year periods (early- (2006-2035), mid- (2036-2065), and end-century (2070-2099)) using an ensemble of five global climate models (GCMs) and four Representative Concentration Pathway (RCP) scenarios. Results show, particularly, that the basins react with a multi-year delay to changes in RCP2.6, so-called 'mitigation' scenario, and consequently to the potential mitigation measures. Then, we assessed the hydrological projections' variability, which is caused by the GCM's and RCP's uncertainties, and found that the variability rises with the time horizon of the projection, and generally, the projection variability is larger for the Mackenzie than for the Lena. We finally compared the mean annual runoff anomalies projected under the GCM-based data for the twenty-first century with the corresponding anomalies projected under a modified observed climatology using the delta-change method in the Lena basin. We found that the compared projections are closely correlated for the early-century period. Thus, for the Lena basin, the modified observed climatology can be used as driving force for hydrological model-based projections and considered as an alternative to the GCM-based scenarios. [ABSTRACT FROM AUTHOR]

Efforts to predict responses to climate change and to interpret modern or paleoclimate indicators are influenced by several levels of potential amplifiers, which increase or exaggerate climate impacts, and/or filters, which reduce or mute impacts. With respect to geomorphic responses and indicators, climate forcings are partly mediated by ecological, hydrological, and other processes which may amplify or filter impacts on surface processes and landforms. Then, geomorphic responses themselves may be threshold-dominated or dynamically unstable, producing disproportionately large and long-lived responses to climate changes or disturbances. Or, responses may be dynamically stable, whereby resistance or resilience of geomorphic systems minimizes the effects of changes. Thus a given geomorphic response to climate could represent (at least) two levels of amplification and/or filtering. An example is given for three fluvial systems in Kentucky, U.S.A, the Kentucky, Green, and Big South Fork Rivers. Climate impacts in the early Quaternary were amplified by glacially-driven reorganization of the ancestral Ohio River system to the North, and by dynamical instability in the down-cutting response of rivers incising plateau surfaces. Effects of more recent climate changes, however, have been filtered to varying extents. Using alluvial terraces as an example, the study rivers show distinctly different responses to climate forcings. The lower Green River has extensive, well-developed terraces recording several episodes of aggradation and downcutting, while the Big South Fork River has no alluvial terraces. The Kentucky River is intermediate, with limited preservation of relatively recent terraces. The differences can be explained in terms of differences among the rivers in (1) filtering effects of constraints on fluvial responses imposed by strongly incised, steep-walled bedrock controlled valleys; and (2) amplifier effects of periodic damming of lower river reaches by glaciofluvial outwash. [ABSTRACT FROM AUTHOR]

Our study is aimed at detection of directional trends in streamflow data observed in large rivers located in different climatic zones and attribution of the detected changes to climate drivers. We consider detection and attribution as interrelated study stages within a suggested hypothesis testing framework with the use of a hydrological model. First, we test the significance of the trends in the observed streamflow data series of 74 to 82 years long and evaluate the model’s ability to reproduce the trends, so that the trends in the simulated data are statistically indistinguishable from the corresponding observed trends. Herewith, the model is forced by the reanalysis climate data. Then, for the basins where the model reproduces the trends, we move to the attribution stage of the study. At this stage, the hydrological model is forced by the counterfactual (detrended) climate data. If the trend is not detected in the counterfactual-climate-forced simulations, we conclude that the detected observed changes are likely to be attributed to the climate trend. The suggested testing procedure is applied for four river basins: Lena, Selenga, Vyatka, and Pechora. The corresponding hydrological models are developed on the basis of the ECOMAG modeling platform. We conclude that the detected trends in the observed annual flow data series for the Lena, Selenga, and Vyatka rivers, as well as the trends in high flow for the Lena and Selenga rivers, can be attributed to climate drivers with a high confidence. Regional differences in basin mechanisms governing the detected changes are analyzed. [ABSTRACT FROM AUTHOR]

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 [ABSTRACT FROM AUTHOR]

Many boreal waters are currently becoming browner with effects on biodiversity, fish production, biogeochemical processes and drinking water quality. The question arises whether and at which speed this browning will continue under future climate change. To answer the question we predicted the absorbance (a) in 6347 lakes and streams of the boreal region under future climate change. For the prediction we modified a numerical model for a spatial variation which we tested on a temporal scale by simulating a inter-annual variation in 48 out of the 6347 Swedish waters. We observed that inter-annual a variation is strongly driven by precipitation that controls the water flushing through the landscape. Using the predicted worst case climate scenario for Sweden until 2030, i.e., a 32 % precipitation increase, and assuming a 10 % increase in imports of colored substances into headwaters but no change in land-cover, we predict that a in the 6347 lakes and streams will, in the worst case, increase by factors between 1.1 and 7.6 with a median of 1.3. This increase implies that a will rise from the present 0.1-86 m (median: 7.3 m) in the 6347 waters to 0.1-154 m (median: 10.1 m), which can cause problems for the preparation of drinking water in a variety of waters. Our model approach clearly demonstrates that a homogenous precipitation increase results in very heterogeneous a changes, where lakes with a long-term mean landscape water retention time between 1 and 3 years are particularly vulnerable to climate change induced browning. Since these lake types are quite often used as drinking water resources, preparedness is needed for such waters. [ABSTRACT FROM AUTHOR]

Deals with a study which assessed the hydrologic sensitivity to climate change of several continental river basins. Experimental design; Precipitation and temperature changes; Seasonal change in temperature; Methodology and results; Discussion.

The purpose of this paper is to analyse the regional impact of recent climate change on the water resources in southern France. We produced spatial reconstructions of the monthly evolutions of temperature, precipitation and water discharge in 15 watersheds of six coastal river basins and examined the major changes based on trend analysis for the last 40 years. In this part of the Mediterranean, the general warming trend was strongly enhanced by changes in the atmospheric circulation patterns, characterized by a northward extension of the subtropical high pressure domain during spring and summer. During these seasons, monthly warming rates could achieve almost twice the mean annual warming rates. Although annual precipitation did not follow clear trends, water discharge significantly decreased in one third of the watersheds and accounted for an estimated 20% reduction of the water resources in this region. This concerns both the highest and lowest watersheds. In the former, the reduction is likely the result of a temperature induced switch of snowfall to rainfall at high altitudes. In the latter, the reduction of discharge seems to come from lower groundwater levels, which may be related to the temperature increase too, but also have other origins. The recent climatic evolution is consistent with most modelling simulations for the future, indicating that the reduction of the water resources will hold on, probably still enhanced by decreases in precipitation. [ABSTRACT FROM AUTHOR]

Our analyses partition the relative influence of progressive climate change and large-scale climate drivers that can be associated with the Quasi-Biennial Oscillation (QBO), El Niño Southern Oscillation (ENSO), North Atlantic Oscillation (NAO), solar sunspot cycle, and multi-decadal oscillations on lake ice breakup dates for thirteen Northern Hemisphere lakes. Oscillatory dynamics explain 26 % of the total variance in the time series compared with 15 % for linear trends, leaving 60 % unexplained and likely attributable, in part, to local weather. Significant oscillatory dynamics include frequencies in 2-3 year periods (9.4 % of the total variance), 3-6 year periods (8.2 %), 10-12 year periods (1.6 %) and various multidecadal periods (0.4-1.3 %). All 13 study lakes, although widely scattered in the Northern Hemisphere, had similar oscillatory dynamics and linear trends, emphasizing that global processes influence lake ice breakup locally. We illustrate that while quasi-periodic dynamics associated with large-scale climate drivers are important, they do not mask the clear evidence for progressive climate change. [ABSTRACT FROM AUTHOR]

Many studies have shown that lake ice-out (break-up) dates in the Northern Hemisphere are useful indicators of late winter/early spring climate change. Trends in lake ice-out dates in New England, USA, were analyzed for 25, 50, 75, 100, 125, 150, and 175 year periods ending in 2008. More than 100 years of ice-out data were available for 19 of the 28 lakes in this study. The magnitude of trends over time depends on the length of the period considered. For the recent 25-year period, there was a mix of earlier and later ice-out dates. Lake ice-outs during the last 50 years became earlier by 1.8 days/decade (median change for all lakes with adequate data). This is a much higher rate than for longer historical periods; ice-outs became earlier by 0.6 days/decade during the last 75 years, 0.4 days/decade during the last 100 years, and 0.6 days/decade during the last 125 years. The significance of trends was assessed under the assumption of serial independence of historical ice-out dates and under the assumption of short and long term persistence. Hypolimnion dissolved oxygen (DO) levels are an important factor in lake eutrophication and coldwater fish survival. Based on historical data available at three lakes, 32 to 46 % of the interannual variability of late summer hypolimnion DO levels was related to ice-out dates; earlier ice-outs were associated with lower DO levels. [ABSTRACT FROM AUTHOR]

We investigate the temporal patterns in inter-annual variability in ice breakup dates for Lakes Mendota and Monona, Wisconsin, between 1905 and 2004. We analyze the contributions of long-term trends attributed to climate change, local weather, indices of sunspots, and large-scale climatic drivers, such as the North Atlantic Oscillation (NAO) and El Niňo Southern Ocean Index (ENSO) on time series of lake-ice breakup. The relative importance of the aforementioned explanatory variables was assessed using linear regression and variation partitioning models accounting for cyclic temporal dynamics as represented by Moran Eigenvector Maps (MEM). Model results explain an average of 58 % of the variation in ice breakup dates. A combination of the long-term linear trends, rain and snowfall in the month prior to breakup, air temperature in the winter prior to breakup, cyclic dynamics associated with sunspot numbers, ENSO, and for Lake Mendota, NAO, all significantly influence the timing of ice breakup. Significant cycle lengths were 3.5, 9, 11, and 50 years. Despite their proximity, Lakes Mendota and Monona exhibit differences in how and which explanatory variables were incorporated into the models. Our results indicate that lake ice dynamics are complex in both lakes and multiple interacting processes explain the residuals around the linear warming trends that characterize lake ice records. [ABSTRACT FROM AUTHOR]

The risks to human populations in coastal areas are changing due to climate and socio-economic changes, and these trends are predicted to accelerate during the twenty-first century. To understand these changing risks, and the resulting choices and pathways to successful management and adaptation, broad-scale integrated assessment is essential. Due to their complexity the two risks of flooding and erosion are usually managed independently, yet frequently they are interconnected by longshore exchange of sediments and the resulting broad scale morphological system behaviour. In order to generate new insights into the effects of climate change and coastal management practises on coastal erosion and flood risk, we present an integrated assessment of 72 km of shoreline over the twenty-first century on the East Anglian coast of England which is a site of significant controversy about how to manage coastal flood and erosion risks over the twenty-first century. A coupled system of hydrodynamic, morphological, reliability and socio-economic models has been developed for the analysis, implemented under scenarios of coastal management, climate and socio-economic change. The study is unique in coastal management terms because of the large spatial scale and extended temporal scale over which the analysis is quantified. This study for the first time quantifies what has for some years been argued qualitatively: the role of sediments released from cliff erosion in protecting neighbouring low-lying land from flooding. The losses and benefits are expressed using the common currency of economic risk. The analysis demonstrates that over the twenty-first century, flood risk in the study area is expected to be an order of magnitude greater than erosion risk. Climate and socio-economic change and coastal management policy have a significant influence on flood risk. This study demonstrates that the choices concerning coastal management are profound, and there are clear tradeoffs between erosion and flood impacts. [ABSTRACT FROM AUTHOR]

Daily rainfall and temperature data were extracted from the multi-ensemble HadRM3H regional climate model (RCM) integrations for control (1960-1990) and future (2070-2100) time-slices. This dynamically downscaled output was bias-corrected on observed mean statistics and used as input to hydrological models calibrated for eight catchments which are critical water resources in northwest England. Simulated daily flow distributions matched observed from Q95 to Q5, suggesting that RCM data can be used with some confidence to examine future changes in flow regime. Under the SRES A2 (UKCIP02 Medium-High) scenario, annual runoff is projected to increase slightly at high elevation catchments, but reduce by ~16% at lower elevations. Impacts on monthly flow distribution are significant, with summer reductions of 40-80% of 1961-90 mean flow, and winter increases of up to 20%. This changing seasonality has a large impact on low flows, with Q95 projected to decrease in magnitude by 40-80% in summer months, with serious consequences for water abstractions and river ecology. In contrast, high flows (> Q5) are projected to increase in magnitude by up to 25%, particularly at high elevation catchments, providing an increased risk of flooding during winter months. These changes will have implications for management of water resources and ecologically important areas under the EU Water Framework Directive. [ABSTRACT FROM AUTHOR]

Abstract Arctic environments are generally believed to be highly sensitive to human-induced climatic change. In this paper, we explore the impacts on the hydrological system of the sub-arctic Tana Basin in Northernmost Finland and Norway. In contrast with previous studies, attention is not only given to river discharge, but also to the spatial patterns in snow coverage and evapotranspiration. We used a distributed water balance model that was coupled to a regional climate model in order to calculate a scenario of climate change by the end of this century. Three different model experiments were performed, adopting different approaches to using the climate model output in the hydrological model runs. The results were largely consistent, indicating a much shorter snow season and, accordingly, decreased sublimation, an increase in evapotranspiration, and a shift in the annual runoff peak. As the snow-free season is extended, the amount of solar radiation that is received during this period increases significantly. The results also show important local differences in the hydrological response to climate change. For example, in the scenario runs, the snow season was more than 30 days shorter at higher elevations, but in some of the river valleys, this was up to 70 days. [ABSTRACT FROM AUTHOR]

Abstract A numerical stream temperature model that accounts for kinematic wave flow routing, and heat exchange fluxes between stream water and the atmosphere, and stream water and the stream bed is developed and calibrated to a data-set from the Lower Madison River, Montana, USA. Future climate scenarios were applied to the model through changes to the atmospheric input data based on air temperature and solar radiation output from four General Circulation Models (GCM) for the region under atmospheric CO2 concentration doubling. The purpose of this study was to quantify potential climate change impacts on water temperature for the Lower Madison River, and to assess possible impacts to aquatic ecosystems. Because water temperature is a critical component of fish habitat, this information could be of use in future planning operations of current reservoirs. We applied air temperature changes to diurnal temperatures, daytime temperatures only, and nighttime temperatures only, to assess the impacts of variable potential warming trends. The results suggest that, given the potential climatic changes, the aquatic ecosystem downstream of Ennis Lake will experience higher water temperatures, possibly leading to increased stress on fish populations.Daytime warming produced the largest increases in downstream water temperature. [ABSTRACT FROM AUTHOR]

The results of an experimental `end to end' assessment of the effects of climate change on water resources in the western United States are described. The assessment focuses on the potential effects of climate change over the first half of the 21st century on the Columbia, Sacramento/San Joaquin, and Colorado river basins. The paper describes the methodology used for the assessment, and it summarizes the principal findings of the study. The strengths and weaknesses of this study are discussed, and suggestions are made for improving future climate change assessments. [ABSTRACT FROM AUTHOR]

Investigates the effects of climate change due to increasing atmospheric carbon dioxide on the major tributaries to the Swan River in Perth, Western Australia. General Circulation Models; 1000 year time series; Stochastic weather generator; Conceptual rainfall-runoff model.

The following study examines climate change in Mali, and its impacts on food security. This will be explored through the experiences of women, using feminist political ecology as an analytical framework. This research builds upon previous work that explores the intra-gender power imbalances that exacerbate the impacts of climate change within agrarian households. We find that polygynous households are sites of power differences, which perpetuates food insecurity. Within households, women are often excluded from decision-making processes that help mitigate climate-stressed food production. Beyond households, options to collaborate and seek support do exist, and are successful when women are granted agency to determine how resources are used. However, these strategies are available to a minority of individuals, and access is often limited to elder women. That said, despite the potential of women-led groups within and outside of households, such groups are subject to unequal distribution of power. As a result, women-led networks are not yet able to thoroughly address climate-sensitive agricultural challenges and continue to marginalize young women. [ABSTRACT FROM AUTHOR]

The long-term ice record (from 1964 to 2008) of an Arctic lake in northern Europe (Lake Kilpisjärvi) reveals the response of lake ice to climate change at local and regional scales. Average freeze-up and ice breakup occurred on 9 November and 19 June, respectively. The freeze-up has been significantly delayed at a rate of 2.3 d per decade from 1964 onward ( P < 0.05). No significant change has taken place in ice breakup. Annual average ice thickness has become smaller since the mid-1980s ( P < 0.05). Air temperature during the early ice season significantly affected the ice thickness. The freeze-up date exhibits the highest correlation with the 2-month average daily minimum air temperature centered at the end of October, while the ice breakup date exhibits the highest correlation with the 2-month average daily maximal air temperature centered in mid May. A 1°C increase in the surface air temperature corresponds to a freeze-up later by 3.4 days and an ice breakup earlier by 3.6 days. Snow cover is a critical factor in lake-ice climatology. For cumulative November to March precipitation of less than 0.13 m, the insulating effect of the snow dominated, while higher rates of precipitation favored thicker ice due to the formation of snow ice. Variations in ice records of Lake Kilpisjärvi can serve as an indicator of climate variations across the northern Europe. The North Atlantic Oscillation (NAO) does not significantly affect the ice season there, although both the local air temperatures and winter precipitation contain a strong NAO signal. [ABSTRACT FROM AUTHOR]

Water temperature is a key variable affecting fish habitat in rivers. The Sockeye salmon (Oncorhynchus nerka), a keystone species in north western aquatic ecosystems of North America, is profoundly affected by thermal regime changes in rivers, and it holds a pivotal role in ecological and economic contexts due to its life history, extensive distribution, and commercial fishery. In this study, we explore the effects of climate change on the thermal regime of the Nechako River (British Columbia, Canada), a relatively large river partially controlled by the Skins Lake Spillway. The CEQUEAU hydrological-thermal model was calibrated using discharge and water temperature observations. The model was forced using the Fifth generation of ECMWF Atmospheric Reanalysis data for the past and meteorological projections (downscaled and bias-corrected) from climate models for future scenarios. Hydrological calibration was completed for the 1980–2019 period using data from two hydrometric stations, and water temperature calibration was implemented using observations for 2005–2019 from eight water temperature stations. Changes in water temperature were assessed for two future periods (2040–2069 and 2070–2099) using eight Coupled Model Intercomparison Project Phase 6 climate models and using two Shared Socioeconomic Pathway scenarios (4.5 and 8.5 W/m2 by 2100) for each period. Results show that water temperatures above 20°C (an upper threshold for adequate thermal habitat for Sockeye salmon migration in this river) at the Vanderhoof station will increase in daily frequency. While the frequency of occurrence of this phenomenon is 1% (0–9 days/summer) based on 2005–2019 observations, this number range is 3.8–36% (0–62 days/summer) according to the ensemble of climate change scenarios. These results show the decreasing habitat availability for Sockeye salmon due to climate change and the importance of water management in addressing this issue. [ABSTRACT FROM AUTHOR]

This paper quantifies the vulnerability of and risk to water resources (VRWR) under a scenario of climate change in the arid and semi-arid region of West China. A new approach integrating hazard, sensitivity, resilience, exposure and risk is developed to assess the VRWR from climate change. Drought is regarded as the key hazard, with its frequency and severity defined using a surface humidity index. Exposure is quantitatively linked with indicators of population and social and economic characteristics using statistical and Geographical Information System (GIS) methodologies. Risk is defined as the product of hazard, exposure and vulnerability, while vulnerability is treated as a function of sensitivity and adaptation. Vulnerability and risk in the water resources system in the coming 20 years are assessed for the RCP 4.5 scenario. The results reveal that both hazard and exposure of water resources display strong spatial variation in the study area. High hazard and exposure are found in the northern Tianshan Mountain as well as the eastern part of Hexi Corridor. Water resources are particularly sensitive to variation in precipitation and potential evapotranspiration in the upstream areas of Hexi Corridor, rivers in Central Asia, headwater streams of Tarim River and most of Chang Tang Plateau. Our assessment shows that there is high vulnerability of and risk to water resources in the study area, especially in the areas of Hexi Corridor, northern Tianshan Mountain and Tarim River. Under the RCP 4.5 climate change scenario, the vulnerability and risk decline over the entire area but remain at a serious level in inland rivers in Hexi Corridor, northern Tianshan Mountain and headwater streams of Tarim River. Thus, these areas are the highest priority for strengthening policy measures to adapt to climate change and reduce exposure and vulnerability and their risk to water resources. [ABSTRACT FROM AUTHOR]

The Greater Horn of Africa region increasingly experiences high risk of water scarcity. A combination of frequent droughts, rapid population growth and rising urbanisation has reduced streamflow and intensified water abstraction, causing water and food shortages. Estimates of future streamflow changes in the region have so far been highly uncertain and evaluations using ground-based measurements are still limited. Here, future streamflow changes are estimated using a distributed hydrological model forced with an ensemble of high-resolution climate simulations produced using the European community Earth-System Model v3.1. The simulated streamflow is evaluated using observed data from 29 stations from river basins across different climate zones in the region. Evaluation results show large sub-regional variations in the performance of simulated streamflow. The sign and magnitude of future streamflow changes vary between climate simulations and river basins, highlighting the uncertainties in the hydrologic projections. Overall, the streamflow projections indicate large (seasonal, long-term mean and extreme) streamflow decreases for all major rivers in Ethiopia and increases in the equatorial parts of the region at the end of the century. The ensemble mean shows a 10 to 25% decrease in the long-term mean flow in Ethiopia and a 10% increase in the equatorial part of the region in 2080s. Similarly, there is a substantial change in high flows in 2080s, with up to − 50% reduction in the northern and 50% increase in the equatorial parts of the region. These findings are critical because the rivers provide water supply to a rapidly changing socio-economy of the region. [ABSTRACT FROM AUTHOR]

Warmer climatic conditions have been associated with numerous hydrologic changes that may impact riverbank erosion in cold regions, but the net effect is not well understood. We used regression and correlation analyses to examine the relationships among subarctic riverbank erosion and seasonal hydrology, the impact of climate change and variability, and the societal implications. Geomorphic change (loss and gain of vegetated land) was mapped along several river reaches in the Yukon River Basin, Alaska, throughout 1984 and 2017 using Landsat satellite imagery. Annual erosion rates were estimated from these spatial data. At most study sites, erosion rates (km2/year) were either positively correlated (r = 0.68–0.84, p = 0.0085–0.061) with monthly mean discharge within the cold season or inversely correlated (r = − 0.74 – −0.62, p < 0.10) with river ice breakup date in the spring. These proximate controls on erosion, in turn, were influenced both by climate variability and long-term climatic change. We conclude that increased cold season discharge and earlier freshet that occurs under warmer conditions enhance riverbank erosion in most areas. Climate-related changes to fluvial dynamics may impact communities through effects on infrastructure, travel safety, channel navigability, fish and wildlife habitat, and access to subsistence resources. [ABSTRACT FROM AUTHOR]

This study investigates the attribution of climate change to trends in river discharge during six decades from 1955 until 2014 in 12 selected river catchments across six Central Asian countries located upstream of the main rivers. For this purpose, the semi-distributed eco-hydrological model SWIM (Soil and Water Integrated Model) was firstly calibrated and validated for all study catchments. Attributing climate change to streamflow simulation trends was forced by factual (reanalysis) and counterfactual climate data (assuming the absence of anthropogenic influence) proposed in the framework of the ISIMIP (Inter-Sectoral Impact Model Intercomparison Project) or ESM without anthropogenic forcing that were firstly tested and then compared. The trend analysis was performed for three variables: mean annual discharge and high flow (Q5) and low flow (Q95) indices. The results show that trends in the annual and seasonal discharge could be attributed to climate change for some of the studied catchments. In the three northern catchments (Derkul, Shagan, and Tobol), there are positive trends, and in two catchments (Sarysu and Kafirnigan), there are negative streamflow trends under the factual climate, which could be attributed to climate change. Also, our analysis shows that the average level of discharge in Murghab has increased during the historical study period due to climate change, despite the overall decreasing trend during this period. In addition, the study reveals a clear signal of shifting spring streamflow peaks in all catchments across the study area. [ABSTRACT FROM AUTHOR]

Recent water resources planning studies have proposed climate adaptation strategies in which infrastructure and policy actions are triggered by observed thresholds or "signposts." However, the success of such strategies depends on whether thresholds can be accurately linked to future vulnerabilities. This study presents a framework for testing the ability of adaptation thresholds to dynamically identify vulnerable scenarios within ensemble projections. Streamflow projections for 91 river sites predominantly in the western USA are used as a case study in which vulnerability is determined by the ensemble members with the lowest 10% of end-of-century mean annual flow. Illustrative planning thresholds are defined through time for each site based on the mean streamflow below which a specified fraction of scenarios is vulnerable. We perform a leave-one-out cross-validation to compute the frequency of incorrectly identifying or failing to identify a vulnerable scenario (false positives and false negatives, respectively). Results show that in general, this method of defining thresholds can identify vulnerable scenarios with low false positive rates (< 10%), but with false negative rates for many rivers remaining higher than random chance until roughly 2060. This finding highlights the tradeoff between frequently triggering unnecessary action and failing to identify potential vulnerabilities until later in the century, and suggests room for improvement in the threshold-setting technique that could be benchmarked with this approach. This testing framework could extend to thresholds defined with multivariate statistics, or to any application using thresholds and ensemble projections, such as long-term flood and drought risk, or sea level rise. [ABSTRACT FROM AUTHOR]

Semi-arid regions are known for erratic precipitation patterns with significant effects on the hydrological cycle and water resources availability. High temporal and spatial variation in precipitation causes large variability in runoff over short durations. Due to low soil water storage capacity, base flow is often missing and rivers fall dry for long periods. Because of its climatic characteristics, the semi-arid north-eastern region of Brazil is prone to droughts. To counter these, reservoirs were built to ensure water supply during dry months. This paper describes problems and solutions when calibrating and validating the eco-hydrological model SWIM for semi-arid regions on the example of the Pajeú watershed in north-eastern Brazil. The model was calibrated to river discharge data before the year 1983, with no or little effects of water management, applying a simple and an enhanced approach. Uncertainties result mainly from the meteorological data and observed river discharges. After model calibration water management was included in the simulations. Observed and simulated reservoir volumes and river discharges are compared. The calibrated and validated models were used to simulate the impacts of climate change on hydrological processes and water resources management using data of two representative concentration pathways (RCP) and five earth system models (ESM). The differences in changes in natural and managed mean discharges are negligible (< 5%) under RCP8.5 but notable (> 5%) under RCP2.6 for the ESM ensemble mean. In semi-arid catchments, the enhanced approach should be preferred, because in addition to discharge, a second variable, here evapotranspiration, is considered for model validation. [ABSTRACT FROM AUTHOR]

Impacts of climate change at 1.5, 2 and 3 °C mean global warming above preindustrial level are investigated and compared for runoff, discharge and snowpack in Europe. Ensembles of climate projections representing each of the warming levels were assembled to describe the hydro-meteorological climate at 1.5, 2 and 3 °C. These ensembles were then used to force an ensemble of five hydrological models and changes to hydrological indicators were calculated. It is seen that there are clear changes in local impacts on evapotranspiration, mean, low and high runoff and snow water equivalent between a 1.5, 2 and 3 °C degree warmer world. In a warmer world, the hydrological impacts of climate change are more intense and spatially more extensive. Robust increases in runoff affect the Scandinavian mountains at 1.5 °C, but at 3 °C extend over most of Norway, Sweden and northern Poland. At 3 °C, Norway is affected by robust changes in all indicators. Decreases in mean annual runoff are seen only in Portugal at 1.5 °C warming, but at 3 °C warming, decreases to runoff are seen around the entire Iberian coast, the Balkan Coast and parts of the French coast. In affected parts of Europe, there is a distinct increase in the changes to mean, low and high runoff at 2 °C compared to 1.5 °C, strengthening the case for mitigation to lower levels of global warming. Between 2 and 3 °C, the changes in low and high runoff levels continue to increase, but the changes to mean runoff are less clear. Changes to discharge in Europe's larger rivers are less distinct due to the lack of homogenous and robust changes across larger river catchments, with the exception of Scandinavia where discharges increase with warming level. [ABSTRACT FROM AUTHOR]

In the snowmelt dominated hydrology of arid western US landscapes, late summer low streamflow is the most vulnerable period for aquatic ecosystem habitats and trout populations. This study analyzes mean August discharge at 153 streams throughout the Central Rocky Mountains of North America (CRMs) for changes in discharge from 1950-2008. The purpose of this study was to determine if: (1) Mean August stream discharge values have decreased over the last half-century; (2) Low discharge values are occurring more frequently; (3) Climatic variables are influencing August discharge trends. Here we use a strict selection process to characterize gauging stations based on amount of anthropogenic impact in order to identify heavily impacted rivers and understand the relationship between climatic variables and discharge trends. Using historic United States Geologic Survey discharge data, we analyzed data for trends of 40-59 years. Combining of these records along with aerial photos and water rights records we selected gauging stations based on the length and continuity of discharge records and categorized each based on the amount of diversion. Variables that could potentially influence discharge such as change in vegetation and Pacific Decadal Oscillation (PDO) were examined, but we found that that both did not significantly influence August discharge patterns. Our analyses indicate that non-regulated watersheds are experiencing substantial declines in stream discharge and we have found that 89% of all non-regulated stations exhibit a declining slope. Additionally our results here indicate a significant (α ≤ 0.10) decline in discharge from 1951-2008 for the CRMs. Correlations results at our pristine sites show a negative relationship between air temperatures and discharge and these results coupled with increasing air temperature trends pose serious concern for aquatic ecosystems in CRMs. [ABSTRACT FROM AUTHOR]

Since the early 1970s, the agricultural frontier of southeastern Amazon has undergone extensive land use changes. These alterations, combined with regional climate changes, have the potential to influence the hydrologic cycle at small to large scales. We evaluated a 40-year time series (1976 to 2015) of rainfall and water yield and related them to land use changes in the Upper Xingu River Basin (UX). We acquired data from six rainfall stations and four river gauges and mapped land use changes. Mann-Kendall trend analysis and Pettitt's change point detection were employed to describe annual and seasonal changes in the time series. Monthly water yield from the Xingu River was used to derive annual, seasonal, and monthly water yield, as well as the runoff coefficient. The largest changes in land use occurred during the last two decades and approximately 60,900 km2 in the Upper Xingu Basin were deforested between 1985 and 2015. Rainfall in the Xingu Basin decreased by about 245 mm over the period but there was no trend in water yield. The number of rainy days and intensity of events also decreased, but the length of the rainy season and seasonal and annual water yield did not change. Although watershed deforestation has increased water yield in other Amazon rivers, the reduction in rainfall in the Upper Xingu Basin was high enough to mask this effect. [ABSTRACT FROM AUTHOR]

Climate change will affect future flow and thermal regimes of rivers. This will directly affect freshwater habitats and ecosystem health. In particular fish species, which are strongly adapted to a certain level of flow variability will be sensitive to future changes in flow regime. In addition, all freshwater fish species are exotherms, and increasing water temperatures will therefore directly affect fishes’ biochemical reaction rates and physiology. To assess climate change impacts on large-scale freshwater fish habitats we used a physically-based hydrological and water temperature modelling framework forced with an ensemble of climate model output. Future projections on global river flow and water temperature were used in combination with current spatial distributions of several fish species and their maximum thermal tolerances to explore impacts on fish habitats in different regions around the world. Results indicate that climate change will affect seasonal flow amplitudes, magnitude and timing of high and low flow events for large fractions of the global land surface area. Also, significant increases in both the frequency and magnitude of exceeding maximum temperature tolerances for selected fish species are found. Although the adaptive capacity of fish species to changing hydrologic regimes and rising water temperatures could be variable, our global results show that fish habitats are likely to change in the near future, and this is expected to affect species distributions. [ABSTRACT FROM AUTHOR]

A general increase in precipitation has been observed in Germany in the last century, and potential changes in flood generation and intensity are now at the focus of interest. The aim of the paper is twofold: a) to project the future flood conditions in Germany accounting for various river regimes (from pluvial to nival-pluvial regimes) and under different climate scenarios (the high, A2, low, B1, and medium, A1B, emission scenarios) and b) to investigate sources of uncertainty generated by climate input data and regional climate models. Data of two dynamical Regional Climate Models (RCMs), REMO (REgional Model) and CCLM (Cosmo-Climate Local Model), and one statistical-empirical RCM, Wettreg (Wetterlagenbasierte Regionalisierungsmethode: weather-type based regionalization method), were applied to drive the eco-hydrological model SWIM (Soil and Water Integrated Model), which was previously validated for 15 gauges in Germany. At most of the gauges, the 95 and 99 percentiles of the simulated discharge using SWIM with observed climate data had a good agreement with the observed discharge for 1961-2000 (deviation within ±10 %). However, the simulated discharge had a bias when using RCM climate as input for the same period. Generalized Extreme Value (GEV) distributions were fitted to the annual maximum series of river runoff for each realization for the control and scenario periods, and the changes in flood generation over the whole simulation time were analyzed. The 50-year flood values estimated for two scenario periods (2021-2060, 2061-2100) were compared to the ones derived from the control period using the same climate models. The results driven by the statistical-empirical model show a declining trend in the flood level for most rivers, and under all climate scenarios. The simulations driven by dynamical models give various change directions depending on region, scenario and time period. The uncertainty in estimating high flows and, in particular, extreme floods remains high, due to differences in regional climate models, emission scenarios and multi-realizations generated by RCMs. [ABSTRACT FROM AUTHOR]

Seaports are located in vulnerable areas to climate change impacts: on coasts susceptible to sea-level rise and storms or at mouths of rivers susceptible to flooding. They serve a vital function within the local, regional, and global economy. Their locations in the heart of sensitive estuarine environments make it an imperative to minimize the impacts of natural hazards. Climate impacts, like a projected SLR of .6 m to 2 m and doubling of Category 4 and 5 hurricanes by 2100, will result in more extreme events at many seaports. To assess the current state of knowledge on this issue, we surveyed port authorities from around the world about how administrators felt climate change might impact their operations, what sea-level change would create operational problems, and how they planned to adapt to new environmental conditions. The planned rapid expansion of ports reported by the survey respondents indicates that adaptation measures should be considered as ports construct new infrastructure that may still be in use at the end of the century. Respondents agreed that the ports community needs to address this issue and most felt relatively uninformed about potential climate impacts. Although most ports felt that SLR would not be an issue at their port this century, sea-level rise was nevertheless an issue of great concern. Our results suggest opportunities for the scientific community to engage with port practitioners to prepare proactively for climate change impacts on this sector. [ABSTRACT FROM AUTHOR]

This study presents a method to assess the sensitivity of hydropower generation to uncertain water resource availability driven by future climate change. A hydrology-electricity modelling framework was developed and applied to six rivers where 10 hydropower stations operate, which together represent over 85% of Ecuador's installed hydropower capacity. The modelling framework was then forced with bias-corrected output from 40 individual global circulation model experiments from the Coupled Model Intercomparison Project 5 for the Representative Concentration Pathway 4.5 scenario. Impacts of changing climate on hydropower resource were quantified for 2071-2100 relative to a baseline period 1971-2000. Results show a wide annual average inflow range from + 277% to − 85% when individual climate experiments are assessed. The analysis also show that hydropower generation in Ecuador is highly uncertain and sensitive to climate change since variations in inflow to hydropower stations would directly result in changes in the expected hydropower potential. Annual hydroelectric power production in Ecuador is found to vary between − 55 and + 39% of the mean historical output when considering future inflow patterns to hydroelectric reservoirs covering one standard deviation of the CMIP5 RCP4.5 climate ensemble. [ABSTRACT FROM AUTHOR]

Changes in river discharge regimes are regarded as the primary drivers of change of many in-stream ecological processes. While a lot of assessments addressing the hydrological alteration caused by human activities have been conducted for many river basins worldwide, a comprehensive analysis of hydrological alteration over major river basins worldwide under climate change is still limited to date. This study aims to address multi-dimensional hydrological alterations (alterations of multiple river flow characteristics) under climate change for four major rivers on three continents, by means of a consolidated framework consisting of two hydrological models, bias-corrected scenarios from five general circulation models (GCMs), and three Representative Concentration Pathways (RCPs) scenarios. The multi-dimensional hydrological alterations are quantified via the general Indicators of Hydrological Alteration approach (IHA) and two modified IHA methods based on dimensionality reduction. The reliability and advantages for the modified IHA methods are also analyzed. The results show that: (1) A modified IHA method ('NR-IHA method') where the selected non-redundant IHA indices are basin specific is a valid alternative to the conventional IHA method for evaluating flow regime alteration, in consideration that high agreements in the simulated overall flow regimes alteration degree between it and the conventional IHA method are found during historical and future scenario periods, over four basins (the Upper Yellow River, the Lena River, the Tagus River and the Upper Amazon River). (2) Climate change is expected to remarkably alter overall flow regimes in the Tagus River and Upper Yellow River, especially at the end of the 21st century and under high RCP scenarios, whereas the dominant alteration extent tends to be low in the Lena River and Upper Amazon River in the two future periods. (3) The modified IHA method, preventing double-counting some aspects of the flow regime when assessing alteration degree of overall flow regimes, can save 65 % computation time and is more efficient than the conventional IHA method. It could be beneficial to figure out adaptive countermeasures for water resource management and restoration of eco-environmental systems under climate change. [ABSTRACT FROM AUTHOR]

Climate change and its effects on the hydrologic regime of the Amazon basin can impact biogeochemical processes, transportation, flood vulnerability, fisheries and hydropower generation. We examined projections of climate change on discharge and inundation extent in the Amazon basin using the regional hydrological model MGB-IPH with 1-dimensional river hydraulic and water storage simulation in floodplains. Future projections (2070-2099) were obtained from five GCMs from IPCC's Fifth Assessment Report CMIP5. Climate projections have uncertainty and results from different climate models did not agree in total Amazon flooded area or discharge anomalies along the main stem river. Overall, model runs agree better with wetter (drier) conditions over western (eastern) Amazon. Results indicate that increased mean and maximum river discharge for large rivers draining the Andes in the northwest contributes to increased mean and maximum discharge and inundation extent over Peruvian floodplains and Solimões River (annual mean-max: +9 % - +18.3 %) in western Amazonia. Decreased river discharges (mostly dry season) are projected for eastern basins, and decreased inundation extent at low water (annual min) in the central (−15.9 %) and lower Amazon (−4.4 %). [ABSTRACT FROM AUTHOR]

This study presents an analysis of climate-change impacts on the water resources of two basins located in northern France, by integrating four sources of uncertainty: climate modelling, hydrological modelling, downscaling methods, and emission scenarios. The analysis focused on the evolution of the water budget, the river discharges and piezometric heads. Seven hydrological models were used, from lumped rainfall-discharge to distributed hydrogeological models, and led to quite different estimates of the water-balance components. One of the hydrological models, CLSM, was found to be unable to simulate the increased water stress and was, thus, considered as an outlier even though it gave fair results for the present day compared to observations. Although there were large differences in the results between the models, there was a marked tendency towards a decrease of the water resource in the rivers and aquifers (on average in 2050 about −14 % and −2.5 m, respectively), associated with global warming and a reduction in annual precipitation (on average in 2050 +2.1 K and −3 %, respectively). The uncertainty associated to climate models was shown to clearly dominate, while the three others were about the same order of magnitude and 3–4 times lower. In terms of impact, the results found in this work are rather different from those obtained in a previous study, even though two of the hydrological models and one of the climate models were used in both studies. This emphasizes the need for a survey of the climatic-change impact on the water resource. [ABSTRACT FROM AUTHOR]

Northern Indian rivers are primarily fed by wintertime (December, January, February-DJF) precipitation, in the form of snow-yielded by eastward moving synoptic weather systems called Western Disturbances (WDs), over the western Himalayas (WH). This accumulated snow melts during ablation period. In the context of today's warming atmosphere, it is imperative to study the changes in the temperature and precipitation patterns over the WH to assess the impact of global warming on climatic conditions of the region. Keeping that in mind, observational analysis of temperature and precipitation fields is planned. In the present study various climatic indices are analyzed based on wintertime (DJF) data of 30 years (1975-2006) obtained from the Snow and Avalanche Study Establishment (SASE), India. Results indicate enhancement in the surface air temperature across the WH. Percent number of warm (cold) days have increased (decreased) during 1975-2006 over the WH. Further analysis of precipitation reveals slightly decreasing but inconsistent trends. [ABSTRACT FROM AUTHOR]

The author reflects on climate change and the quality of stream water. The author states that water quality is influenced by land and water use, as well as climatic factors including pollution, and air and water temperature. The author mentions factors in determining water quality including extreme events and cycling nutrients and pollutants. The author concludes that there is an unsatisfactory understanding on the relation between climatic changes and water quality.

This paper reviews the land cover changes on the Tibetan Plateau during the last 50 years partly caused by natural climate change and, more importantly, influenced by human activities. Recent warming trends on the plateau directly influence the permafrost and snow melting and will impact on the local ecosystem greatly. Human activities increased rapidly on the plateau during the last half century and have significant impacts on land use. Significant land cover changes on the Tibetan Plateau include permafrost and grassland degradation, urbanization, deforestation and desertification. These changes not only impact on local climate and environment, but also have important hydrological implications for the rivers which originate from the plateau. The most noticeable disasters include the flooding at the upper reaches of Yangtze River and droughts along the middle and lower reaches of Yellow River. Future possible land cover changes under future global climate warming are important but hard to assess due to the deficits of global climate model in this topographically complex area. Integrated investigation of climate and ecosystems, including human-beings, are highly recommended for future studies. [ABSTRACT FROM AUTHOR]

Reindeer husbandry represents a major land use in the Barents region, and has been predicted to be adversely affected by climate change. This paper considers the likely response of reindeer husbandry to changes both in climate and in socio-economic circumstances in the four countries of the Barents region from 1990 to 2080. Key natural factors include vegetation distribution, and a range of meteorological variables including temperature, wind, snow cover and freezing of rivers. The potential impact of these factors is evaluated quantitatively using the tolerable windows method, the results of which indicate a general but spatially non-uniform decline in the suitability of the region for reindeer husbandry. Relevant socio-economic factors include regional patterns of politics, management and knowledge. A focus on herders' own perceptions of environmental change and flexibility of response, derived particularly from study sites in Russia, suggests that models of vulnerability to climate change should be tempered by paying greater attention to changes in socio-economic factors. When compared with the potential effect of changing these socioeconomic factors, the vulnerability of reindeer husbandry to projected climate change appears to be comparatively small. [ABSTRACT FROM AUTHOR]