Modeling effects of climate change on Yakima River salmonid habitats

We evaluated the potential effects of two climate change scenarios on salmonid habitats in the Yakima River by linking the outputs from a watershed model, a river operations model, a two-dimensional (2D) hydrodynamic model, and a geographic information system (GIS). The watershed model produced a discharge time series (hydrograph) in two study reaches under three climate scenarios: a baseline (1981–2005), a 1-°C increase in mean air temperature (plus one scenario), and a 2-°C increase (plus two scenario). A river operations model modified the discharge time series with Yakima River operational rules, a 2D model provided spatially explicit depth and velocity grids for two floodplain reaches, while an expert panel provided habitat criteria for four life stages of coho and fall Chinook salmon. We generated discharge-habitat functions for each salmonid life stage (e.g., spawning, rearing) in main stem and side channels, and habitat time series for baseline, plus one (P1) and plus two (P2) scenarios. The spatial and temporal patterns in salmonid habitats differed by reach, life stage, and climate scenario. Seventy-five percent of the 28 discharge-habitat responses exhibited a decrease in habitat quantity, with the P2 scenario producing the largest changes, followed by P1. Fry and spring/summer rearing habitats were the most sensitive to warming and flow modification for both species. Side channels generally produced more habitat than main stem and were more responsive to flow changes, demonstrating the importance of lateral connectivity in the floodplain. A discharge-habitat sensitivity analysis revealed that proactive management of regulated surface waters (i.e., increasing or decreasing flows) might lessen the impacts of climate change on salmonid habitats.     

Hydrologic effects of climate change in the Yukon River Basin

A monthly water balance (WB) model was developed for the Yukon River Basin (YRB). The WB model was calibrated using mean monthly values of precipitation and temperature derived from the Precipitation-elevation Regression on Independent Slopes Model (PRISM) data set and by comparing estimated mean monthly runoff with runoff measured at Pilot Station, Alaska. The calibration procedure used the Shuffled Complex Evolution global search. Potential hydrologic effects of climate change were assessed for the YRB by imposing changes in precipitation and temperature derived from selected Inter-governmental Panel for Climate Change (IPCC) climate simulations. Scenarios from five general circulation model (GCM) simulations were used to provide a range of potential changes. Results from the scenarios indicate an increase in annual runoff in the twenty-first century for the YRB with simulated increases in precipitation having the greatest effect on increases in runoff. Simulated increases in temperature were found to alter the timing of snow accumulation and melt.     

Uncertainties in projected impacts of climate change on European agriculture and terrestrial ecosystems based on scenarios from regional climate models

The uncertainties and sources of variation in projected impacts of climate change on agriculture and terrestrial ecosystems depend not only on the emission scenarios and climate models used for projecting future climates, but also on the impact models used, and the local soil and climatic conditions of the managed or unmanaged ecosystems under study. We addressed these uncertainties by applying different impact models at site, regional and continental scales, and by separating the variation in simulated relative changes in ecosystem performance into the different sources of uncertainty and variation using analyses of variance. The crop and ecosystem models used output from a range of global and regional climate models (GCMs and RCMs) projecting climate change over Europe between 1961–1990 and 2071–2100 under the IPCC SRES scenarios. The projected impacts on productivity of crops and ecosystems included the direct effects of increased CO₂ concentration on photosynthesis. The variation in simulated results attributed to differences between the climate models were, in all cases, smaller than the variation attributed to either emission scenarios or local conditions. The methods used for applying the climate model outputs played a larger role than the choice of the GCM or RCM. The thermal suitability for grain maize cultivation in Europe was estimated to expand by 30–50% across all SRES emissions scenarios. Strong increases in net primary productivity (NPP) (35–54%) were projected in northern European ecosystems as a result of a longer growing season and higher CO₂ concentrations. Changing water balance dominated the projected responses of southern European ecosystems, with NPP declining or increasing only slightly relative to present-day conditions. Both site and continental scale models showed large increases in yield of rain-fed winter wheat for northern Europe, with smaller increases or even decreases in southern Europe. Site-based, regional and continental scale models showed large spatial variations in the response of nitrate leaching from winter wheat cultivation to projected climate change due to strong interactions with soils and climate. The variation in simulated impacts was smaller between scenarios based on RCMs nested within the same GCM than between scenarios based on different GCMs or between emission scenarios.     

Identifying stakeholder-relevant climate change impacts: A case study in the Yakima River Basin,Washington, USA

Designing climate-related research so that study results will be useful to natural resource managers is a unique challenge. While decision makers increasingly recognize the need to consider climate change in their resource management plans, and climate scientists recognize the importance of providing locally-relevant climate data and projections, there often remains a gap between management needs and the information that is available or is being collected. We used decision analysis concepts to bring decision-maker and stakeholder perspectives into the applied research planning process. In 2009 we initiated a series of studies on the impacts of climate change in the Yakima River Basin (YRB) with a four-day stakeholder workshop, bringing together managers, stakeholders, and scientists to develop an integrated conceptual model of climate change and climate change impacts in the YRB. The conceptual model development highlighted areas of uncertainty that limit the understanding of the potential impacts of climate change and decision alternatives by those who will be most directly affected by those changes, and pointed to areas where additional study and engagement of stakeholders would be beneficial. The workshop and resulting conceptual model highlighted the importance of numerous different outcomes to stakeholders in the basin, including social and economic outcomes that go beyond the physical and biological outcomes typically reported in climate impacts studies. Subsequent studies addressed several of those areas of uncertainty, including changes in water temperatures, habitat quality, and bioenergetics of salmonid populations.     

Hydrologic impacts of climate change on the Nile River Basin: implications of the 2007 IPCC scenarios

We assess the potential impacts of climate change on the hydrology and water resources of the Nile River basin using a macroscale hydrology model. Model inputs are bias corrected and spatially downscaled 21st Century simulations from 11 General Circulation Models (GCMs) and two global emissions scenarios (A2 and B1) archived from the 2007 IPCC Fourth Assessment Report (AR4). While all GCMs agree with respect to the direction of 21st Century temperature changes, there is considerable variability in the magnitude, direction, and seasonality of projected precipitation changes. Our simulations show that, averaged over all 11 GCMs, the Nile River is expected to experience increase in streamflow early in the study period (2010–2039), due to generally increased precipitation. Streamflow is expected to decline during mid- (2040–2069) and late (2070–2099) century as a result of both precipitation declines and increased evaporative demand. The predicted multimodel average streamflow at High Aswan Dam (HAD) as a percentage of historical (1950–1999) annual average are 111 (114), 92 (93) and 84 (87) for A2 (B1) global emissions scenarios. Implications of these streamflow changes on the water resources of the Nile River basin were analyzed by quantifying the annual hydropower production and irrigation water release at HAD. The long-term HAD release for irrigation increases early in the century to 106 (109)% of historical, and then decreases to 87 (89) and 86 (84)% of historical in Periods II and III, respectively, for the A2 (B1) global emissions scenarios. Egypt’s hydropower production from HAD will be above the mean annual average historical value of about 10,000 GWH for the early part of 21st century, and thereafter will generally follow the streamflow trend, however with large variability among GCMs. Agricultural water supplies will be negatively impacted, especially in the second half of the century.     

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.     

Effects of projected climate change on the hydrology in the Mono Lake Basin, California

The Californian Mono Lake Basin (MLB) is a fragile ecosystem, for which a 1983 ruling carefully balanced water diversions with ecological needs without the consideration of global climate change. The hydroclimatologic response to the impact of projected climatic changes in the MLB has not been comprehensively assessed and is the focus of this study. Downscaled temperature and precipitation projections from 16 Global Climate Models (GCMs), using two emission scenarios (B1 and A2), were used to drive a calibrated Soil and Water Assessment Tool (SWAT) hydrologic model to assess the effects on streamflow on the two significant inflows to the MLB, Lee Vining and Rush Creeks. For the MLB, the GCM ensemble output suggests significant increases in annual temperature, averaging 2.5 and 4.1 °C for the B1 and A2 emission scenarios, respectively, with concurrent small (1–3 %) decreases in annual precipitation by the end of the century. Annual total evapotranspiration is projected to increase by 10 mm by the end of the century for both emission scenarios. SWAT modeling results suggest a significant hydrologic response in the MLB by the end of the century that includes a) decreases in annual streamflow by 15 % compared to historical conditions b) an advance of the peak snowmelt runoff to 1 month earlier (June to May), c) a decreased (10–15 %) occurrence of ‘wet’ hydrologic years, and d) and more frequent (7–22 %) drought conditions. Ecosystem health and water diversions may be affected by reduced water availability in the MLB by the end of the century.     

A stakeholder project to model water temperature under future climate scenarios in the Satus and Toppenish watersheds of the Yakima River Basin in Washington,USA

The goal of this study was to support an assessment of the potential effects of climate change on select natural, social, and economic resources in the Yakima River Basin. A workshop with local stakeholders highlighted the usefulness of projecting climate change impacts on anadromous steelhead (Oncorhynchus mykiss), a fish species of importance to local tribes, fisherman, and conservationists. Stream temperature is an important environmental variable for the freshwater stages of steelhead. For this study, we developed water temperature models for the Satus and Toppenish watersheds, two of the key stronghold areas for steelhead in the Yakima River Basin. We constructed the models with the Stream Network Temperature Model (SNTEMP), a mechanistic approach to simulate water temperature in a stream network. The models were calibrated over the April 15, 2008 to September 30, 2008 period and validated over the April 15, 2009 to September 30, 2009 period using historic measurements of stream temperature and discharge provided by the Yakama Nation Fisheries Resource Management Program. Once validated, the models were run to simulate conditions during the spring and summer seasons over a baseline period (1981–2005) and two future climate scenarios with increased air temperature of 1 °C and 2 °C. The models simulated daily mean and maximum water temperatures at sites throughout the two watersheds under the baseline and future climate scenarios.     

Impact of projected climate change on hydrologic regime of the Upper Paraguay River basin

We present an assessment of climate change impacts on the hydrologic regime of the 600,000 km² Upper Paraguay River basin, located in central South America based on predictions of 20 Atmospheric/Ocean General Circulation Models (AOGCMs). We considered two climate change scenarios from the Intergovernmental Panel on Climate Change (IPCC) and two 30-years time intervals centered at 2030 and 2070. Projected temperature and precipitation anomalies estimated by the AOGCMs for the study site are spatially downscaled. Time series of projected temperature and precipitation were estimated using the delta change approach. These time series were used as input to a detailed coupled hydrologic-hydraulic model aiming to estimate projected streamflow in climate change scenarios at several control points in the basin. Results show that impacts on streamflow are highly dependent on the AOGCM used to obtain the climate predictions. Patterns of temperature increase persist over the entire year for almost all AOGCMs resulting in an increase in the evapotranspiration rate of the hydrological model. The precipitation anomalies show large dispersion, being projected as either an increase or decrease in precipitation rates. Based on these inputs, results from the coupled hydrologic-hydraulic model show nearly one half of projections as increasing river discharge, and other half as decreasing river discharge. If the mean or median of the predictions is considered, no discernible change in river discharge should be expected, despite the dispersion among results of the AOGCMs that reached +/?10 % in the short horizon and +/? 20 % in the long horizon, at several control points.     

Modeling of climate change effects on stream temperatures and fish habitats below dams and near groundwater inputs

A deterministic heat transport model was developed to calculate stream water temperatures downstream of reservoir outlets (tailwaters) and groundwater sources. The model calculates heat exchange between the atmosphere, the water and the sediments and is driven by climate and stream hydrologic parameters. Past and projected climate conditions were used as input to the stream water temperature model. To produce a projected future weather scenario, output from the Columbia University Goddard Institute for Space Studies (GISS) global circulation model (GCM) for a doubling of atmospheric CO₂ were used to adjust past (1955–1979) weather parameters. Stream reach lengths, within which water temperatures are suitable for survival or good growth of 28 fish species, were determined for four selected streams. Several alternative upstream inflow conditions were chosen: Discharges from surface (epilimnion) and bottom (hypolimnion) outlets of reservoirs, and two groundwater inflow scenarios. By applying water temperature criteria for fish survival and good growth (Stefanet al., 1993) to simulated stream temperatures, it was possible to estimate stream lengths with suitable habitat. When simulated suitable habitat was compared to actual fish observations, good agreement was found. For projected climate change, the simulations showed how much of the available stream habitat would be lost. In the examples presented the effect of cold hypolimnetic water release from a reservoir or groundwater discharges is felt as far as 48 km (30 miles) downstream from its source, especially in smaller shaded streams. The impact of climate change on stream temperatures below dams is more pronounced when the water release is from the epilimnion (reservoir surface) rather than the hypolimnion (deep water). Examples used for this study show elimination of coldwater habitat for rainbow trout when the upstream release is from the surface of a reservoir, but only reductions of coldwater habitat when the upstream release is from a reservoir hypolimnion.     

Impacts of future Indian greenhouse gas emission scenarios on projected climate change parameters deduced from MAGICC model

The MAGICC (Model for the Assessment of Greenhouse gas Induced Climate Change) model simulation has been carried out for the 2000–2100 period to investigate the impacts of future Indian greenhouse gas emission scenarios on the atmospheric concentrations of carbon dioxide, methane and nitrous oxide besides other parameters like radiative forcing and temperature. For this purpose, the default global GHG (Greenhouse Gases) inventory was modified by incorporation of Indian GHG emission inventories which have been developed using three different approaches namely (a) Business-As-Usual (BAU) approach, (b) Best Case Scenario (BCS) approach and (c) Economy approach (involving the country’s GDP). The model outputs obtained using these modified GHG inventories are compared with various default model scenarios such as A1B, A2, B1, B2 scenarios of AIM (Asia-Pacific Integrated Model) and P50 scenario (median of 35 scenarios given in MAGICC). The differences in the range of output values for the default case scenarios (i.e., using the GHG inventories built into the model) vis-à-vis modified approach which incorporated India-specific emission inventories for AIM and P50 are quite appreciable for most of the modeled parameters. A reduction of 7% and 9% in global carbon dioxide (CO₂) emissions has been observed respectively for the years 2050 and 2100. Global methane (CH₄) and global nitrous oxide (N₂O) emissions indicate a reduction of 13% and 15% respectively for 2100. Correspondingly, global concentrations of CO₂, CH₄ and N₂O are estimated to reduce by about 4%, 4% and 1% respectively. Radiative forcing of CO₂, CH₄ and N₂O indicate reductions of 6%, 14% and 4% respectively for the year 2100. Global annual mean temperature change (incorporating aerosol effects) gets reduced by 4% in 2100. Global annual mean temperature change reduces by 5% in 2100 when aerosol effects have been excluded. In addition to the above, the Indian contributions in global CO₂, CH₄ and N₂O emissions have also been assessed by India Excluded (IE) scenario. Indian contribution in global CO₂ emissions was observed in the range of 10%–26%, 6%–36% and 10%–38% respectively for BCS, Economy and BAU approaches, for the years 2020, 2050 and 2100 for P50, A1B-AIM, A2-AIM, B1-AIM & B2-AIM scenarios. CH₄ and N₂O emissions indicate about 4%–10% and 2%–3% contributions respectively in the global CH₄ and N₂O emissions for the years 2020, 2050 and 2100. These Indian GHG emissions have significant influence on global GHG concentrations and consequently on climate parameters like RF and ∆T. The study reflects not only the importance of Indian emissions in the global context but also underlines the need of incorporation of country specific GHG emissions in modeling to reduce uncertainties in simulation of climate change parameters.     

Climate change impacts on water management and irrigated agriculture in the Yakima River Basin, Washington, USA

The Yakima River Reservoir system supplies water to ~180,000 irrigated hectares through the operation of five reservoirs with cumulative storage of ~30% mean annual river flow. Runoff is derived mostly from winter precipitation in the Cascade Mountains, much of which is stored as snowpack. Climate change is expected to result in earlier snowmelt runoff and reduced summer flows. Effects of these changes on irrigated agriculture were simulated using a reservoir system model coupled to a hydrological model driven by downscaled scenarios from 20 climate models archived by the 2007 Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report. We find earlier snowmelt results in increased water delivery curtailments. Historically, the basin experienced substantial water shortages in 14% of years. Without adaptations, for IPCC A1B global emission scenarios, water shortages increase to 27% (13% to 49% range) in the 2020s, to 33% in the 2040s, and 68% in the 2080s. For IPCC B1 emissions scenarios, shortages occur in 24% (7% to 54%) of years in the 2020s, 31% in the 2040s and 43% in the 2080s. Historically unprecedented conditions where senior water rights holders suffer shortfalls occur with increasing frequency in both A1B and B1 scenarios. Economic losses include expected annual production declines of 5%–16%, with greater probabilities of operating losses for junior water rights holders.     

气候变化对石羊河流域生态环境的影响分析

利用石羊河流域1959—2018年气象、水文和卫星遥感资料,采用线性倾向率、滑动t检验和相关系数(Pearson)等方法,分析石羊河流域内生态环境因素的变化事实及相互关系,得到气候变化对流域生态环境的影响程度。结果表明：石羊河流域气温呈显著上升趋势,增温速度为下游0.42℃·(10 a)^-1>中游0.36℃·(10 a)^-1>上游0.35℃·(10 a)^-1,近10 a增温最显著,较20世纪60年升高了1.67℃。四季气温均呈显著上升趋势,增温速度为冬季>秋季>春季>夏季。降水呈缓慢增加趋势,增幅为上游8.3 mm·(10 a)^-1>中游7.0 mm·(10 a)^-1>下游4.1 mm·(10 a)^-1,近10 a增加最显著,较20世纪60年代增加了17%。四季降水呈弱增加趋势,增加幅度为夏季>春季>秋季>冬季。河流流量基本持平,植被覆盖面积和归一化植被指数(NDVI)显著增大。近20 a流域气候...     

气候变化情景下澜沧江流域极端洪水事件研究

以澜沧江流域为研究对象,基于ISIMIP2b协议中提供的GFDL-ESM2M、HadGEM2-ES、IPSL-CM5A-LR、MIROC5这4种全球气候模式,通过4种模式的输出数据耦合VIC模型,分析4种模式在历史时期（1961—2005年)对洪峰洪量极值(年最大洪峰流量、3 d最大洪量)、极端洪水的模拟能力,比较RCR2.6和RCP6.0两种情景下未来时期（2021—2050年)年均径流量较基准期（1971—2000年)的变化情况,并结合P-III型分布曲线预估了澜沧江流域在两种情景下未来时期极端洪水的强度变化情况。结果表明：VIC模型在该流域能够较好地模拟极端洪水;HadGEM2-ES和MIROC5两种气候模式的输出数据在澜沧江流域有较好的径流模拟适用性;在RCP2.6情景下,澜沧江流域未来时期年均径流量没有明显变化,可能会有略微的增加,而在RCP6.0情景下,未来时期年均径流量有较大可能增加;澜沧江流域未来时期极端洪水较基准期,在RCP2.6情景下无明显变化,而在RCP6.0情景下,洪峰、洪量增加的可能性较大,极端洪水频率和强度也较大可能增加。     

Current and projected water demand and water availability estimates under climate change scenarios in the Weyib River basin in Bale mountainous area of Southeastern Ethiopia

ENSO has been known to influence the trends of summer warming over Southern Africa. In this work, we used observational and reanalysis data to analyze the relationship between ENSO and maximum surface air temperature (SAT_max) trends during the three epochs created by the ENSO phase shifts around 1977 and 1997 for the period 1960 to 2014. We observed that while ENSO and cloud cover remains the dominant factor controlling SAT_max variability, the first two epochs had the predominant La Niña (El Niño)-like events connected to robust positive (negative) trends in cloud fraction. However, this established relationship reversed in the post-1997 La Niña-like dominated epoch which coincided with a falling cloud cover trend. It is established that this deviation from the previously established link within the previous epochs could be due to the post-1998 era in which SAT_min was suppressed while SAT_max was enhanced. The resulting increase in diurnal temperature range (DTR) could have discouraged the formation of low-level clouds which have relatively more extensive areal coverage and hence allowing more solar energy to reach the surface to boost daytime SAT_max. It is noted that these relationships are more pronounced from December to March.     

Relative effects of climate change and wildfires on stream temperatures: a simulation modeling approach in a Rocky Mountain watershed

Freshwater ecosystems are warming globally from the direct effects of climate change on air temperature and hydrology and the indirect effects on near-stream vegetation. In fire-prone landscapes, vegetative change may be especially rapid and cause significant local stream temperature increases but the importance of these increases relative to broader changes associated with air temperature and hydrology are not well understood. We linked a spatially explicit landscape fire and vegetation model (FireBGCv2) to an empirical regression equation that predicted daily stream temperatures to explore how climate change and its impacts on fire might affect stream thermal conditions across a partially forested, mountainous landscape in the western U.S. We used the model to understand the roles that wildfire and management actions such as fuel reduction and fire suppression could play in mitigating stream thermal responses to climate change. Results indicate that air temperature increases associated with future climates could account for a much larger proportion of stream temperature increases (as much as 90 % at a basin scale) than wildfire. Similarly, land management scenarios that limited wildfire prevalence had negligible effects on future stream temperature increases. These patterns emerged at broader spatial scales because wildfires typically affected only a subset of a stream’s network. However, at finer spatial and temporal scales stream temperatures were sensitive to wildfire. Although wildfires will continue to cause local, short-term effects on stream temperatures, managers of aquatic systems may need to find other solutions to cope with the larger impact from climate change on future stream warming that involves adapting to the increases while developing broad strategies for riparian vegetation restoration.     

The impact of climate change on the Niger River Basin hydroclimatology, West Africa

Climate change has the potential to reduce water availability in West Africa. This study aims to quantify the expected impact of increased greenhouse gases (GHGs) on hydroclimatology of Niger River Basin (NRB). Boundary data from a general circulation model are used to force a regional climate model, to produce dynamically downscaled hydroclimatic variables of NRB under present-day (PRS) and future climate scenarios. The data were further analyzed to detect changes in atmospheric and surface water balance components and moisture recycling ratio (β). The results show that elevated GHGs (under A1B scenario) would produce a drier climate during the rainy season and a wetter climate during the dry season. A warmer climate over NRB in all months was projected. Highest temperature increase of 3 °C occurs about 14°N in May and June, and the smallest increase of 0.5 °C occurs below 8°N in wet-dry transition period. Evaporation reduces during wet season and increases during the dry periods. Humidity increases by 2 % in the dry season, but decreases by 2–4 % in the wet season. Maximum change in moisture influx of 20.7 % and outflux of 20.6 % occur in June and July, respectively. β is projected to decrease in 75 % of the months with biggest relative change of ?18.4 % in June. The projected decrease in precipitation efficiency (ρ) during the wet season reaches ?20.3 % in June. For PRS run, about 66 % of the available atmospheric moisture in NRB precipitates between June and September, of which around 21 % originates from local evaporation. The result suggests that under enhanced GHGs, local evaporation will contribute less to atmospheric moisture and precipitation over the basin. Projected changes in rainfall and streamflow for Upper Niger and Benue sub-basin are significantly different during the wet season.     

Potential impact of climate change on the water availability of South Saskatchewan River Basin

The potential hydrologic impact of climatic change on three sub-basins of the South Saskatchewan River Basin (SSRB) within Alberta, namely, Oldman, Bow and Red Deer River basins was investigated using the Modified Interactions Soil-Biosphere-Atmosphere (MISBA) land surface scheme of Kerkhoven and Gan (Advances in Water Resources 29:808–826 2006). The European Centre for Mid-range Weather Forecasts global re-analysis (ERA-40) climate data, Digital Elevation Model of the National Water Research Institute, land cover data and a priori soil parameters from the Ecoclimap global data set were used to drive MISBA to simulate the runoff of SSRB. Four SRES scenarios (A21, A1FI, B21 and B11) of four General Circulation Models (CCSRNIES, CGCM2, ECHAM4 and HadCM3) of IPCC were used to adjust climate data of the 1961–1990 base period (climate normal) to study the effect of climate change on SSRB over three 30-year time periods (2010–2039, 2040–2069, 2070–2099). The model results of MISBA forced under various climate change projections of the four GCMs with respect to the 1961–1990 normal show that SSRB is expected to experience a decrease in future streamflow and snow water equivalent, and an earlier onset of spring runoff despite of projected increasing trends in precipitation over the 21st century. Apparently the projected increase in evaporation loss due to a warmer climate over the 21st century will offset the projected precipitation increase, leading to an overall decreasing trend in the basin runoff of SSRB. Finally, a Gamma probability distribution function was fitted to the mean annual maximum flow and mean annual mean flow data simulated for the Oldman, Bow and Red Deer River Basins by MISBA to statistically quantify the possible range of uncertainties associated with SRES climate scenarios projected by the four GCMs selected for this study.