Impacts of Climate Change on Saskatchewan’s Water Resources

The purposes of this report are two-fold, i) documenting the expected impacts of climate change on Saskatchewan's water resources, ii) outlining the options for adaptation of water resource management practices, policies and infrastructure to minimize the risk associated with the impacts of climate change. Prairie province hydrology is dominated by cold regions processes so that snowmelt is the primary hydrological event of the year for both the major rivers that derive from the Rocky Mountains and small streams and rivers that arise in Saskatchewan. Climate change impacts on water resources are therefore focussed on changes to snow accumulation, snowmelt and infiltration to frozen soils. Climate change scenarios suggest generally warmer and wetter winters for Saskatchewan. Large scale hydrological models that take these scenarios into account suggest changes in the annual streamflow of the South Saskatchewan River ranging from an 8% increase to a 22% decrease, with an 8.5% decrease being an average prediction. Small scale hydrological models for prairie streams suggest a 24% increase in spring runoff by 2050 followed by a 37% decrease by 2080 is possible as the winter snowcover becomes discontinuous. Both model results suggest that there is not a dramatic drying of the prairies to be anticipated under climate change and that in some cases streamflow will increase for certain scenarios and under moderate degrees of climate change. For the major rivers draining from Alberta into Saskatchewan, more efficient water use for irrigation or a reduction in irrigated acreage in Alberta could compensate for the reduced water availability, which is due mainly to reduced mountain snowmelt. Current minimum tillage and continuous cropping systems are resilient for most climate changes to agricultural water resources. Initially there will be increases in prairie runoff but as climate change progresses later in the 21st C there will be dramatic drops in runoff and the flow of small streams to wetlands and depressions and to small prairie rivers. Infrastructure will have difficulty keeping up with this level of change unless agricultural land management is used to compensate for changes in hydrology. New crop varieties and tillage methods which are able to leave some water for runoff to natural ecosystems will need to be devised. Drainage of wetlands may have to be reversed to limit high spring streamflows and wetland/lake levels. Integrated basin management of the South Saskatchewan River across both Alberta and Saskatchewan and for smaller watersheds in Saskatchewan is the preferred adaptation method for dealing with these uncertainties. Integrated basin management plans with apportionment powers, enforceable land use controls and agricultural management incentives will need to be 2 implemented to deal with rapid changes and increased uncertainties in water management designs. In all cases the uncertainties in the model outputs and driving hydrometeorological data for current simulations make recommending adaptation measures very difficult as the range of predictions is from a decrease to an increase in available streamflow compared to current estimates. It is imperative that the scientific basis of these hydrological models be improved so that there is reduced uncertainty in model predictions. The current climate and water resources available in the headwater basins are themselves uncertain and need to be better quantified to permit more reliable comparisons of future climate and water resource predictions with the current situation.

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