Climate Change, Water Demands and Irrigation
First, let me provide some background on the South Saskatchewan River (SSR). The SSR drains much of Southern Alberta from Red Deer to Calgary and south to Lethbridge and Medicine Hat. The major tributaries include the Red Deer, Bow, and Oldman rivers. The river serves as a primary water source for about two million people in the basin, as well as some outside of the basin, since water is diverted into Buffalo Pound Lake.
The SSR has been characterized as a canal carrying water from the eastern slopes of the Rocky Mountains to Hudson Bay (Pomeroy et al. 2007). The semi-arid conditions in the southern parts of Alberta and Saskatchewan and the relatively flat topography mean that very little of the water that falls in the prairies makes it to the SSR. Most of it evaporates, is absorbed into aquifers, or collects in prairie potholes. This characteristic means that the amount of water in Lake Diefenbaker depends almost exclusively on how much water makes it out of Alberta.
How much water makes its way out of Alberta will depend on economic development and population growth in the Calgary-Red Deer-Lethbridge triangle, and on climate change. Despite the large capacity of Lake Diefenbaker, the amount of water available for irrigation in the future may not be as large as one would imagine. The supply of water will need to be managed carefully to sustain other important sectors beyond irrigation.
The semi-arid conditions in the southern parts of Alberta and Saskatchewan and the relatively flat topography mean that very little of the water that falls in the prairies makes it to the SSR. Most of it evaporates, is absorbed into aquifers, or collects in prairie potholes. This characteristic means that the amount of water in Lake Diefenbaker depends almost exclusively on how much water makes it out of Alberta.
The 1969 Master Agreement on Apportionment signed by the Government of Canada and the governments of Alberta, Saskatchewan and Manitoba ensures that water in all rivers flowing across provincial boundaries is equally shared among the Prairie Provinces. The sharing rule is simple: "Alberta and Saskatchewan may each take up to one half of the natural flow of water originating within its boundaries and one half of the flow entering the province. The remainder is left to flow into Manitoba" (PPWB 2007). There are also provisions that ensure that minimum flow requirements are met and for apportionment in dry years. Alberta has invested heavily in irrigation infrastructure in southern Alberta and withdraws significant amounts of water from the SRR. To date, Alberta has always met its apportionment agreements (as has Saskatchewan) and has committed to do so in the future. The net effect of high population growth and expanded irrigation in southern Alberta is that Alberta is getting very close to using its full share of water. This has forced the government of Alberta to place a moratorium on new water licenses. Despite this moratorium, investments within the irrigation sector mean that a greater fraction of water licenses are being exploited and less water makes its way back into the river system to flow into Lake Diefenbaker (see Alberta's South Saskatchewan River Basin (SSRB): Irrigation in the 21st Century for more details.)
Climate change adds another dimension to the supply equation. Current climate change research suggests that the total amount of precipitation in the SSR basin is unlikely to change too much in the next 40 years. However, there is considerable uncertainty around this estimate. Flows in the SSR could rise by upwards of 8% or fall by 22% (Bruneau and Toth, 2007). The most likely effect of climate change is that it will alter the timing of water flows over the year. The expectation is that spring flows will be earlier and stronger, summer and late summer flows will be weaker, while winter flows will be higher. Compounding this is a diminishment of glacier runoff in the late summer. Though glaciers contribute only a small percentage of annual water flows, this runoff occurs in the late summer when river flows are already low (Pomeroy et al. 2007).
At the same time that river flows are changing, the higher temperatures will increase evaporation and reduce soil moisture reserves. There is also the possibility that the frequency of extreme weather events, such as heavy rains or droughts, will increase and droughts may become longer and more severe. Another factor is the recognition that in-stream water flows need to be maintained at some minimum levels throughout the year to sustain aquatic ecosystems. As the climate warms, water temperatures rise and water quality can fall. To maintain ecosystem health may require increases in minimum flow requirements.
These climate induced changes in the timing and/or quantity of water flows will increase the burden placed on the management of water reservoirs throughout the basin. Water managers may need to raise the amount of unallocated water as a form of insurance or to preserve minimum in-stream flow needs. This will reduce the amount of water that can be withdrawn from reservoirs for irrigation purposes.
In addition to economic growth in southern Alberta, climate change can also alter the demand for water (or access to water). First, the effects of climate change will likely increase the demand for irrigation, both here and in Alberta. The higher evaporation rates increase the payoff from irrigation and the increased risk of droughts makes irrigation a better hedge against the weather. Longer growing seasons may allow farmers to alter crop choices that, in turn, can increase water demands. Climate change may also increase the demand for Canadian agricultural products as production in more climate-sensitive regions of the world contracts.
There is also a legitimate economic argument, only now being articulated and implemented, for water trading among major users. Alberta is experimenting with it right now. Currently, there is no proposal to trade water across provincial boundaries. Pressures to shift some of Saskatchewan's "excess capacity" upstream to Alberta with its extensive irrigation developments will only increase. An important question might be whether it is in Saskatchewan's interest to sell the water upstream (and make some profits) or to invest in irrigation directly.
Together, changes in economic growth, climate, and regulations will place greater stress on water availability in the SSR and the current excess capacity for irrigation likely overestimates the amount of water available for irrigation in the future. It will be important for Alberta and Saskatchewan to continue to cooperate and keep the lines of communication open to ensure the SSR remains a healthy ecosystem that meets the needs of future generations in both provinces.
References
Bruneau, Joel F. and Brenda Toth, 2007. "Dove-Tailed Physical and Socioeconomic Results in the SSRB", in Climate Change and Water: SSRB Final Technical Report, edited by Martz, Bruneau, and Rolfe.
This blog entry was authored by Joel Bruneau, a professor in the Economics Department at the University of Saskatchewan. To read additional Illative Blog entries or to leave comments on this entry, please visit www.illativeblog.ca. The Illative Blog is an initiative by the Knowledge Impact in Society (KIS) Project based out of the University of Saskatchewan. Email correspondence can be sent to kis.project@usask.ca
In view of the seasonality of water in the SSRB is not the suggestion of weirs and dams to create reservoirs a reasonable one.
The suggestion of dams and weirs to ensure reliable flows is a costly knee-jerk reaction that serves to feed the prairies insatiable appetite for water.
Look to the Murray-Darling Basin in NSW Australia as a warning of what may in store for the prairies. They have dammed the river and grown rice and cotton in a semi-arid to arid climate for decades - crops which require tremendous amounts of water. Long pipelines divert water from the river to supply the city of Adelaide and now there has been no outflow from the mouth of the Murray River for 6 years and some regions are getting only 18% of their irrigation allocation. Australia is the canary in the irrigation mine.
A more forward-thinking reaction, in light of climate change and population growth is to adjust lifestyles, farming and industry practices to foster water conservation and efficient use. As irrigation is by far the largest consumer of water in the prairies, we should be investing in more efficient irrigation technologies and shifting to crops which require less water. Its high time that the myth of water abundance in the prairies was addressed.
A consideration of dams and weirs on the Saskatchewan system is hardly a knee jerk reaction since it has been debated and carried out since the prairies were first settled. However, the primary reason for developing a system of managing the waters of the South and North Saskatchewan Rivers at this time is to ensure a minimum flow throughout the season, rather than a peak and hollow. Then to make the best use of the stored waters, city, industrial and irrigation can be considered appropriate to the supply.