New Challenges

Our watershed management strategy must contemplate new challenges from population growth, climate change, and drought.

Growth in Population and Growth in Water Use

The population in the SSRB is expected to grow by almost 50 percent to more than two million people by 2021. By 2046, the population of the SSRB is expected to triple to more than 3 million people.[1] Large increases in municipal, industrial, and stockwatering demands are predicted.

Demand for non-irrigation water withdrawals is forecasted to increase by as much as 66 percent by 2021. By 2046, consumptive use of water (excluding irrigation) is expected to increase between 63 to 132 percent. The greatest volumetric increase in water withdrawals is expected to take place in the Bow River basin.[2]

Future demands for water are also expected to increase with expansion of irrigation. Previously, under the Water Resource Act, specified acreage limits were set. However, a new Irrigation Districts Act past in 2000 removed current area limitations, allowing districts to expand so long as the expansion occurs within existing licenses. The new act also allows for the transferring of water rights between land parcels. It is very important to note that on overage only 67 percent of total licensed allocations are currently used annually by the 13 districts. Alberta Agriculture has identified the potential to expand an additional 78,180 hectares within Alberta

Global Climate Change

From 1998 through 2004, we saw unusually warm temperatures and low precipitation levels in the western prairies, suggesting that climate change is already occurring. Most scientists predict an additional warming of several degrees by the latter part of the 21^st century. Average annual temperatures across the prairies have increased by almost 1 degree Centigrade in the past 65 years. By 2050, the prairie region is forecast to warm by 2° to 5° C.

Some models indicate the predicted warming could increase evaporation by up to 55 percent in some parts of the western prairie provinces. While most climate models predict increases in precipitation, increases in evapo-transpiration will likely offset this greater rainfall.

The long-term impact of the overall warming trend on the Bow River is not completely clear. There is increasing evidence that snowpacks are, on average, decreasing in volume from year to year. Snowpacks deliver a significant portion of the river's flows in the summer months. It has been projected that there will be a 40 percent decline in snowpack between 2020 and 2050 in the Bow River Basin.

Another indicator of global climate change is glacial recession. The Bow glacier, which provides an important contribution of water to the river in the late summer and early fall, has already receded significantly due to these warming trends. While glacial runoff only contributes a small percentage to river flows overall (about 1 to 2 percent annually), they make up a larger percentage of the river's flow in the summer.

On average, glacial runoff in the Bow River contributes 17 percent of its summer flows. Most large glaciers feeding rivers in the SSRB have shrunk by 25 percent in the past century.

Drought

Canada is considered a water-rich country, but its western prairies - an area of approximately two million square kilometers - encompass some of the driest lands in southern Canada. At the source of the watershed, there is a seemingly high volume of water emerging from the "water towers" in the Canadian Rockies where precipitation can exceed 1,500 millimetres (mm) annually. But most of the South Saskatchewan River watershed exists in a semi-arid region where there is little rainfall and high evaporation rates. Average annual precipitation is low: The southeastern portion of Alberta that receives between 300 to 350 mm annually.[3] Consequently, water is exceptionally limited in this part of Canada particularly in the late summer and early fall with the passage of the spring runoff.

Droughts are a reality in this landscape, and the probability of drought should be considered in our water management planning. Paleoecological studies using climate proxies (including tree rings) indicate that recent climate in the western prairies has been unusually moist. Looking over the past several thousand years, there were several droughts per century - and some lasted for a decade or longer. The most recent drought in southern Alberta was in 2001 and had a profound impact on water availability in the region.

Footnotes

[1] South Saskatchewan River Basin Water Management Plan: Phase Two Background Studies. June 2003. Alberta Environment. P. 11.

[2] South Saskatchewan River Basin Water Management Plan: Phase Two Background Studies. June 2003. Alberta Environment. P. 11

[3] Alberta Environment.

Illustration credit: Turner, R.J.W., Franklin, R.G., Grasby, S.E., and Nowlan, G.S. 2005: Bow River Basin Waterscape; Geological Survey of Canada, Miscellaneous Report 90, 2005. NRCAN