Publication: Saskatoon Star Pheonix; Date:2006 Jul 04; Section:LifeStyle; Page Number: B3
COMMENTARY Environment

Scientists predict South Saskatchewan flow to decrease

PAUL HANLEY

The best prediction of scientists studying the South Saskatchewan River Basin (SSRB) is that river flows will be down almost 10 per cent by 2070, due in part to climate change. This is likely to have significant implications for the province in a variety of areas.
The prediction is based on a couple of studies presented to the climate change and water conference in Saskatoon on June 22 by Lawrence Martz and Alain Pietroniro. The conference was organized by Partners for the South Saskatchewan River Basin, the National Water Research Institute and the University of Saskatchewan.
In most years, a 10 per cent reduction of flow may not significantly effect human consumption of water, but it could have significant long-term implications for ecosystems in the SSRB. People can always build the infrastructure that allows them to access the water that is there. Ecosystems live or die with what people leave for them.
Here’s how the SSRB future scenario breaks down. Climate change is going to impact the amount of water that flows into the river from the surrounding watersheds. Hotter and on the whole drier conditions will reduce the water flow. Meanwhile population in the basin will double over the period, driving up demand.
The big demand for water, at present, is agriculture, especially irrigation. In most of Canada, agriculture makes a relatively small dent in the water supply. In the Prairies, about half of the withdrawals from water systems are for agriculture. In the SSRB, about 86 per cent of water withdrawals are for agriculture. Much of that is in Alberta, where irrigation is extensive. In the Saskatchewan portion of the SSRB, agricultural withdrawals are 56 per cent. Agricultural use of water is also a highly consumptive and returns little of the water used to the river.
The population of the basin is expected to more than double from 1.5 to 3.5 million by around 2046. Total water consumption will go up by 100 per cent. Municipal water consumption, which is now about eight per cent of water withdraws in the basin and 30 per cent in the Saskatchewan portion, will probably go up about 70 per cent. Irrigation, which represents the largest demand, will rise another 20 per cent and the demand for water for livestock will rise by 40 per cent due to herd growth.
A number of other demand increases are anticipated. Industrial withdrawals, which are currently rather small overall, but represent 13 per cent of demand in Saskatchewan, are expected to jump 270 per cent due to increased activity. Thermal electric withdrawals, the water used to operate power plants, will go up 140 per cent due to demand for power.
What all this amounts to is that the flow in the South Saskatchewan at Outlook is likely to fall by 8.5 per cent on average sometime in this century. What most effects stream flow is agricultural withdrawals and climate change. Water demand for uses other than irrigation are not that significant a threat to water resources in the basin. When it comes to irrigation water, any gains in water efficiency will likely be limited by the growth of irrigated acres. For example, irrigation will be more efficient but there will be a lot more of it.
By the way, we can do all the household water conservation we want, by turning off our taps and using low flow toilets, etc., and it won’t make a great deal of difference to water resources. (There are other very strong reasons to reduce our consumption of municipal water, however, that I won’t go into here.)
Another thing that is likely to be very significant is variation in flow from year to year. Climate change scenarios predict more weather extremes, floods and droughts. Although a 10 per cent decrease in flow may not seem too worrisome, in very dry years the availability of water could be severely restricted.
The other thing is the impact of lower flows on ecosystems. Ecosystems provide invaluable but often unrecognized and undervalued services. It is very hard to quantify the impacts of reduced flows on ecosystems, but there is little doubt that reduced water flows in this century will significantly decrease ecological values of the SSRB.