Water demands leading to watershed degradation

CITY DOING ITS PART TO KEEP DEMAND IN CHECK

While drought continues to be the biggest threat to the southern Alberta economy and the health of the Oldman River watershed as whole, long-term climate change and the increasing demand for water use to further economic growth and irrigation are also significant contributors to watershed degradation.

According to the Oldman Watershed Council, river levels have declined 57 per cent over the past century due to increasing human-driven demands and the creation of large reservoirs in the region for irrigation, industrial and consumption purposes.

“If you look at the numbers of water licences, we are overallocated,” confirms Shannon Frank, executive director of the Oldman Watershed Council. “There are more licences to withdraw water than there is water in the river. That is a challenge, but not everyone is using their max licence. A lot of irrigators, and even the city, use way below what they could withdraw, and that is keeping things just fine (in terms of usage).

“In terms of river health,” she adds, “overall for the Oldman River the health is fair, but in certain reaches, especially on the Prairies and further downstream areas it is poor — so it is too low. We would like to see more water in the river in certain times of year for fish and trees, and those are things which are being worked on; specifically with releases from the dams.”

As recently stated in the City’s “Environment and Historic Resources Report,” the most significant impact of the declining water levels in the Oldman in the Lethbridge area over time has been degradation of the cottonwood forests, confirms Doug Kaupp, manager of water, wastewater and stormwater for the City of Lethbridge.

“What the cottonwood forests need is really flood-stage situations — high flows for a number of weeks at the right time of year in order for the seeds to take hold,” explains Kaupp. “If the high water doesn’t happen, there is no new growth. And if that highstaging drops off too fast then the seedlings are left high and dry, too. There is a natural cycle of spring flooding the trees have evolved to take advantage of, and that is being interrupted and messed with. The challenge for water managers is to imitate nature when you have the opportunity in light of all that has been removed.”

While the situation is concerning, says Kaupp, it is not the City of Lethbridge itself which poses the biggest challenge to river levels.

“The demand for water the City has, if we stopped withdrawing water for even a week it wouldn’t add enough water to save a tree,” he states. “The City of Lethbridge represents at most two per cent of all the water that is being removed from the river. The impact on the cottonwoods has more to do with the reservoir dam operations and the large amount of water which is removed for irrigation.

“The cottonwoods are longlived trees,” he adds, “but after 100 years of not enough water they are on the decline big-time. There are some really dramatic examples like on the St. Mary River where there used to be forests and now there is nothing along the river.”

On other measures of water efficiency, Lethbridge has actually been improving despite new growth over the past 30 years, says Kaupp.

“Surprisingly as Lethbridge has grown it has become more efficient in the context of water use at the same time,” he states. “Every new house that gets stamped out uses less water than ones built 20 or 30 years older. For example, even though 2017 was an extremely dry year, and the peaks days impact on our water system to supply had been unseen in 30 years, the highest peak demands on the water system in the history of the city were in the 1980s when the population of Lethbridge was closer to 60,000 than 100,000, and we didn’t have these big french fry plants.”

However, Kaupp and Frank acknowledge while technology has created better efficiency in water usage in the region, there is no denying the longer term effects of climate change.

“The climate change predictions are the snowpack will decline up to another 30 per cent; so we will see even less spring run-off from snow than we do now,” states Frank. “That is the conversation that needs to happen. As climate change increases and the snowpacks get worse and worse, and we see more droughts, then it is going to get more serious. There is nothing we can do about supply, so we have to be able to manage the human end.” Kaupp concurs. “There is a balancing act, and we have extracted a lot of economic value from the river the last 100 years. And there may have to be in the long run some rerationalizing of exactly what’s reasonable to take out for our economy,” said Kaupp.

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