Hydrologist urges more aquifer research
Millions rely on little understood water resource
The water drops as rain and snow in the Sweetgrass Hills of Montana and then disappears beneath the prairie landscape, some of it flowing slowly north beneath the Canada-U.S. border.
Alfonso Rivera stresses the “slowly.”
Drill a well into the aquifer near the Alberta town of Taber, 100 kilometres north of the hills, and the water can be close to a half million years old, says Rivera, Canada’s chief hydrogeologist.
His team is piecing together a 3-D model of the aquifer straddling the Alberta-Montana border in the most comprehensive look yet at the underground waterworks shared by Canada and the U.S.
Canada has been described as the “Saudi Arabia of the freshwater world,” but Rivera likes to point out that Canadians are increasingly dependent on the groundwater that is poorly understood and often under-appreciated.
He is determined to help fill the knowledge gap with his mapping projects and a new book, Canada’s Groundwater Resources, which is aimed at the public. “I wanted my grandmother to be able to read it,” Rivera said of the 803-page illustrated tome he recently published with colleagues from across the country.
It details how almost onethird of Canadians now depend on groundwater. Many aquatic ecosystems also rely on water seeping through the ground — especially in dry summer months.
Yet as Rivera puts it in his introduction to the book: “Nationally we have no idea what our groundwater resources are.” There is no national monitoring network to assess its quality and use, Rivera says. This even though groundwater “supplies clean, abundant and relatively cheap fresh water” to more than 10 million Canadians and could be a “strategic” resource for coping with climate change and drought.
He says Canada should learn from California’s current crisis. The state, which supplies both the U.S. and Canada with fresh fruits and vegetables year round, is using its store of groundwater much faster than it is being replenished. Wells are running dry, forcing many desperate California farmers to abandon their crops and orchards.
Part of the problem is that a lot of groundwater is “fossil water” that has been trapped underground for thousands of years in aquifers that are not always “rechargeable” — at least not in the short term, Rivera says.
Some aquifers are topped up by rainwater and snowmelt that percolates through the ground, with some receiving 100 centimetres a year. Other aquifers, confined by impenetrable or deep rock formations, get zero recharge.
Canada does, however, have an enormous “pool” of groundwater. Rivera estimates 70,000 cubic kilometres of water is sitting within 150 metres of the surface — almost three times as much water as there is in the Great Lakes combined.
“But we don’t how much we can use, if it is sustainable, how it interacts with ecosystems,” said Rivera, who works for the Geological Survey of Canada.
He has been pushing for years for the agency to step up efforts to assess the dimensions, dynamics and quality of the country’s underground water. Natural Resources Canada committed in 2003 to assess 30 of the country’s “priority” aquifers and still has 11 to go, he said.
Aquifers vary in size. The Northern Great Plains Aquifer lies beneath large swaths of southern Saskatchewan and Manitoba, most of North and South Dakota, half of Montana and a third of Wyoming. Much of the water that been underground since the last ice age, or earlier, and moves through complex rock formations.
Rivera is keen to map the Northern Great Plains Aquifer used by farmers, ranchers and oil and gas companies, but has his hands full with the smaller Milk River Aquifer straddling the Alberta-Montana border.
Concern about the Milk River Aquifer goes back to the 1950s, when water levels started to drop because of intensive use by farmers. Complicating the situation today are shale gas operators using groundwater from the aquifer in Montana.
For the 3-D modelling project, the scientists have spent two years studying how water moves and migrates underground constrained by the region’s sandstone.
Field crews have also been measuring well levels and collecting water samples for testing. Isotopes and contaminants reveal how long water has been underground and if it’s fit for consumption.
The aquifer is named after the Milk River but it stretches far beyond the river, cutting through the parched prairie landscape.
The aquifer underlines about 50,000 square kilometres of Montana and Alberta.
The 3-D model will provide the most detailed assessment to date of an aquifer Canada shares with the U.S., says Rivers, noting it will reveal the water “fluxes” across the border.
He says it will also show where the aquifer is replenished — mostly in the Sweetgrass Hills — how the water flows north, “and how much you can sustainably pump.”
While water from the northern reaches of the aquifer near Taber, can be half a million years old, he says it tends to be younger — “just” decades or hundreds of years old — closer to the border.
Assessing the dynamics underground is not easy, but Rivera says it was also a challenge getting water users and various levels of government to partner on the project.
“The key is not just the science, but in bringing the people together,” says Rivera. He says a First Nations group in Montana wouldn’t agree to participate but six jurisdictions — federal, state, provincial and regional — are cooperating on the project.
The 3-D model, which should be complete next year, should lead to better management of the aquifer.
And it may help lay the groundwork for a formal international agreement between the two countries on how to share the water, said Rivera, who is also involved with a UNESCO initiative to improve transboundary management of aquifers.