Groundwater pumping drains rivers in BC and globally

Water scarcity and stalled well licensing belie BC's 'myth of abundance'

Gavin MacRae

Coho, steelhead, and cutthroat trout struggled to survive this August in “severely degraded” habitat caused by bottomed-out flow levels on the Koksilah River, south of Duncan on Vancouver Island.

Three summers running, provincial officials had requested voluntary reductions in water use on the Koksilah, but this time it wasn’t enough, and the province issued a mandatory restriction on water draws.

What made the stop-order unique is that for the first time in BC, groundwater wells were included.

It’s unlikely to be the last.

An estimated 70% of the water drawn from the Koksilah watershed is groundwater, and essential for crop irrigation, businesses, and rural homes. But many of the wells tap shallow aquifers hydraulically connected to the river.

It’s a textbook example of groundwater pumping affecting streamflows, and could have made a fitting case study for new hydrological modelling by an international team of researchers, published in October in Nature.

The findings of the study show that globally, unsustainable groundwater pumping is causing a “slow desiccation” of thousands of streams and rivers, with “potential devastating effects” on aquatic ecosystems.

“We studied when and where the river levels drop to the point that streams cannot maintain healthy ecosystems anymore,” says Inge de Graaf, lead author of the study and a hydrologist and assistant professor at the University of Freiburg, Germany. “With the model, I was able to simulate groundwater heads and also the impact of groundwater extraction on the heads and on the flow, and the groundwater-surface water interaction.” (Head is the measure of the potential energy in a body of water to move or do some type of work).

The modelling found that the “environmental flow limit” – when the flow of a stream or river becomes low enough to threaten aquatic life – has already been reached in 15-to-21% of watersheds worldwide where groundwater is drawn for human use. By 2050, the model predicts the same ecological tipping point will be reached in 42-to-79% of those watersheds.

What’s more, the researchers were surprised to find that even small declines in groundwater can affect flow levels.

“What we have seen in the model is that only small head declines are already causing this environmental limit to be reached,” De Graaf says. “That showed us that these ecosystems are super sensitive to groundwater extraction, and also that we reach the environmental limit before we will reach significant groundwater depletion.”

“Groundwater is definitely stressed in certain areas of the province.”

The lag between groundwater pumping and diminished streamflow can be months, years, or even decades. As the study puts it, this turns unsustainable groundwater pumping into a “ticking time bomb” for life in streams and rivers.

That fuse has already burned short in arid regions that rely heavily on groundwater for irrigation (globally, 70% of irrigation relies on groundwater). Hotspots include the southern Great Plains of the US, California’s Central Valley, parts of Mexico, and the Upper Ganges and Indus Basins in Asia.

Yet for most British Columbians, no travel is needed to witness a stressed watershed.

“Groundwater is definitely stressed in certain areas of the province,” says Mike Wei, a hydrogeologist and former head of Aquifer and Watershed Science with the BC Ministry of Environment and Climate Change Strategy. “Typically in the southern interior, the Okanagan, Kamloops area, the Lower Mainland and the east coast of Vancouver Island.”

Despite the “myth of abundance,” a new report by the Watershed Watch Salmon Society, Tapped Out: a special report on water scarcity and water solutions in British Columbia, finds that water scarcity is now a pressing issue for British Columbians, wildlife, and the economy.

The report estimates 2.9 million people, or 63% of BC’s population, live in water-stressed areas. Of these, the areas with the highest levels of water stress cover only 3.7% of the province, but include nearly a quarter of BC’s population.

That’s because since the 1970s, BC’s population has doubled, agriculture has intensified, and well-drilling technology has improved, ramping up pressure on groundwater, says Tanis Gower, a biologist with Watershed Watch Salmon Society and co-author of Tapped Out.

BC’s unique geology is also a contributing factor.

“In Alberta, Saskatchewan, Manitoba, those aquifers are typically deep down and aren’t that well connected to streams.” says Wei. “But if you look at British Columbia, for example the Kettle River or Okanagan River, there’s sand and gravel aquifers right next to the river, with wells pumping to supply small towns. And the groundwater is directly connected to the stream.”

Climate change is also affecting water availability in several ways. The most obvious is more frequent and longer summer droughts – increasing demand for groundwater when streamflows are lowest. The growing season will extend in some areas of BC, too, exerting water demand over a longer irrigation period. At the same time, smaller snowpacks will store less water for release into streams and aquifers. And by 2100, most of BC’s glaciers are forecast to disappear, eliminating an important source of summer streamflow.

But there is some good news. With the passing of the Water Sustainability Act in 2016, BC gained the tools to govern surface and groundwater as one resource, and with an eye to protecting environmental flow limits.

“Some people are laissez-faire about [licensing their wells], like ‘yeah whatever.’ But it’s not going to be ‘whatever’ if you try to sell your property ten years from now.”

There’s only one problem. Previous to 2016, the province didn’t regulate groundwater, except for very large extractions. That’s left an estimated 20,000 existing well owners to be retroactively licensed, and so far, Gower says, getting them to buy into the new system has been a “huge mess.”

“This is a once-a-century kind of event, to try and integrate groundwater users into the system, and it hasn’t been going very well,” says Gower. “The uptake has been low. In the agricultural community there’s a lot of distrust of government, and people don’t want to have to ask to use what they’ve always considered to be theirs.”

Wei believes the level of compliance for existing groundwater users applying for a licence is low, likely in the ballpark of 15%. So low, apparently, that the province was forced to extend the three-year transition period intended to grandfather-in existing users another three years, until March, 2022.

Groundwater users who miss the deadline will lose their priority over subsequent well owners under the “first in time, first in right” principal written into the Water Sustainability Act.

“Some people are laissez-faire about it, like ‘yeah whatever,’” says Wei. “But it’s not going to be ‘whatever’ if you try to sell your property ten years from now. People will be looking for a water licence registered on the property …  If you never bothered, and you’re using water without authorization, how much will your property be worth then?”

There is a carrot as well as a stick, especially for commercial groundwater users. Water use information from the wells would fill in a long-standing data gap, informing watershed-wide strategies for water management – and making knee-jerk and economically costly water restrictions less likely.

“Groundwater licensing needs to happen. That’s the key thing,” Gower says. “We really need that information so that we can understand how much water is being taken, and in those watersheds where water extraction is excessive – because there are many places where there’s already over-extraction – there can be some sort of thoughtful planning to address how we’re going to deal with it.”

The Tapped Out report recommends a “critical shift in approach over the short term, including a fully resourced implementation plan and an effective communications program” to ensure compliance by the 2022 deadline. “We recommend extra effort be applied in areas of known water stress,” the report adds.

Over the long term, there are other ways to protect groundwater that could be adopted at a global scale. More efficient irrigation, and a shift to less water-intensive crops can ease demand. Supply can be protected with engineered solutions such as artificial recharge, where surface water is injected into an aquifer during times of abundant flow, to be used at times of year when surface flows decline.

Artificial recharge is being used in Washington, Oregon, California, and Arizona, Wei says, but not yet in BC. “It’s something that people are probably starting to look at,” he says.

Although the clock is ticking to deal with groundwater over-extraction, De Graaf says there is still time to act. “I would say it’s something we can still change if we are aware of the problem right now. It doesn’t really mean that it necessarily needs to be that way in 50 years.”

 


Cover image: Watershed Sentinel Dec-Jan 2019 | Deep TimeThis article appears in our December 2019-January 2020 issue.

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