Water Supplies from the Ground Up

Consider that water is essential to so many facets of our everyday lives—energy and food production, for example—and it’s understandable that the World Economic Forum has identified a global water shortage as the most significant threat to our existence on the planet, with consequences estimated higher than those posed by global warfare and looming food shortages. And, in terms of likelihood, global water shortage ranks just below a major climate change scenario.

While the global impacts of climate change become all the more real, the threat of a water crisis is also becoming more likely. By 2030, global requirements are expected to exceed sustainable water supplies by 40 percent. Water issues aren’t anything new to the drier (and often poorer) parts of the world, where an estimated 750 million people lack access to safe drinking water—and 2.5 billion don’t have access to sanitation that satisfies Western standards.

Tapping into our water supply

When we look for solutions at home, it’s important that we understand our relationship with the earth’s hydrologic cycle (the ongoing circulation of water from precipitation, to surface water, to groundwater, and back again).

Freshwater makes up just 2.5 percent of the world’s water—the rest is found in our oceans and is too saline for human consumption. Of our freshwater, 68.7 percent is frozen in glaciers and polar icecaps, while 0.4 percent flows above ground in our lakes, rivers, and streams. The remaining 30.9 percent resides below the earth’s surface in the form of groundwater.

Aquifers

Dig down deep enough almost anywhere and you’ll eventually hit groundwater. Groundwater refers to water that permeates the sand, rock, gravel, and other materials beneath what’s called the water table. This area is characterized by the complete saturation of underground materials, leaving no room for air. An aquifer is a localized accumulation of groundwater that can be extracted for human consumption. They are, essentially, large underground reservoirs.

According to the Government of Canada, about 25 to 30 percent of Canadians rely on aquifers for daily water needs. The proportion of those who rely on groundwater is as high as 47.9 percent in the Yukon, 66.5 percent in New Brunswick, and 100 percent in PEI. In the US, it’s estimated that groundwater makes up half of all drinking water, and in Australia, the earth’s driest continent, about 17 percent.

It’s no secret that human activity affects both the quantity and quality of groundwater, but what’s becoming more relevant is the fact that the state of our groundwater affects our surface resources as well.

Groundwater depletion

Groundwater is part of the hydrologic cycle. It gets charged from precipitation collected on the surface in streams and lakes. Use too much groundwater before it has a chance to recharge and the underground stores will begin to disappear. For those who rely on wells, this often necessitates digging deeper to reach water far beneath the surface. Redrilling wells or digging new ones can be costly—and water often grows more saline the deeper you go.

Depletion of groundwater affects surface quantities as well. According to Steve Conrad, associate director of the Pacific Water Research Centre at Simon Fraser University (SFU), this is because the two sources are ultimately connected. “They’re the same water,” says Conrad. “If you pull too much from your groundwater supplies, you eliminate your [surface].”

From our aquifers, groundwater eventually permeates back to the surface—into low-lying streams, lakes, or oceans—before evaporating back into the atmosphere. Groundwater can flow up to several metres per day through porous materials—and mere centimetres over the course of a century through more impermeable materials.

In other words, while the abundance of groundwater may seem like the solution to the world’s water woes, it really isn’t. “If you over-pull water from the ground, when water flows through the river, it will permeate directly into the ground, and you’ll have continuously low-flowing streams,” says Conrad. Reduced surface water can threaten local wildlife habitats and natural ecologies, especially wetland areas and riverbanks. This can also increase soil erosion and the severity and frequency of droughts.

“Basically,” says Conrad, “there’s no free water.”

Groundwater contamination

Groundwater is more sensitive to contamination than surface water. Surface water flows continuously and constantly flushes away pollutants. “Groundwater doesn’t have that capacity—at least not in a time scale that would be important for us,” says Conrad.

Instead, contaminants accumulate in ground surfaces. “One of the only ways to [remove],” says Conrad, “is to literally pump all the water out, treat it, and let it all permeate back in.” Needless to say, this is a costly and time-consuming process.

While some aquifers can be highly isolated, most are well connected to surrounding water systems, which means groundwater with enough contaminants may pollute neighbouring areas.

“You contaminate a river, and that river spreads that contamination into the soil. As you flush in more water, that contaminant will move into other systems downstream,” says Conrad. “That’s the challenge. You really don’t have, except in very isolated cases, a purely isolated system.”

Natural gas hydrofracking and tar sand oil extraction have been topical issues for groundwater contamination, but tainted water from municipal landfills and agricultural runoff also pose major risks for groundwater resources.

Myth of abundance

Canada is typically considered a water-rich country, carrying an estimated 20 percent of the world’s freshwater resources. However, much of this is frozen, and 60 percent of rainfall flows toward the Arctic Circle—meaning, without significant diversions, it isn’t much use to the more populated southern areas. High consumption periods also happen to coincide with seasons with the lowest supply. “Canada has lots of water, but it’s not necessarily where we want it,” says Conrad.

Beyond underlying groundwater resources, areas supplied by surface water have their own challenges. Purveyors rely on costly municipal infrastructure to manage supply during the summer months. For municipalities dependent on above-ground reservoirs, “the amount of surface water we have is dependent upon the size of the dams and reservoirs we build,” says Conrad. “The question is, when we have a growing population or some particularly dry years, do we build more and bigger dams to store that water? Or, do we ask people to conserve?”

For most city planners, it’s best to ask residents to conserve. “You don’t want to spend billions for a reservoir that you use only once every 10 to 15 years,” says Conrad.

For surface-water systems, reservoirs typically overflow during much of the winter and into the spring. “But here’s the problem,” says Conrad, “it’s really challenging to tell people to conserve water only for a period of time. You want to create these habits to conserve year-round.”

Aquifers also benefit from conservation all year, as consumption should never exceed the slower recharge rate. In other words, whether relying on groundwater or surface reservoirs, conserving water all year is important to preserve the precious resources we have.