Water: A Precious and Shared Resource
- Marc S. Tremblay
- 7 hours ago
- 6 min read
Living on an island gives us a close connection to water. This blog offers insight into why conservation matters here, and how everyday choices, made by guests and residents alike, help protect water, a precious and shared resource.
Where Mayne Island’s Water Comes From
Water is so fundamental to daily life that it’s easy to forget how fragile our supply can be.
Here on Mayne Island, water doesn’t arrive through a pipeline from away. It’s not stored in a lake or a reservoir. What we have is what nature provides: rainfall that slowly makes its way underground into aquifers, which are then accessed through hundreds of wells, some privately owned and others operated by community water districts.
Because our aquifers are small, fractured-bedrock systems with limited storage, their capacity fluctuates seasonally. They're also highly sensitive to dry summers and heavy demand.
Provincial mapping shows that Mayne Island sits atop four distinct aquifers:
Aquifer 447 (North side of the island, including Georgina Point to Edith Point)
3.7 km2
105 wells (sum of well correlated to the aquifer + those uncorrelated, but within mapped aquifer)
1 artesian well
Aquifer 619 (Bennett Bay, up to Wilks Road, across to Miners Bay, Helen Point)
8 km2
230 wells (correlated + uncorrelated)
13 artesian wells
Aquifer 620 (Horton Bay, Mariners Way, Village Bay)
7.7 km2
221 wells (correlated + uncorrelated)
2 artesian wells
Aquifer 632 (South side of the island, from St-John’s Point, all the way to Dinner Bay Park and Japanese Memorial Garden)
3.9 km2
96 wells (correlated + uncorrelated)
1 artesian well
All four are fractured sedimentary bedrock aquifers of the Nanaimo Group. The Nanaimo Group is a sequence of sedimentary rocks, including sandstone, shale, and conglomerate, formed about 80–90 million years ago. It's the dominant rock formation that makes up Mayne Island.
Bedrock aquifers behave very differently from the sand and gravel aquifers found in many river valleys. Unlike large sand‑and‑gravel basins, our bedrock aquifers store relatively little water and depend on a narrow recharge window. This means: limited storage, highly variable well yields, strong seasonal fluctuations, and greater vulnerability to saltwater intrusion.
A helpful way to picture Mayne Island aquifers is not as underground lakes, but as a slow moving network of water held in fractured rock.
Wells, Water Districts, and Shared Responsibility
There are 10 water districts on the island. The water storage capacity of all water districts combined is about 584,000 gallons, which supplies 872 households.
To put this storage volume in perspective, 584,000 gallons would be totally depleted in just under one week, based on 872 2-person households, each using 100 gallons a day (Statistics Canada reports a daily average of 223 litres for water usage, or 59 US gallons, per person, per day). Thankfully, the aquifers continuously replenish the storage tanks, but the math illustrates how little a buffer we have, especially during summer months, when demand is high and recharge is months away.
There are over 600 water wells on Mayne Island that draw from these four aquifers. While each well serves an individual property or a water district, all wells draw from the same finite groundwater system. What happens at one site, especially during the dry season, can affect water levels and quality elsewhere. This is why water use on islands is best understood as a collective responsibility, not just a private one.
When Do Aquifers Refill?
On the Southern Gulf Islands, most groundwater recharge occurs in late fall and winter, when sustained rainfall can soak into soils and fractured bedrock. During this period, plant water use is low, allowing a greater proportion of rain to percolate downward and replenish aquifers rather than being taken up by vegetation or lost to evaporation.
Provincial observation well # 484, located on Mariners Way near East West Road, shows a consistent pattern: once sustained autumn rains arrive, groundwater levels rebound within two to four weeks and reach their seasonal peak by November-December. This is followed by a gradual drawdown through spring and summer.
It is important to note that water levels can rebound within weeks, but the actual renewal of deeper groundwater storage happens on longer timescales, which is why careful summer use still matters after a wet November.
Can Aquifers Run Dry or Become Contaminated?
The short answer is yes. In fractured bedrock, wells can experience rapid declines near the end of the dry season, particularly if demand is high. Some wells may temporarily run dry even if others nearby do not.
Because Mayne Island is surrounded by ocean, fresh groundwater sits above denser seawater underground. If groundwater levels drop too low, due to drought or over-pumping, saltwater could move inland and upward, contaminating wells.
This risk is well documented across the Southern Gulf Islands and is one reason careful summer water use is so important. Once saltwater enters a well or fracture network, recovery can take years, and in some cases may not fully reverse.
How Much Water is in the Aquifers?
For fun, we can do a simple "back-of-the-envelope" calculation to estimate the amount of water stored under Mayne Island. To do so, we need to make broad general assumptions:
Total area of aquifers: 23 km2 or 23.3 million m²
Assume (conservatively; see sources below):
Saturated thickness: 20 m
Effective porosity: 2%
Water volume:
23.3 million m² × 20 m × 0.02 = 9.32 million m³
1 m³ = 264 US gallons
≈ 2.46 billion gallons
Based on the typical properties of fractured bedrock aquifers, the four aquifers beneath Mayne Island may collectively store billions of gallons of groundwater. This calculation is merely an illustration of how much the aquifers could hold, however, fractured‑bedrock storage is not a usable reservoir per se. Only a very small fraction of that water can be withdrawn sustainably, underscoring why careful water use remains essential.
The Well at The Grove B&B
Our own water system reflects the realities of living on a small island. Our well was drilled in 1981 and reaches a depth of 93 feet. It yields about only about one gallon per minute.
By conventional standards, a one-gallon-per-minute well is considered "low-yield." For comparison, many mainland homes rely on wells producing five to ten gallons per minute or more. Low-yield wells are common on Mayne Island, yet, they can function reliably when water use is managed carefully. While a one-gallon-per-minute well can supply more than 1,400 gallons of water per day, it cannot support heavy peak demand such as multiple showers, toilet flushing, and laundry all at once, let alone garden irrigation.
This reality shaped how we designed the water systems at The Grove.
Why We Collect Rainwater
To reduce demand on groundwater, especially during the dry summer months, we invested in a rainwater catchment system. Collected rainwater is used exclusively for flushing toilets, a task that does not require potable water quality.
This took additional planning and upfront investment, but the results have been meaningful.
What the Numbers Show
We tracked our water use over an 18-month period:
30,780 gallons of well water used for drinking, cooking, laundry
7,560 gallons of rainwater used for toilets
That means roughly 20% of our total water use was supplied by rainwater rather than the aquifer, leaving thousands of gallons underground. This significantly reduces pressure on our aquifer during the times of year when it's most vulnerable.
How Guests Can Help
If you’re visiting Mayne Island, a few simple habits go a long way:
Take shorter showers
Turn off taps while brushing teeth or shaving
Run dishwashers and laundry only with full loads
Be mindful of water use during dry summer months
These small choices help protect the same aquifers that supply homes, ecosystems, and future visitors.
A Shared Island Story
At The Grove B&B, sustainability isn’t about perfection, it’s about thoughtful choices rooted in place. Our rainwater system won’t solve water scarcity on its own, but it’s one practical step toward reducing pressure on Mayne Island’s fragile groundwater system.
We’re grateful to be part of a community that values stewardship, and we appreciate every guest who helps care for this remarkable island, one thoughtful choice at a time.
Water connects us all. On an island, that connection is impossible to ignore.
Sources:
