Groundwater is a critical element that supports the health of our ecosystems and the hydrological function of watersheds. The concern today is that changes in seasonal precipitation, evapotranspiration, recharge, and saltwater intrusion are threatening this precious resource.
Groundwater – A Primer
The unsaturated zone above the water table contains soil moisture which constantly moves within the soil and rocks. Below this region, groundwater occupies the saturated zone where water is stored between rock particles and within bedrock fractures. Areas where moisture-bearing rocks transmit water to well or springs are called aquifers. Generally, the water that recharges the aquifer follows the most permeable pathways from the point of infiltration, with the rate of recovery being subject to seasonal fluctuations in precipitation and ground permeability. The recovery of groundwater reserves is significantly affected by the amount of forest cover and soil compaction as well as the presence of drainage ditches.
In addition to being indispensable as a source of domestic water (including its use by wastewater and sewage systems), groundwater enables heating and cooling by way of ground source heat pumps.
Threats to Groundwater
Groundwater supplies have long been threatened by contamination from underground oil storage tanks, malfunctioning septic systems, landfills, spills of hazardous materials, and overuse. This was always a challenge, but today climate change is presenting additional issues. Changes in precipitation affect groundwater quantity, and sea level rise leads to saltwater intrusion into coastal aquifers, a process which is difficult to reverse.
It is good news that the Local Planning Service for the Islands Trust is currently researching groundwater recharge potential, groundwater availability, and land-use planning strategies that will mitigate the effects of climate change.
The Southern Gulf Islands Groundwater Sustainability Strategy includes investigations on Galiano, Mayne, North and South Pender, and Saturna islands, employing Terrestrial Ecosystem Mapping (TEM) and Groundwater Terrestrial Infiltration Ratios (GW-TEIR) to calculate potential recharge capacity in different ecosystems. As groundwater recharge varies with topography, geology, biogeography, climate and land-use it is important to take this kind of ecosystem approach to both research and management. This will lead to a greater understanding of groundwater recharge and how it functions on specific sites throughout the Southern Gulf Islands which in turn will inform local managers and landowners.
In the meantime, when you buy a home in the Southern Gulf Islands it’s important to:
- Understand that forests and natural ecosystems play a critical role in groundwater recharge, and that retaining these features on your property makes essential contributions to our community’s water supply.
- Be aware that changes in the landscape such as removal of forest cover, soil compaction, and installation of drainage ditches and impervious surfaces reduce groundwater recharge capacity.
- Find out whether there is a current yield test and/or a well record or driller’s log describing the characteristics of your existing well. The well record typically notes the amount of water available, and the characteristics of the material the driller encountered. Test your well water regularly, while planning for future well, pump or drain field replacement.
- Maintain your onsite wastewater treatment systems.
- Understand how past land uses may affect your property. If it was previously used for agriculture or as a waste disposal site, there may be ongoing effects on the groundwater and the surrounding aquifer.
- Minimize impervious surfaces (buildings and driveways) that reduce ground water recharge and consider how to mitigate these impacts with raingardens, bioswales and other stormwater management strategies.
- Reduce or eliminate the use of fertilizers or pesticides so they are not absorbed into the ground.
- Minimize the chance that oil, gas, or antifreeze from vehicles are spilled and run off into the soil.
If you are building a new home, it’s a good idea to:
- Understand the land use history of your property and its soil properties (including the infiltration rate).
- Remember that the distances required by the BC Building Code between wells and onsite wastewater treatment systems prevent cross-contamination from wastewater.
In either new or existing homes, it is important to reduce water use by:
- Installing low flow toilets and showers which are widely available and make a real difference to the level of consumption over the course of a year.
- Planting gardens with native species that demand less water over the growing season.
If you have a community water system, the continual withdrawal of ground water can be significant. Therefore, it is important to consider adding stormwater management features that encourage infiltration to mitigate the water loss and protect downstream marine ecosystems.