Aquifers are large reservoirs of underground water, or "groundwater". Aquifers are formed where water, usually from the surface, makes its way into the ground via cracks in the bedrock, or through sand or gravel. This water accumulates in a region and acts like a giant underground storage area. The water is not usually stagnant; rather, it flows through the aquifer region being filtered as it moves.
Image courtesy District of Nanaimo
When an aquifer forms in an area made mostly of sand and gravel deposited by moving surface water (rivers), the aquifer is termed a "Fluvial Aquifer". Fluvial Aquifers are usually formed relatively close to the surface and are intimately connected to the surface water systems, and as such are very vulnerable to contamination from surface pollutants.
The Chemainus River Aquifer is a fluvial aquifer fed primarily from surface water in and around the Chemainus River. This Aquifer is a critical water source for the Halalt First Nation. Situated below the Chemainus River Valley, this aquifer is formed in the sediment that has been deposited here by the Chemainus River; and it is fed from surface water from the Chemainus River Valley area. As with many fluvial aquifers, the Chemainus River Aquifer is at a high risk for contamination, so the North Cowichan District has an active groundwater protection plan in place. They have identified a region in which they request that people take extra precautions to prevent contaminants from entering the system. These contaminants include antifreeze, household cleaners, fertilizers, gasoline, oil, manure, paint, pesticides, and sewage.
Photo: Chris Edley
The coordinates will take you to a location where there is a beautiful view of the Chemainus River delta, and plenty of room to pull over and prepare for your aquifer adventure. You will need to take a coordinate reading at two locations, or reset your odometer at one location, so make sure you know how to do this. Your task is to measure the width of the groundwater protection zone in the area spanned by the road from Crofton to Chemainus. This will give you a good idea of the size of the area that feeds this aquifer.
IMPORTANT: Please respect the posted speed limits, especially through the Halalt First Nation land.
In order to log this EarthCache, do the following:
Starting at the coordinates, drive north (towards Chemainus) until you see a sign on the side of the road that indicates the start of the Groundwater Protection Zone. At this point, slow down and set your trip-odometer to zero OR if you have a passenger, slow down and have your passenger capture the coordinates of the location on a GPS. There is no need to stop or get out of your car.
Image courtesy District of Nanaimo
Drive towards Chemainus... shortly after you cross the Chemainus river, you will see a sign indicating the other side of the Groundwater Protection Zone. Note: it is facing the other way, but is before Ashcroft Road. Either note your odometer reading, or pull over nearby and capture the coordinates of the sign.
Send us an email (through our geocaching profile) that has the answers to the following questions:
1. What is the distance between the two signs (and therefore the width of the Groundwater Protection Zone here). Either send us a calculated distance based on your coordinates, or your odometer reading... do not send us the coordinates, we know where the signs are!
2. Based on what you see on your drive (and in the nearby area), identify three potential contamination hazards for this aquifer that are within the protection zone.
In 2011, the Halalt First Nation won a BC Supreme Court challenge to prevent the District from pumping water from this aquifer. An Environmental assessment had shown that the river and the aquifer were not separate systems, and that pumping from one would affect the other, potentially impacting the salmon habitat of the Chemainus River. This is surface-water / groundwater relationship is typical of fluvial aquifers.
Generally, the faster-moving a river is the larger will be the particulate that it deposits. Larger particulate deposits create fluvial aquifers that are more productive, however less filtering takes place and surface water conditions affect the groundwater conditions very quickly.