Aquifer Concerns

Hornby Island Bedrock Aquifers and Their Classifications

Hornby Island Aquifers

Hornby Island Aquifers


The classifications for the four bedrock aquifers were determined by W. S. Hodge, Hydrogeologist with the Groundwater Section of the Provincial Government as follows:

West Aquifer – Rated – II A – II A – (Moderately Developed, High Vulnerability).

South Aquifer – Rated – III A – (Lightly Developed, High Vulnerability).

Central Aquifer – Rated – II A – (Moderately Developed, High Vulnerability).

East Aquifer – Rated – I A – (Heavily Developed, High Vulnerability). – Note: There are a limited number of aquifers in this most critical classification in all of British Columbia.

A copy of the 2001 draft report HORNBY ISLAND AQUIFER CLASSIFICATION is available for viewing in the Water Stewardship Library.

Since three of  the aquifers, West, Central and South,  are affected by Mt. Geoffrey recharge,  it is important that the surface runoff from the mountain be enabled to filter in the ground, and not flow directly into the ocean.


How do you know if an aquifer is full?

The aquifers don’t really ‘fill up.’   The water is always moving.  When the ground gets saturated, the water doesn’t really stop, it just moves more slowly to the sea, if it is allowed to slow down with vegetation, etc.  We capture different parts of this movement each time we draw from our wells.  That is why at one time a well will show  contamination and at another it may have cleared or been reduced, or vice versa.  Each water test is a snap shot of a particular time, not a particular body of water. The fractured rock that makes up the geology of the island allows the water to run in all directions, so there is no way of saying ‘this aquifer is now full.’

There are three wells – one at the top of Sandpiper, one on a property near Lea Smith Road and the third out in the Anderson Road area.  These wells were established by Groundwater Branch of the Ministry of Environment and monitored by Bill Hodge for many years.  The Hodge Report is in our files.  These wells measured how precipitation recharged groundwater as it moved through.  His report recorded the rate at which each of these wells rose or fell depending on precipitation at different times of the year and registered a definable pattern.

The study done on 12 wells in  Sandpiper  indicated how quickly/slowly wells are recharged (again, by moving water) by a rainstorm after average household drawdown. Every well had different results due to variations in depth, location and use.  The island geology is so complex that measurement in any one area will prove nothing for another.   Ditching and continual surface modifications by individual property owners, or Highways, has diverted water away from historical patterns and without records based on long-term studies in every area,  the “do no harm” principle is all we can go on.


Do earthworms come to the surface when the soil is saturated?

According to the Scientific American, soil experts now think earthworms surface during rain storms for migration purposes. It gives them an opportunity to move greater distances across the soil surface than they could do through soil. They can even survive several days fully submerged in water.


All water migrates to the sea.


Harlequins.   Photo by Paule Corteau