COWICHAN VALLEY REGIONAL DISTRICT
SOUTH COWICHAN WATER PLAN STUDY
V19830100 : Rev B : 11 February 2009
Page 19
Table 5 Aquifer vulnerability, recharge and groundwater flow information
Tag Aquifer
Vulnerability
Confining Unit
Thickness (m)
Depth to Water
(
mbgs)
Inferred Recharge Mechanisms
Groundwater Flow
Direction
197
Low
20.0 (0 - 87.8)
27.4 (0 - 93.0)
Precipitation
North to Cowichan Bay
199
Low
No aquifer classification worksheet available
201
Low
10.7 (0 - 48.2)
6.1 (2.4 - 25.9)
Precipitation, runoff
West to Koksilah River
205
Low
23.5 (0 - 65.5)
12.8 (0 - 37.8)
Precipitation (probably)
Not determined
206
High
7.5 (0 - ??)
6.7 (0 - 38.1)
Precipitation and/or upslope zones North and northeast
196
Low
7.5 (0 - 69.5)
8.5 (1.2 - 89.6)
Precipitation, runoff surficial aquifers To Cowichan River
198
Low
13.6 (0 - 41.1)
9.7 (0.5 - 49.7)
Precipitation, surficial aquifers
Not determined
200
Moderate
3.0 (0 - 28.7)
11.9 (0 - 44.2)
Not determined (precipitation)
Not determined
202
Moderate
2.1 (0 - 53.3)
8.4 (0 - 81.7)
Not determined (precipitation)
Not determined
203
High
0.3 (0 - 59.7)
5.9 (0 - 59.7)
Precipitation, runoff
To Shawnigan Lake
204
Moderate
3.0 (0 - 62.5)
5.2 (0 - 50.3)
Not determined (precipitation)
Toward Saanich Inlet
207
Moderate
4.6 (0 - 64.3)
7.6 (0 - 61.0)
Not determined (precipitation)
East and/or north
208
High
1.2 (0 - 16.2 )
15.8 (1.5 - 76.2)
Precipitation, runoff
Toward Saanich Inlet
2.5.9
Aqui fer Product ivi ty / We l l Yie lds
Surficial aquifers within the South Cowichan region are generally more productive than the bedrock
aquifers, as indicated by the summary of well yields in Table 6 below. Reported bedrock aquifer
productivity (MOE, 1994) generally increases eastward from low to moderate. However, these
conclusions may be of limited relevance since estimates of aquifer productivity have been based primarily
on airlifted well yields at the time of well development and not on aquifer yield and sustainability data from
extended pump testing (not presently recorded by MOE). Long-duration pump testing of any new wells
developed within the Study Area is prudent to determine whether local groundwater extraction rates are
sustainable during dry summer conditions, and to confirm that such extraction does not result in
deleterious effects on ambient environmental receptors or neighbouring human interests.
Given the comparatively large size and structural complexity of the region’s bedrock aquifers,
opportunities may exist for increasing bedrock groundwater use in the South Cowichan area. However,
identifying productive bedrock groundwater zones may prove to be technically challenging and costly
since the majority of bedrock groundwater is hosted by fracture systems of unknown morphologies and
orientations. Comprehensive assessment of the area’s fractured bedrock groundwater potential will
require more site-specific hydrogeologic information than is presently available. Lithological and/or
structural evaluations of the region’s bedrock and surficial deposit groups could provide a more reliable
depiction of their primary and secondary porosity potentials
