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below ground surface, it may take up to 34 years for infiltration to reach the groundwater system based on
a rate of 295 mm/yr. As such, regional-scale groundwater systems may respond relatively slowly to
climate change and other regional influences (e.g., water abstraction) and it may take years or decades
for corresponding effects to fully establish.
Additional work is required to better estimate groundwater recharge rates on a regional basis (i.e. for the
Study Area as a whole). This work could be based on a combination of approaches:
Well hydrograph analyses (e.g., from MOE’s observation well network) to assess aquifer hydraulic
properties and aquifer responses to seasonal and inter-annual variations in recharge conditions.
Well hydrograph analysis is complicated by the influence of both recharge conditions and water
withdrawals on measured groundwater levels and as a stand-alone option is therefore not expected
to yield reliable results regarding groundwater recharge rates;
Hydrograph separation / base flow regression analyses to estimate groundwater discharge fluxes
from seasonal low flows. Apart from the fact that limited gauging data exists for the Study Area,
base flow regression analyses are complicated by the fact that streams are regulated and (or)
influenced by water diversions. As such, this approach is not expected to yield reliable results; and
Groundwater recharge calculations as the residual of precipitation, evaporation, surface runoff and
soil water storage using either the HELP (Hydrologic Evaluation of Landfill Performance) model
(
Schroeder et al., 1994) or the MIKE-SHE model (Abbott et al., 1986; Refsgaard and Storm, 1995).
Both models have been used for this purpose in a variety of settings in British Columbia (e.g.,
Scibec and Allen, 2006; Denny et al., 2007). This is considered the most promising approach.
Once estimates of recharge rates are obtained, this information would ideally be combined in a
groundwater model for the Study Area that also incorporates information on well yields (aquifer
transmissivity) and groundwater levels. These data would be used to calibrate the groundwater model to
ensure that it accurately represents groundwater flow directions, rates and volumes. The purpose of the
groundwater model would be to better evaluate groundwater budgets for aquifers within the Study Area
and to assess groundwater availability within the context of climate change and water demand projections.
The groundwater model could also be used to generate planning densities (i.e. by preferentially locating
population in designated areas linked to high-yielding (portions of) aquifers), although planning at this level
of detail would likely require much more comprehensive, quantitative, and site-specific hydrogeologic
information than is presently available.
Development of maps of groundwater flow directions, while planned for this project, was hampered by
limitations of the WELLS database. Once groundwater surface elevations have been determined from the
WELLS database, this information could be used to map groundwater flow directions directly. However,
the preferred option would be to use this information to calibrate a groundwater flow model, which could
be used to quantitatively assess flow directions, velocities, and recharge/discharge relationships,
including:
Hydraulic connectivity of aquifers with surface waters and highland recharge areas; and
Hydraulic connectivity between overburden and bedrock aquifers.
