Service Description: An SSWCA is defined in the Growth Plan for the Greater Golden Horseshoe (2020) as, “Areas, generally
associated with headwater catchments, that contribute to baseflow volumes which are significant to
the overall surface water flow volumes within a watershed.” Municipalities have sought further clarity
from the province, herein the definition of SSWCAs is focused on contribution to baseflow volumes
that are significant to surface water flow volumes, which is more specific than simply delineating
headwaters. This does not include headwaters into SSWCAs, because SSWCAs only protect
groundwater contribution in some headwater areas. See also previous TRCA memos on ESGRAs, other
KHFs, and technical methodologies for SGRAs and HVAs under the Credit Valley – Toronto Region –
Central Lake Ontario (CTC) Source Protection Area (CTC-SPC 2015).
Based on discussion with municipal staff the following methodology was offered for delineating
SSWCAs, “SSWCAs are those areas which are both SGRAs and ESGRAs; the methodologies used to
delineate SGRAs and ESGRAs should be used to identify SSWCAs.” Under this definition, SSWCAs would
therefore comprise the areas of overlap between ESGRAs and SGRAs (or in the case of SGRAs,
unclipped layers based on Technical Rule 45, e.g. High Volume Recharge Areas). SGRAs were identified
for the Source Protection Program based on the volume of recharge that occurs, not where water
resources contributing to recharge expresses itself in streams. Conversely, ESGRAs are identified as
the most likely site of groundwater recharge for the receiving feature that they support (streams and
wetlands), but not based on the volume of water that they contribute. Those overlap areas then, are
areas that provide a large volume of groundwater recharge, and where that recharge has been found
through groundwater modelling to support sensitive areas like coldwater streams and wetlands. In
other words, the “significant” component of the SSWCA term would be covered through volume
contri
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