The Trust area's largest island draws its water from fractured rock the Province re-mapped in 2018 — and rated High vulnerability across every one of its main aquifers.
Island homes drink groundwater. Every figure here is the Province of British Columbia's own — from its aquifer mapping and its GWELLS well registry — shown verbatim and linked to source. The Province maps 4 aquifers beneath Salt Spring Island's 6,457 land lots, carrying 2,262 registered wells, 149 of them with provincial water-chemistry data, and 6 provincial observation wells recording long-term water levels.
Bedrock — Fractured sedimentary rock; 48.9 km²; mapped 2018. Beneath 3,205 of Salt Spring Island's lots.
Vulnerability High; productivity Low; quality concern Local. Rock unit: Nanaimo Group.
1,053 wells on record; 3 water licences; 8 artesian; 65 wells with provincial water-chemistry data; 4 provincial observation wells (#276 Inactive, #227 Inactive, #281 Active, #438 Active).
Bedrock — Fractured sedimentary rock; 36.4 km²; mapped 2018. Beneath 1,290 of Salt Spring Island's lots.
Vulnerability High; productivity Low; quality concern Local. Rock unit: Nanaimo Group.
491 wells on record; 4 water licences; 21 artesian; 40 wells with provincial water-chemistry data; 1 provincial observation well (#373 Active).
Bedrock — Fractured crystalline bedrock; 48.8 km²; mapped 2018. Beneath 835 of Salt Spring Island's lots.
Vulnerability High; productivity Low; quality concern Local. Rock unit: Nitinat Formation and the Saltspring Intrusive Suite.
480 wells on record; 8 artesian; 36 wells with provincial water-chemistry data; 1 provincial observation well (#223 Inactive).
Bedrock — Fractured crystalline bedrock; 51.4 km²; mapped 2018. Beneath 371 of Salt Spring Island's lots.
Vulnerability High; productivity Low; quality concern Isolated. Rock unit: Sick Group / Buttle Lake Group.
238 wells on record; 5 artesian; 8 wells with provincial water-chemistry data.
Salt Spring's mapped groundwater is divided among several bedrock aquifers — a mix of fractured sedimentary and fractured crystalline rock — covering the north, the central Ganges area, and the south. The Province rates every one of them High vulnerability and Low productivity. Three smaller sand-and-gravel aquifers at Ganges Harbour, Fulford Harbour and Walker Hook are rated Moderate vulnerability and cover only a fraction of the island's lots.
Salt Spring's bedrock aquifers carry a 2018 mapping year and the harbour aquifers 2019 — among the most recently reviewed classifications in the Trust area. The Province's newer aquifer records do not carry the older demand rating, so that field is blank here rather than guessed at.
Salt Spring has more lots, more people and more registered wells than any other island in this network, drawing on rock the Province rates as offering little natural protection from surface contamination. Its water-quality monitoring footprint — wells with provincial water-chemistry (EMS) data — is correspondingly the largest of any island here.
The Province classifies each mapped aquifer's intrinsic vulnerability — how easily contamination at the surface could reach the water — as Low, Moderate or High, based on factors like depth to water and what covers the aquifer. A High rating means relatively little natural protection between the surface and the water people draw from. It describes susceptibility, not current contamination. Productivity describes how readily the aquifer yields water; demand describes the level of use. These are the Province's classifications, not ours.
Most Gulf and Northern Gulf island aquifers are fractured rock: water sits in cracks in sedimentary or crystalline bedrock rather than in a porous bed of sand and gravel. Fractured-rock aquifers store comparatively little water and move it unevenly, which is why neighbouring wells on the same island can report very different yields, and why the Province rates most of these aquifers Low productivity.
Aquifer boundaries are a toggleable layer on the island map. This page presents provincial data with explanatory context; it makes no claims about individual wells or properties.