The Greater Victoria Water Supply Area is dominated by Douglas fir forest, with minor components of western red cedar, western hemlock, white pine, alder, maple, and arbutus. Unlogged stands of forest greater than 140 years old are concentrated on ridge tops, steep slopes and higher elevations. The oldest trees recorded to date are 700 year old Douglas fir on Horton Ridge to the west of Sooke Lake Reservoir. Most of these older forest stands appear to have regenerated after large-scale wildfires. Smaller scale disturbances such as wind throw, root rot, snow press and small fires, create small patches of younger trees in these older forest stands. Wetlands and bedrock outcrops are dotted throughout.
A wide range of wildlife species are found in the Greater Victoria Water Supply Area. Most species are associated with forest communities and favour large contiguous areas of forest. Large mammal species include black bear, cougar, wolves, Roosevelt elk, and Columbia black-tailed deer.
The Greater Victoria Water Supply Area is also home or a breeding place for a number of species at risk such as the northern goshawk, marbled murrelet, western screech owl, northern pygmy owl, ermine, and the Vancouver Island subspecies of the American water shrew.