Groundwater is a hidden, often forgotten resource, yet it meets about half of the total water needs of areas not served by the North Shore reservoirs. Groundwater is supplied from over 10 000 wells in the Fraser Valley. Most of these are small household wells, but some high-yield wells support large communities and industries. Groundwater quality in many areas has been degraded by fertilizers, pesticides, septic field effluent, farm animal waste, and industrial chemicals. This carelessness results, perhaps, from the attitude "out of sight, out of mind".
Groundwater in the Vancouver area occurs in two main types of materials - modern and Ice Age sands and gravels, and fractured bedrock. The water is stored in pores between grains in sediments and in fractures in bedrock.