Many municipalities rely on wells to supply drinking water to their residents. Wells of all types, municipal and private, urban and rural, pump water from under the ground. A wellhead is simply the physical structure of the well above ground. A wellhead protection area (WHPA) is the area around the wellhead where land use activities have the potential to affect the quality of water that flows into the well. The amount of land involved in a wellhead protection area is determined by a variety of factors such as the way the land rises or falls, the amount of water being pumped, the type of aquifer, the type of soil surrounding the well, and the direction and speed that groundwater travels. All of these factors help to determine how long it takes water to move underground to the well itself and how much land around the wellhead should be protected.
The wellhead protection areas are as follows:
- WHPA‐A: The area within a 100‐metre radius from a wellhead, considered the most vulnerable area for groundwater intakes.
- WHPA‐B: The area within which the time of travel to the well (within the aquifer) is up to and including 2 years (excluding WHPA‐A).
- WHPA‐C: The area within which the time of travel to the well (within the aquifer) is up to and including 5 years (excluding WHPA‐A and WHPA‐B).
- WHPA‐D: The area within which the time of travel to the well (within the aquifer) is up to and including 25 years (excluding WHPA‐A, WHPA‐B, and WHPA‐C).
- WHPA‐E: This area is only delineated where a well is influenced by surface water. It is delineated the same way as the IPZ‐2 for a surface water intake from the best known point of interaction between the aquifer and the surface water body.