What is a Wellhead Protection Area?

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.

Five wellhead protection areas have been designated in terms of proximity to the wellhead as well as the speed with which underground water travels to the wellhead:

  • 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

This is a schematic showing a typical map of a Wellhead Protection Area

Wellhead Schematic Showing Protection Areas

Reasons for Protecting Wellheads

Pollutants can sometimes seep into the ground and contaminate the water in a well. Wellhead protection is a good way to prevent municipal drinking water from becoming polluted because it requires landowners to manage activities that could become potential sources of contamination in the area supplying water to a public well. Much can be done to prevent groundwater contamination. Under the Clean Water Act, 2006, local Source Protection Committees develop plans for protecting municipal well water. They will look at potential sources of groundwater contamination in their area, rank them based on their potential to contaminate groundwater, and then determine the best method of managing land and water uses that pose a significant risk to drinking water. Protecting the area around a well, helps protect a healthy supply of water.

Pollutants from a variety of activities on the land can seep into the ground and move toward a well. Examples of activities that could negatively affect groundwater if not managed properly include:

  • Chemical storage
  • Spreading of sewage treatment sludge
  • Storage and spreading of road salt
  • Animal feedlots
  • Use and spilling of fertilizers and pesticides
  • Accidental spills of hazardous materials
  • Septic systems
  • Underground storage tanks
  • Underground pipelines or sewers
  • Landfills
  • Private and abandoned wells

A big concern is Dense Non-Aqueous Phase Liquids or DNAPLs.  DNAPLs are liquids that are denser than water and are immiscible (do not dissolve) in water.  The term DNAPL is used to describe contaminants in groundwater, surface water and sediments. DNAPLs tend to sink below the water table when spilled in significant quantities and only stop when they reach impermeable bedrock. Their penetration into an aquifer makes them difficult to locate and remediate. DNAPL Information 

You can access the Ministry of the Environment Source Protection Information Atlas here: MOE Source Protection Information Atlas  NOTE: This link takes a while to load because of the volume of data.

You can access the Conservation Authority Drinking Water Source Protection maps here CA Drinking Water Source Protection  Once the map has loaded simply scroll to your area of interest.

Images of the wellhead protection areas in Alnwick/Haldimand, Brighton and Cramahe are available here Wellhead Protection Maps  These maps highlight areas where development must be managed in a careful and controlled fashion.  You can zoom in on the maps to see more detail.

History of Source Water Protection

In May 2000, water contaminated by a deadly strain of E. coli bacteria made its way into the municipal water system of the community of Walkerton, Ontario. Tragically, seven people died and thousands of others became ill from drinking the contaminated water.

In response to recommendations from the Walkerton Inquiry, the Ontario Government introduced the Clean Water Act in October 2006.  This legislation focussed on the protection of rivers, lakes and groundwater that supply municipal drinking water systems.

On January 1st, 2015 the Trent and Ganaraska Source Protection Plans came into effect. These plans have a bearing on land use planning. Municipalities need to tread carefully when approving development in the vicinity of wellheads or sources of drinking water.  Source Water Protection History