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→Wellhead Protection Areas (WHPAs)
# '''WHPA-C''' – the zone through which it takes groundwater to travel between five and two years
# '''WHPA-C''' – the zone through which it takes groundwater to travel between five and two years
# '''WHPA-D''' – the zone through which it takes groundwater to travel between 25 and five years
# '''WHPA-D''' – the zone through which it takes groundwater to travel between 25 and five years
# '''WHPA-E''' – the area on ground surface through which surface water flows in two hours to a point close to the well. This wellhead protection area is only delineated when studies have shown that surface water can relatively easily seep through the soil and impact the quality of the water at the well. This situation is known as groundwater under the direct influence of surface water, or a GUDI well<br>(Halton-Hamilton Source Protection Region, 2010;<ref>Halton-Hamilton Source Protection Region. 2010. Wellhead Protection Areas (WHPAs). Planning Process - Vulnerable Areas. Accessed 02 June 2022. http://protectingwater.ca/planning.cfm?smocid=1440&parentcatid=841#:~:text=A%20wellhead%20protection%20area%20(WHPA,both%20domestic%20and%20municipals%20wells.</ref>CTC SPR, 2019<ref name="example2" />)}}
# '''WHPA-E''' – the area on ground surface through which surface water flows in two hours to a point close to the well. This wellhead protection area is only delineated when studies have shown that surface water can relatively easily seep through the soil and impact the quality of the water at the well. This situation is known as groundwater under the direct influence of surface water, or a GUDI well<br>(Halton-Hamilton Source Protection Region, 2010;<ref name="example3">Halton-Hamilton Source Protection Region. 2010. Wellhead Protection Areas (WHPAs). Planning Process - Vulnerable Areas. Accessed 02 June 2022. http://protectingwater.ca/planning.cfm?smocid=1440&parentcatid=841#:~:text=A%20wellhead%20protection%20area%20(WHPA,both%20domestic%20and%20municipals%20wells.</ref>CTC SPR, 2019<ref name="example2" />)}}
'''Vulnerability'''
As mentioned, WHPAs identify an area on the surface that reflects a zone within the underlying aquifer below where groundwater flows to a well. That said, this area is generally not equal to the total contributing water area that drains towards the well over a given duration of time. This contributing area is the location seen on the surface where water can infiltrate into the soil and still reach the well far away. Due to its distance there may be more urbanization within this expanded area and other contributing contaminants that can pollute the groundwater as it flows to the well. This area generally requires the most protection by the associated SPR/SPA, associated Conservation Authorities located within the area and subsequent municipalities as it is the area/zone most prone to surface contamination (Halton-Hamilton Source Protection Region, 2010<ref name="example3" />).
Vulnerability for source water is simply calculated by:
# Determining the amount of time it takes for water to travel through the "unsaturated zone" above the water table; and,
# Adding that number to the modelled time it takes for groundwater to flow from the water table to the well based on the WHPA zone.
As a result, these surface to well duration periods are categorized as "low" for over 25 years, "medium" for 5 - 25 years, and "high" for 0 - 5 years. These surface to well advection times are categorized as low for over 25 years, medium for 5 to 25 years, and high for 0 to 5 years of travel. The mapped groundwater vulnerability areas are overlain on the wellhead protection areas A through D in order to assign vulnerability scoring between 2 (lowest vulnerability) and 10 (highest vulnerability).
The location within the wellhead protection areas and its vulnerability score are used to assign significance to identified or potential activities that have been deemed threats to the drinking water sources. This topic is discussed in more detail on the Drinking Water Threats webpage.
====Intake Protection Zones (IPZs)====
====Intake Protection Zones (IPZs)====