Upper Welland River Watershed Plan - Niagara Peninsula ...

UPPER WELLAND RIVER WATERSHED PLANthreats that may affect the recharge of an aquifer”. As described earlier, recharge areasare classified as „significant‟ when they supply more water to an aquifer used as adrinking water source that the surrounding area. Once SGRA‟s are delineated, they arefurther subdivided by areas of groundwater vulnerability (NPCA 2010c).Figure 16 illustrates areas with high, medium and low groundwater vulnerability. TheUpper Welland River watershed has been delineated as having predominately lowgroundwater vulnerability due to the thick deposits of clay and silt of the Haldimand ClayPlain. This material restricts the downward movement of infiltrating surface water,making the underlying groundwater much less susceptible to associated contamination(WHI 2005). However, the Dunnville Sand Plain and areas along the Niagara FallsMoraine in the headwaters have been delineated as Highly Vulnerable Aquifers (HVA)through the NPCA Groundwater Study and the Assessment Report and therefore have ahigh groundwater vulnerability due to the high permeability of the overburden with little tono low conductivity layers overlying the aquifer. Under The Clean Water Act-OntarioRegulation 187/07 an HVA is defined as “an aquifer on which external sources have orare likely to have a significant adverse effect, and includes the land above the aquifer”.Highly Vulnerable Aquifers are illustrated in red on Figure 16.Areas of medium groundwater vulnerability are found in the central portion of the studyarea. These areas typically coincide with areas where the overburden is less than 20meters in thickness. These areas are illustrated in orange on Figure 16.56