The Lake Simcoe Protection Plan contains policies requiring that each subwatershed in the Lake Simcoe Watershed undergo a Water Budget and Stress Assessment to understand the water demand and how the watershed will likely respond to future conditions such as land-use change, increases in water demand, and drought. The Plan also calls for the protection of significant groundwater recharge areas that sustain sensitive features such as cold-water streams and wetlands.

The study watersheds included the North Oro, South Oro, and Hawkestone Creeks subwatersheds which drain to Lake Simcoe. These catchments intersect the Oro Moraine, an area of high recharge that provides headwater flow to numerous streams that drain to Lake Simcoe, Minesing Swamp and Georgian Bay. A broader understanding of the hydrology and hydrogeology of the Oro Moraine was necessary to characterize the three subwatersheds and, in particular, understand the movement of groundwater across subwatershed boundaries that could influence groundwater pathways. Accordingly, a fully-integrated surface water/ groundwater model was developed for the entire Oro Moraine region using the open-source U. S. Geological Survey GSFLOW code. The integrated model was developed with a particular focus on the shallow groundwater flow system, headwater streams, and wetlands that form on the flanks of the Oro Moraine. The geology is complex and consists of alternating tills and sand deposits which have been dissected by glacial tunnel channels.

The cross-section shown highlights the predominantly vertical flow through the aquitards and lateral flow through the aquifers underlying the Oro Moraine. The tracks also show the direct linkage between the Oro Moraine and the wetlands on its flanks. It is this direct connection to the groundwater stored in the Oro Moraine helps sustain these features during prolonged drought.

The delineation of ecologically significant groundwater recharge areas (ESGRAs) required establishing the hydraulic connection between natural features and the areas of land that contribute significant recharge to their maintenance. Particle-tracking analyses indicated that both local recharge and regional recharge from the Oro Moraine helped sustain streams and wetlands. Regional recharge from the Oro Moraine dominated in the headwaters of Hawkestone Creek and in the Oro North subwatershed; local recharge dominated in the lower reaches of Hawkestone Creek and in the Oro South subwatershed.