Harwich Water Department Water Quality

Understanding the Monomoy Lens

Where does the water come from?

Groundwater of the Monomoy Lens is replenished or recharged from rain and snow that percolate down through the ground. Approximately 60 million gallons per day slowly pass through the aquifer, as pictured above, and are ultimately discharged to the surrounding marine waters. The map below shows how different portions of the aquifer discharge to specific marine embayments. In this respect, groundwater in the aquifer is always moving, keeping a balance of recharge and discharge. Groundwater moves from areas of higher elevation to lower elevation at a fairly slow rate of one foot per day. Flow from the middle of the lens to the shore --a distance of 10,000 feet-takes 10,000 days, or nearly 30 years. This is an extremely long time for the aquifer to flush itself. So contaminants that are introduced to the lens degrade water quality and can ruin our drinking water for generations.

What is a recharge area?

The map above shows the major water resources of the Monomoy Lens and their recharge areas. A recharge area is the portion of the aquifer that contributes groundwater flow to wells, ponds or coastal embayments. The recharge area to a well is commonly called a wellhead protection area or Zone II.