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Images: 'Seasonal Pump' Moves Water Between Ocean and Aquifers

WHOI Assistant Scientist Ann Mulligan examines a data logger that has been lowered into a well in Waquoit Bay, Mass. The probe measures the conductivity, temperature, and water level in the well.

This schematic shows the hydrologic (water) cycle near the coast. Water precipitates out of and evaporates into the atmosphere. It gets taken up by plants, flows into streams, or infiltrates the ground and recharges aquifers. Underground water flows from inland locations to lakes, streams, or coastal waters. On the seaward side, denser salt water enters sediments and establishes equilibrium with fresh groundwater. Tides and mixing along the freshwater-saltwater interface results in seawater circulation through the sediments.

Ann Mulligan lowers a manual water level meter into a groundwater well near Waquoit Bay. Researchers measure the water level and chemical composition of groundwater to detect whether it is flowing landward or seaward.