The Cape Cod aquifer system is the primary source of freshwater discharge to the nearly 100 embayments and estuaries that dominate the Cape Cod coastline. These coastal embayments are becoming enriched by nutrients from increased land development and population growth throughout Cape Cod. Ground water may flow through kettle ponds and discharge into streams before eventually discharging to coastal areas. Alternatively, ground water can discharge directly to the embayments. In the past, the sources of water to embayments, or the mapped areas through which precipitation recharges the aquifer and discharges to embayments, commonly were delineated independently of one another. This resulted in a physically unrealistic overlap of contributing areas to adjacent embayments.

In this investigation, the contributing areas to the embayments in western Cape Cod, and to the streams and ponds that lie within the contributing areas to these embayments, were determined simultaneously by a regional-scale steady-state, three-dimensional ground-water flow model (MODFLOW) coupled with a particle-tracking algorithm (MODPATH). The ground-water flow model also was used to determine ground-water travel times from the water table to the ponds, streams, and embayments, and the total discharge of ground water to these natural receptors.

Results of this investigation illustrate that understanding the interconnectedness of the flow system and accounting for all of the recharge that eventually discharges to the coast are critical for determining nutrient sources and total loads to coastal areas. An internally consistent, regional analysis of the source of water to the coastal embayments, and to the ponds and streams that lie within these contributing areas, is necessary for the protection of these natural resources.