Surface water

The Ipswich River basin covers about 155 mi2 in northeastern Massachusetts. About 74 percent of the basin is forested, and about 10 percent is covered by lakes, ponds, and marshes. There are a total of 75 lakes and ponds, 36 of which are at least 10 acres in area. The largest lake is Putnamville Reservoir in Danvers, which is 270 acres. The Ipswich River begins in wetlands in northern Burlington and follows a meandering, northeasterly course for about 35 mi to its mouth in Plum Island Sound. Much of the course of the river and its tributaries is through wetlands, and stream gradients in the basin are low.

From the river's headwaters area to the USGS streamflow-gaging station near Ipswich, a distance of about 27 river mi, the channel slope of the Ipswich River averages about 2.5 ft/mi.The base flow of the Ipswich River is derived mainly from discharge of water from groundwater and from wetlands. During much of late summer and early fall, when evapotranspiration rates are high, streamflow in the Ipswich River basin is severely affected by groundwater withdrawals. In addition, streamflow is significantly reduced by out-of-basin diversions of surface water and ground water.