Flows in most tributaries dwindled to a trickle or dried up altogether. On the mainstem Ipswich, the effects of low flows are most obvious in reaches that have a slight slope or gradient. The low flows in these reaches leaves large stretches of streambed exposed, and streamside habitat features such as undercut banks, root masses, aquatic vegetation, and overhanging vegetation are left high and dry, and are not available to support support aquatic life. In low-gradient reaches that are pooled behind riffles, woody debris, or dams, water velocities slow, temperatures increase, and algal blooms are common.
Many fish become concentrated in isolated pools.
Water levels will remain low until substantial rainfalls replenish the watershed. As the dry weather persists, and available habitat in the river stays low, and the remaining aquatic life is increasingly stressed due to high water temperatures, lower levels of dissolved oxygen, dwindling food supplies, and predation. River flow was measured at 2.4 inches deep in a 3-inch wide flume, June 23, 1999. 28 in North Reading, June 17, 1999. Exposed mussel in streambed of Ipswich River downstream of Chestnut Street, North Reading, June 23, 1999.