THE INFLUENCE OF IMPOUNDMENT RELEASES ON RIVER WATER TEMPERATURE AND THE IMPLICATIONS FOR AQUATIC HABITATS

The Musconetcong River in northern New Jersey has been recognized by state and federal agencies as an important water resource for recreation, wildlife habitat, and water quality. Recent dam removal efforts have increased the river’s habitat connectivity and highlighted the potential for its use by migratory fish species. However, the river begins at the outflow of Lake Hopatcong, a lake managed mostly for recreation and aesthetic uses. The lake’s management and subsequent control of its outflow has drastic effects on the water quality of the upper stretch of the Musconetcong, particularly the temperature of the river water. Temperature can be an important limiting factor for the quality of aquatic habitats, especially for temperature-sensitive species such as trout. Water temperature sensors were deployed during the summers of 2011, 2012, and 2013 at various locations downstream of the lake outflow to determine the water temperature at the beginning of the river and determine how the temperature changes spatially. Recorded air temperatures and river water temperatures have a strong positive correlation, while lake discharge and water temperature are negatively correlated. During periods of low discharge, air temperature has a greater influence over water temperature than at higher discharge. Additional discharge may lower the river water temperature, but Lake Hopatcong management is not required to take river water temperature into account. Also, there were long stretches when the recorded river water temperature exceeded the regulatory standard for trout waters. More adaptive and creative lake management combined with in-stream modifications such as the introduction of large woody debris may increase the quality of the habitat along this stretch of the Musconetcong River.