Field Measurements on Side Arms of Lake Anna, Va.

Abstract

An extensive set of velocity and temperature measurements has been collected on two side arms of Lake Anna, a cooling lake in Virginia. The data are consistent with the basic pattern of two layer exchange flow postulated in several mathematical models of side arm circulation. Analysis suggests that circulation is controlled in large part by inertial resistance and head loss caused by constrictions which are formed by highway bridge abutments located near the entrances of each side arm. In addition to the entrance constrictions, flow is further complicated by irregular shorelines and bathymetry within the side arm and by transient forcing, including seasonal stratification, in the main lake outside the side arm. Data suggest that heat loss in the two side arms is about half of that expected for similar side arms without constriction.