EXCHANGE FLOW IN A SHALLOW LAKE EMBAYMENT

Convectively driven currents can arise in the littoral zones of lakes, as a result of either differential heating or differential cooling of the shallow water. The result of these flows is to produce a surface flow away from shore with a bottom return flow or a bottom flow away from shore with a surface return flow. Measurements taken in a shallow embayment of Clear Lake, California, USA, show the presence of both kinds of convectively driven flows under a large variety of summer conditions. The magnitude of these flows is sufficient to transport material a distance on the order of 0.5 km during such events. Through both advection and dispersion the net result of this process would be to reduce the accumulation of particles and particle-associated contaminants such as mercury in the littoral zone and to move them offshore where they are more prone to permanent burial or further transport.