Thermal Mediation by Littoral Wetlands and Impact on Lake Intrusion Depth

Abstract

Lake inflow dynamics can be affected by the thermal mediation provided by shallow littoral regions such as wetlands. In this study, wetland thermal mediation is evaluated using a linearized dead-zone model. Its impact on lake inflow dynamics is then assessed by applying the model sequentially to the river reach, wetland, and lake. Our results suggest that littoral wetlands can dramatically alter the inflow dynamics of reservoirs located in small or forested watersheds, for example, by raising the temperature of the inflow during the summer and creating surface intrusions when a plunging inflow would otherwise exist. Consequently, river-borne nutrients, contaminants, and pathogens enter directly into the epilimnion, where they enhance eutrophication and the risk of human exposure. The addition of a littoral wetland has less significant effects in larger watersheds, where the water has already equilibrated with the atmosphere upon reaching the wetland and sun shading is less prominent.