Chapter 7 - Lakes and Reservoirs: Physiography

Abstract

This chapter focuses on the physiography of lakes and reservoirs. A variety of processes form lake basins, including tectonic, glacial, fluvial, volcanic, and damming processes. Lake basin morphology is described with various parameters, including mean depth, area, maximum depth, volume, shoreline development (DL), and watershed area relative to lake surface area. Shallow lakes with large watersheds and highly dissected shorelines are generally the most productive. Reservoirs are unique habitats that have characteristics of both streams and lakes. Reservoirs can have profound impacts on upstream and downstream habitats and communities depending upon how they are constructed and managed. Stratification can alter the water circulation in lakes and thus alter biogeochemical, ecosystem, and community properties. Mixing can occur often (polymictic), once a year (monomictic), twice a year (dimictic), or rarely (amictic or meromictic), depending on climate and type of stratification. High concentrations of dissolved substances can also lead to stratified layers in lakes. Movement of wind is generally the main cause of waves across lakes, although motorboat activity can cause significant wave action.