A hydrogeomorphic and condition classification for Maine, USA, lakes

Abstract

Deeds J, Amirhbahman A, Norton SA, Bacon LC. 2020. A hydrogeomorphic and condition classification for Maine, USA, lakes. Lake Reserv Manage. 36:122–138. The water quality of lakes is influenced by natural landscape features, anthropogenic watershed activities, and local-scale characteristics of lake basins. Lake assessment for water quality standards is enhanced by a lake classification framework that allows for comparison of lakes of similar types and the creation of benchmark water quality values from reference lakes. Conventional lake classifications, such as those based on trophic state alone, commonly do not incorporate the natural features of the landscape or lake-specific characteristics that influence lake condition. We present a hydrogeomorphic (HGM)-based lake classification, tested with linear mixed effects modeling, to determine which natural features of lakes and their watersheds show the greatest influence on lake condition. A priori classification schemes were created for model testing using combinations of various HGM features. Model strength was evaluated based on ability to predict mean lake total phosphorus and specific conductivity values. Aggregated Level IV Ecoregions stratified by 2 categories of maximum lake depth offered the most robust lake classification. We defined condition classes of reference, intermediate, and altered lakes based on the gradient of developed watershed area that is unique to each lake class. This approach to lake classification has implications for any region or study, as HGM variables relevant to the population of lakes of interest may be tested for efficacy in a variety of schemes to suit the goals of the classification.