Dangars Lagoon is one of about thirty freshwater lagoons in New England. These lagoons were originally formed by glacial action, then gradual sedimentation over thousands of years. Being located on the top of the Great Divide, they have very limited catchments, and as a result are not always full. Most lagoons have been substantially modified for agriculture, to provide additional grazing land or increased water supply. Although it has been modified, it is one of the few lagoons that retains water most of the time. This makes it a very important link in a chain of wetlands for resident and migrating waterbirds.