ALSC Lake Classification System

Adirondack lakes fall into two major groups: seepage lakes and drainage lakes. Drainage lakes have an outlet, while seepage lakes do not. Both lake types receive water from various sources including surface runoff, groundwater, and direct precipitation, although in different relative amounts. Drainage lakes receive a higher proportion of water from surface runoff, whereas seepage lakes receive water primarily from direct precipitation and groundwater. Mounded seepage lakes are perched above the water table and receive most of their water input from direct precipitation Because of that, they are potentially good indicators of change in atmospheric deposition.

The lake selection process for the Long-Term Monitoring project was based on the results of earlier ALSC studies (1984-1988) and a lake classification system developed by Newton and Driscoll (1990). The seven major categories include; mounded and flow through seepage lakes; thin, medium, and thick till drainage lakes; carbonate influenced lakes; and salt impacted lakes. Salt impacted lakes, which typically are found near major roadways, were not considered for inclusion in the LTM study. The focus of the LTM project is on lakes that fall into the thin till, mounded seepage, medium till categories. These categories contain most of the lakes that are of interest for long-term monitoring because they represent the majority of lakes that are acidic (pH 5.0 or ANC < 0.0µeq/L) lakes and lakes potentially vulnerable to episodic acidification (ANC < 40.0µeq/L).

ALTM Lake Class Table
Lake Class Diagram

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