Citation:

Handler, A., T. Barnum, J. Compton, M. Dumelle, Rick Greene, A. Neale, Steve Paulsen, A. Rea, B. Schaeffer, AND M. Weber. Mountain Lakes Condition and Threats Across the US. National Water Quality Monitoring Conference, Virginia Beach, VA, April 24 - 28, 2023.

Impact/Purpose:

Mountain lakes are important resources for recreation, drinking water, and aquatic habitat. With the threats of changing climate, air pollution, wildfire, harmful algal blooms, and human development, there is an acute need to assess the trends in mountain lake condition. This presentation for the National Water Quality Monitoring Conference highlights the physical, chemical, and biological condition of mountain lakes across the contiguous US. The analysis leverages the National Lakes Assessment (NLA), Cyanobacteria Assessment Network (CyAN) and Monitoring Trends in Burn Severity (MTBS) program. This project illustrates EPA’s work to provide information about the national condition of waterbodies as well as factors threatening water quality across the country. The conference is attended by scientists and water professionals from federal, state, tribal, nonprofit, and academic organizations. Their knowledge and feedback is invaluable to this analysis that encompasses the many considerations and threats to mountain lakes.

Description:

Mountain lakes are important resources for recreation, drinking water, and aquatic habitat but these lakes are particularly vulnerable to changing climate, air pollution, wildfire, harmful algal blooms, and human development. We investigated the condition of and threats to mountain lakes across the contiguous US by leveraging the National Lakes Assessment (NLA), Cyanobacteria Assessment Network (CyAN) and Monitoring Trends in Burn Severity (MTBS) program. For NLA and MTBS, we divided mountain lakes into alpine (>10,000 ft) and subalpine (6,000-10,000 ft) populations. There are approximately 5,050 alpine lakes and 19,400 subalpine lakes larger than 1 hectare across the conterminous US, and nearly all are in the western US. Based on the NLA surveys of total nitrogen and total phosphorus, more than 90% of alpine lakes and more than 65% of subalpine lakes are in good or fair condition compared to nearly 50% of lower elevation lakes. The cyanobacterial toxin microcystin is present in approximately 5% of alpine and subalpine lakes compared to nearly 30% in lower elevation lakes. The large subalpine lakes that can be assessed by CyAN tended to have lower frequency and smaller spatial extents of cyanobacterial blooms than lower elevation lakes, however; the bloom magnitudes were similar in subalpine and lower elevation lakes. While mountain lakes are generally in better condition than lower elevation lakes, they may be vulnerable to multiple threats including human lakeshore disturbance and wildfire. There is a high degree of lakeshore human disturbance for 10% of alpine lakes and nearly 25% of subalpine lakes. According to MTBS, the cumulative area burned each year in sub-watersheds containing mountain lakes has at least doubled in the last decade compared to the 1980’s. This work helps to identify the factors that may be contributing to poor conditions in specific mountain lakes across the US. The views expressed in this article are those of the authors and do not necessarily represent the views or policies of the U.S. Environmental Protection Agency.

Record Details: