National Lakes Assessment 2012 Water chemistry, lake morphometry, and watershed characteristics of Minnesota's 2012 NLA lakes

Minnesota's 2012 National Lakes Assessment (NLA) effort was led by the Minnesota Pollution Control Agency (MPCA) and Minnesota Department of Natural Resources (MDNR). Numerous other collaborators included the U.S. Forest Service (USFS), Minnesota Department of Agriculture (MDA), and U.S. Geological Survey. USFS staff assisted with the sampling of remote lakes in the Boundary Waters Canoe Area Wilderness (BWCAW) and the National Park Service assisted in Voyageurs National Park. The Red Lake Band of the Chippewa and White Earth Band of the Ojibwe provided valuable assistance for lakes that were located on their reservations. Minnesota received 42 lakes as a part of the original draw of lakes for the national survey and added 8 to allow for state-based assessment. All 50 lakes were sampled in accordance with the national (EPA) protocols, including nearshore habitat assessments. Minnesota added 100 more lakes to the survey to yield 50 lakes per aggregated Level 3 ecoregion (Northern Forests [NF], Eastern Temperate Forests [ETF], and Great Plains [GP]). These lakes were sampled for water chemistry, biology, and physical measurements at the index site, in accordance with national protocols. Summer 2012 drought led to a large number of lakes being dropped from the survey because they were dry or too shallow (<1m water depth). Small lakes were most affected. When lakes were dropped, replacements were made from the randomized list provided by U.S. Environmental Protection Agency (EPA). In some instances, nearby replacements were used to ensure good spatial coverage across each ecoregion. The GP ecoregion was most affected and replacements resulted in one lake being sampled twice and thus only 49 lakes were available in the final tally for that region.