St. Olaf Lake is a relatively deep, small lake located 3 miles east of New Richland, MN in Waseca county. The watershed-to-lake ratio is small (2.1:1) with agriculture as the dominant land use. There is a small county park containing a boat ramp, beach, and picnic area on the north shore of the lake and much of the remaining shoreline has been developed for residential properties.
The lake has a fairly abundant and diverse aquatic plant community. It has been infested with the non-native Curly-leaf Pondweed since the mid-20th century. While this species has become integrated into the plant community, it may be contributing to the decreasing trend in water quality observed during recent years.
The fish community of St. Olaf is dominated by Centrachids (Bluegill, Black Crappie, and Largemouth Bass) and Northern Pike. Despite its small size, St. Olaf boasts a high quality population of Northern Pike, with 20% of individuals sampled greater than 30 inches in length during the most recent fisheries survey. A special regulation protecting Northern Pike under 30 inches from harvest has been in place since 1998.
St. Olaf was chosen for the Sentinel Lakes program as a representative of deeper prairie lakes with Centrachid dominated fish communities and significant amounts of aquatic plants.