Sentinel Lake Assessment Report Hill Lake (01-0142) Aitkin County, Minnesota

The Minnesota Pollution Control Agency (MPCA) and the Minnesota Department of Natural Resources (MDNR) are working in partnership on the Sustaining Lakes in a Changing Environment (SLICE) Sentinel Lakes Program. The focus of this interdisciplinary effort is to improve understanding of how major drivers of change such as development, agriculture, climate change, and invasive species can affect lake habitats and fish populations, and to develop a long-term strategy to collect the necessary information to detect undesirable changes in Minnesota Lakes (Valley 2009). To increase our ability to predict the consequences of land cover and climate change on lake habitats, SLICE utilizes intensive lake monitoring strategies on a wide range of representative Minnesota lakes. This includes analyzing relevant land over and land use, identifying climate stressors, and monitoring the effects on the lake's habitat and biological communities. The Sentinel Lakes Program has selected 24 lakes for long-term intensive lake monitoring (Figure 1). The "Deep" lakes typically stratify during the summer months only. "Shallow" lakes are defined as mixing continuously throughout the summer. "Cold Water" lakes are defined as lakes that either harbor cisco, lake whitefish, or lake trout or are the focus of research funded by the Environmental Trust Fund. "Super sentinel" lakes also harbor cold-water fish populations and research on these lakes is also funded by the Environmental Trust Fund. Hill Lake was selected to represent a moderately deep, mesotrophic lake in the Northern Lakes and Forests (NLF) ecoregion. Hill Lake is a 315 hectare (780 acre lake), located within Hill City, Minnesota in Aitkin County, within the Mississippi River (Grand Rapids) major watershed. Hill Lake is divided into two basins by State Highway 210. The north basin (NB) is 265 hectares (656 acres) with a maximum depth of 14.6 meters (48 feet) and a mean depth of 7.4 meters (24.3 feet). The south basin (SB) is 50 hectares (124 acres) with a maximum depth of 7.3 meters (24 feet) and a mean depth of 2.8 meters (9.1 feet). The lake is 39 percent littoral with two public accesses. The total contributing watershed for the NB is 3,703 hectares (9,165 acres). The contributing watershed for the SB is much larger at 10,394 hectares (25,728 acres).