HYDROLOGIC CHANGES AT LONG LOST LAKE, WHITE EARTH INDIAN RESERVATION, MINNESOTA

Long Lost Lake, a closed-basin lake in Clearwater County, Minnesota, has risen about 4 meters over the past decade. The rise in water level resulted in flooding of lakeside homes and roads. The purpose of this study was to establish a detailed temporal record of lake levels and to relate this record to ground-water levels and precipitation data. As part of this study, lake levels were recorded continuously from July 2003 through December 2004 and ground-water levels were measured periodically in 5 observation wells near the lake from September 2002 through December 2004. Wetland and pond levels also were measured based on the assumption that they were a visible extension of the ground-water table. The lake altitude generally declined between August 2003 and December 2004. The highest lake altitude was 492.58 meters on August 5, 2003 with a low of 492.11 meters on August 29, 2004. Results of water-level measurements in the observation wells and 14 wetlands and ponds show that ground-water levels were substantially higher on the north side of the lake, providing the hydraulic head necessary for inflow into Long Lost Lake. In contrast, on the south and east sides of the lake, ground-water levels were similar to lake levels. This indicates that the ground-water generally discharges into the north side of the lake and lake water discharges to ground water at the south-southeast side. Results of a lake-temperature survey support the direction of water inflow and outflow. Because of limited field data, aerial photography and a geographic information system were used to construct a historical lake record of changes in the lake level from 1939 to 2001. Lake-level increases during this time period related to increases in precipitation, suggesting a strong link between the two. Results show that lake-level increases in Long Lost Lake appear to primarily be due to natural rather than anthropogenic causes.