Surface water evaporation from mine pits in Minnesota.
Adams-JL; Liebfried-RT; Spoden-GJ; Alderdice-L
Achieving land use potential through reclamation: proceedings of the 9th Annual National Meeting of the American Society for Surface Mining and Reclamation, June 14-18, 1992, Duluth, Minnesota. Princeton, WV: American Society for Surface Mining and Reclamation, 1992 Jun; :268-279
Taconite mining on Minnesota's Mesabi Iron Range produces exceptionally large pits, located near major watershed divides. Basic information about how these pits have changed local hydrology is needed for mine land reclamation and impact evaluation of post-mining land-use proposals. Evaporation from mine pits in Minnesota is a major component of a pit's water balance, and is believed to differ from natural lakes because of unique morphology. In a cooperative effort by the U.S. Bureau of Mines and the Minnesota Department of Natural Resources, the evaporation pan coefficient method is being refined for application to mine pits in Minnesota. Two standard Class A evaporation pans were installed, one on land at the study pit, and the other partially immersed in pit water to simulate the pit's energy regime. Pressure transducers and data loggers record average hourly water levels in the pans. Related, on-site meteorological data serves as input for the Modified Penman-Monteith (MPM) method, in an attempt to extrapolate study results to other pits. Limited MPM estimates were consistently lower than in-pit pan measurements. After two open-water seasons, in-pit pan evaporation averages about 600 mm per season, compared to an estimate of 450 mm using published monthly evaporation for lakes and reservoirs in the study area. The average monthly ratio of in-pit to on-land pan evaporation ranges from about 0.6 during May to about 1.7 during October, averaging nearly 1.0 for the season, compared to a published annual coefficient of 0.78 for lakes and reservoirs in the study area. The study will be continued for at least two years.
Hydrology; Mesabi Iron Range; groundwater; mine pit; hydrologic balance
Achieving land use potential through reclamation: proceedings of the 9th Annual National Meeting of the American Society for Surface Mining and Reclamation, June 14-18, 1992, Duluth, Minnesota