Nitrate and Pesticides in Surficial Aquifers and Trophic State and PhosphorusSources for Selected Lakes, Eastern Otter Tail County, West-Central Minnesota, 1993-96

摘要

The purpose of this report is to describe the susceptibility of surficialaquifers to contamination by nitrate and pesticides and of selected lakes to enrichment of phosphorus in the eastern two-thirds of Otter Tail County of west-central Minnesota. The analysis of the aquifers addressed: (1) the areal distribution, temporal variation, and sources of nitrate; (2) factors that affect nitrate concentration; and (3) the areal distribution of pesticides. The analysis of the lakes addressed: (1) the trophic state of Little Pine, Big Pine, Rush and Otter Tail Lakes; and (2) sources of phosphorus in Little Pine and Big Pine Lakes. Data collected from 1993 to 1996 included: (1) concentrations of nitrogen and phosphorus species, chloride, and triazine herbicides in water from 73 wells completed in the surficial aquifers; (2) concentrations of about 80 pesticides in water from 25 of these wells; (3) concentrations of nitrogen and phosphorus species, chlorophyll a and b, and triazine herbicides in water from 17 sites on Little Pine, Big Pine, Rush, and Otter Tail Lakes; and (4) concentrations of phosphorus species in stream water and discharge and stage at streamflow gaging stations on the Toad and Otter Tail Rivers near two inlets and one outlet for Big Pine Lake.