Research about Filson Creek, Omaday Lake

USGS2010

The effect of snowmelt on the water quality of Filson Creek and Omaday Lake, northeastern Minnesota

Sulfate concentration and p H were determined in surface water, groundwater, and precipitation samples collected in the Filson Creek watershed to evaluate the sources of sulfate in Filson Creek. During and immediately after snowmelt, sulfate concentrations in Filson Creek increased from about 2 to 14 mg/l. Concurrently, H + ion activity increased from an average of 10 −6.6 to 10 −5.5 . These changes suggest that sulfate acidity is concentrated in the snowpack at snowmelt, which is similar to changes reported in Scandinavia in areas subject to acid precipitation. Mass balance calculations indicate that the sulfate contribution from groundwater during snowmelt was minimal in comparison to that from snow. During base flow, sulfate did not appreciably increase from the headwaters of Filson Creek to the mouth, even though sulfate was as high as 58 mg/l in groundwater discharging to the creek from surficial materials overlying a sulfide-bearing mineralized zone in the lower third of the watershed. Approximately 10.6 kg of sulfate per hectare per year was retained in 1977.

Minnesota↗

USGS1981

Effect of snowmelt on the quality of Filson Creek and Omaday Lake, northeastern Minnesota

Concentrations of major constituents were determined in the surface water, ground water, and precipitation in Filson Creek watershed to evaluate the effects of acid precipitation on surface-water quality during snowmelt. Concentrations of sulfate increased in Filson Creek and Omaday Lake during snowmelt from less than 2 to 12 milligrams per liter in 1977 and from less than 2 to 4 milligrams per liter in 1979. Hydrogen-ion activity increased from 10 -6.5 to 10 -5.0 during snowmelt in 1977 and from 10 -6.5 to 10 -6.0 in 1979. The magnitude of the increases of sulfate and hydrogen-ion concentrations depend on the (1) timing of the snowmelt, (2) concurrent precipitation, and (3) antecedent soil-moisture conditions. Alkalinity and concentrations of total calcium, magnesium, and sodium in the creek during snowmelt reflect the simple dilution of streamflow with more dilute precipitation. The mixing process is defined by hyperbolic curves of concentration versus discharge and can be modeled by use of a mass-balance equation. Concentrations of silica and total potassium in the creek during snowmelt are less than that at base flow because of dilution and uptake by diatoms and plants, respectively. A quality-assurance study was made to determine the accuracy and precision of the turbidimetric, complexometric (methylthymol blue), and ion-chromatographic methods used to determine concentrations of sulfate in water. Results suggest that the ion-chromatographic method is more accurate and more precise in the detection of sulfate at concentrations of 5 milligrams per liter or less. To obtain accuracy with either the turbidimetric or the complexometric methylthymol blue method, color blanks and turbidity should be determined if concentrations of sulfate are expected to be low, such as in precipitation, or where water is colored by organic material. Interference by color and turbidity is not a factor in the ion-chromatographic method.

Minnesota↗