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B.D. Schaap

Publications and source records attributed to B.D. Schaap.

4 recordsLinked to original sources
USGS1998

Quality of ground water used for selected municipal water supplies in Iowa, 1982-96 water years

The Iowa ground-water-quality monitoring program has been conducted cooperatively since 1982 by the Iowa Department of Natural Resources, Geological Survey Bureau; the University of Iowa Hygienic Laboratory, and the U.S. Geological Survey. The original objectives of the program were to provide baseline ground-waterquality data throughout the State for the major aquifers and to address any new areas of water-quality concern. Since the program began, the emphasis and objectives of the program have changed several times. For water years 1992 through 1996, more emphasis has been placed on determining trends in ground-water quality and correlating water quality with possible contributing factors such as location, land use, aquifer, aquifer depth, and precipitation. From 1982 through 1996, a total of 2,529 water samples has been collected from 1,158 municipal wells throughout Iowa. The samples consisted of 1,048 alluvial aquifer samples (387 wells), 530 Pleistocene aquifer samples (224 wells), 139 Cretaceous aquifer samples (86 wells), 187 Carboniferous aquifer samples (104 wells), 447 Silurian-Devonian aquifer samples (222 wells), 177 Cambrian-Ordovician aquifer samples (134 wells), and 1 Precambrian aquifer sample (1 well). Some samples had concentrations greater than or equal to drinking-water regulations established by the U.S Environmental Protection Agency. Of 1,901 samples analyzed for dissolved sulfate, 137 samples had concentrations greater than or equal to the Maximum Contaminant Level for sulfate. Of 2,510 samples analyzed for dissolved nitrite plus nitrate as nitrogen, 198 samples had concentrations greater than or equal to the Maximum Contaminant Level for nitrite plus nitrate. Of 1,945 samples analyzed for dissolved iron, 1,022 samples had concentrations greater than or equal to the Secondary Maximum Contaminant Level for iron. Of 1,946 samples analyzed for dissolved manganese, 1,082 samples had concentrations greater than or equal to the Secondary Maximum Contaminant Level for manganese. Of 1,659 samples analyzed for alachlor, atrazine, and cyanazine, 401 samples had concentrations greater than or equal to the respective minimum reporting levels. One sample had concentrations of alachlor, atrazine, and cyanazine greater than the respective drinking-water regulations. Maps show the general location of wells that have been sampled in the various aquifers. Other maps show the location of wells where sulfate and nitrite plus nitrate concentrations exceed the respective Maximum Contaminant Levels and wells where concentrations of the pesticides alachlor, atrazine, or cyanazine exceeded the respective minimum reporting levels. The compact disc included with this report has information about water-quality properties and concentrations of dissolved solids, major ions, nutrients, trace elements, radionuclides, total organic carbon, pesticides, and synthetic organic compounds for water years 1982 through 1996.

Iowa↗
USGS1995

Agricultural chemicals in ground and surface water in a small watershed in Clayton County, Iowa, 1988-91

An investigation was conducted from October 1988 through September 1991 to (1) describe the quality of water in shallow, unconsolidated materials in the 1.09-square-mile Deer Creek watershed in Clayton County, Iowa, and to (2) define the quantity and seasonal distribution of selected agricultural chemicals in water from this watershed. Surficial unconsolidated aquifer materials that discharge water to Deer Creek include alluvium, loess, and glacial till. More than 80 percent of the watershed is used for row and cover crops. Median nitrate concentrations ranged from 16 mg/L (milligrams per liter) in water from the top of the 10-foot thick alluvial aquifer to less than 0.10 mg/L near the bottom. Atrazine was detected in more than 85 percent of the ground-water samples collected at or less than 5.5 feet below land surface. Only one sample collected at 7.0 feet below land surface in the alluvial aquifer had an atrazine concentration greater than the detection limit of 0.10 ug/L (micrograms per liter). Nitrogen and herbicide concentrations were largest in late spring and early summer. Sources of agricultural chemicals in the alluvial aquifer include vertical infiltration through the soil and lateral transport from upslope unconsolidated materials. Nitrogen was present in all water samples from Deer Creek. Nitrate concentrations ranged from 0.70 to 17 mg/L. Alachlor was detected in 11 percent of the samples, atrazine in 69 percent, cyanazine in 19 percent, and metolachlor in 33 percent. Alachlor concentrations ranged from less than 0.10 to 0.53 ug/L, atrazine ranged from less than 0.10 to 55 ug/L, cyanazine ranged from less than 0.10 to 12 ug/L, and metolachlor ranged from less than 0.10 to 69 ug/L. Herbicide detections occurred most frequently in late spring and early summer during or just following chemical application. Overland flow is an important source of nitrogen and herbicides to Deer Creek. Substantial amounts of agricultural chemicals are transported from the watershed. As much as 4,700 pounds, or 6.7 pounds per acre, of nitrogen were estimated to be transported from the watershed in 1 year. Nitrogen loads transported from the Deer Creek watershed were less during dry years than during years with average or greater than average rainfall.

Iowa↗
USGS1994

Selected nutrients in stormwater runoff from Davenport, Iowa, 1992

Flow-weighted composite samples of stormwater runoff from areas of different land use in Davenport, Iowa, were collected in the summer and fall of 1992 and analyzed for selected nutrients. Annual constituent loads were estimated for the area drained by the Davenport storm-sewer network. In all cases, the regression-equation estimate of mean annual load is less than the estimate obtained by using the method of the U.S. Environmental Protection Agency. The largest mean annual loads for total nitrite nitrogen, total nitrate nitrogen, total nitrite and nitrate nitrogen, total organic nitrogen, total ammonia and organic nitrogen, total nitrogen, and total phosphorus are associated with residential land, which covers 67.2 percent of the area drained. Using concentration data from this study, it is estimated that an average storm-producing runoff during the 7-day, 10-year low-flow discharge of the Mississippi River would contribute about 4 percent of the total ammonia and organic nitrogen load in the river. Precipitation-chemistry data indicate that substantial parts of the nitrate nitrogen and ammonia nitrogen contained in the stormwater runoff could be from precipitation.

Iowa↗