Geology topics
Research about Iowa
Source-linked reports with geographic coverage including Iowa.
Effects of climatic variations over 11 years on nitrate-nitrogen concentrations in the Raccoon River, Iowa
Nitrate-nitrogen (NO3-N) concentrations at public water supply intakes on the Des Moines and Raccoon Rivers in Iowa exceeded the maximum contaminant level (MCL) of 10 mg L-1 for public water supplies established by the USEPA for extended periods of time from March through early August 1990. The excessive NO3-N levels followed 2 yr of less-than normal precipitation in 1988 and 1989. The largest daily NO3-N load (771 t) transported during the last 17 yr in the Raccoon River occurred in June 1990. The streamflow hydrograph for the Raccoon River for March 1990 prior to seasonal fertilizer application indicates that high NO3-N concentrations characterize the recession side of the hydrograph. High NO3-N concentrations in streamflow persisted as streamflow decreased to baseflow conditions. This implies that substantial quantities of NO3-N were being leached from the soil and transported by subsurface flow during early 1990. A multiple linear-regression model was developed to predict NO3-N concentrations in the Raccoon River from readily-obtainable streamflow and climatic data. The four-variable model explained about 70% of the variability in the concentration of NO3-N. The mean streamflow for the previous 7-d period accounted for about 50% of the total variability.
Agricultural chemical interchange between ground water and surface water, Cedar River basin, Iowa and Minnesota: A study description
A review of the data collected in the Cedar River basin, Iowa and Minnesota, indicates that atrazine is consistently detected in the main-stem river at concentrations greater than 0.10 microgram per liter even during periods of extended base flow. The primary source of atrazine in the river during these periods of base flow is not known. This study is designed to determine how atrazine and other agricultural chemicals move between ground water and surface water in an alluvial aquifer adjacent to a river. A site has been selected in an unfarmed area adjacent to the Cedar River near Bertram, Iowa, to determine how the concentrations of agricultural chemicals in the alluvial aquifer change as a result of bank storage of surface water. Research also is planned to determine the contribution of agricultural chemicals discharged by the alluvial aquifer into the river during base flow.
Estimating design-flood discharges for streams in Iowa using drainage-basin and channel-geometry characteristics
Drainage-basin and channel-geometry multiple-regression equations are presented for estimating design-flood discharges having recurrence intervals of 2, 5, 10, 25, 50, and 100 years at stream sites on rural, unregulated streams in Iowa. Design-flood discharge estimates determined by Pearson Type-Ill analyses using data collected through the 1990 water year are reported for the 188 streamflow-gaging stations used in either the drainage-basin or channel-geometry regression analyses. Ordinary least-squares multiple-regression techniques were used to identify selected drainage-basin and channel-geometry characteristics and to delineate two channel-geometry regions. Weighted least-squares multiple-regression techniques, which account for differences in the variance of flows at different gaging stations and for variable lengths in station records, were used to estimate the regression parameters. Statewide drainage-basin equations were developed from analyses of 164 streamflow-gaging stations. Drainage-basin characteristics were quantified using a geographic-informationsystem procedure to process topographic maps and digital cartographic data. The significant characteristics identified for the drainage-basin ^equations included contributing drainage area, relative relief, drainage frequency, and 2-year, 24-hour precipitation intensity. The average standard errors of prediction for the drainagebasin equations ranged from 38.6 to 50.2 percent. The geographic-information-system procedure expanded the capability to quantitatively relate drainage-basin characteristics to the magnitude and frequency of floods for stream sites in Iowa and provides a flood-estimation method that is independent of hydrologic regionalization. Statewide and regional channel-geometry regression equations were developed from analyses of 157 streamflow-gaging stations. Channel-geometry characteristics were measured onsite and on topographic maps. Statewide and regional channel-geometry regression equations that are dependent on whether a stream has been channelized were developed on the basis of bankfull and active-channel characteristics. The significant channel-geometry characteristics identified for the statewide and regional regression equations included bankfull width and bankfull depth for natural channels unaffected by channelization, and active-channel width for stabilized channels affected by channelization. The average standard errors of prediction ranged from 41.0 to 68.4 percent for the statewide channel-geometry equations and from 30.3 to 70.0 percent for the regional channel-geometry equations. Procedures provided for applying the drainage-basin and channel-geometry regression equations depend on whether the design-flood discharge estimate is for a site on an ungaged stream, an ungaged site on a gaged stream, or a gaged site. When both a drainage-basin and a channel-geometry regression-equation estimate are available for a stream site, a procedure is presented for determining a weighted average of the two flood estimates. The drainage-basin regression equations are applicable to unregulated rural drainage areas less than 1,060 square miles, and the channel-geometry regression equations are applicable to unregulated rural streams in Iowa with stabilized channels.
Water quality of Corydon Reservoir before implementation of agricultural best-management practices in the basin, Wayne County, Iowa, September 1990 to September 1991
A hydrologic investigation to define the water quality of Corydon Reservoir before implementation of agricultural best-management practices in the basin was conducted from September 1990 to September 1991. Runoff from the 1,680-acre basin is the primary source of water to the 58-acre reservoir. Current water quality of the reservoir is affected substantially by runoff from the agricultural basin. Total-solids, total-nitrogen, and total-phosphorus concentrations were largest during April through July 1991, the months of greatest rainfall. Herbicide concentrations increased substantially in June after application. The concentration of the sum of all triazines was greater than 50 micrograms per liter in one sample, with the predominant herbicides being atrazine and cyanazine. Atrazine concentrations, estimated from immunoassay, were greater than 8.0 micrograms per liter from June through September 1991 as a result of reservoir storage. Atrazine concentrations commonly were less at the surface than at depth. Algal populations remained constant even though nutrient concen- trations increased during the summer months. This may be due to the presence of suspended sediment that reduces light penetration and herbicides that inhibit photosynthesis.
Scour at a bridge over the Weldon River, Iowa
Contraction scour at the State Highway 2 bridge over the Weldon River in south-central Iowa was caused by a flood of record proportions on September 14 and 15, 1992. The peak discharge was 1, 930 cubic meters per second,which was 4 times the probable 100-year flood used to design the bridge, and resulted in road overflow. Contraction scour exposed the pier footings, but a subsurface layer of glacial clay apparently resisted additional vertical scour and caused the scouring process to move laterally. The embankment at the left abutment was eroded away, exposing 3 m of vertical abutment piling.
Preliminary results of the U.S. Geological Survey-Iowa Department of Natural Resources Geological Survey Bureau Manson Core Drilling Project
The U.S. Geological Survey and Iowa Department of Natural Resources Geological Survey Bureau completed, in 1992, a two-year core drilling program in the Manson Impact Structure, a 35-km-diameter, Cretaceous-Tertiary boundary-age feature located in north-central Iowa. A total of 12 cores sampled in excess of 1,200 m (4,000 ft) of crater rocks, supplementing the two previously drilled shallow cores from the structure. The cores penetrated the three major terranes in the Manson Impact Structure, the terrace terrane, crater moat, and central peak. Preliminary interpretations identified several important impact-related lithologies in these cores. The most widespread is sedimentary clast breccia, a postimpact polymictic breccia or mixtite that mantles at least part of all crater terranes. Two types of crystalline clast breccias were cored on the central peak, one with a melt matrix, the other with a matrix dominated by silt- to sand-sized grains. Large blocks of basement gneiss that formed the interior of the central peak were encountered in several cores. Within the terrace terrane, structurally preserved Cretaceous strata and an overturned ejecta flap of Proterozoic and Paleozoic sedimentary rocks were encountered. Only sedimentary clast breccia was encountered in the crater moat. The preliminary investigation of these cores has provided significant information on the geometry and history of the Manson Impact Structure, but it has also prompted many more questions.
A summary of water-resources activities of the U.S. Geological Survey in Iowa, fiscal year 1992
Water-resources activities of the U.S. Geological Survey in Iowa consist of collecting hydrologic data and conducting interpretive studies. Hydrologic investigations in Iowa are made through three basic types of projects: (1) hydrologic data-collection programs; (2) local or areal studies; and (3) statewide or regional investigations. These projects are funded through cooperative joint-funding agreements with Federal, State, and local agencies and direct Federal funds. The data and the results of the interpretive studies are published or released by either the U.S. Geological Survey or by cooperating agencies. This report describes: (1) the hydrologic data-collection programs; (2) the local or areal hydrologic investigations; and (3) statewide or regional studies conducted by the U.S. Geological Survey in Iowa during fiscal year 1992 and provides a list of selected water-resources references for Iowa.
The ground-water-level monitoring network in Iowa
The ground-water-level monitoring network in Iowa consists of 202 wells completed in the principal bedrock and surficial aquifers that supply ground water to numerous users throughout the State. The bedrock aquifers include the Cambrian-Ordovician aquifer system, the Silurian-Devonian aquifer, the Mississippian aquifer, localized Pennsylvanian aquifers, and the Dakota aquifer. The surficial aquifers can be divided into three types: (1) buried channel, (2) alluvial, and (3) glacial drift. Information about the location, date of construction, and depth of each well, and the year water-level measurements began are provided for wells completed in each aquifer. The objectives of the ground-water-level monitoring network in Iowa are to provide the data needed to: (1) determine the change in aquifer storage, (2) document the effects of climatic stress and human activities on discharge and recharge to the principal aquifers, (3) quantify the physical characteristics of ground-water flow including the transmissivity, hydraulic conductivity, and specific capacity of aquifers; and (4) provide historical baseline data for future research. The design of the ground-water-level monitoring network in Iowa that satisfies these objectives includes three types of data: (1) hydrologic data, (2) water-management data for use by State and local officials, and (3) baseline data.
Hydrologic data for a study of pre-Illinoian glacial till in Linn County, Iowa, water year 1991
Hydrologic data for a study of pre-lllinoian glacial till were collected during the 1991 water year at a site in Linn County, east-central Iowa. A hydrologic-data-collection network, consisting of a meteorological station, 22 observation wells, and a water-quality minimonitor, was installed at the site to investigate the hydraulic properties of the till. Recorders were installed on 12 of the observation wells to continuously monitor water levels. Rainfall at the study site from October 1990 to September 1991 was 17.86 inches. The greatest monthly rainfall (4.07 inches) occurred in March. The smallest monthly rainfall (0.06 and 0.04 inch) occurred in June and July, respectively. The highest water levels measured in 22 observation wells were recorded from March through May 1991. Water levels in three of the deeper wells, completed in the unweathered glacial till, continued to rise from the time the wells were initially installed in November 1989 until they were bailed for water-quality sampling in May 1991. One well had water levels greater than the top of the well casing for most of the period from March to mid-July. Ten unvented, vibrating-wire pressure transducers with internal thermistors were buried in two boreholes at upgradient and downgradient locations to record hydraulic pressure and water temperature at selected depths. A water-quality minimonitor was installed near the top of the water table to monitor temporal changes in ground-water quality. For October 1990 through September 1991, the daily mean water temperatures ranged from 7.3 to 14.9 degrees Celsius, and the daily median pH values ranged from 6.9 to 7.5 standard units. Herbicide concentrations in rainfall ranged from 0.05 to 1.3 micrograms per liter. Herbicides detected in the largest concentrations included alachlor, atrazine, and metolachlor. Metribuzin was the only herbicide detected in ground-water samples at a concentration of 0.10 micrograms per liter in water from one observation well.
Hydrologic data for the Big Spring basin, Clayton County, Iowa, water year 1990
Hydrologic data were collected in the Big Spring basin located in Clayton County, Iowa, during the 1990 water year. The data were collected by the U.S. Geological Survey in cooperation with the Iowa Department of Natural Resources, Geological Survey Bureau, to provide information on variation and movement of agricultural chemicals in the hydrologic cycle in the basin. Precipitation, surface-water, and ground-water data were collected. Rainfall recorded during water year 1990 at a monitoring site on Roberts Creek totaled 43.67 inches. The greatest monthly rainfall (14.45 inches) occurred in August. Calcium and sulfate were the predominant ions in the rain, and the median concentrations of nitrate and ammonia as nitrogen were 0.35 and 0.48 milligrams per liter, respectively. Stream discharge, specific conductance, pH, and water temperature were monitored continuously, and monthly water-quality samples were collected at three sites in the basin. The predominant ions in samples from Roberts Creek at the point where it leaves the basin were calcium, magnesium, and bicarbonate. Nitrite plus nitrate as nitrogen concentrations in 42 samples ranged from less than 0.10 to 18 milligrams per liter. Pesticide concentrations in 34 samples ranged from less than 0.10 to 12 micrograms per liter. Alachlor was detected in 56 percent of the samples; atrazine in 100 percent; cyanazine in 68 percent; and metolachlor in 47 percent. At Big Spring, the ground-water discharge point, the daily mean specific conductance ranged from 378 to 796 microsiemens per centimeter at 25 degrees Celsius, the daily median pH ranged from 6.5 to 7.2, and the daily mean water temperature ranged from 5.5 to 11.5 degrees Celsius. Calcium, magnesium, and bicarbonate generally were the predominant ions in solution. Concentrations of nitrite plus nitrate as nitrogen in 32 samples ranged from 3.4 to 16 milligrams per liter. Alachlor was detected in 22 percent of the samples; atrazine in 100 percent; cyanazine in 44 percent, and metplachlor in 6 percent. The maximum atrazine concentration was 4.5 micrograms per liter. During a low-flow seepage study, May 29 and 30,1990, the measured discharge lost by streams in the basin was 8.56 cubic feet per second, the measured dissolved nitrogen load lost was 0.29 ton per day, and the measured atrazine load lost was 0.028 pound per day. The total measured discharge and total dissolved nitrogen load leaving the basin in streams were 3.63 cubic feet per second and about 0.04 ton per day, respectively.
Floods of 1986 and 1990 in the Raccoon River basin, west-central Iowa
Explore the source record for details and available documents.
Water resources data, Iowa, water year 1991
Water resources data for the 1991 water year for Iowa consist of records of stage discharge,and water quality of streams; stage, contents, and water quality of lakes and reservoirs; ground water levels and water quality of ground-water wells. This report contains records of water discharge for 118 stream-gaging stations; stage or contents for 9 lakes and reservoirs; water quality for 6 stream-gaging stations; sediment records for 11 stream-gaging stations; water levels for 213 observation wells; and chemical analyses for 233 municipal wells. Also included are 124 crest-stage partial-record stations. Additional water data were collected at various sites, not part of the systematic data-collection program, and are published as miscellaneous discharge measurements and miscellaneous water-quality analyses.
Water resources data, Iowa, water year 1992
Explore the source record for details and available documents.
Time of travel and dispersion in a selected reach of Roberts Creek, Clayton County, Iowa
Time of travel and dispersion were determined in a 9.4-river-mile reach of Roberts Creek in northwestern Clayton County, Iowa, in the spring of 1990. Time of travel was determined so that a discrete parcel of water could be sampled through the study area during medium to low streamflow conditions. Dispersion characteristics were determined to identify solute-transport differences under two streamflow conditions. Time of travel was determined by dye tracing, using rhodamine WT as the tracer. One dyeinjection site and three sampling sites were used to measure time of travel. Two dye-tracing tests were conducted at discharges having flow-duration values of 48 and 80 percent. The discharges at the time of the two dye-tracing tests approximated medium- and low-flow conditions. The average stream velocity in the study area was 0.23 foot per second during medium-flow conditions, March 20 to 22,1990, and 0.07 foot per second during low-flow conditions, April 30 to May 12, 1990. The injected dye dispersed in a plume that lasted about 18 hours during medium flow and about 64 hours during low flow at the downstream site.
Availability and quality of water from the alluvial, glacial-drift, and Dakota aquifers and water use in southwest Iowa
A ground-water resources investigation was conducted in southwest Iowa to describe the availability, quality, and use of water from the alluvial, glacial-drift, and Dakota aquifers in a nine-county area. Historical water quality was examined for each aquifer, and water samples were collected for major ions, trace metals, radionuclides, and selected pesticides. Selected aspects of surface-water resources in the study area also were examined to more fully evaluate alluvial aquifers. The flood plain of the Missouri River valley was not included except for the accounting of the water use in the area. Four principal alluvial aquifers consisting of sand and gravel deposits in the valleys of the Nishnabotna, Tarkio, Nodaway, and One Hundred and Two Rivers are present. Yields to wells have been reported as large as 2,000 gallons per minute; however, most yields are less than 100 gallons per minute. Nitrate concentrations greater than the drinking-water regulation and agricultural herbicides have been detected in 6 of 27 samples from municipal water supplies. Four types of glacial-drift aquifers are present-loess, inter-till sand and gravel, basal sand and gravel, and buried-channel aquifers. The glacial-drift aquifers are most commonly used by rural water users or users that do not have access to alluvial aquifers. These aquifers are discontinuous and unpredictable in location. Hydraulic and water-quality data generally are unavailable for these aquifers. Wells completed in loess commonly yield less than 10 gallons per minute, although there are reports of yields as large as 20 gallons per minute. Yields of 10 to 120 gallons per minute appear to be possible for inter-till and basal sand and gravel aquifers. Yields of more than 150 gallons per minute are possible from some buried-channel aquifers. The Dakota aquifer is comprised of bedrock of Cretaceous age and is present as erosional remnants and outliers in several counties, mainly Cass and Montgomery. Yields of more than 150 gallons per minute to wells completed in the Dakota aquifer have been reported, although yields of 20 gallons per minute or less are more typical. The drinking-water regulation for nitrate has been exceeded in some samples from the Dakota aquifer. The quantity of water withdrawn for municipal, rural-domestic, livestock, and other permitted water users was determined for each of the three principal aquifer types. The total water use within the study area was about 91.8 million gallons per day; 35.3 percent was from alluvial ground-water sources. Alluvial aquifers supplied most of the water from ground-water sources. The largest use of water is for permitted irrigation purposes, mostly from the Missouri River alluvial aquifer.