Geology topics

Research about Iowa

Source-linked reports with geographic coverage including Iowa.

At least 325 records · Page 18Linked to original sources

USGS1992

Evaluation of selected methods for determining streamflow during periods of ice effect

Seventeen methods for estimating ice-affected streamflow are evaluated for potential use with the U.S. Geological Survey streamflow-gaging station network. The methods evaluated were identified by written responses from U.S. Geological Survey field offices and by a comprehensive literature search. The methods selected and techniques used for applying the methods are described in this report. The methods are evaluated by comparing estimated results with data collected at three streamflow-gaging stations in Iowa during the winter of 1987-88. Discharge measurements were obtained at 1- to 5-day intervals during the ice-affected periods at the three stations to define an accurate baseline record. Discharge records were compiled for each method based on data available, assuming a 6-week field schedule. The methods are classified into two general categories-subjective and analytical--depending on whether individual judgment is necessary for method application. On the basis of results of the evaluation for the three Iowa stations, two of the subjective methods (discharge ratio and hydrographic-and-climatic comparison) were more accurate than the other subjective methods and approximately as accurate as the best analytical method. Three of the analytical methods (index velocity, adjusted rating curve, and uniform flow) could potentially be used at streamflow-gaging stations, where the need for accurate ice-affected discharge estimates justifies the expense of collecting additional field data. One analytical method (ice-adjustment factor) may be appropriate for use at stations with extremely stable stage-discharge ratings and measuring sections. Further research is needed to refine the analytical methods. The discharge-ratio and multiple-regression methods produce estimates of streamflow for varying ice conditions using information obtained from the existing U.S. Geological Survey streamflow-gaging network.

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USGS1991

Evaluation of wetland development and waterbird response at Elk Creek Wildlife management area, Lake Mills, Iowa, 1961 to 1990

A waterfowl habitat development project along 7.5 miles (12.07 km) of stream was evaluated after 27 years. There was a modest 12% net increase in wetlands in impounded areas, but much of the wetland vegetation changed from seasonally flooded, nonpersistent and persistent emergents to shallow, open-water areas. An unimpounded, downstream reference area had drier plant communities, probably resulting from reduced flooding. The loss of shallow vegetated wetlands could have significant impacts on both water quality functions and waterbird populations. The overall project goal of increasing numbers and diversity of waterfowl was met, but waterfowl numbers and species composition changed more because of transplanting and nest-box programs than habitat modifications. Although impacts on birds of shallow wetlands such as rails and songbirds were not quantitatively assessed, it is likely that the numbers of such birds were reduced because their preferred habitats were reduced markedly. Use of smaller lateral impoundments and increased management for emergents would diversity waterbird populations and increase dabbling duck production. © 1991 Society of Wetland Scientists.

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USGS1991

Hydrologic data for a study of pre-Illinoian glacial till in Linn County, Iowa, water year 1990

Hydrologic data for a study of pre-lllinoian glacial till were collected during the 1990 water year at a site in Linn County, Iowa. A hydrologic-data-collection network, consisting of 22 observation wells and a meteorological station, was installed at the site to describe the hydraulic properties of the till. Recorders were installed on 12 of the wells to continuously monitor water levels. Rainfall at the study site from April to October 1990, totaled 35.49 inches. The greatest monthly rainfall (13.15 inches) occurred in June. The greatest daily rainfall (6.00 inches) occurred on June 16. For the 16 wells less than 50 feet in depth, the highest water levels were recorded during the 4 months of greatest rainfall (May-August 1990). Water levels in the four deepest wens, completed in unconsolidated material, rose throughout the data-collection period. One well had water levels greater than the top of the well casing for most of the period from mid-May to mid-September 1990. A water-quality minimonitor was installed on one observation well near the top of the water table to monitor temporal changes in groundwater quality. For April through September 1990, the daily mean specific conductance ranged from 705 to 864 microsiemens per centimeter at 25 degrees Celsius, the daily mean water temperature ranged from 5.2 to 15.6 degrees Celsius, and the daily median pH remained nearly constant at 7.0 to 7.2 standard units. Ten unvented, vibrating-wire, pressure transducers with internal thermistors were buried in two boreholes at upgradient and downgradient locations to record hydraulic pressure arid water temperature at selected depths.

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USGS1991

Hydrologic data for the Big Spring basin, Clayton County, Iowa; water year 1989

Hydrologic data were collected in the Big Spring Basin located in Clayton County, Iowa, during the 1989 water year. The data were collected 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 Big Spring Basin. Precipitation, stream, and ground-water data were collected. Total rainfall in the basin ranged from 20.0 to 24.4 inches. The greatest monthly rainfall was in August. Calcium and sulfate were the predominant ions in the rain and the median nitrate and ammonia concentrations as nitrogen were 0.40 and 0.63 mg/L (milligrams per liter), respectively. Stream discharge, water temperature, specific conductance, and pH were monitored continuously, and monthly water-quality samples were collected at three sites in the basin. The predominant ions in Roberts Creek, at the site where it leaves the basin, were calcium, magnesium, and bicarbonate. Nitrate plus nitrite as nitrogen concentrations ranged from 0.2 to 6.2 mg/L. Pesticide concentrations in 23 samples ranged from less than 0.10 μ /L (micrograms per liter) to 4.4 μ /L. Atrazine was detected in 100 percent of the samples, cyanazine and metolachlor in 43 percent of the samples and alachlor in 35 percent of the samples. At Big Spring, the ground-water discharge point, the daily mean water temperature ranged from 5.1 to 10.6 degrees Celsius, the daily mean specific conductance ranged from 271 to 793 micro Siemens per centimeter at 25 degrees Celsius, and the daily median pH ranged from 63 to 7.1. Calcium, magnesium, and bicarbonate were the predominant ions in solution. Nitrate plus nitrite as nitrogen concentrations ranged from 2.0 to 7.4 mg/L. Atrazine was detected in 95 percent of the samples, cyanazine was detected in 26 percent of the samples, and metolachlor and alachlor were detected in 16 percent of the samples. The maximum atrazine concentration was 3.3 μ /L. Water levels in the unconsolidated aquifers and the Galena aquifer were highest in the spring after snowmelt and in September after the greatest monthly rainfall. Water levels in the Saint Peter aquifer declined by approximately 0 J to 3.0 feet. During a baseflow seepage study, August 16 and 17, the measured discharge lost by streams in the basin was 2.82 cubic feet per second, the measured dissolved nitrogen load lost was 80 pounds per day, and the measured atrazine load lost was 0.002 pound per day. The total measured discharge and total dissolved nitrogen load leaving the basin in streams was 0.07 cubic feet per second and less than 20 pounds per day, respectively.

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USGS1991

Analysis of the ground-water flow system, geochemistry, and underseepage in the vicinity of the Red Rock Dam near Pella, Iowa

The U.S. Army Corps of Engineers operates the Red Rock Dam on the Des Moines River in Marion County, Iowa. The dam consists of a gravity concrete control structure between two earthen embankments and has an impoundment storage capacity of 1,700,000 acre-feet. Since the impoundment of Lake Red Rock commenced during 1969, water seepage beneath the dam has been significant enough to cause continuing investigation by the Corps of Engineers of its source and implications. The St. Louis Limestone, which consists of interbedded sandstones and carbonates with solution collapse features resulting from partial removal of a basal evaporite zone, forms the bedrock foundation of the dam in the river valley. The soluble gypsum and anhydrite in the evaporite zone have the potential to be removed in greater quantity with increasing seepage velocities and volumes. Solution channels may develop as material is removed from the bedrock foundation, which could result in the collapse of overlying strata, thereby threatening the integrity of the earthen dam. The potentiometric surface in the overburden on the southwest side of the dam has an extremely steep hydraulic gradient from the reservoir through the dam to the downstream observation wells, which implies expected small permeability and minimal seepage through the dam and embankment materials. A lesser hydraulic gradient exists on the northeast side of the dam, which could indicate excessive seepage through embankment material from larger than expected hydraulic conductivity or underseepage through bedrock. Statistical analysis of water-level changes in the reservoir and in observation wells completed in the evaporite stratigraphic horizon on the northeast side of the dam indicates a hydraulic connection between the reservoir and the wells. Direct evidence of the existence of a connection between the reservoir and the ground-water system is provided by chloride concentration data. Maximum chloride concentrations occurred in the reservoir water in the early spring of 1989. Chloride concentrations reached a maximum in ground water from bedrock and overburden observation wells on the northeast side of the dam 1 to 4 months after their maximum in the reservoir. Underseepage of reservoir water occurs through the basal evaporite zone of the St. Louis Limestone and through the glacial sands in the northeast bluff between the bedrock surface and the base of the dam fill. The increased hydraulic head imposed on the system by the impounded waters of Lake Red Rock causes recharge and flow to the deeper bedrock aquifers in the immediate vicinity of the dam. This effect is manifested in the observation wells along and downstream from the dam axis, implying flow through the grout curtain in the bedrock foundation of the dam. There is potential for dissolution of the gypsum and anhydrite in the bedrock foundation, because reservoir water and shallow ground water in the vicinity of the dam are undersaturated with respect to these evaporite minerals.

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USGS1990

Geology, geophysics, and geochronology of the Manson impact structure

A problem with the impact hypothesis for the Cretaceous/Tertiary (K/T) mass extinction is the apparent absence of an identifiable impact site. The Manson impact structure is a candidate site because of its size (the largest such structure recognized in the United States); in addition, the largest and most abundant shocked quartz grains at the K/T boundary are found relatively close by, and its age is indistinguishable from that of the K/T boundary. The region of northwest central Iowa that contains the Manson impact structure is covered by Quaternary glacial deposits, which are underlain by Phanerozoic sedimentary rocks (mostly flat-lying carbonates) and Proterozoic red clastic, metamorphic, volcanic, and plutonic rocks. In a circular area about 22 mi (35 km) in diameter around Manson, Iowa, this normal sequence is absent or “disturbed.” Within the structure, three roughly concentric zones of rock associations have been identified: an outer zone of displaced strata, a zone of completely disrupted strata, and a central area in which basement igneous and metamorphic rocks have been uplifted at least 1,220 ft (4,000 m). Gravity, magnetic, and seismic refraction surveys readily identify the central uplift within the structure. Manson is established as an impact structure based on its circular shape, its central uplift, and the presence of shocked quartz within the granitic central uplift. Paleontological evidence, a fission track age, and preliminary 40 Ar/ 39 Ar dating all allowed a K/T boundary age for the Manson structure. Improved 40 Ar/ 39 Ar age spectra may be interpreted in terms of samples that were incompletely degassed during heating due to the Manson impact. An age of 65.7 ± 1.0 Ma was obtained, a value indistinguishable from that of the K/T boundary.

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USGS1990

Midwestern Holocene paleoenvironments revealed by floodplain deposits in northeastern Iowa

Pollen analysis of pond deposits in the upper reaches of a stream from northeastern Iowa, an area beyond the last glacial margin, provides a nearly complete record of vegetational changes during the last 12.5 thousand years. Sixty-one radiocarbon dates provide good chronological control. Spruce forest was replaced by deciduous forest before 9 1 thousand years ago, followed by prairie from 5.4 to 3.5 thousand years ago, and oak savanna from 3.5 thousand years ago until presettlement times. The prairie invasion was nearly 3 thousand years later here than at other sites in Iowa and Minnesota, documenting a late Holocene, rather than an early-middle Holocene, period of maximum warmth and dryness for the southern part of the upper Midwest.

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USGS1990

Statistical summaries of selected Iowa streamflow data through September 30, 1988

Statistical summaries of streamflow data collected at 144 active and discontinued stream-gaging stations in Iowa through water year 1988 are presented in the report. The summaries for each streamgaging station include: 1) station description, 2) the most recent stage-discharge rating table, 3) statistics of monthly and annual mean discharges, 4) boxplots of monthly and annual mean discharges, 5) monthly and annual flow durations, 6) probabilities of annual high discharges, 7) probabilities of annual low discharges, and 8) probabilities of seasonal low discharges. The minimum period of record at stations included in the report is 10 years. The location of each station is shown on a map of Iowa.

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USGS1990

Evaluation of selected methods for determining streamflow during periods of ice effect

Seventeen methods for estimating ice-affected streamflow are evaluated for potential use for the U.S. Geological Survey streamflow-gaging station network. The methods evaluated were identified by written responses from U.S. Geological Survey field offices and by a comprehensive literature search. The methods selected and techniques used for applying the methods are described in the report. The methods are evaluated by comparing estimated results to data collected at three streamflow-gaging stations in Iowa during the winter of 1987-88. Discharge measurements were obtained at 1- to 5-day intervals during the ice-affected periods at the three stations to define an accurate baseline record. Discharge records were compiled for each method based on data available assuming a 6-week field schedule. The methods are classified into two general categories, subjective and analytical, depending on whether individual judgement is necessary for method application. On the basis of results of the evaluation for the three Iowa stations, two of the subjective methods (discharge ratio and hydrographic-and-climatic comparison) were more accurate than the other subjective methods, and approximately as accurate as the best analytical method. Three of the analytical methods (index velocity, adjusted rating curve, and uniform flow) could potentially be used for streamflow-gaging stations where the need for accurate ice-affected discharge estimates justifies the expense of collecting additional field data. One analytical method (ice adjustment factor) may be appropriate for use for stations with extremely stable stage-discharge ratings and measuring sections. Further research is needed to refine the analytical methods. The discharge ratio and multiple regression methods produce estimates of streamflow for varying ice conditions using information obtained from the existing U.S. Geological Survey streamflow-gaging network.

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USGS1990

A summary of water-resources activities of the U.S. Geological Survey in Iowa; fiscal year 1990

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 hydrologic 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 1990 and provides a list of selected water-resources references for Iowa.

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USGS1990

Water resources data, Iowa, water year 1990

Water resources data for the 1990 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 117 stream-gaging stations; stage or contents for 9 lakes and reservoirs; water quality for 6 stream-gaging stations; sediment records for 10 stream-gaging stations; water levels for 185 observation wells; and chemical analyses for the 248 municipal wells. Also included are 120 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.

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USGS1990

Water quality of alluvial aquifers, Carroll and Guthrie counties, Iowa, with emphasis on the occurrence of nitrate and pesticides, 1986-87

Samples collected from wells in Carroll and Guthrie Counties, Iowa, were analyzed to describe the chemical quality of the ground water in shallow aquifers. The study began in June 1986 with the selection of 20 shallow wells in Carroll County and 22 shallow wells in Guthrie County. These wells were sampled in the summer and fall of 1986 and 1987. Samples from the wells were analyzed for major ions, nutrients, trace elements, radiochemicals, nitrate, and pesticides. Median and mean nitrate concentrations were 95 and 11 milligrams per liter. About 60 percent of the samples had nitrate concentrations greater than 5.0 milligrams per liter. Detectable concentrations of a least one pesticide were in 27 percent of the samples. Atrazine, the most prevalent pesticide, was detected in 25 percent of the samples; alachlor was detected in 6 percent; and cyanazine was detected in 5 percent. Dicamba, metolachlor, trifluralin, and2,4-D were detected in 2 percent or less of the samples. In the summer and fall 1986,43 and 45 percent of the water samples had nitrate concentrations larger than 10 milligrams per liter, the maximum contaminant level for public drinking water specified by the State of Iowa; in the summer and fall 1987,41 and 55 percent of the samples had nitrate concentrations larger than the maximum contaminant level. In the summer and fall 1986,23 and 18 percent of the samples contained detectable concentrations of at least one pesticide; in the summer and fall 1987,21 and 47 percent of the samples contained detectable concentrations of at least one pesticide. Detection frequencies ofatrazine, alachlor, and cyanazine increased for samples collected in October 1987. Pesticides were more frequently detected along Brushy Creek, and the East Nishnabotna, Middle, North Raccoon, and South Raccoon Rivers. However, pesticides also were detected along the Middle Raccoon and West Nishnabotna Rivers. Detection frequencies were greatest (50 percent) for the East Nishnabotna River and Middle River alluvial settings. Increased nitrate concentrations generally were observed in the shallower wells and were larger than those previously reported for shallow municipal wells. Pesticide detection relative to well depth was inconsistent with the trend observed for nitrate. Pesticide detection frequencies were greater for wells that were 40 to 80 feet deep (about 40 percent) than for wells less that 40 feet deep (about 20 percent). Of the water samples with nitrate concentrations greater than or equal to 5.0 milligrams per liter, 33 percent had detectable pesticide concentrations. Conversely, for those samples with detectable pesticide concentrations, 76 percent had nitrate concentrations larger than or equal to 5.0 milligrams per liter and 67 percent were larger than or equal to 10 milligrams per liter. The median concentration of nitrate for samples containing at least one detectable pesticide was 15 milligrams per liter and was greater than the overall median nitrate concentration of 95 milligrams per liter. The median for samples that did not contain a detectable pesticide was 73 milligrams per liter.

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USGS1990

Automatic tracer-dilution method used for stage-discharge ratings and streamflow hydrographs on small Iowa streams

An automatic system was designed to concurrently measure stage and discharge for the purpose of developing stage-discharge ratings and high flow hydrographs on small streams. Stage, or gage height, is recorded by an analog-to-digital recorder and discharge is determined by the constant-rate tracer-dilution method The system measures flow above a base stage set by the user. To test the effectiveness of the system and its components, eight systems, with a variety of equipment, were installed at crest-stage gaging stations across Iowa A fluorescent dye, rhodamine-WT, was used as the tracer. Tracer-dilution discharge measurements were made during 14 flow periods at six stations from 1986 through 1988 water years. Ratings were developed at three stations with the aid of these measurements. A loop rating was identified at one station during rapidly-changing flow conditions. Incomplete mixing and dye loss to sediment apparently were problems at some stations. Stage hydrographs were recorded for 38 flows at seven stations. Limited data on background fluorescence during high flows were also obtained.

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USGS1989

Hydrologic data for the Big Spring basin, Clayton County, Iowa, water year 1988

Hydrologic data was collected during the 1988 water year in cooperation with the Iowa Department of Natural Resources Geological Survey Bureau in the Big Spring ground-water basin located in Clayton County, Iowa. Information on precipitation, streams, and ground water was collected in the basin. Total rainfall at Big Spring was 24.08 inches. The greatest monthly rainfall was in September. Calcium and sulfate were the predominant ions in the rain and the median ammonia and nitrate concentrations as nitrogen were 0.40 and 0.37 mg/L (milligrams per liter), respectively. Stream discharge, water temperature, specific conductance, and pH were monitored continuously and monthly water-quality samples were collected at three sites in the basin. In the streams, water temperature and pH vary diurnally and are greatest during the day. Specific conductance varies inversely with water temperature and pH. The predominant ions in the streams were calcium, magnesium, and bicarbonate. Nitrate plus nitrite as nitrogen concentrations ranged from 0.5 to 15 mg/L. Pesticide concentrations ranged from less than 0.10 µ g/L (micrograms per liter) to 0.72 µ g/L. Atrazine was detected in 12 of 13 stream samples and cyanazine was detected in 4 of 13 samples. The daily mean temperature of the water in Big Spring ranged from 9.7 to 10.6 degrees Celsius, the daily mean specific conductance ranged from 698 to 735 microsiemens per centimeter at 25 degrees Celsius, and the daily median pH ranged from 6.7 to 7.1. Calcium, magnesium, and bicarbonate were the predominant ions in solution. Nitrate plus nitrite as nitrogen concentrations ranged from 7.5 to 11 mg/L. Atrazine was the only pesticide detected in the monthly samples from Big Spring. Atrazine concentrations were greater than the detection limit in six of seven samples and ranged from less than 0.10 to 0.26 µ g/L. During a baseflow seepage study, June 28 and 29, the discharge lost by streams in the basin was 5.57 cubic feet per second and the dissolved nitrogen load lost was 0.19 tons per day. The discharge and total dissolved nitrogen leaving the basin in streams was 2.93 cubic feet per second and 0.02 tons per day, respectively.

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USGS1989

Water resources data Iowa, water year 1988

Water resources data for the 1988 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 117 stream-gaging stations; stage or contents for 7 lakes and reservoirs; water quality for 9 stream-gaging stations; sediment records for 8 stream-gaging stations; water levels for 108 observation wells; and chemical analyses for 153 municipal wells. Also included are 113 crests-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.

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USGS1989

Water resources data, Iowa, water year 1989

Water resources data for the 1989 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 117 stream-gaging stations; stage or contents for 8 lakes and reservoirs; water quality for 6 stream-gaging stations; sediment records for 10 stream-gaging stations; water levels for 185 observation wells; and chemical analyses for the 135 municipal wells. Also included are 113 crest-stage partial-record stations. Additional water data were collected at various sites, not part of of the systematic data-collection program, and are published as miscellaneous discharge measurements and miscellaneous water-quality analyses.

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USGS1989

Ground-water-quality-monitoring program in Iowa: Nitrate and pesticides in shallow aquifers

Concern exists about the occurrence of agricultural chemicals, primarily nitrate and pesticides, in shallow ground water. In response to this concern, the focus of the Iowa ground-water-quality-monitoring program has shifted to emphasize nonpoint contaminants. The program, which began in 1982, is operated by the U.S. Geological Survey in cooperation with the University of Iowa Hygienic Laboratory and the Iowa Department of Natural Resources, Geological Survey Bureau and Environmental Protection Division. The objectives are to describe and assess the long-term chemical quality of the principal aquifers in Iowa and to direct water-quality assessment and sampling toward regional ground-water-quality concerns. In the spring of 1985, emphasis was placed on the analysis of pesticides in water samples collected from wells completed in surficial aquifers in Quaternary deposits or from wells less than 200 feet deep or both. Samples from these wells were analyzed for nitrate and selected pesticides. In water samples collected from 515 individual shallow wells, 6 percent had nitrate concentrations larger than the maximum contaminant level for public drinking water of 10 milligrams per liter as nitrogen. The concentrations ranged from less than 0.1 to 53 milligrams per liter as nitrogen. Eighteen percent of the samples had concentrations of nitrate between 5 and 10 milligrams per liter as nitrogen. Water samples from 355 individual municipal wells less than 200 feet deep have been analyzed for pesticides at least once. Detectable concentrations of at least one pesticide, including alachlor, atrazine, cyanazine, dicamba, metolachlor, or metribuzin, were detected in 20 percent of the samples. Atrazine was the most prevalent pesticide; concentrations, which ranged from 0.10 to 21 micrograms per liter, were detected in 18 percent of the samples. The results of the monitoring program indicate a relation between decreasing well depth and the presence of detectable concentrations of nitrate and pesticides. Most nitrate and pesticide detection was in areas where surficial aquifers in Quaternary deposits are the principal source of ground water. Pesticides were detected in samples collected throughout the year; samples collected in late spring and early summer more frequently contained pesticides than the other samples.

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USGS1989

Water resources of northeast Iowa

In 1965 a cooperative investigation with the U.S. Geological Survey produced Water Atlas No. 1 (Twenter and Coble, 1965). It presented information on the occurrence, availability, use, quality, and future demand of water in 10 counties in the central part of the state. Subsequent investigations produced Water Atlases No. 4 (Coble and Roberts, 1971) for southeast Iowa, No. 5 (Cagle and Heinitz, 1978) for south-central Iowa, No. 6 (Wahl et al., 1978) for east-central Iowa, and No. 7 (Buchmiller et al., 1985) for north-central Iowa. The present study, Water Atlas No. 8 (1989), describes the surface-water and groundwater resources of 11 counties in extreme northeast Iowa. With the publication of this report, water atlases are now available for the eastern two-thirds of the state.

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