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Research about Wisconsin

Source-linked reports with geographic coverage including Wisconsin.

At least 613 records · Page 34Linked to original sources
USGS1996

Sediment transport, particle size, and loads in North Fish Creek in Bayfield County, Wisconsin, water years 1990-91

North Fish Creek is underused as a trout and salmon hatchery despite its excellent water quality. The shifting-sand streambed in the lower 9 miles of the stream inhibits successful spawning and is a poor habitat for macroinvertebrates, the primary food for juvenile trout and salmon. To provide data necessary for evaluation of potential sand-loading-control practices, the U.S. Geological Survey determined total-sediment transport, particle size, and loads for three sites, designated A, B, and C, on North Fish Creek during water years 1990-91. At site C, the most upstream site, all sediment was transported as suspended sediment. The average annual total-sediment load during 1990- 91 was 479 tons. About 88 percent of the load was transported during periods of snowmelt or storm runoff. About 75 percent of the sediment load was silt- and clay-size particles; the remainder was sand. Total-sediment discharge was calculated by the modified-Einstein procedure to determine total sediment transport-rate relations for site A, the most downstream site, and for site B. Annual totalsediment load was 11,960 tons in water year 1990 and 18,430 tons in water year 1991 at site B. About 97 percent of the total load was transported during periods of snowmelt and storm runoff. About 60 percent of the total-sediment load was sand-size particles. Annual total-sediment loads were 20,690 tons and 33,100 tons in water years 1990 and 1991, respectively, at site A. About 67 percent of the total-sediment load was sand-size particles. Annual average streamflow, as indicated by flow in the Bois Brule River, was about 16 percent below average in water year 1990, and about 4 percent above average in water year 1991. There was little relation between watershed area and sediment loads for the three sites. The watershed of site C is about 41 percent of that of site A, but the sand load at site C was only 1 percent of that at site A. The watershed area between sites B and C is 40 percent of that above site A, but this area yielded 49 percent of the sand load at site A. Nineteen percent of the watershed above site A is between sites A and B, yet this area yielded about 50 percent of the sand load at site A.

Wisconsin↗
USGS1996

Environmental setting of benchmark streams in agricultural areas of eastern Wisconsin

This report describes the environmental setting of 20 benchmark streams in agricultural areas of eastern Wisconsin that are part of the Western Lake Michigan Drainages, National Water-Quality Assessment Program. Benchmark streams are defined as those that show minimal adverse effects from human activity, and they were selected on the basis of field reconnaissance and the following criteria: (1) available invertebrate or fisheries data that indicated good to excellent water quality, (2) instream habitat restoration for fisheries enhancement, and (3) land management to protect riparian vegetation. Information gathered from these benchmark sites can be used as a standard of reference to compare the health of other streams in agricultural areas on the basis of aquatic-biota communities, habitat, and water-quality characteristics. The information included in this report serves as background information that will be useful for a series of studies at these benchmark-stream sites in the Western Lake Michigan Drainages study unit as part of the National Water-Quality Assessment Program. Four relatively homogeneous units (RHU's) in agricultural areas that differed in bedrock and surficial geology were selected for study. RHU 1 (clayey surficial deposits over carbonate bedrock) and RHU 3 (sandy-till surficial deposits over carbonate bedrock) are in adjacent agricultural areas in the Southeastern Wisconsin Till Plains ecoregion. RHU 20 (sandy/sand and gravel surficial deposits over igneous and metamorphic bedrock) and RHU 26 (sandy/sand and gravel surficial deposits over sandstone bedrock) are in adjacent areas of agriculture and mixed forests in the North Central Hardwood Forests ecoregion. Differences in land use/land cover, and riparian vegetation and instream habitat characteristics are presented. Summaries of field measurements of water temperature, pH, specific conductance and concentrations of dissolved oxygen, total organic plus ammonia nitrogen, dissolved ammonium, nitrate plus nitrte as nitrogen, total phosphorus, dissolved orthophosphate, and atrazine are listed. Concentrations of dissolved oxygen for the sampled streams ranged from 6 A to 14.3 and met the standards set by the Wisconsin Department of Natural Resources (WDNR) for supporting fish and aquatic life. Specific conductance ranged from 98 to 753 u,Scm with values highest in RHU's 1 and 3, where streams are underlain by carbonate bedrock. Median pH did not vary greatly among the four RHU's and ranged from 6.7 to 8.8 also meeting the WDNR standards. Concentrations of total organic plus ammonia nitrogen, dissolved ammonium, total phosphorus, and dissolved orthophosphate show little variation between streams and are generally low, compared to concentrations measured in agriculturally-affected streams in the same RHU's during the same sampling period. Concentrations of the most commonly used pesticide in the study unit, atrazine, were low in all streams, and most concentrations were below trn 0.1 u,g/L detection limit. Riparian vegetation for the benchmark streams were characterized by lowland species of the native plant communities described by John T. Curtis in the "Vegetation of Wisconsin." Based on the environmental setting and water-quality information collected to date, these streams appear to show minimal adverse effects from human activity.

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USGS1996

Habitat characteristics of benchmark streams in agricultural areas of eastern Wisconsin

Stream habitat characteristics were measured at twenty sites in agricultural areas of eastern Wisconsin by the U.S. Geological Survey in May and June, 1993 as part of the National Water-Quality Assessment Program Western Lake Michigan Drainages study unit. These "benchmark" stream sites were selected for study to represent standards of reference for comparison to other streams in similar physical settings that appear to be more detrimentally affected by agriculture. The agricultural benchmark streams were selected from four physical settings, or relatively homogeneous units (RHU's), that differ in bedrock type and texture of surficial deposits. Habitat characteristics at streams in these four physical settings are described and compared to each other, and a habitat classification scheme was used to rank the quality of habitat in these streams. Additional aquatic information was collected along with the habitat data: water-quality data and population surveys of fish, invertebrates, and algae. Habitat data were collected at three levels: drainage basin, stream segment between major tributaries (length from 1 to 14 km), and stream reach (approximately 150m). Results of statistical analyses show that, in general, most correlations are among basin-level habitat characteristics. Few correlations were observed among reach- and basin-level characteristics. Principal components analysis (PCA) on basin-level data resulted in principal components that reflect RHU, land use or latitude, and basin size. Groupings of habitat characteristics at the reach level are less clearly attributed to some outside environmental factor. Streams that have undergone habitat restoration for fisheries group closely together on PCA ordination plots. Less than half of the habitat characteristics were found to be significantly different between one RHU and the other three. Characteristics that differed between RHU's were mainly at the basin level but also included some reach-level characteristics. Stream-habitat characteristics were classified according to the Michigan Department of Environmental Quality, Great Lakes Environmental Assessment Section (GLEAS) Procedure 51. No relation was found between GLEAS scores and RHU or the percentage of agricultural land in the drainage basins above the benchmark-stream sites. GLEAS scores were varied in each RHU. Streams with high GLEAS scores (rated good or excellent) can be considered benchmark or reference streams as far as habitat is concerned. Of the 20 streams sampled, 16 met this criterion.

Wisconsin↗
USGS1996

Benthic invertebrates of benchmark streams in agricultural areas of eastern Wisconsin — Western Lake Michigan drainages

This study describes the benthic invertebrate communities of 20 benchmark streams in agricultural areas of eastern Wisconsin. Streams with minimal adverse effects from human activity were selected from four agricultural areas with differing surficial deposits and bedrock types (relatively homogeneous units, or RHU's). Most aquatic invertebrate orders were well represented in the 20 benchmark stream samples; 217 species and 151 genera within 56 families were identified. Diptera was the best represented order (96 species), followed by Trichoptera (42 species) and Ephemeroptera (26 species). Diptera were the most abundant organisms in terms of numbers of individuals in the sample (28 percent of the total) followed by Trichoptera (25 percent) and Ephemeroptera (13 percent). Nine species of freshwater mussels were found, but only in 5 of the 20 benchmark streams. Community measures were calculated for the following: total number of individuals; number of species; number of families; Margalef's diversity index; percent dominant family; percent Ephemeroptera-Plecoptera-Trichoptera (EPT); ratio of EPT to Chironomidae; percent shredders; ratio of scrapers to collectors-gatherers-filterers; Hilsenhoff's Biotic Index; Hilsenhoff's family level biotic index; and mean tolerance value. The S AS statistical software package was used for calculations of variance and correlations, normality checks, and principal components analysis of these measures and to find relations between benthic-invertebrate data and environmental-setting, habitat, and water-quality data. Coefficients of variation within the RHU's were as great or greater than those for all 20 streams for most measures and RHU's. The specific taxa assemblages present at the sites did not show distinct differences between RHU's or similarities within the RHU's. The covariance and the Kruskal-Wallis tests showed that the benthic invertebrate measures were not related to RHU. These results all indicate that the combined effect of the RHU variables (bedrock geology, texture of surficial deposits, and land use/land cover) were not elemental in describing invertebrate communities in the study-area streams. A principal components analysis (PCA) was done on the 20 benchmark streams which used the invertebrate population measures as variables. A three-dimensional ordination plot of these components revealed that 18 of the 20 streams could be divided into three groups relative to stream size, available habitat, and water quality. The three classifications of streams include large, warmer streams with slight pollution; deep, mixed-water streams with minimal pollution; and small, cold, pristine headwater streams. The two streams not defined by the three PCA groupings were not suitable to represent benchmark conditions. One site lacked suitable quality habitat or sufficient nutrients to support a healthy population of invertebrates, causing low measures of diversity. The other site appeared to be affected by sedimentation and low flows. The classification groupings did not show any significant relations to percentage agricultural land use. Percentage of agricultural land use varied greatly within each group and the means for each group were similar. All streams in this study had some level of protection from agricultural practices in their basins. Although the intensity of agriculture is known to be a factor causing deterioration of invertebrate populations in past studies, the finding in this study indicated that the level of protection the stream received and other factors such as environmental setting and habitat could be more important to benthic invertebrates than the percentage of agriculture in the basin. Information gathered from these benchmark streams can be used as a regional reference for comparison with other streams in agricultural areas, based on communities of aquatic biota, habitat, and water quality.

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USGS1996

Phosphorus dynamics in Delavan Lake Inlet, southeastern Wisconsin, 1994

Removal of rough fish from Delavan Lake Inlet in southeastern Wisconsin transformed the inlet from a shallow, turbid-water system with few macrophytes to a clear-water system with an abundance of macrophytes and increased phosphorus concentrations. To understand the changes in the phosphorus dynamics, the U.S. Geological Survey and the U.S. Army Corps of Engineers, in cooperation with the Town of Delavan, constructed a detailed phosphorus budget for the inlet for April through September 1994. The budget included inputs from the drainage basin, atmosphere, sediments (as a function of pH and the fraction of the day under anoxic conditions), and ground water. Laboratory studies estimated phosphorus flux rates under various conditions. Field studies documented ambient conditions in the inlet and fluxes of phosphorus into and out of the inlet. Phosphorus released from the sediments was estimated by coupling the flux rates, estimated in the laboratory, with ambient conditions in the inlet. The detailed phosphorus budget indicated that the increase in phosphorus concentrations was caused primarily by elevated pH resulting from increased photosynthetic activity of the macrophytes and a high release of phosphorus from the sediments. The release of phosphorus from the sediments was the largest source of phosphorus to the inlet in the spring and summer of 1994 and in other years of low to near normal runoff; however, in years of high runoff, phosphorus input from the inlet's drainage basin was the largest source of phosphorus. A less-detailed phosphorus budget constructed for the period from February 1993 to September 1994 demonstrated that, over the entire year, runoff from the drainage basin was the dominant source in the phosphorus budget. During April-September 1994, the input of phosphorus from the inlet may especially affect the summer productivity in Delavan Lake because almost 80 percent of the phosphorus loading during this time was in the form of dissolved orthophosphate.

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USGS1996

Variation in the relation of rainfall to runoff from residential lawns in Madison, Wisconsin, July and August 1995

The quality of runoff from residential lawns is a concern for municipal stormwater management programs. Land-use based computer models are increasingly being used to assess the impact of lawn runoff on urban watersheds. To accurately model the runoff for residential lawns, the variation in the relation of rainfall to runoff from lawns must be understood. The study described in this report measures the runoff parameters from 20 residential lawns in Madison, Wisconsin, using a rainfall simulator. It was determined that the saturated hydraulic conductivity does not vary significantly within a single residential lawn, but does vary significantly from one lawn to another. This variation is recognized in the entire rainfall-runoff relation from one lawn to another. The age of a lawn, or the years since development and turf establishment, is used as a surrogate of several lawn and soil characteristics to describe the variability in lawn runoff volumes. Runoff volumes from newly developed lawns are significantly greater than runoff from older lawns. This is an important consideration when modeling runoff for new developments. For older lawns, the date since lawn establishment does not explain the variation in the rainfall-runoff relation. In order for simple land-use based computer models to adequately account for the volume of runoff from pervious landscapes, field data from individual lawns would be necessary. A more realistic, alternative method may be to consider a basin-scale analysis of runoff from pervious landscapes.

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USGS1996

Hydrogeology of the sand and gravel aquifer in the vicinity of the Wild Rose State Fish Hatchery, north-central Waushara County, Wisconsin

The sand and gravel aquifer in the vicinity of the Wild Rose State Fish Hatchery is approximately 200 feet thick. The aquifer consists mostly of sand that was deposited as glacial till and outwash approximately 15,000 years ago. Hydraulic conductivity of the aquifer at the hatchery, calculated from slug tests, is approximately 18 feet per day. Ground water recharges west of the hatch ery, flows from northwest to southeast, and discharges to streams, lakes, springs, and flowing wells. Springs and flowing wells are common at the hatchery because of upward hydraulic gradients in the sand and gravel aquifer. Total flow from springs and wells at the hatchery is approximately 3 million gallons per day. The recharge area for the ground water discharging at the hatchery extends at least 5 miles to the west. Ground water may flow from or under the Pine River to wells and springs at the hatchery.

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USGS1996

Ground-water quality in the western part of the Cambrian-Ordovician aquifer in the Western Lake Michigan Drainages, Wisconsin and Michigan

Ground-water samples were collected during the summer of 1995 from 29 wells in the western part of the Cambrian-Ordovician aquifer in the Western Lake Michigan Drainages study unit of the National-Water Quality Assessment Program. Analyses of ground-water samples from these wells were used to provide an indication of waterquality conditions in this heavily used part of the aquifer. Ground-water samples from domestic, institutional, and public-supply wells were analyzed for major ions, nutrients, dissolved organic carbon (DOC), pesticides, volatile organic compounds (VOCs), radon-222, and tritium, as well as field measurements of temperature, pH, specific conductance, dissolved oxygen, and bicarbonate. The results of water-quality analyses indicate that the presence of the Maquoketa-Sinnipee confining unit has an important effect on the ground-water quality in the study area. Where the study area is overlain by the confining unit (that is, where it is regionally confined) sampled water was older (based on tritium analyses) and often contained relatively high concentrations of dissolved solids, up to 2,800 mg/L. Additionally, contaminants such as nitrate and pesticides were typically detected at lower concentrations and detected less frequently in samples from the regionally confined part of the study area. The dominant ions in samples from the study area were calcium, magnesium, and bicarbonate which resulted from the dissolution of carbonate minerals such as dolomite and calcite. Sulfate was also a dominant ion in water from some of the deeper wells in the regionally confined part of the study area. Radon-222 was detected in all samples and 66 percent (19 of 29) had concentrations that exceed the U.S Environmental Protection Agency (USEPA) proposed maximum concentration level of 300 pCi/L. Concentrations greater than 300 pCi/L were detected in samples from wells throughout most of the study area except the southwest. The higher concentrations were found in samples from a variety of geohydrologic conditions and do not appear to correlate to a particular formation or location. Dissolved nitrate and ammonium were the most commonly detected nutrients. Dissolved nitrate concentrations were significantly higher in ground-water samples from the regionally unconfined part of the study area. The highest concentrations were detected in samples from the agricultural southwestern part of the study area from relatively shallow wells that produced modern water. Dissolved ammonium concentrations were significantly higher in samples from the regionally confined part of the study area and probably resulted from nitrate reduction. Seven pesticides or metabolites were detected in ground-water samples, and at least one pesticide was detected in samples from 24 percent (7 of 29) of wells. Most of the pesticides were detected at low concentrations and were from wells in the regionally unconfined, agricultural, southwest part of the study area. Atrazine was the most commonly detected pesticide and was typically detected in samples from wells that produced modern water.

Wisconsin↗
USGS1996

Hydrology and water quality of Lauderdale Lakes, Walworth County, Wisconsin, 1993-94

Water and phosphorus budgets were determined for the Lauderdale Lakes (the interconnected Green, Middle, and Mill Lakes) in Walworth County, southeastern Wisconsin to provide background information for a wastewater management plan to limit the input of phosphorus to the lakes. The most significant components of the water and phosphorus budgets were determined independently by intensive data collection from November 1993 through October 1994. In addition to development of the water and phosphorus budgets, in-lake water quality, and trophic state of the lakes were evaluated. The lakes (treated as one lake with three basins) have a total surface area of 807 acres. The lakes have a surface-water outlet, but have no major surface inlets. Lake level is controlled by a dam and weir at the outlet. Maximum depths of Green, Middle, and Mill Lakes are about 60, 50, and 50 feet, respectively. The total drainage area of the lakes measured from the outlet is 16.1 square miles; only about 2.5 square miles, however, contribute surface runoff directly to the lake. About 70 percent of the 14.7-mile shoreline length is developed. Shoreline development includes 1,010 houses, of which about 30 percent are used year-round. Ground water and precipitation are the primary water-budget inflow components, and during the study period represented 72 and 24 percent of the total annual inflow, respectively. Surface-water inflow from the small nearshore contributing drainage area accounted for only 4 percent of the inflow budget. Total annual phosphorus input to the lakes was 846 pounds. Although surface water accounted for only 4 percent of the water budget, it represented 51 percent of the total annual phosphorus input. Phosphorus input from septic systems was the second largest source, with a probable annual input of 210 pounds, accounting for 25 percent of the total. Positive ground-water gradients to the lake and phosphorus concentrations in ground water were verified by data from nearshore observation wells. Phosphorus concentrations in ground water exceeded background concentrations of 0.008 milligrams per liter in three out of six observation wells in the inflow area of the lakes. Overall, the phosphorus loading to the lakes is small and lake-water quality is good. The trophic state indices calculated for the lakes ranged from oligotrophic to mesotrophic but were in the mesotrophic class for most of the year. An equation to predict phosphorus concentration at spring turnover from loading estimates was fairly accurate in predicting the measured phosphorus concentration for Lauderdale Lakes.

Wisconsin↗
USGS1996

Canvasback mortality from illegal hunting on the upper Mississippi River

To quantify the consequences of local hunting on illegal kill of canvasbacks ( Aythya valisineria ), we studied the behavior of hunters on a 646-ha area open to duck hunting (closed to canvasback hunting) on Lake Onalaska, Navigation Pool 7, Wisconsin, during the 1991 and 1992 waterfowl hunting seasons. Law enforcement officers observed 258 hunting parties for 419 hours. Of 94 hunting parties encountering canvasbacks, 41 (44%) shot at the ducks on 56 occasions, or 27% of 207 encounters observed, Based on a ratio estimator, there were 790 (95% CI = 376) attempts to shoot at canvasbacks on the Lake Onalaska study area during 1991 and 837 (95% CI = 390) during 1992. Mortality of canvasbacks, excluding crippling loss, was estimated to be 128 during 1991 and 166 during 1992. Thus, total canvasback losses may be higher than currently estimated on a flyway or national basis. This estimating technique offers a promising method for enumerating hunter take of protected and legal species.

Wisconsin↗
USGS1995

Long-term simulation of PCB export from the Fox River to Green Bay

A mass balance approach was used to model long-term PCB transport in the Fox River (Wisconsin) from Lake Winnebago to Green Bay. The objectives of this research were to (1) extend the modeling approach for the Fox River to permit realistic long-term simulations of contaminant transport and fate, (2) forecast long-term PCB export from the Fox River to Green Bay, and (3) develop a rational approach for evaluating sediment remediation alternatives. Field data collected as part of the Green Bay Mass Balance Study during 1988-90 and additional data collected by the Wisconsin Department of Natural Resources and the U.S. Geological Survey during 1992-93 were used to develop the model. A 10-year hindcast was conducted to confirm long-term model predictions. A series of 25-year forecasts were then conducted to explore the potential effects of hydrograph structure, extremely high flows, and sediment remediation on long-term PCB export from the Fox River to Green Bay. PCB export from the Fox River is forecast to decrease, and most (75%) of the PCB reservoir in Fox River sediment is expected to remain in place. However, extremely high flows in future years are forecast to cause significant PCB resuspension and export. Model forecasts suggest that long-term PCB export is only mildly sensitive to changes in hydrograph structure. Sediment remediation is forecast to reduce but not eliminate PCB export.

Wisconsin↗
USGS1995

Management briefs: Phototaxis of larval and juvenile northern pike

Age-0 northern pike Esox lucius prefer vegetated habitats that are difficult to sample with standard towed gears. Light traps can be effective for sampling larval fishes in dense vegetation, given positive phototaxis offish. We evaluated the phototactic response of young northern pike by comparing the catches of larvae and juveniles obtained with plexiglass traps deployed with a chemical light stick versus traps deployed without a light source (controls) in a laboratory raceway and in a vegetated pond. In the laboratory tests, catches of protolarvae and mesolarvae in lighted traps were 11–35 times greater than catches in control traps. The catches of juvenile northern pike in field and laboratory experiments were 3–15 times greater in lighted traps than in control traps, even though the maximum body width of the larger juveniles was similar to the width of the entrance slots of the traps (5 mm). Larval and juvenile northern pike were photopositive; thus, light traps should effectively sample age-0 northern pike for at least 6 weeks after hatching.

Wisconsin↗
USGS1995

Applying computer simulation models as learning tools in fishery management

Computer models can be powerful tools for addressing many problems in fishery management, but uncertainty about how to apply models and how they should perform can lead to a cautious approach to modeling. Within this approach, we expect models to make quantitative predictions but only after all model inputs have been estimated from empirical data and after the model has been tested for agreement with an independent data set. I review the limitations to this approach and show how models can be more useful as tools for organizing data and concepts, learning about the system to be managed, and exploring management options. Fishery management requires deciding what actions to pursue to meet management objectives. Models do not make decisions for us but can provide valuable input to the decision‐making process. When empirical data are lacking. preliminary modeling with parameters derived from other sources can help determine priorities for data collection. When evaluating models for management applications, we should attempt to define the conditions under which the model is a useful, analytical tool (its domain of applicability) and should focus on the decisions made using modeling results, rather than on quantitative model predictions. I describe an example of modeling used as a learning tool for the yellow perch Perca flavescens fishery in Green Bay, Lake Michigan.

Wisconsin↗
USGS1995

Wisconsin: A summary of cooperative water-resources investigations 1995

The objectives of this study are to provide continuous discharge records for selected rivers at specific sites to supply the needs for regulation, analytical studies, definition of statistical properties, trends analysis, determination of the occurrence, and distribution of water in streams for planning. The project is also designed to determine lake levels and to provide discharge for floods, low-flow conditions, and for water-quality investigations. Requests for streamflow data and information relating to streamflow in Wisconsin are answered. Basic data are published annually in the report "Water Resources Data-Wisconsin".

Wisconsin↗
USGS1995

Evaluating barnyard Best Management Practices in Wisconsin using upstream-downstream monitoring

The Nonpoint Source Water Pollution Abatement Program was created in 1978 by the Wisconsin Legislature. The goal of the program is to improve and protect the water quality of lakes, streams, wetlands, and ground water within selected priority watersheds by controlling sources of nonpoint pollution. For each selected watershed, the Wisconsin Department of Natural Resources drafts a management plan that guides the implementation of pollution-control strategies known as Best Management Practices (BMP's). This plan summarizes resource and land-use inventories, describes the results of pollution-source modeling, and suggests pollution reduction goals. The U.S. Geological Survey, through a cooperative effort with the Wisconsin Department of Natural Resources, is monitoring water-quality improvements that result from the implementation of BMP's. The data collected are then compared to the watershed plans to assess progress and determine whether goals are being realized. This fact sheet describes the data-collection efforts, preliminary results, and planned data-analysis techniques of monitoring projects for pre-BMP conditions at two barnyards, one each on Otter Creek and Halfway Prairie Creek.

Wisconsin↗
USGS1995

Distribution and transport of polychlorinated biphenyls in Little Lake Butte des Morts, Fox River, Wisconsin, April 1987-October 1988

Polychlorinated biphenyls (PCB's) in the bottom sediment and water column of Little Lake Butte des Morts were studied by the Wisconsin Department of Natural Resources and the U.S. Geological Survey. The lake is a 8-kilometer-long impoundment of the Fox River between Lake Winnebago and Appleton, Wisconsin. Discharge of PCB's into the lake by paper mills and waste-treatment plants has resulted in their accumulation in the bottom sediment. The accumulation of PCB's in the sediment was estimated to be 1,100 kilograms in October 1987. The concentrations of PCB's in bottom-sediment core samples were as much as 190 micrograms per gram dry sediment. The congener distribution of the PCB's present in the lake most closely resembles that for the Aroclor 1242 PCB's mixture. Thirty-two water samples were collected at the outlet of the lake to determine concentrations of PCB's. Concentrations of PCB's in the water column varied seasonally and ranged from 3.5 to 137 nanograms per liter. Concentrations of PCB's decrease in the winter and increases in the summer months. Concentrations of PCB's in the water column for particulates generally were 2.5 times that of dissolved PCB's. The suspended-solids concentrations ranged from 3 to 44 milligrams per liter. Correlation analysis was used to identify the physical characteristics and water-quality characteristics having the highest degree of association with PCB's concentration in the water column. The highest correlation coefficients (r) for dissolved PCB's concentration were with water temperature (7=0.88) and particulate organic carbon concentration (7=0.72). The highest correlation coefficients for particulate PCB's concentration were with suspended- particulates concentration (r=0.77) and water temperature (n=0.70). Correlation coefficients for total PCB's (the sum of dissolved and particulate PCB's) concentration were similar to those for particulate PCB's concentration. The mass of PCB's transported from the lake in streamflow during 1987-88 was calculated to be 110 kilograms annually. The PCB's transport rate decreased 50 percent from 1987 to 1988, for the period April through September. Transport of PCB's was greatest during April and May of each year. The average flux rate of PCB's into the water column from the bottom sediment in the lake was estimated to be 1.2 milligrams per square meter per day. The PCB's load seems to increase at river discharges greater than 212 cubic meters per second. This increase in PCB's load might be caused by resuspension of PCB's-contaminated bottom-sediment deposits. There was little variation in PCB's load at flows less than 170 cubic meters per second. The bottom sediments are a continuing source of PCB's to Little Lake Butte des Morts and the lower Fox River.

Wisconsin↗
USGS1995

Simulation of stage and the the hydrologic budget of Devils Lake, Sauk County, Wisconsin

Water clarity of Devils Lake, in the Driftless Area of southwestern Wisconsin, has been decreasing because of blue-green algal blooms. An understanding of the hydrology of Devils Lake is needed to develop a mitigation plan to reduce phosphorus input. A model was developed to test the current understanding of the hydrology of the lake including stage and hydrologic budget and to estimate the effects of proposed mitigation plans on lake stage. Daily lake stage was simulated in the model by summing estimates of hydrologic-budget components. The Devils Lake hydrologic-budget components are precipitation on the lake surface, evaporation from the lake surface, runoff (consisting of overland flow to the lake and an intermittent stream flowing into the lake), and ground-water flow into and out of the lake. The model was calibrated to measured lake stage for the period 1980-92. Simulated stage compares reasonably well with historical stage data for Devils Lake. The root mean square of the differences of simulated and measured daily lake stages for the period 1980-92 is 0.83 foot. Simulated lake stage is very sensitive to small changes in runoff and evaporation coefficients, and ground-waterflow rates used in the model. The average model-calculated annual amounts of each hydrologic-budget component for the 1980-92 simulation period, in order of increasing volume, are evaporation (791 acre-feet), precipitation (973 acre-feet), runoff (1,107 acre-feet), and net ground-water flow, which is out of the lake (1,323 acre-feet). Three mitigation plans were simulated. Mitigation plan 3, which includes the addition of water from a basin adjacent to the northeastern side of the Devils Lake Basin, allows for withdrawals of hypolimnetic water and maintaining lake stage closer to optimal levels than would result without mitigation.

Wisconsin↗