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Research about Wisconsin

Source-linked reports with geographic coverage including Wisconsin.

At least 199 records · Page 11Linked to original sources
USGS2019

Variation in Bluegill catch rates and total length distributions among four sampling gears used in two Wisconsin lakes dominated by small Ffsh

Many Bluegill Lepomis macrochirus populations are dominated by fish ≤125 mm total length (TL) that may be underrepresented when using standard sampling gears. To identify efficient sampling methods for these populations, we compared catch per unit effort (CPUE) and TL frequency distributions of Bluegill captured in cloverleaf traps, boat electrofishing, mini-fyke nets, and beach seine hauls from two northern Wisconsin lakes supporting populations dominated by fish ≤125 mm TL. Mean Bluegill CPUE ranged from 41 (SE = 11) fish per cloverleaf trap lift to 16 (SE = 8) fish per beach seine haul. Cloverleaf traps generally captured smaller Bluegill relative to other gears and were the only gear to consistently capture Bluegill ≤80 mm TL. Conversely, boat electrofishing captured the widest TL range of Bluegill, and fish ≥80 mm TL composed a greater proportion of catch (37%) relative to other gears. With few exceptions, the effort required to detect 10% or 25% changes in Bluegill CPUE was >100 units of effort regardless of lake, sampling gear, or month. Furthermore, there was no consistency between lakes or months in terms of which sampling gear required the fewest number of samples to detect a 50% change in CPUE. Estimated units of effort needed to detect 10% or 25% changes in mean Bluegill TL were ≤16 for all sampling gears on the lake with consistently higher CPUE (i.e., more fish to measure per unit). In the lake with lower CPUE, cloverleaf traps consistently required less effort to detect changes in mean TL. We note that comparing sample size requirements among gears is not straightforward because gears are sampling differing segments of the Bluegill population. Our study emphasizes the importance of evaluating gear biases and sampling efficiency so that fisheries managers can develop suitable sampling protocols.

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USGS2019

Characterizing angler preferences for Largemouth Bass, Bluegill, and Walleye fisheries in Wisconsin

Managing recreational fisheries in lake-rich landscapes with diverse fish communities and anglers alike presents a social and biological challenge for managers. Understanding angler preferences is central to navigating these challenges and can aid in predicting shifts in angler behavior in response to management actions or changing fish populations. Species-specific angler surveys do not incorporate tradeoffs inherent in multispecies fisheries, thus limiting their application to real-world management issues. To better understand angler preferences in relation to realistic tradeoffs among different fishing opportunities, we conducted a survey of Wisconsin anglers in 2013–2014 that included questions requiring anglers to choose between fisheries providing different outcomes. We used stated-preference modeling to quantify angler preferences associated with Bluegill Lepomis macrochirus , Largemouth Bass Micropterus salmoides , and Walleye Sander vitreus fisheries. Next, we conducted a latent class analysis using survey responses to classify anglers into subgroups. Finally, we assessed the sensitivity of angler choice to changes in fishing opportunities. Results of the stated-preference models indicated that both residents and nonresidents largely prefer “quality” (i.e., moderate catch rate and size structure) over “action” or “trophy” Bluegill fisheries and that characteristics of Largemouth Bass fisheries have more value to nonresidents than to residents. Aspects of the Bluegill fishery were most important in choosing among hypothetical lakes for resident respondents. Five angler subgroups were identified that show the importance of Bluegill and Walleye but shed additional light on anglers’ commitment level and nonresidents’ preference for Largemouth Bass. In addition, simulations of changes in Walleye, Largemouth Bass, and Bluegill fisheries indicated that maintenance of quality Bluegill fisheries is important to ensuring continued angler participation, while the retention of high-yield Walleye fisheries is likely paramount to a subgroup of anglers. Our results offer insight into angler preferences across the lake-rich landscape of Wisconsin and demonstrate how angler behavior may shift in response to transitions in fishing opportunities.

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USGS2019

Denitrification in the river network of a mixed land use watershed: Unpacking the complexities

River networks have the potential to permanently remove nitrogen through denitrification. Few studies have measured denitrification rates within an entire river network or assessed how land use affect rates at larger spatial scales. We sampled 108 sites throughout the network of the Fox River watershed, Wisconsin, to determine if land use influence sediment denitrification rates, and to identify zones of elevated sediment denitrification rates (hot spots) within the river network. Partial least squares regression models identified variables from four levels of organization (river bed sediment, water column, riparian zone, and watershed) that best predicted denitrification rates throughout the river network. Nitrate availability was the most important predictor of denitrification rates, while land cover was not always a good predictor of local-scale nitrate concentrations. Thus, land cover and denitrification rate were not strongly related across the Fox River watershed. A direct relationship between denitrification rate and watershed land cover occurred only in the Wolf River sub-watershed, the least anthropogenically disturbed of the sub-watersheds. Denitrification hot spots were located throughout the river network, regardless of watershed land use, with hot spot location being determined primarily by nitrate availability. In the Fox River watershed, when nitrate was abundant, river bed sediment character influenced denitrification rate, with higher denitrification rates at sites with fine, organic sediments. These findings suggest that denitrification occurring throughout an entire river network, from headwater streams to larger rivers, can help reduce nitrogen loads to downstream water bodies.

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USGS2019

Laboratory for Infectious Disease and the Environment (LIDE)

The Laboratory for Infectious Disease and the Environment (LIDE) studies the occurrence, fate and transport, and health effects of human and agricultural zoonotic pathogens in the environment. The LIDE is an interagency collaborative effort between the U.S. Geological Survey and the U.S. Department of Agriculture-Agricultural Research Service that conducts research to inform decision makers and advance scientific knowledge. The LIDE collaborates with public agencies and academic researchers in partnerships and works cooperatively or independently on all aspects of the research process. The LIDE's laboratory capabilities include quantitative polymerase chain reaction and pathogen culture.

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USGS2019

Assessment of skin and liver neoplasms in white sucker (Catostomus commersonii) collected in the Sheboygan River Area of Concern, Wisconsin, in 2017

Two hundred adult white sucker ( Catostomus commersonii ), age 3 years and older, were collected from the lower Sheboygan River Area of Concern in 2017, during the spring spawning run. Fish were euthanized, weighed, and measured, and any visible abnormalities were documented. Pieces of raised skin lesions as well as five to eight pieces of liver were removed and preserved for histopathological analyses. Skin and liver neoplasm prevalence was determined for assessment of the Fish Tumors or Other Deformities Beneficial Use Impairment. Although 45.5 percent of the suckers had raised skin lesions, the prevalence of skin neoplasms, either papilloma or squamous cell carcinoma, was 29.5 percent. This observation was similar to the prevalence (32.6 percent) of skin neoplasms in 2012; however, the percentage of squamous cell carcinoma was higher in 2017 (9.5 percent) than in 2012 (2.1 percent). The prevalence of liver neoplasms in 2017 (8.5 percent) was similar to that in 2012 (8.3 percent).

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USGS2019

The dilemma of pest suppression in the conservation of endangered species

In the conservation of endangered species, active suppression of a population of one native species to benefit another native species poses particular challenges. Obvious examples include predator control and nest parasite reduction. Less obvious is the control of blood-feeding arthropods. We present a case study on the effect of blood-feeding black flies (Simulium spp.) on reintroduced Whooping Cranes (Grus americana). Our intent is to provide a transferrable, science-driven approach for determining the effects of blood-feeding arthropods on endangered vertebrates, and demonstrate an approach for guiding selection of management actions for managers faced with competing objectives. A multi-year experiment demonstrated that black flies reduce nest success in reintroduced cranes by driving the birds off their nests during incubation. Deciding how to respond, however, is complicated because the target black flies are native species that serve important ecological functions. We suggest that a decision-analytic approach can inspire the development of creative management alternatives and facilitate a transparent process that evaluates trade-offs among competing objectives. Recognizing that these decisions involve trade-offs, which must be weighed in the context of each case, is crucial to identifying alternatives that best balance multiple management objectives. Given the uncertainty about the population dynamics of blood-feeding arthropods, an adaptive management approach will offer substantial benefits.

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USGS2019

Absence of PCB hot spot effect in walleye Sander vitreus from lower Green Bay of Lake Michigan

Under certain conditions, polychlorinated biphenyl (PCB) concentration in individuals of one sex of an adult fish population may exceed that of the other sex by more than a factor of two. This phenomenon, known as the PCB hot spot effect, has been postulated to be contingent upon the following two conditions: (1) presence of a PCB hot spot in the bottom sediments of the aquatic ecosystem such that prey PCB concentrations in the hot spot region are substantially higher than prey PCB concentrations in locations distant from the hot spot, and (2) habitat use varying between the sexes such that individuals of one sex inhabit the hot spot region to a considerably greater degree than individuals of the other sex. To test whether PCB concentrations in walleye Sander vitreus from lower Green Bay of Lake Michigan displayed a PCB hot spot effect, whole-fish PCB concentrations were determined in 10 female and 10 male adult walleye from the population spawning in the Fox River, the main tributary to lower Green Bay. In addition, mark-recapture data for the Fox River walleye population were analyzed to determine differences in spatial distributions between the sexes. Results revealed that the ratio of mean PCB concentration in males to mean PCB concentration in females was only 1.13, indicating the absence of a PCB hot spot effect. This result was corroborated by the mark-recapture data analysis, which showed no significant difference in habitat use between the sexes. Thus, although condition 1 was met, condition 2 was not met, and consequently the PCB hot spot effect was not observed in the Fox River walleye population. Lack of a significant difference in PCB congener distributions between the sexes further corroborated our conclusions.

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USGS2019

Effects of flood inundation, invasion by Phalaris arundinacea, and nitrogen enrichment on extracellular enzyme activity in an Upper Mississippi River floodplain forest

The community structures and ecosystem functions of floodplains are primarily driven by variation in flood inundation. However, global changes, such as invasive species and nutrient enrichment, may alter the effects of flooding in these systems. We added nitrogen (N) to correspond with twice the annual atmospheric deposition rate of the south-west Wisconsin, USA region within mature floodplain forest plots and patches of an invasive grass (reed canarygrass, Phalaris arundinacea ) along a floodplain elevation gradient in an Upper Mississippi River floodplain forest. We measured soil physicochemical properties and the activity of six extracellular enzymes during 3 months that varied in flooding conditions. Multivariate analyses (distance-based redundancy analysis) revealed that floodplain elevation, month of sampling, and vegetation type were all significant predictors of variation in soil physicochemical properties, while elevation and month were significant predictors of multivariate extracellular enzyme activity (EEA). The best model for predicting EEA consisted of nitrogen availability, soil porosity, and water filled pore space. Although the categorical fertilization and invasion treatments were not significant predictors of EEA, our results suggest that their effects depend on the degree to which they modify N availability and soil moisture. In this system, spatial and temporal patterns in flooding appear to be the main driver of these properties, but N enrichment and invasion may have the potential to further modify them.

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USGS2019

Stormwater-quality performance of line permeable pavement systems

Three permeable pavements were evaluated for their ability to improve the quality of stormwater runoff over a 22-month period in Madison, Wisconsin. Using a lined system with no internal water storage, permeable interlocking concrete pavers (PICP), pervious concrete (PC), and porous asphalt (PA) were able to significantly remove sediment and sediment-bound pollutant loads from runoff originating from an asphalt parking lot five times larger than the receiving permeable pavement area. Reductions in total suspended solids were similar for all three surfaces at approximately 60 percent. Clogging occurred after approximately one year, primarily due to winter sand application that led to high sediment load in spring runoff. Winter road salt application resulted in high chloride load that was initially attenuated in all three permeable pavements but later released during subsequent spring runoff events. Total phosphorus load was reduced by nearly 20 percent for PICP and PA, and 43 percent for PC. These values were likely tempered by the export of dissolved phosphorus observed in PICP and PA, but not PC. Average removal efficiencies for metals were 40, 42, and 49 percent in PA, PICP, and PC, respectively. A median pH of 10.2 in PC effluent could explain elevated removal efficiency of phosphorus and select metals in PC over PICP and PA (median = 7.5 and 7.8, respectfully) through enhanced precipitation. Elevated pH values in PC may also have led to higher removal efficiencies for select metals than PICP or PA. The environmental benefits as well as potential unintended consequences of stormwater practices like permeable pavement that utilize infiltration as a form of treatment warrant consideration in management of urban runoff.

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USGS2019

Assessment of site-specific agricultural Best Management Practices in the Upper East River watershed, Wisconsin, using a field-scale SWAT model

The Great Lakes “Priority Watershed” effort targeted the Upper East River watershed, a 116.5 km2 tributary watershed to Green Bay in Wisconsin, to reduce sediment and nutrients entering Green Bay. A Soil and Water Assessment Tool (SWAT) model was created to determine the effectiveness of Best Management Practices (BMPs) derived from the U.S. Department of Agriculture-Natural Resources Conservation Service National Conservation Planning (NCP) Database. The model was calibrated at the monthly timestep for flow, sediment, dissolved reactive phosphorus (DRP), total phosphorus (TP), and total nitrogen (TN). Field- and watershed-scale sediment and nutrient reductions were calculated due to the implementation of 74 BMP combinations on dairy and cash grain rotations. Modeling results indicated that when multiple BMPs are placed on a field, especially those that included filter strips and grassed waterways, generally reduced sediment and nutrient loads more than a single BMP implementation. The most effective in-field practice at reducing DRP and TP on dairy fields was a combination of 5 different BMPs: cover crops, crop rotation, nutrient management plan, reduced tillage, and a filter strip. Conservation cover was the most effective practice at reducing sediment and nutrient yields. Sediment and nutrient loads decreased at the watershed scale as the quantity and coverage of BMPs increased. When all contracted NCP BMPs were simulated at the watershed scale, sediment loads were reduced 2%, while TP, DRP, TN and nitrate loads were reduced 20%, 9%, 24%, and 17%, respectively. Modeling scenarios indicated that as the number and area of BMPs were increased, sediment and nutrient load reductions were also increased.

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USGS2019

An integrated statistical and deterministic hydrologic model for analyzing trace organic contaminants in commercial and high-density residential stormwater runoff

Urbanization can dramatically alter stormwater, both the quantity and quality, by engendering larger peak flows and through the introduction of contaminants into runoff. The current study builds on previous research that developed relationships between a suite of nonpoint source contaminants, known as trace organic contaminants (TOrCs), and hydrologic measurements for a series of storms (one site had 15 storms and the other had 19 storms) in Madison, WI, by creating statistical and deterministic models. Correlations and regressions were calculated between TOrC loads and hydrologic measurements for a series of storms for both a commercial site and a high-density residential site. From the regressions, it became evident that loading responses to precipitation were not the same between the two land covers for some TOrCs, indicating varying load responses for TOrCs depending on land cover. The regressions were utilized in the Source Loading and Management Model for Windows (WinSLAMM), an event-based hydrologic and water-quality model, to demonstrate that it can be used to model novel contaminants. The regressions were also used to estimate mean annual loads of TOrCs from all commercial and high-density residential areas in Madison, WI, for the watersheds to which Madison discharges its stormwater. The mean annual loads varied between grams per year to tens of thousands of grams per year depending on the TOrC and watershed. This work will ultimately allow managers to simulate the presence of, establish total maximum daily loads for, and mitigate the loads of TOrCs through stormwater best management practices.

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USGS2019

Evaluation of stormwater treatment vault with Coanda-effect screen for removal of solids and phosphorus in urban runoff

Catch basins commonly are used by cities as part of a stormwater management plan to remove sediment and associated contaminants from stormwater, keeping them in compliance with regulations. Recently, the city of Madison, Wisconsin modified traditional catch basins by incorporating a fine-mesh (1-mm) Coanda-effect screen into the design with the goal of increasing removal of sediment and organic matter from stormwater. The US Geological Survey (USGS), in cooperation with the City of Madison, installed a water-quality monitoring station at such a catch basin to quantify reductions in total suspended solids (TSS), volatile suspended solids (VSS), suspended sediment concentration (SSC), total phosphorus (TP), and dissolved phosphorus (DP) from urban stormwater before entering Lake Monona. A comparison of the cumulative load from 33 samples collected during the summers of 2016 and 2017 showed 23% and 45% reductions in TSS and SSC, respectively. A smaller reduction was observed for TP, 16%, whereas DP remained unchanged. Reported traditional catch basin sediment removal varies greatly, although typical removal rates are similar. Results from this study will help regulated municipalities determine whether the use of screened catch basins can help meet water-quality goals.

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USGS2019

Seasonal variation in sediment and phosphorus yields in four Wisconsin agricultural watersheds

Agricultural water quality projects in two distinct topographic regions in Wisconsin collected 5 to 10 yr of continuous stream discharge, suspended sediment (SS), total P (TP), and total dissolved P (TDP) in four watersheds (2100–5000 ha) from 2006 to 2016. Previous agricultural nonpoint SS and TP reduction efforts in two of these watersheds documented cold versus warm season differences in water quality response. The goal of this study was to identify seasonal partitioning of SS, TP, and TDP in storm event loads to inform stream water quality protection efforts. We used National Weather Service Coop Observer frost depth reports to identify dates when watershed soils were frozen. By comparing daily mean event discharge for dates relative to frost, we identified a 32‐d post‐frost high‐discharge “thaw” period. Combined, the frozen and thaw periods contributed about half of the annual SS and TP runoff event loads, ranging from 47 to 63% for SS and from 45 to 51% for TP. The proportion of runoff event TDP during this time was even higher, 62 to 79%, with the majority during thaw. Watershed average volumetric runoff coefficients (event flow/precipitation and snowmelt) were two to four times higher during the freeze and the thaw compared with the rest of the year. To reduce total stream loads in regions with similar climates to Wisconsin, this study indicates that using management practices that curb sediment and P delivery to streams in the winter and early spring may be as important as those designed for nonfrozen conditions.

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USGS2019

Groundwater flow model for Western Chippewa County–Including analysis of water resources related to industrial sand mining and irrigated agriculture

A groundwater flow model for western Chippewa County, Wisconsin, was developed by the Wisconsin Geological and Natural History Survey (WGNHS) and the U.S. Geological Survey (USGS) using the computer program MODFLOW. The model is the result of a five-year groundwater study commissioned by Chippewa County in 2012 to evaluate the effects of industrial sand mining and irrigated agriculture on the county’s water resources. The study incorporates existing data and newly acquired data from fieldwork conducted within the study area. The groundwater model may be useful for future investigations, such as evaluation of proposed high-capacity well sites, development of municipal wellhead protection plans, and studies that seek to further quantify surface water-groundwater relationships. The model conceptualizes the hydrostratigraphy of western Chippewa County as six stacked layers. Each layer is distinct, beginning with unlithified glacial material at the surface, and alternating between sandstones (that act as aquifers) and shale units (that serve as aquitards). The model is bounded below by Precambrian crystalline bedrock and its perimeter was derived from a regional-scale groundwater flow model. The MODFLOW model represented average conditions during 2011–2013 with “steady-state” assumptions, meaning that simulated water levels do not fluctuate seasonally or from year to year. Steady-state models simplify natural variability, making results of scenario simulations easier to interpret and compare while also maximizing effects of stressors because the simulated stress is always applied (not halted after a few months or years). Model calibration used the parameter estimation code (PEST), and calibration targets included heads (groundwater levels) and streamflows. Calibration focused on 2011–2013 because a large amount of head and streamflow data were available for that period. The MODFLOW model explicitly simulates all sources and sinks of water, including groundwater/surface-water interaction with streamflow routing. Model input included estimates of aquifer hydraulic conductivity and a spatial groundwater recharge distribution developed using a GIS-based soil-water-balance (SWB) model applied to the model area. Groundwater withdrawals were simulated for 269 high-capacity wells across the entire model domain, which includes western Chippewa County and adjacent portions of Dunn, Barron, and Rusk Counties. Collectively, these wells withdrew about 1.14 million gallons per year between 2011 and 2013. Once the model was calibrated, it was applied to two distinct scenarios of increased groundwater withdrawals: one evaluating hydrologic effects of more intensive industrial sand mining and the second evaluating the hydrologic effects of more intensive agricultural irrigation practices. Each scenario was developed with input from Chippewa County and a stakeholder group established expressly for this study. The scenarios were designed to represent reasonable future buildout conditions for both mining and irrigated agriculture. The mining scenario underscores the potential hydrologic effects related to changing land-use practices (i.e., hilltops and farmland becoming sand mines), while the irrigated agriculture scenario illustrates the potential hydrologic effects of intensifying existing land-use practices (i.e., installing new wells to irrigate farm fields). While each scenario evaluated distinctly different conditions, modeling results demonstrated the potential of both scenarios to lower the water table and reduce baseflows in headwater streams within the modeled area. In the case of irrigated agriculture, hydrologic effects were associated directly with groundwater withdrawals. By assuming that irrigation did not decrease, this steady-state simulation represented a sustained future effect. By contrast, hydrologic effects of industrial sand mining were the result of both groundwater withdrawals at mines and land-use changes that effectively reduced recharge to groundwater over distinct phases of active mining. This scenario included a post-mining phase, during which groundwater withdrawals stopped and mined areas were reclaimed to undeveloped prairie grass cover. If reclamation to undeveloped prairie indeed occurs as simulated, long-term increases in the water table and stream baseflows are possible. In this sense, the scenario representing build out of irrigated agriculture led to long-term baseflow declines while the future buildout of industrial sand mining led to declines that dissipated following mine reclamation to undisturbed prairie. Future investigations in similar hydrogeologic settings may find the following insights gleaned from this study useful: ❚❚ The characterization of hydrogeologic properties, delineation of hydrogeologic units, and calibration of groundwater flow models benefited from incorporation of accurate well construction reports, high-quality borehole geophysical logs, and streamflow gaging data. ❚❚ Infiltration testing performed in active mining areas provided evidence that reducing the degree and extent of compaction and enhancing areas designed to retain and infiltrate stormwater runoff could potentially reduce runoff and increase groundwater recharge. ❚❚ Similarly, reclaiming mined areas to prairie grasses would be expected to reduce runoff and increase groundwater recharge by reducing compaction and improving soil structure and vegetation that can slow runoff and enhance infiltration.

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USGS2019

Stream corridor sources of suspended sediment and phosphorus from an agricultural tributary to the Great Lakes

Fine-grained sediment and phosphorous are major contaminants in the Great Lakes and their tributaries. Plum Creek, Wisconsin (92 km2), a tributary to the Lower Fox River, has a Total Maximum Daily Load (TMDL) requiring reductions of suspended sediment and phosphorus loading by 70% and 77%, respectively. In 2016-18, an integrated sediment fingerprinting and stream corridor-based sediment budget study was conducted to help quantify upland and stream corridor sources of suspended sediment and phosphorus at a loads monitoring station on Plum Creek. Sediment fingerprinting results indicated that the proportion of upland and stream corridor sources of suspended sediment in Plum Creek varied by season and the amount of runoff; however, bank and gully erosion accounted for 51% and 24% of the suspended sediment annual load, with one or both sources present in all seasons. The next most common source was roadside ditches (11%), which was also present in all seasons. Cropland and woodland sources accounted for small proportions of the suspended sediment, with cropland mainly in summer and woodland in winter, spring, and summer. Relative source proportions for sediment-bound phosphorus were similar to suspended sediment but made up less of the overall loading because on average 27% of the phosphorus load resides in the dissolved phase. Soft fine-grained streambed sediment had source signatures of mainly bank, gully, and ditches (ordered by decreasing proportion). Results from the field-based rapid geomorphic assessment supported the sediment fingerprinting results and in general showed that the amount of bank erosion increases in a downstream direction. The high proportion of sources from banks and gullies is due, in part, to a 20-km long, deeply entrenched valley and steep eroding bluffs between the majority of cropland and the Plum Creek water monitoring station.

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USGS2018

Human-associated indicator bacteria and human-specific viruses in surface water: a spatial assessment with implications on fate and transport

Hydrologic, seasonal, and spatial variability of sewage contamination was studied at six locations within a watershed upstream from water reclamation facility (WRF) effluent to define relative loadings of sewage from different portions of the watershed. Fecal pollution from human sources was spatially quantified by measuring two human-associated indicator bacteria (HIB) and eight human-specific viruses (HSV) at six stream locations in the Menomonee River watershed in Milwaukee, Wisconsin from April 2009 to March 2011. A custom, automated water sampler, which included HSV filtration, was deployed at each location providing unattended, flow-weighted, large-volume (30-913 L) sampling. In addition, wastewater influent samples were composited over discrete seven-day periods from the two Milwaukee WRFs. Of the eight HSV only three were detected, present in up to 38% of the 228 stream samples, while at least one HSV was detected in all WRF influent samples. HIB occurred more often with significantly higher concentrations than the HSV in stream and WRF influent samples (p<0.05). HSV yield calculations showed a loss from upstream to the most downstream sub-watershed of the Menomonee River, and in contrast, a positive HIB yield from this same sub-watershed emphasizes the complexity in fate and transport properties between HSV and HIB. This study demonstrates the utility of analyzing multiple HSV and HIB to provide a weight of evidence approach for assessment of fecal contamination at the watershed level, provides an assessment of relative loadings for prioritizing areas within a watershed, and demonstrates how loadings of HSV and HIB can be inconsistent, inferring potential differences in fate and transport between the two indicators of human fecal presence.

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USGS2018

Water-quality response to changes in phosphorus loading of the Winnebago Pool Lakes, Wisconsin, with special emphasis on the effects of internal loading in a chain of shallow lakes

The Winnebago Pool is a chain of four shallow lakes (Lake Poygan, Lake Winneconne, Lake Butte des Morts, and Lake Winnebago) that are fed primarily by the Fox and Wolf Rivers, two large agriculturally dominated rivers in Wisconsin, United States. Because the lakes have received extensive phosphorus inputs from their watershed, they have become highly eutrophic with much phosphorus in the water column as well as trapped in their sediments. Each of the four Winnebago Pool lakes has been included on the Wisconsin Department of Natural Resources impaired waters list because of their high total phosphorus concentrations, water-quality use restrictions, and excess algal growth. The study described in this report is part of a Total Maximum Daily Load investigation to determine what actions are needed to improve the water quality (trophic status) of these lakes and thus be able to be removed from the impaired waters list and restore their designated uses. As part of this study, data were collected to describe the existing water quality of the lakes, detailed phosphorus budgets were developed for each of the lakes to describe the different sources of the phosphorus, and two eutrophication models (BATHTUB and Jensen models) were used to determine how much of the phosphorus being input to the lakes needs to be reduced for the lakes to be removed from the impaired waters list and restore their designated uses. In-lake water-quality data indicated that each of the lakes had extensive vertical mixing that resulted in their water quality deteriorating throughout summer. Each of the lakes had mean summer total phosphorus concentrations exceeding 0.088 milligram per liter (mg/L), well above the 0.040 mg/L criterion for the lakes. Detailed phosphorus budgets for the lakes indicated that the primary sources of phosphorus were from their tributaries (for the most upstream lake in the Winnebago Pool–Lake Poygan) or from a combination of input from the upstream lakes and phosphorus release from the bottom sediment when only the summer months were considered (for the other three lakes). Model simulations with the BATHTUB and Jensen models indicated that (1) the lakes should have almost linear response in their total phosphorus concentrations to changes in their phosphorus inputs; (2) phosphorus inputs need to be reduced by about 60 percent to the Upper Pool Lakes and 69–73 percent to Lake Winnebago to reduce their mean summer total phosphorus concentrations to 0.040 mg/L; and (3) if all the anthropogenic phosphorus inputs to the lakes could be eliminated, their best possible mean summer total phosphorus concentrations should decrease to about 0.022–0.028 mg/L in the Upper Pool Lakes and to 0.032–0.033 mg/L in Lake Winnebago. The effects of any reduction in phosphorus loading will take many years (50 to more than 75 years) to be fully realized in lake water quality because of phosphorus release from the lake sediments. The effects of nutrient reductions in the watershed of a chain of lakes, such as the Winnebago Pool, gradually cascades down the chain, which has beneficial and detrimental effects. Any action made in the watershed of upstream lakes to reduce phosphorus inputs should improve the water quality of all downstream lakes; however, the upstream lakes delay the response in the downstream lakes, especially in lakes where internal phosphorus loading is important.

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