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USGS1988

Water resources of the Apostle Islands National Lakeshore, northern Wisconsin

The Apostle Islands National Lakeshore consists of 21 islands, part of the Bayfield Peninsula, and the adjacent waters of Lake Superior. Selected water resources of the Apostle Islands National Lakeshore were assessed to aid the National Park Service in developing and managing the Lakeshore and to provide a data base against which future changes can be compared. This summary of water-resources data, collected by the U.S. Geological Survey during 1979-84, provides a qualitative description of selected hydrologic components of the Lakeshore. Streamflow in the Lakeshore area is characterized by typical seasonal fluctuations. Flow in Sand River at State Highway 13 ranged from 3.9 to 1,630 cubic feet per second. The recurrence interval of the maximum observed discharge was about 4 years. The minimum observed 7-day low flow was 3.86 cubic feet per second. The greatest concentrations of most chemical constituents in Bayfield Peninsula streams occurred during base flow. Annual sediment loads in Sand River at State Highway 13 ranged from 977 tons in 1980 water year to 24,600 tons in 1984 water year.The average annual sediment load transported by Bayfield Peninsula streams to the National Lakeshore area of Lake Superior is estimated to be 44,000 tons. Annual phosphorus loads ranged from 1,400 pounds in 1980 water year to 11,100 pounds in 1984 water year. The average annual phosphorus load transported by Bayfield Peninsula streams to the National Lakeshore area of Lake Superior is estimated to be 21,500 pounds. Few island streams flow perennially, but Oak Island streams generally yield more base-flow runoff than Stockton Island streams. The base flow of Oak Island streams is dominated by ground-water discharge, whereas Stockton Island stream base flow is sustained by seepage from wetlands and beaver ponds. There are two major lagoons in the Lakeshore, the Outer Island Lagoon's area is 53 acres and its maximum depth is 7 feet. Dominant inflow to the lagoon is from precipitation on its surface and seepage from an adjacent bog. Outflow during open-water periods is dominated by evaporation. Ground-water seepage from the lagoon toward Lake Superior occurs yearround. The lagoon's water is acidic and has low specific conductance and generally small concentrations of most chemical constituents. The Michigan Island Lagoon is about 4 acres in area and its maximum depth is 6.5 feet. The most significant sources of inflow appear to be precipitation and wave washover from Lake Superior. Water from four deep-water monitoring sites in Lake Superior revealed concentrations of total phosphorus, organic carbon, and recoverable mercury ranging from <0.01 to 0.02 milligrams per liter, 1.1 to 5.3 milligrams per liter and <0.1 to 0.1 micrograms per liter, respectively. Neither pesticide residues nor fecal coliform bacteria were detected in the water column. Total phosphorus concentrations in bottom sediment ranged from 50 to 470 milligrams per kilogram and were related directly to the percentage of fine-grained (< 0.0625 millimeters) sediment particles. Traces of only two pesticide residues- DDE and DDT were detected in sediment. The most abundant benthic macroinvertebrate was Pontoporeia affinis, which was found in densities of from 960 to 2,100 organisms per square meter. No adverse affects resulting from visitor use were detected in the shallow-water, heavy-use areas in Presque Isle Bay off Stockton Island or in the waters between Rocky and South Twin Islands. Phosphorus and organic-carbon concentrations were similar to those observed in the deep-water area; mercury was not detected in water from either area. Ground-water use in the National Lakeshore is primarily for consumption by Lakeshore visitors and employees. Of 14 wells constructed from 1979-84, 4 were finished in glacial sand and gravel, and 10 were finished in sandstone. Specific capacities ranged from 0.63 to 50 gallon per minute per foot. Average concentrations of dissolved solids are moderate and concentrations of heavy metals did not exceed Wisconsin's primary health standard.

Wisconsin↗

USGS2012

Water-quality characteristics of Michigan's inland lakes, 2001-10

The U.S. Geological Survey and the Michigan Department of Environmental Quality (MDEQ) jointly monitored for selected water-quality constituents and properties of inland lakes during 2001–10 as part of Michigan's Lake Water-Quality Assessment program. During 2001–10, 866 lake basins from 729 inland lakes greater than 25 acres were monitored for baseline water-quality conditions and trophic status. This report summarizes the water-quality characteristics and trophic conditions of the monitored lakes throughout the State; the data include vertical-profile measurements, nutrient measurements at three discrete depths, Secchi-disk transparency (SDT) measurements, and chlorophyll a measurements for the spring and summer, with major ions and other chemical indicators measured during the spring at mid-depth and color during the summer from near-surface samples. In about 75 percent of inland lake deep basins (index stations), trophic characteristics were associated with oligotrophic or mesotrophic conditions; 5 percent or less were categorized as hypereutrophic, and 80 percent of hypereutrophic lakes had a maximum depth of 30 feet or less. Comparison of spring and summer measurements shows that water clarity based on SDT measurements were clearer in the spring than in the summer for 63 percent of lakes. For near-surface measurements made in spring, 97 percent of lakes can be considered phosphorus limited and less than half a percent nitrogen limited; for summer measurements, 96 percent of lakes can be considered phosphorus limited and less than half a percent nitrogen limited. Spatial patterns of major ions, alkalinity, and hardness measured in the spring at mid-depth all showed lower values in the Upper Peninsula of Michigan and a southward increase toward the southern areas of the Lower Peninsula, though the location of increase varied by constituent. A spatial analysis of the data based on U.S. Environmental Protection Agency Level III Ecoregions separated potassium, sulfate, and chloride concentrations fairly well, with a pattern of lower values in northern ecoregions trending toward higher values in southern ecoregions; lower and higher concentrations of magnesium, hardness, calcium, and alkalinity were well separated, but middle-range concentrations in central Michigan ecoregions were mixed. The highest concentrations of chloride and sodium were in the southeastern area of the Lower Peninsula. Lakes with multiple basins showed few statistically significant differences in constituent concentrations at the 95-percent confidence level among combinations of depths between basins. The most statistically significant differences were found for water temperature, with significant differences in somewhat less than half the combinations in the spring and just a few combinations in the summer. The lack of significant differences between major basins of multibasin lakes indicates that monitoring of trophic characteristics in all major basins might not be necessary for the majority of constituents in future sampling programs. Trophic characteristics based on the 2001–10 dataset were compared to trophic characteristics resulting from other Michigan sampling programs, including the volunteer Cooperative Lakes Monitoring Program coordinated by the MDEQ (measurements on 250 lakes in 2011), trophic-state predictions produced by relating existing measurements to remotely sensed data (measurements for about 3,000 lakes), and the National Lakes Assessment (NLA) statistically valid, probability-designed lakes program (measurements for 50 lakes in Michigan and about 1,100 lakes nationally). A higher percentage of oligotrophic lakes resulted when using SDT from the volunteer data and the 2001–10 dataset than when using the predicted measurements from remotely sensed data or the NLA. Comparing trophic characteristics from differently designed programs provides multiple interpretations of lake water-quality status in Michigan lakes. No directional statistically significant difference was found at the 95-percent confidence level among historical nutrients and trophic characteristics when comparing 445 lakes with historical data for 1974–84 with the 2001–10 dataset, though SDT did show statistically significant differences at the 95-percent confidence level. Depending on the primary indicator, 50–66 percent of lakes did not change trophic-status class, 13–23 percent moved towards the oligotrophic end of the TSI scale, and 20–25 percent moved a class towards the eutrophic end of the TSI scale. Increasing percentages of urban-dominant land cover in the drainage areas of lakes had a more positive correlation with chloride concentration than did increased percentages of other land-cover classes; there was also a slight correlation of urban-dominant land cover and calcium concentration. Removing data for lakes in southeastern Lower Michigan, known from previous reports to be higher in chloride, still resulted in a positive relation even though the coefficient of determination (R 2 value) decreased from 0.55 to 0.39. Dominant land-cover drainage areas were not strongly related to nutrients with respect to a linear relation, nor were lake drainage-area sizes.

Michigan↗

USGS2023

PCB source assessment in the lower Clinton River, Clinton River Area of Concern, Mount Clemens, Michigan

Polychlorinated biphenyls (PCBs), some of the earliest “forever chemicals,” were used for decades in the United States before 1979 when PCB manufacturing was banned. High PCB concentrations were found recently in the lower Clinton River in the Great Lakes drainage. To determine the possible existence, location, and significance of a current source of PCBs, the U.S. Geological Survey (USGS) deployed passive water samplers (SPMDs, semipermeable membrane devices) in the river at 15 sites for 1 month in 2019 near outfalls of interest and other locations. USGS also deployed passive stream sediment samplers at a subset of four sites during the same period and collected bank sediment samples at a subset of four sites. Sediment from nearby catch basins was also collected. Samples were assayed for 209 individual PCB congeners, and patterns in total and individual congeners were evaluated; ancillary sediment data included grain size, total organic carbon, and moisture. U.S. Army Corps of Engineers (USACE) data for total PCBs and 209 PCB congeners in surficial sediment samples collected in 2019 were also evaluated. In general, total PCBs were highest in streambed sediment, followed by catch basin sediment, bank sediment, and then water as estimated from SPMDs. Total PCBs in sediment were low in all catch basins but one (sample CB19–02) that drains from an historical landfill area to one of two adjacent outfalls of interest: the outfall for a nearby wastewater treatment plant and adjacent outfall MTC–R–060, where the highest total PCBs in USGS stream sediment samples were found (site 14, sample 14STRM; 1,260,000 picograms per gram). Also, the SPMD at site 14 was the only water sample with more “light” (three or fewer chlorine atoms) than “heavy” (four or more chlorine atoms) PCB congeners, and the passive sediment sample had the highest proportion of light PCBs in USGS sediment samples. Light PCB congeners degrade more quickly than heavy PCB congeners and results may indicate that one or more current sources of PCBs are contributing to total PCBs in sediment at four river sites. Of 209 possible PCB congeners assayed, 117 congeners were detected in water samples; 155 and 154 congeners were detected in USGS and USACE sediment samples, respectively. PCBs 28, 73, 31, and 18 (highest to lowest) contributed most toward total PCBs in water samples overall; PCBs 20/28, 31, 52, and 44/47/65 contributed most toward total PCBs for sediment in USGS stream samples overall and USACE samples overall; these rankings were also true for catch basins overall except for PCB–31. After omitting coeluting congeners to allow further comparison, 5 key PCB congeners are in the top 20 congeners across all assay groups: 17, 31, 52, 95, and 118. The importance of these congeners in multiple assays aligns with their importance as components of certain Aroclors. Sediment from the high PCB catch basin (sample CB19–02) had a different pattern of top congeners than the other catch basins, and multivariate analyses indicated a high degree of similarity in its overall congener pattern with that of the highest PCB sediment sample (sample 14STRM) collected by the outfalls for the catch basin and the wastewater treatment plant. Similarities in overall congener patterns across sample media as determined by multivariate analyses confirmed some site linkages and the possibility of more than one source of PCBs to the reach. Furthermore, equilibrium partitioning calculations indicated that water concentrations as estimated by SPMDs were high enough to result in the PCB concentrations measured in USGS passive sediment samples but not USACE surficial sediment samples when normalized by organic carbon. However, the SPMDs and passive sediment samples reflect only one month of contribution to the river and higher concentrations would be expected to result with years of PCB accumulation. PCBs contributed to the river water by outfalls could eventually partition to sediment in the reach. Thus, the river could have a current source or sources of PCBs, perhaps one or more outfalls near four sites. Additional investigation is needed to better define the relative significance of each outfall and areas in nearby drainage systems that may be contributing PCBs to outfalls and the river.

Michigan↗

USGS2009

Processing, Analysis, and General Evaluation of Well-Driller Logs for Estimating Hydrogeologic Parameters of the Glacial Sediments in a Ground-Water Flow Model of the Lake Michigan Basin

In 2005, the U.S. Geological Survey began a pilot study for the National Assessment of Water Availability and Use Program to assess the availability of water and water use in the Great Lakes Basin. Part of the study involves constructing a ground-water flow model for the Lake Michigan part of the Basin. Most ground-water flow occurs in the glacial sediments above the bedrock formations; therefore, adequate representation by the model of the horizontal and vertical hydraulic conductivity of the glacial sediments is important to the accuracy of model simulations. This work processed and analyzed well records to provide the hydrogeologic parameters of horizontal and vertical hydraulic conductivity and ground-water levels for the model layers used to simulated ground-water flow in the glacial sediments. The methods used to convert (1) lithology descriptions into assumed values of horizontal and vertical hydraulic conductivity for entire model layers, (2) aquifer-test data into point values of horizontal hydraulic conductivity, and (3) static water levels into water-level calibration data are presented. A large data set of about 458,000 well driller well logs for monitoring, observation, and water wells was available from three statewide electronic data bases to characterize hydrogeologic parameters. More than 1.8 million records of lithology from the well logs were used to create a lithologic-based representation of horizontal and vertical hydraulic conductivity of the glacial sediments. Specific-capacity data from about 292,000 well logs were converted into horizontal hydraulic conductivity values to determine specific values of horizontal hydraulic conductivity and its aerial variation. About 396,000 well logs contained data on ground-water levels that were assembled into a water-level calibration data set. A lithology-based distribution of hydraulic conductivity was created by use of a computer program to convert well-log lithology descriptions into aquifer or nonaquifer categories and to calculate equivalent horizontal and vertical hydraulic conductivities (K and KZ, respectively) for each of the glacial layers of the model. The K was based on an assumed value of 100 ft/d (feet per day) for aquifer materials and 1 ft/d for nonaquifer materials, whereas the equivalent KZ was based on an assumed value of 10 ft/d for aquifer materials and 0.001 ft/d for nonaquifer materials. These values were assumed for convenience to determine a relative contrast between aquifer and nonaquifer materials. The point values of K and KZ from wells that penetrate at least 50 percent of a model layer were interpolated into a grid of values. The K distribution was based on an inverse distance weighting equation that used an exponent of 2. The KZ distribution used inverse distance weighting with an exponent of 4 to represent the abrupt change in KZ that commonly occurs between aquifer and nonaquifer materials. The values of equivalent hydraulic conductivity for aquifer sediments needed to be adjusted to actual values in the study area for the ground-water flow modeling. The specific-capacity data (discharge, drawdown, and time data) from the well logs were input to a modified version of the Theis equation to calculate specific capacity based horizontal hydraulic conductivity values (KSC). The KSC values were used as a guide for adjusting the assumed value of 100 ft/d for aquifer deposits to actual values used in the model. Water levels from well logs were processed to improve reliability of water levels for comparison to simulated water levels in a model layer during model calibration. Water levels were interpolated by kriging to determine a composite water-level surface. The difference between the kriged surface and individual water levels was used to identify outlier water levels. Examination of the well-log lithology data in map form revealed that the data were not only useful for model input, but also were useful for understanding th

Scientific Investigations Report↗

USGS2016

Hydrologic data and groundwater-flow simulations in the Brown Ditch Watershed, Indiana Dunes National Lakeshore, near Beverly Shores and Town of Pines, Indiana

The U.S. Geological Survey (USGS) collected data and simulated groundwater flow to increase understanding of the hydrology and the effects of drainage alterations on the water table in the vicinity of Great Marsh, near Beverly Shores and Town of Pines, Indiana. Prior land-management practices have modified drainage and caused changes in the distribution of open water, streams and ditches, and groundwater abundance and flow paths. Collected hydrologic data indicate that the majority of water entering Great Marsh flows from the southern dune ridge beneath Town of Pines, Indiana. Groundwater flow is intercepted by Brown Ditch in the eastern portion of the study area and Derby Ditch in the western portion of the study area. A smaller amount of groundwater from the northern dune ridge beneath Beverly Shores also contributed water to Great Marsh. Continuous groundwater-level data collected indicate that the predominant north-south groundwater-flow gradients vary during the course of the year due to increased levels of precipitation or during periods of drainage obstructions. Continuous surface-water discharge and surface-water elevation were measured at three USGS streamgages, one each on Brown, Kintzele and Derby Ditches. The monthly mean discharge statistics indicate that during the period of record— June 2012 to September 2013—streamflow in Kintzele Ditch was lowest during July 2012 and highest during April 2013. In Derby Ditch, streamflow also was lowest during July 2012 and highest during April 2013. Periods of relatively high and low groundwater levels during August 1982, March 2013, and April 2014 were examined and simulated by using MODFLOW and companion software. Results from the simulation of conditions during March 2013 include that nearly 100 percent of all water entering the area simulating Town of Pines is from recharge. Of all the water simulated to enter the eastern and western portions of Great Marsh, nearly 20 and 18 percent, respectively, flows from Town of Pines to the western and eastern portions of Great Marsh. The dune ridges beneath Town of Pines and to a lesser extent beneath Beverly Shores are a major source of recharge to the surficial aquifer and Great Marsh. Results from the simulation of the conditions of April 2014 include that, despite increases in the amount of water entering Great Marsh due to a beaver-dam-modified hydrologic condition, there is still virtually zero simulated groundwater flow from Great Marsh to Town of Pines. The volume of water simulated to be entering the zone representing Beverly Shores decreased by 0.43 cubic foot per second from the results of the March 2013 simulation. This simulated difference in water budgets can be attributed to increased simulated recharge in Great Marsh and Town of Pines. Effects of the inclusion of the beaver dam included the increase of the simulated water table and simulated inundated area upstream of the beaver dam due to the effects of ponding surface water. Results from the simulation scenario that includes six proposed pool-riffle control structures in Brown Ditch under the hydrologic conditions of March 2013 indicate areas inundated by water are larger, including areas just to the north of the entrance of Brown Ditch into Great Marsh, and areas north of the confluence of Brown and Kintzele Ditches. Results from the scenario simulating the increase of the Lake Michigan water level to the historical high of May 31, 1998, showed inundated areas of Great Marsh south of Beverly Shores enlarged on both sides of Lakeshore County Road with the greatest enlargement simulated to be southeast of the intersection of Lakeshore County Road and Beverly Drive. For the scenario simulating the decrease of the Lake Michigan water level to the historical low of December 23, 2007, results show little change from the original March 2013 inundated area. The results of this study can be used by water-resource managers to understand how surrounding ditches affect water levels in Great Marsh and other inland wetlands and residential areas. The groundwater model developed can be applied to answer questions about how alterations to the drainage system in the area affects water levels in the public and residential areas surrounding Great Marsh. The modeling methods developed in this study provide a template for other studies of groundwater flow and groundwater/surface-water interactions within the shallow surficial aquifer in northern Indiana, and in similar hydrologic settings that include surficial sand aquifers in coastal areas.

Indiana↗

USGS1998

Geohydrology and simulated ground-water flow in northwestern Elkhart County, Indiana

In 1994, the U.S. Geological Survey, in cooperation with the U.S. Environmental Protection Agency and the City of Elkhart, developed a ground-water model of the Elkhart, Indiana, area to determine the avail-ability and source of water at potential new well fields. The modeled area covered 190 square miles of northwestern Elkhart County and a small part of southern Michigan. Three Superfund sites and several other sites in this area are undergoing environmental cleanup. The model would be used to guide the location of well fields so that Superfund sites and environmental cleanup areas would not be within recharge areas for the well fields. The City of Elkhart obtains its water supply from two aquifers separated by a generally continuous confining unit. The upper aquifer is composed primarily of sand and gravel of glacial origin. Thickness of the upper aquifer ranges from 0 to 116 feet and averages 47 feet. The lower aquifer is composed of sand and gravel with interbedded lenses of silt and clay. Thickness of the lower aquifer ranges from 1 to 335 feet and averages 35 feet. The intervening confining unit is composed of silt and clay with interbedded sand and gravel; the confining unit ranges from 0 to 177 feet, with an average thickness of 27 feet. Flow through the aquifers is generally horizontal vertically downward from the upper aquifer, through the confining unit, and into the lower aquifer, except where flow is vertically upward at the St. Joseph River and other large streams. The hydraulic characteristics of the aquifers and confining unit were estimated by analyzing aquifer-test data from well drillers? logs and by calibration of the model. The horizontal hydraulic conductivity of the upper aquifer is 170 feet per day within about 1 mile of the St. Joseph and Elkhart Rivers and 370 feet per day at distances greater than about 1 mile. The horizontal hydraulic conductivity of the lower aquifer is 370 feet per day throughout the modeled area, with the exception of an area near the center of the modeled area where the horizontal hydraulic conductivity is 170 feet per day. Transmissivity of the lower aquifer increases generally from southwest to northeast; transmissivity values range from near 0 where the lower aquifer is absent to 57,000 square feet per day and average about 8,100 square feet per day. The vertical hydraulic conductivity of the confining unit is 0.07 feet per day; the vertical conductivity of the streambeds commonly is 1.0 foot per day and ranges from 0.05 foot per day to 50 feet per day. The areal recharge rate to the outwash deposits was determined by a base-flow separation technique to be 16 inches per year, and the areal recharge rate to the till was assumed to be 4 inches per year. A two-layer digital model was used to simulate flow in the ground-water system. The model was calibrated on the basis of historical water-use data, water-level records, and gain/loss data for streams during May and June 1979. The model was recalibrated with water-use data and water-level records from 1988. For 1979 data, 49 percent of the inflow to the model area is from precipitation and 46 percent is ground-water inflow across the model boundaries. Most of the ground-water inflow across the model boundary is from the north and east, which corresponds to high values of transmissivity?as high as 57,000 feet squared per day?in the model layers in the northern and eastern areas. Eighty-two percent of the ground-water discharge is to the streams; 5 percent of the ground-water discharge is to wells. Source areas and flow paths to the City of Elkhart public well fields are affected by the location of streams and the geology in the area. Flow to the North Well Field originates north-west of the well field, forms relatively straight flow paths, and moves southeast toward the well field and the St. Joseph River. Flow to the South Well Field begins mostly in the out-wash along Yellow Creek south of the well field, moves northward, and t

Indiana↗

USGS2013

Hydrologic data and groundwater flow simulations in the vicinity of Long Lake, Indiana Dunes National Lakeshore, near Gary, Indiana

The U.S. Geological Survey (USGS) collected data and simulated groundwater flow to increase understanding of the hydrology and the effects of drainage alterations to the water table in the vicinity of Long Lake, near Gary, Indiana. East Long Lake and West Long Lake (collectively known as Long Lake) make up one of the largest interdunal lakes within the Indiana Dunes National Lakeshore. The National Park Service is tasked with preservation and restoration of wetlands in the Indiana Dunes National Lakeshore along the southern shoreline of Lake Michigan. Urban development and engineering have modified drainage and caused changes in the distribution of open water, streams and ditches, and groundwater abundance and flow paths. A better understanding of the effects these modifications have on the hydrologic system in the area will help the National Park Service, the Gary Sanitary District (GSD), and local stakeholders manage and protect the resources within the study area. This study used hydrologic data and steady-state groundwater simulations to estimate directions of groundwater flow and the effects of various engineering controls and climatic conditions on the hydrology near Long Lake. Periods of relatively high and low groundwater levels were examined and simulated by using MODFLOW and companion software. Simulated hydrologic modifications examined the effects of (1) removing the beaver dams in US-12 ditch, (2) discontinuing seepage of water from the filtration pond east of East Long Lake, (3) discontinuing discharge from US-12 ditch to the GSD sewer system, (4) decreasing discharge from US-12 ditch to the GSD sewer system, (5) connecting East Long Lake and West Long Lake, (6) deepening County Line Road ditch, and (7) raising and lowering the water level of Lake Michigan. Results from collected hydrologic data indicate that East Long Lake functioned as an area of groundwater recharge during October 2002 and a “flow-through” lake during March 2011, with the groundwater divide south of US-12. Wetlands to the south of West Long Lake act as points of recharge to the surficial aquifer in both dry- and wet-weather conditions. Among the noteworthy results from a dry-weather groundwater flow model simulation are (1) US-12 ditch does not receive water from East Long Lake or West Long Lake, (2) the filtration pond at the east end of East Long Lake, when active, contributed approximately 10 percent of the total water entering East Long Lake, and (3) County Line Road ditch has little effect on simulated water level. Among the noteworthy results from a wet-weather groundwater flow simulation are (1) US-12 ditch does not receive water from East Long Lake or West Long Lake, (2) when the seepage from the filtration pond to the surficial aquifer is not active, sources of inflow to East Long Lake are restricted to only precipitation (46 percent of total) and inflow from the surficial aquifer (54 percent of total), and (3) County Line Road ditch bisects the groundwater divide and creates two water-table mounds south of US-12. The results from a series of model scenarios simulating certain engineering controls and changes in Lake Michigan levels include the following: (1) The simulated removal of beaver dams in US-12 ditch during a wet-weather simulation increased discharge from the ditch to the Gary Sanitary system by 13 percent. (2) Discontinuation of seepage from the filtration pond east of East Long Lake decreased discharge from US-12 ditch to the Gary Sanitary system by 2.3 percent. (3) Simulated discontinuation of discharge from the US-12 ditch to the GSD sewer system increased the area where the water table was estimated to be above the land surface beyond the inundated area in the initial wet-weather simulation. (4) Simulated modifications to the control structure at the discharge point of US-12 ditch to the GSD sewer system can decrease discharge by as much as 61 percent while increasing the simulated inundated area during dry weather and decrease discharge as much as 6 percent while increasing the simulated inundated area during wet weather. (5) Deepening of County Line Road ditch can decrease the discharge from US-12 ditch by 26 percent during dry weather and 24 percent during wet weather, as well as decrease the extent of flooded areas south and east of the filtration pond near Ogden Dunes. (7) The increase of the Lake Michigan water level to match the historical maximum can increase the discharge from US-12 ditch by 14 percent during dry weather and by 9.6 percent during wet weather. (8) The decrease of the Lake Michigan water level to match the historical minimum can decrease the discharge from US-12 ditch by 7.4 percent during dry weather and by 3.1 percent during wet weather. The results of this study can be used by water-resource managers to understand how surrounding ditches affect water levels in East and West Long Lake and in the surrounding wetlands and residential areas. The groundwater model developed in this study can be applied in the future to answer questions about how alterations to the drainage system in the area will affect water levels in East and West Long Lake and surrounding areas. The modeling methods developed in this study provide a template for other studies of groundwater flow and groundwater/surface-water interactions within the shallow surficial aquifer in northern Indiana, and in similar hydrologic settings that include surficial sand aquifers in coastal settings.

Indiana↗

USGS2017

Estimation of the groundwater resources of the bedrock aquifers at the Kettle Moraine Springs State Fish Hatchery, Sheboygan County, Wisconsin

Groundwater resources information was needed to understand regional aquifer systems and water available to wells and springs for rearing important Lake Michigan fish species at the Kettle Moraine Springs State Fish Hatchery in Sheboygan County, Wisconsin. As a basis for estimating the groundwater resources available, an existing groundwater-flow model was refined, and new groundwater-flow models were developed for the Kettle Moraine Springs State Fish Hatchery area using the U.S. Geological Survey (USGS) finite-difference code MODFLOW. This report describes the origin and construction of these groundwater-flow models and their use in testing conceptual models and simulating the hydrogeologic system. The study area is in the Eastern Ridges and Lowlands geographical province of Wisconsin, and the hatchery property is situated on the southeastern edge of the Kettle Moraine, a north-south trending topographic high of glacial origin. The bedrock units underlying the study area consist of Cambrian, Ordovician, and Silurian units of carbonate and siliciclastic lithology. In the Sheboygan County area, the sedimentary bedrock sequence reaches a thickness of as much as about 1,600 feet (ft). Two aquifer systems are present at the Kettle Moraine Springs State Fish Hatchery. A shallow system is made up of Silurian bedrock, consisting chiefly of dolomite, overlain by unconsolidated Quaternary-age glacial deposits. The glacial deposits of this aquifer system are the typical source of water to local springs, including the springs that have historically supplied the hatchery. The shallow aquifer system, therefore, consists of the unconsolidated glacial aquifer and the underlying bedrock Silurian aquifer. Most residential wells in the area draw from the Silurian aquifer. A deeper confined aquifer system is made up of Cambrian- and Ordovician-age bedrock units including sandstone formations. Because of its depth, very few wells are completed in the Cambrian-Ordovician aquifer system (COAS) near the Kettle Moraine Springs State Fish Hatchery. Three groundwater-flow models were used to estimate the water resources available to the hatchery from bedrock aquifers under selected scenarios of well placement and seasonal water requirements and subject to constraints on the effects of pumping on neighboring wells, local springs, and creeks. Model input data (recharge, water withdrawal, and boundary conditions) for these models were compiled from a number of data and information sources. The first model, named the “KMS model,” (KMS stands for Kettle Moraine Springs) is an inset model derived from a published USGS regional Lake Michigan Basin model and was constructed to simulate groundwater pumping from the semiconfined Silurian aquifer. The second model, named the “Pumping Test model,” was constructed to evaluate an aquifer pumping test conducted in the COAS as part of this project. The Pumping Test model was also used to simulate the local effects of 20 years of groundwater pumping from this deep bedrock aquifer for future hatchery operations. The third model, named the “LMB modified model,” is a version of the published Lake Michigan Basin (LMB) model that was modified with aquifer parameters refined in an area around the hatchery (approximately a 5-mile radius circle, corresponding to the area stressed by the aquifer pumping test). This LMB modified model was applied to evaluate regional effects of pumping from the confined COAS. The available Silurian aquifer groundwater resource was estimated using the KMS model with three scenarios—named “AllConstraints,” “Constraints2,” and “Constraints3”—that specified local water-level and flow constraints such as drawdown at nearby household wells, water levels inside pumping well boreholes, and flow in local streams and springs. Each scenario utilized the MODFLOW Groundwater Management Process (GWM) to select three locations from six candidate locations that provided the greatest combined flow while satisfying the constraints. The three constraint scenarios provided estimates of 430 gallons per minute (gal/min), 480 gal/min, and 520 gal/min pumping from three wells—AllConstraints, Constraints2, and Constraints3, respectively. The same three wells were selected for the scenarios that estimated 480 gal/min and 520 gal/min; the scenario that estimated 430 gal/min shared two of these same wells, but the third selected well was different. The available COAS groundwater resource was estimated by two scenarios with each conducted over a period of 20 years with the Pumping Test model and the LMB modified model . The Pumping Test model was used to simulate local effects of pumping, and the LMB modified model was used to simulate regional effects of pumping. The scenarios simulate a range of total and seasonal pumping rates potentially linked to site activities. Scenario 1 simulates two wells completed in the Cambrian-Ordovician aquifer system, each pumping for 8 months at 300 gal/min, followed by pumping for 4 months at 600 gal/min. The average yearly pumping rate of Scenario 1 is 800 gal/min. Scenario 2 simulates three wells completed in the Cambrian-Ordovician aquifer system pumping for 8 months at 200 gal/min, followed by pumping for 4 months at 500 gal/min. The average yearly pumping rate of Scenario 2 is 900 gal/min. The Pumping Test model simulations confirmed that drawdown in the boreholes of the pumping wells at the selected 2-well or 3-well rates will meet the desired condition that the pumping water level remains at least 100 ft above the highest Cambrian-Ordovician unit open to the well. The LMB modified model was used to evaluate the regional drawdown of the pumping from the confined COAS under the same 2-well and 3-well scenarios. At the nearest known existing COAS well, Campbellsport production well #4, the simulated drawdown for Scenario 1 after 20 years of cyclical pumping with two pumping wells averaging a total of 800 gal/min is 16.9 ft, whereas the simulated drawdown for Scenario 2 after 20 years of pumping with three pumping wells averaging a total of 900 gal/min is 19.0 ft. The total deep aquifer thickness at the Campbellsport location is on the order of 620 ft, meaning that the simulated drawdown for either scenario is about 3 percent of the confined aquifer thickness. The models developed as part of this project are archived in the project data release. The archive includes the model input and output files as well as MODFLOW source code and executables. ( Haserodt and others, 2017 ).

Wisconsin↗

USGS2016

Water quality and hydrology of Silver Lake, Oceana County, Michigan, with emphasis on lake response to nutrient loading

Executive Summary Silver Lake is a 672-acre inland lake located in Oceana County, Michigan, and is a major tourist destination due to its proximity to Lake Michigan and the surrounding outdoor recreational opportunities. In recent years, Silver Lake exhibited patterns of high phosphorus concentrations, elevated chlorophyll a concentrations, and nuisance algal blooms. The U.S. Geological Survey (USGS), in cooperation with the Silver Lake Improvement Board and in collaboration with the Annis Water Resources Institute (AWRI) of Grand Valley State University, designed a study to assess the hydrologic and nutrient inputs to Silver Lake in order to identify the events and conditions that affect the nutrient chemistry and production of algal blooms in the lake. This information can inform water-resource managers in developing various management strategies to prevent or reduce the occurrence of future algal blooms. USGS and AWRI scientists collected data from November 2012 to December 2014 to provide information for future management decisions for Silver Lake. Silver Lake can be classified as a polymictic lake and has a residence time of approximately 223 days. Based on the mean lake Secchi depth, total phosphorus, and total nitrogen concentrations, Silver Lake is classified as a eutrophic lake. In-situ bioassay results indicate that algal growth in Silver Lake is colimited by both nitrogen and phosphorus. The nutrient budget for Silver Lake was calculated using the BATHTUB model based on 2 years of water-quality data collection. The BATHTUB model, developed by the U.S. Army Corps of Engineers, treats the lake as a well-mixed system with multiple inputs and outlets for both water and dissolved constituents, such as nutrients. Based on results of the BATHTUB model, which were conditioned on observed concentrations and flows, the mean annual input of phosphorus to Silver Lake was approximately 1,342 pounds (lb); the mean annual input of nitrogen to Silver Lake was approximately 51,998 lb. The major measured sources of phosphorus loading to Silver Lake were groundwater and Hunter Creek, whereas the major measured sources of nitrogen to Silver Lake were Hunter Creek, groundwater, and atmospheric deposition. The largest loading of phosphorus and nitrogen to Silver Lake occurred during the spring. Minimal phosphorus deposition (if any) occurred in the lakebed sediment; however, of the nitrogen that entered Silver Lake, approximately 42.2 percent was deposited in the lakebed sediment as simulated by the BATHTUB model. In addition to measured sources, a septic load model was used to estimate the likely range of septic contribution to groundwater and adjacent surface waters. The likely septic loading scenario estimates that septic systems contribute 47.8 percent of the phosphorus to groundwater and 22.3 percent of phosphorus to Hunter Creek. These results indicate that septic systems are a major source of phosphorus loading to Silver Lake. The likely septic loading scenario indicated that septic systems account for 0.95 percent of the nitrogen load to Hunter Creek and 1.1 percent of the contribution of nitrogen to groundwater. The BATHTUB model was used to estimate future nutrient loading and eutrophication scenarios based on water-quality data collected from Silver Lake, groundwater, major tributaries, and atmospheric deposition. A separate septic load model was used to estimate the septic contribution to groundwater or directly to surface water, and the nutrient load estimates were modeled using the BATHTUB model to determine subsequent water-quality changes to Silver Lake. BATHTUB model scenarios based on measured data: The first BATHTUB scenario evaluated the condition of Silver Lake and the change to lake water quality (trophic status) as a result of changes in nutrient loading from different sources. Based on BATHTUB model simulations, if groundwater loading of phosphorus and nitrogen only were decreased by 75 percent, and all of the other nutrient inputs stayed the same, the future condition of Silver Lake would most likely remain highly mesotrophic to eutrophic (the current [2014] condition of Silver Lake). If nutrient loading continued to increase in groundwater, the lake would continue to remain eutrophic with more frequent algal blooms. If nutrient loading from Hunter Creek only decreased by 50–75 percent, and all of the other nutrient inputs stayed the same as the baseline dataset, Silver Lake would remain eutrophic to highly mesotrophic. By reducing the input of manageable nutrient sources (Hunter Creek, groundwater, and lawn runoff) by 75 percent, the BATHTUB model simulation indicates that Silver Lake would be classified as mesotrophic, which is indicative of improved water quality, water clarity, and reduced algal bloom frequency. Simulations also were run using the BATHTUB model to evaluate the number of days Silver Lake could experience algal blooms (algal blooms are defined as modeled chlorophyll a in excess of 10 micrograms per liter [µg/L]) as a result of an increase/decrease in phosphorus and nitrogen loading from groundwater, Hunter Creek, and (or) a combination of sources. If the phosphorus and nitrogen loading from Hunter Creek is decreased (and all other sources are not altered), Silver Lake will continue to experience algal blooms, but less frequently than what is currently experienced. The same scenario holds true if the nutrient loading from groundwater is decreased. Another scenario was simulated using a combination of sources, which includes increases and decreases in phosphorus and nitrogen loading from sources that are the most likely to be managed, and includes groundwater (as a result of conversion of household septic to sewers), Hunter Creek (conversion of household septic to sewers), and lawn runoff. Results of the BATHTUB model indicated that a 50-percent reduction of phosphorus and nitrogen from these sources would result in a considerable decrease in algal bloom frequency (from 231 to 132 days) and severity, and a 75-percent reduction would greatly reduce algal bloom occurrence on Silver Lake (from 231 to 57 days). BATHTUB model scenarios based on septic load model: A scenario also was conducted using the BATHTUB model to simulate the conversion of septic to sewer and included a low, high, and medium (likely) scenario of nutrient loading to Silver Lake. Simulations of the BATHTUB model indicated that, under the likely scenario, the conversion of all onsite septic treatment to sewers would result in an overall change in lake trophic status from eutrophic to mesotrophic, thereby reducing the frequency of algal blooms and algal bloom intensity on Silver Lake (chlorophyll a >10 µg/L, from 231 to 184 days per year, or chlorophyll a >20 µg/L, from 80 to 49 days per year).

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