Geology topics

Steven R. Corsi

Publications and source records attributed to Steven R. Corsi.

69 records · Page 4Linked to original sources

USGS2013

Effects of best-management practices in Bower Creek in the East River priority watershed, Wisconsin, 1991-2009

Hydrologic and water-quality data were collected at Bower Creek during the periods before best-management practices (BMPs), and after BMPs were installed for evaluation of water-quality improvements. The monitoring was done between 1990 and 2009 with the pre-BMP period ending in July 1994 and the post-BMP period beginning in October 2006. BMPs installed in this basin included streambank protection and fencing, stream crossings, grade stabilization, buffer strips, various barnyard-runoff controls, nutrient management, and a low degree of upland BMPs. Water-quality evaluations included base-flow concentrations and storm loads for total suspended solids, total phosphorus, and ammonia nitrogen. The only reductions detected between the base-flow samples of the pre- and post-BMP periods were in median concentrations of total phosphorus from base-flow samples, but not for total suspended solids or dissolved ammonia nitrogen. Differences in storm loads for the three water-quality constituents monitored were not observed during the study period.

Wisconsin↗

USGS2013

Organic waste compounds in streams: Occurrence and aquatic toxicity in different stream compartments, flow regimes, and land uses in southeast Wisconsin, 2006–9

An assessment of organic chemicals and aquatic toxicity in streams located near Milwaukee, Wisconsin, indicated high potential for adverse impacts on aquatic organisms that could be related to organic waste compounds (OWCs). OWCs used in agriculture, industry, and households make their way into surface waters through runoff, leaking septic-conveyance systems, regulated and unregulated discharges, and combined sewage overflows, among other sources. Many of these compounds are toxic at elevated concentrations and (or) known to have endocrine-disrupting potential, and often they occur as complex mixtures. There is still much to be learned about the chronic exposure effects of these compounds on aquatic populations. During 2006–9, the U.S. Geological Survey, in cooperation with the Milwaukee Metropolitan Sewerage District (MMSD), conducted a study to determine the occurrence and potential toxicity of OWCs in different stream compartments and flow regimes for streams in the Milwaukee area. Samples were collected at 17 sites and analyzed for a suite of 69 OWCs. Three types of stream compartments were represented: water column, streambed pore water, and streambed sediment. Water-column samples were subdivided by flow regime into stormflow and base-flow samples. One or more compounds were detected in all 196 samples collected, and 64 of the 69 compounds were detected at least once. Base-flow samples had the lowest detection rates, with a median of 12 compounds detected per sample. Median detection rates for stormflow, pore-water, and sediment samples were more than double that of base-flow samples. Compounds with the highest detection rates include polycyclic aromatic hydrocarbons (PAHs), insecticides, herbicides, and dyes/pigments. Elevated occurrence and concentrations of some compounds were detected in samples from urban sites, as compared with more rural sites, especially during stormflow conditions. These include the PAHs and the domestic waste-water-indicator compounds, among others. Urban runoff and storm-related leaks of sanitary sewers and (or) septic systems may be important sources of these and other compounds to the streams. The Kinnickinnic River, a highly urbanized site, had the highest detection rates and concentrations of compounds of all the sampled sites. The Milwaukee River near Cedarburg—one of the least urban sites—and the Outer Milwaukee Harbor site had the lowest detection rates and concentrations. Aquatic-toxicity benchmarks were exceeded for 12 of the 25 compounds with known benchmarks. The compounds with the greatest benchmark exceedances were the PAHs, both in terms of exceedance frequency (up to 93 percent for some compounds in sediment samples) and magnitude (concentrations up to 1,024 times greater than the benchmark value). Other compounds with toxicity-benchmark exceedances include Bis(2-ethylhexyl) phthalate (a plasticizer), 2-Methylnapthalene (a component of fuel and oil), phenol (an antimicrobial disinfectant with diverse uses), and 4-Nonylphenol (sum of all isomers; a detergent metabolite, among other uses). Analyzed as a mixture, the suite of PAH compounds were found to be potentially toxic for most non-base-flow samples. Bioassay tests were conducted on samples from 14 streams: Ceriodaphnia dubia in base-flow samples, Ceriodaphnia dubia and Hyallela azteca in pore-water samples, and Hyallela azteca and Chironomus tentans in sediment samples. The greatest adverse effect was observed in tests with Chironomus tentans from sediment samples. The weight of Chironomus tentans after exposure to sediments decreased with increased OWC concentrations. This was most evident in the relation between PAH results and Chironomus tentans bioassay results for the majority of samples; however, solvents and flame retardants appeared to be important for one site each. These results for PAHs were consistent with assessment of PAH potency factors for sediment, indicating that PAHs were likely to have adverse effects on aquatic organisms in many of the streams studied.

Wisconsin↗

USGS2013

Developing and implementing the use of predictive models for estimating water quality at Great Lakes beaches

Predictive models have been used at beaches to improve the timeliness and accuracy of recreational water-quality assessments over the most common current approach to water-quality monitoring, which relies on culturing fecal-indicator bacteria such as Escherichia coli (E. coli.) . Beach-specific predictive models use environmental and water-quality variables that are easily and quickly measured as surrogates to estimate concentrations of fecal-indicator bacteria or to provide the probability that a State recreational water-quality standard will be exceeded. When predictive models are used for beach closure or advisory decisions, they are referred to as “nowcasts.” During the recreational seasons of 2010-12, the U.S. Geological Survey (USGS), in cooperation with 23 local and State agencies, worked to improve existing nowcasts at 4 beaches, validate predictive models at another 38 beaches, and collect data for predictive-model development at 7 beaches throughout the Great Lakes. This report summarizes efforts to collect data and develop predictive models by multiple agencies and to compile existing information on the beaches and beach-monitoring programs into one comprehensive report. Local agencies measured E. coli concentrations and variables expected to affect E. coli concentrations such as wave height, turbidity, water temperature, and numbers of birds at the time of sampling. In addition to these field measurements, equipment was installed by the USGS or local agencies at or near several beaches to collect water-quality and metrological measurements in near real time, including nearshore buoys, weather stations, and tributary staff gages and monitors. The USGS worked with local agencies to retrieve data from existing sources either manually or by use of tools designed specifically to compile and process data for predictive-model development. Predictive models were developed by use of linear regression and (or) partial least squares techniques for 42 beaches that had at least 2 years of data (2010-11 and sometimes earlier) and for 1 beach that had 1 year of data. For most models, software designed for model development by the U.S. Environmental Protection Agency (Virtual Beach) was used. The selected model for each beach was based on a combination of explanatory variables including, most commonly, turbidity, day of the year, change in lake level over 24 hours, wave height, wind direction and speed, and antecedent rainfall for various time periods. Forty-two predictive models were validated against data collected during an independent year (2012) and compared to the current method for assessing recreational water quality-using the previous day’s E. coli concentration (persistence model). Goals for good predictive-model performance were responses that were at least 5 percent greater than the persistence model and overall correct responses greater than or equal to 80 percent, sensitivities (percentage of exceedances of the bathing-water standard that were correctly predicted by the model) greater than or equal to 50 percent, and specificities (percentage of nonexceedances correctly predicted by the model) greater than or equal to 85 percent. Out of 42 predictive models, 24 models yielded over-all correct responses that were at least 5 percent greater than the use of the persistence model. Predictive-model responses met the performance goals more often than the persistence-model responses in terms of overall correctness (28 versus 17 models, respectively), sensitivity (17 versus 4 models), and specificity (34 versus 25 models). Gaining knowledge of each beach and the factors that affect E. coli concentrations is important for developing good predictive models. Collection of additional years of data with a wide range of environmental conditions may also help to improve future model performance. The USGS will continue to work with local agencies in 2013 and beyond to develop and validate predictive models at beaches and improve existing nowcasts, restructuring monitoring activities to accommodate future uncertainties in funding and resources.

Great Lakes↗

USGS2010

Characterization of suspended solids and total phosphorus loadings from small watersheds in Wisconsin

Knowledge of the daily, monthly, and yearly distribution of contaminant loadings and streamflow can be critical for the successful implementation and evaluation of water-quality management practices. Loading data for solids (suspended sediment and total suspended solids) and total phosphorus and streamflow data for 23 watersheds were summarized for four ecoregions of Wisconsin: the Driftless Area Ecoregion, the Northern Lakes and Forests Ecoregion, the North Central Hardwoods Ecoregion, and the Southeastern Wisconsin Till Plains Ecoregion. The Northern Lakes and Forests and the North Central Hardwoods Ecoregions were combined into one region for analysis due to a lack of sufficient data in each region. Urban watersheds, all located in the Southeastern Wisconsin Till Plains, were analyzed separately from rural watersheds as the Rural Southeastern Wisconsin Till Plains region and the Urban Southeastern Wisconsin Till Plains region. Results provide information on the distribution of loadings and streamflow between base flow and stormflow, the timing of loadings and streamflow throughout the year, and information regarding the number of days in which the majority of the annual loading is transported. The average contribution to annual solids loading from stormflow periods for the Driftless Area Ecoregion was 84 percent, the Northern Lakes and Forests/North Central Hardwoods region was 71 percent, the Rural Southeastern Wisconsin Till Plains region was 70 percent, and the Urban Southeastern Wisconsin Till Plains region was 90 percent. The average contributions to annual total phosphorus loading from stormflow periods were 72, 49, 61, and 76 percent for each of the respective regions. The average contributions to annual streamflow from stormflow periods are 20, 23, 31, and 50 percent for each of the respective regions. In all regions, the most substantial loading contributions for solids were in the late winter (February through March), spring (April through May), and early summer (June through July), with fall (October through November) and early winter (December through January) contributing the smallest loadings. The Northern Lakes and Forests/North Central Hardwoods region had some substantial loading in September. There was a similar pattern for total phosphorus loading in all regions, with the pattern somewhat less pronounced in urban watersheds. As with the loading results, average monthly streamflow values were greatest in late winter, spring, and early summer, with the lowest values typically in fall and early winter. Loading contributions were greater from stormflow than from base flow in all instances, except total phosphorus in the Northern Lakes and Forests/North Central Hardwoods region, which had equal or greater base-flow contribution for several months. Base flow constituted a greater percentage of the total streamflow than stormflow in all rural watersheds for all regions. Only a few storms each year dominated the annual loading totals for solids and total phosphorus. When daily loading values were ranked for the year, all regions reached 50 percent of the annual solids loading in the 5 highest loading days and nearly 50 percent of the annual total phosphorus loading in the 14 highest loading days.

Scientific Investigations Report↗

USGS2010

Alternative aircraft anti-icing formulations with reduced aquatic toxicity and biochemical oxygen demand

The current research was conducted to identify alternative aircraft and pavement deicer and anti-icer formulations with improved environmental characteristics compared to currently used commercial products (2007). The environmental characteristics of primary concern are the biochemical oxygen demand (BOD) and aquatic toxicity of the fully formulated products. Except when the distinction among products is necessary for clarity, “deicer” will refer to aircraft-deicing fluids (ADFs), aircraft anti-icing fluids (AAFs), and pavementdeicing materials (PDMs).

Report↗

USGS2008

Formulations for aircraft and airfield deicing and anti-icing: aquatic toxicity and biochemical oxygen demand

The Airport Cooperative Research Program (ACRP) has sponsored research on environmental characteristics of aircraft and pavement deicers and anti-icers focusing primarily on biochemical oxygen demand (BOD) and aquatic toxicity of formulated products and individual chemical components of formulations. This report presents a background of issues leading to this research, objectives of this document, and a description of the efforts and findings of this research. Except when the distinction among products is necessary for clarity, “deicer” will refer to aircraft-deicing fluids (ADFs), aircraft anti-icing fluids (AAFs), and pavement-deicing materials (PDMs) generally. The efforts of this project have included the following: A review of regulations and specifications related to the performance and environmental characteristics of deicer formulations A review of issues related to the impact that deicers have on aquatic systems and causes of those impacts Laboratory testing of current-use deicers to establish benchmark values for aquatic toxicity, BOD, and chemical oxygen demand (COD) A review of deicer formulations under development and their relevant performanceand environmental-related characteristics A review of operational and infrastructure considerations A synopsis of current analytical methods used in environmental characterization of airport deicing runoff A toxicity-based investigation of current-use deicers to determine components responsible for toxicity and identify component classes to focus a search for alternative components Identification of gaps in knowledge and data pertaining to the above topics

Report↗

USGS2005

Effects of best-management practices in Otter Creek in the Sheboygan River Priority Watershed, Wisconsin, 1990-2002

The U.S. Geological Survey and the Wisconsin Department of Natural Resources began a comprehensive, multidisciplinary evaluation-monitoring program in 1989 to assess the effectiveness of the Wisconsin Nonpoint Source Program. Hydrologic, water-quality, habitat, and fish data were collected at Otter Creek from 1990 to 2002 with the pre-BMP (best-management practice) period ending in September 1993 and the post-BMP period beginning in October 1999. BMPs installed in this basin included streambank protection and fencing, stream crossings, grade stabilization, buffer strips, various barnyard-runoff controls, nutrient management, and a low degree of upland BMPs. Reductions between pre- and post-BMP periods were detected in median concentrations of base-flow samples for total suspended solids and BOD5 but not for total phosphorus or dissolved ammonia nitrogen; fecal coliform concentrations in base-flow samples increased over the study period. Reductions in rainfall storm loads between the pre- and post-BMP periods during the non-vegetative season (November through May) were detected for all three constituents monitored (total suspended solids, total phosphorus, and dissolved ammonia nitrogen). Differences in rainfall storm loads of these three constituents for the vegetative season (June through October) were not detected. When considering rainfall data from the entire year, reductions in storm loads were detected for total suspended solids and dissolved ammonia nitrogen (reductions were estimated at 58 percent for total suspended solids and 41 percent for dissolved ammonia nitrogen). Annual reductions in rainfall storm loads for the non-vegetative season were estimated at 58 percent for total suspended solids, 48 percent for total phosphorus, and 41 percent for dissolved ammonia nitrogen. Habitat and fish data were collected each year of the study to track the effects of BMPs on stream habitat and fish communities. Final trend analysis was performed using habitat quality index scores, an index of biotic integrity, and some of the originally measured fish and habitat variables. Habitat was improved for stream segments that had either natural riparian buffer or where streambank fencing was installed, but not at the station where the riparian area was pasture and no streambank fencing was installed. The results also suggest that BMP implementation in Otter Creek substantially modified fish community structure, but the overall community quality was not improved.

Wisconsin↗

USGS2004

Effectiveness of a pressurized stormwater filtration system in Green Bay, Wisconsin: A study for the environmental technology verification program of the U.S. Environmental Protection Agency

A pressurized stormwater filtration system was installed in 1998 as a stormwater-treatment practice to treat runoff from a hospital rooftop and parking lot in Green Bay, Wisconsin. This type of filtration system has been installed in Florida citrus groves and sewage treatment plants around the United States; however, this installation is the first of its kind to be used to treat urban runoff and the first to be tested in Wisconsin. The U.S. Geological Survey (USGS) monitored the system between November 2000 and September 2002 to evaluate it as part of the U.S. Environmental Protection Agency's Environmental Technology Verification Program. Fifteen runoff events were monitored for flow and water quality at the inlet and outlet of the system, and comparison of the event mean concentrations and constituent loads was used to evaluate its effectiveness. Loads were decreased in all particulate-associated constituents monitored, including suspended solids (83 percent), suspended sediment (81 percent), total Kjeldahl nitrogen (26 percent), total phosphorus (54 percent), and total recoverable zinc (62 percent). Total dissolved solids, dissolved phosphorus, and nitrate plus nitrite loads remained similar or increased through the system. The increase in some constituents was most likely due to a ground-water contribution between runoff events. Sand/silt split analysis resulted in the median silt content of 78 percent at the inlet, 87 percent at the outlet, and 3 percent at the flow splitter.

Wisconsin↗

USGS2003

Nonylphenol ethoxylates and other additives in aircraft deicers, antiicers, and waters receiving airport runoff

Samples of nine different formulations of aircraft deicer and antiicer fluids (ADAF) were screened for the presence of selected surfactants. Nonylphenol ethoxylates (NPnEO) were identified in three ADAF formulations, octylphenol ethoxylates were identified in two formulations, and six formulations contained alcohol ethoxylates. A preliminary field study was conducted at General Mitchell International Airport, Milwaukee, WI, to quantify NPnEO (n = 1-15) and one of its byproducts, nonylphenol (NP), in airport runoff. Samples were collected from two airport outfalls, from the receiving stream, and from an upstream reference site during intensive ADAF application events. NPnEO was measured at concentrations up to 1190microg/L in airport outfall samples, up to 77 ug/L in samples from the receiving stream and less than 5.0 microg/L from the upstream reference. Concentrations of glycol and other ADAF-related constituents, including NPnEO, were reduced by approximately 1 order of magnitude between the outfall sites and the receiving stream site; however, concentrations of NP in the receiving stream remained similar to those from the outfalls (< 0.04 microg/L at the upstream reference, 0.98 and 7.67 microg/L at outfalls, and 3.89 microg/L in the receiving stream). The field data suggest that NP is generated through degradation of NPnEO from airport runoff.

Wisconsin↗

USGS2001

Evaluation of nonpoint-source contamination, Wisconsin: water year 1999

The objective of the watershed-management evaluation monitoring program in Wisconsin is to evaluate the effectiveness of best-management practices (BMPs) for controlling nonpoint-source pollution in rural and urban watersheds. This progress report provides a summary of the data collected by the U.S Geological Survey for the program and a discussion of the results from several different detailed analyses conducted within this program. A land-use and best-management-practice inventory is ongoing for each evaluation monitoring project to track the different sources of nonpointsource pollution in each watershed and to document implementation of best-management programs that may cause changes in the water quality of streams. Updated information is gathered each year, mapped, and stored in a geographic-information-system database. Summaries of BMP-implementation data collected through the 1999 water year are presented in this report. Suspended sediment and total phosphorus storm-load and annual-load data are summarized for eight rural sites. For all 8 rural sites a sufficient number of pre-BMP storm samples have been collected; for two of the sites (Brewery and Garfoot Creeks), a sufficient number of post-BMP storm samples have been collected to allow for a final assessment of the effectiveness of the BMPs. For the remaining sites, numerous transitional storm samples have been collected, but in all cases BMP implementation has lagged such that there are insufficient post-BMP storm samples for final analysis. For two sites (Rattlesnake and Kuenster Creeks) there are not enough planned BMPs to warrant further data collection. Continuous dissolved-oxygen data collected at 5 rural sites are summarized. In terms of instantaneous concentrations when comparing pre-BMP data to transitional and post-BMP data, the general trend is a reduction in the number of days that the dissolved oxygen concentration was less than the state standard. These results are anecdotal, however; the differences have not been rigorously tested statistically. For a level of dissolved oxygen sustained over a continuous hour, the results are mixed. In general the number of days with standard violations has decreased, but there are notable exceptions. For the four urban streams, the pre-BMP data were examined to determine the level of improvement that could potentially be detected with a statistical analysis. Regression analyses were performed relating constituent loads of suspended solids, total phosphorus and total copper to various independent variables, including seasonal terms and variables related to rainfall. On the basis of the residuals from the regressions, there is a wide range of potential change that could be detected with an analysis of pre- and post-BMP loads. This is likely a result of the high degree of variability in the data, particularly from site to site. For suspended solids, total phosphorus, and total recoverable copper the minimum detectable changes ranges from 20-80, 30-70 and 30-90 percent, respectively. For two of the eight rural streams (Rattlesnake and Kuenster Creeks) minimal BMP implementation has occurred, hence a comparison of pre- BMP and data collected after BMP implementation began is not warranted. For two other rural streams (Brewery and Garfoot Creeks), BMP implementation is complete. For the four remaining rural streams (Bower, Otter, Eagle, and Joos Valley Creeks), the pre-BMP load data were compared to the transitional data to determine if significant reductions in the loads have occurred as a result of the BMP implementation to date. For all sites, the actual constituent loads for suspended solids and total phosphorus exhibit no statistically significant reductions after BMP installation. Multiple regressions were used to remove some of the natural variability in the data. Based on the residual analysis, for Otter Creek, there is a significant difference in the suspended-solids regression residuals between the pre-BMP and transitional periods, indicating a potential reduction as a result of the BMP implementation after accounting for natural variability. For Joos Valley Creek, the residuals for suspended solids and total phosphorus both show a significant reduction after accounting for natural variability. It is possible that the other sites will also show statistically significant reductions in suspended solids and total phosphorus if additional BMPs are implemented.

Wisconsin↗

USGS1999

Evaluation of the Multi-Chambered Treatment Train, a retrofit water-quality management device

This paper presents the results of an evaluation of the benefits and efficiencies of a device called the Multi-Chambered Treatment Train (MCTT), which was installed below the pavement surface at a municipal maintenance garage and parking facility in Milwaukee, Wisconsin. Flow-weighted water samples were collected at the inlet and outlet of the device during 15 storms, and the efficiency of the device was based on reductions in the loads of 68 chemical constituents and organic compounds. High reduction efficiencies were achieved for all particulate-associated constituents, including total suspended solids (98 percent), total phosphorus (88 percent), and total recoverable zinc (91 percent). Reduction rates for dissolved fractions of the constituents were substantial, but somewhat lower (dissolved solids, 13 percent; dissolved phosphorus, 78 percent; dissolved zinc, 68 percent). The total dissolved solids load, which originated from road salt storage, was more than four times the total suspended solids load. No appreciable difference was detected between particle-size distributions in inflow and outflow samples.

Wisconsin↗

USGS1997

Unit-area loads of suspended sediment, suspended solids and total phosphorus from small watersheds in Wisconsin

Watershed planners in the Wisconsin Department of Natural Resources (WDNR) and in Wisconsin county governments use estimates of loads of total solids and total phosphorus in streams for numerous management purposes. A few examples of these are to establish load reduction goals, to estimate the relative magnitude of nonpoint sources compared to point sources, and to estimate phosphorus loads to lakes. Solids and phosphorus are two of the most common nonpoint contaminants resulting from agricultural activity. Loads can be estimated either by monitoring the water quantity and water quality in a watershed or by modeling those same factors. Monitoring is the most accurate method for load estimation, but it is also time consuming and expensive. A simple method of estimating loads of chemical constituents or suspended solids in a watershed is to use unit-area loads that have been calculated from monitored data to estimate loads in watersheds where monitoring data are not available. A "unit-area load" is defined as the mass of a particular constituent transported by a stream, divided by the drainage area of the watershed.

Wisconsin↗

USGS1997

Evaluation of Nonpoint-Source Contamination, Wisconsin: Selected Topics for Water Year 1995

The objective of the watershed-management evaluation monitoring program in Wisconsin is to evaluate the effectiveness of best-management practices (BMP's) for controlling nonpoint-source contamination in eight rural and four urban watersheds. This report, the fourth in an annual series of reports, presents a summary of the data collected for the program by the U.S. Geological Survey and the results of several detailed analyses of the data. To complement assessments of water quality, a land-use and BMP inventory is ongoing for 12 evaluation monitoring projects to track nonpoint sources of contamination in each watershed and to document implementation of BMP's that were designed to cause changes in the water quality of streams. Each year, updated information is gathered, mapped, and stored in a geographic-information-system data base. Summaries of land-use, BMP implementation, and water-quality data collected during water years 1989-95 are presented. Storm loads, snowmelt-period loads, and annual loads of suspended sediment and total phosphorus are summarized for eight rural sites. Storm-load data for suspended solids, total phosphorus, total recoverable lead, copper, zinc, and cadmium are summarized for four urban sites. Quality-assurance and quality-control (QA/QC) samples were collected at the eight rural sites to evaluate inorganic sample contamination and at one urban site to evaluate sample-collection and filtration techniques for polycyclic aromatic hydrocarbons (PAR's). Some suspended solids and fecal coliform contamination was detected at the rural sites. Corrective actions will be taken to address this contamination. Evaluation of PAR sample-collection techniques did not uncover any deficiencies, but the small amount of data collected was not sufficient to draw any definite conclusions. Evaluation of PAR filtration techniques indicate that water-sample filtration with O.7-um glass-fiber filters in an aluminum filter unit does not result in significant loss of PAR.

Wisconsin↗

USGS1995

Evaluation of nonpoint-source contamination, Wisconsin; selected streamwater-quality data, land-use and best-management practices inventory, and quality assurance and quality control, water year 1993

The objective of the watershed-management evaluation monitoring program in Wisconsin is to evaluate the effectiveness of the best-management practices (BMPs) for rural streams, urban streams, and urban storm sewers. This report is an annual summary of the data collected for the program and a report of the results from several different special studies conducted within this program. Suspended sediment and total phosphorus storm-load data are summarized for eight rural sites and suspended sediment, total phosphorus, total recoverable lead, total recoverable copper, total recoverable zinc, and total recoverable cadmium storm-load data are summarized for four urban sites. Dissolved-oxygen data is summarized and compared with Wisconsin's waterquality standards for summer 1993 for seven rural sites. The dissolved-oxygen concentrations declined to levels below these standards at least one time at all seven sites during summer 1993. Total-recoverable hardness concentrations were compared with dissolved-hardness concentrations at two urban streams and two urban storm sewers. Least-squared linear regressions resulted in stronger relations for low-flow conditions than for high-flow conditions, indicating that most hardness during low flow is dissolved hardness. Pesticide data are summarized for four urban sites and six rural sites. Herbicides were detected at urban and rural sites; whereas insecticides were detected only at urban sites. A land-use and best-management-practice inventory is ongoing for each evaluation monitoring project to track the different sources of nonpoint pollution in each watershed and to document implementation of best-management programs that may cause changes in water quality of streams. Updated information is gathered each year, mapped, and stored in a geographic-information-system data base. The quality-assurance/quality-control plan for the urban watershed-management evaluation program consisted of a series of blank samples. These blank samples were used to identify and isolate contamination by inorganic and organic components throughout the collection and processing of urban streamwater samples. A dissolved trace-metal contamination problem was identified and resolved by using different laboratory- supplied sample bottles. A special study was done to determine the effect of holding time on fecal coliform colony counts. A linear regression indicated that the mean decrease in colony counts over 72 hours was 8.2 percent per day. Results after 24 hours showed that colony counts increased in some samples and decreased in others.

Wisconsin↗

USGS1995

Discharge ratings for tainter gates and roller gates at Lock and Dam No. 7 on the Mississippi River, La Crescent, Minnesota

The water-surface elevations on the Inland Waterway Navigation System of the upper Mississippi River are controlled during normal operating conditions by various flow controls at 29 locks and dams. The headwater (navigation pool) and tailwater elevations at Lock and Dam No. 7 are controlled by the regulation of 11 tainter gates and 5 roller gates. Discharge ratings for these tainter and roller gates were developed for use in computing discharge through Dam No. 7 and to aid in regulating the navigation pool within its normal operating limits of 639.00 ± 0.20 feet (NGVD 1912). Hydraulic-control variables and discharges were measured at the tainter and roller gates and analyzed for this report. Fifty-two current-meter measurements of discharges that ranged from discharges too low to measure to 12,600 cubic feet per second were made in the forebays of the tainter and roller gates. The measured discharges were used to define flow regimes as a function of static-headwater depth (hi), static-tailwater depth (03), and vertical height of tainter or roller gate opening (hg). Submerged-orifice flow is the predominant flow regime at Lock and Dam No. 7. Twenty-four discharge measurements were used to develop submerged-orifice discharge coefficient relations for the 11 tainter gates. Twenty discharge measurements were used to develop a submerged-orifice discharge coefficient relation for the five roller gates. Coefficients of discharge (Cgs) ranged fron 0.126 (hg = 1 foot) to 1.089 (hg = 10 feet) for tainter gates and from 0.050 (hg = 1 foot) to 0.302 (hg = 14 feet) for roller gates. Disch^ge was measured at three different tainter gates with the gates closed (hg = 0) to evaluate tH tainter-gate leakage-discharge relations. No measurable leakage was observed. The resulting equations can be used to compute discharge at Lock and Dam No. 7 for the tainter and re Her gates under normal flow conditions. Discharge rating tables for the tainter and roller gates are given with a headwater elevation of 639.00 feet normal pool elevation for selected tailwate" elevations and gate openings.

Minnesota↗