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At least 307 records · Page 17Linked to original sources
USGS2022

Refining sources of polychlorinated biphenyls in the Back River watershed, Baltimore, Maryland, 2018–2020

Older urban landscapes present unique and complex stressors to urban streams and their habitats through the introduction of legacy and emerging toxic contaminants. Contaminant sources are often associated with various developed land uses such as older residential areas, active and former industrial sites, contaminated sites, and effluents from municipal wastewater treatment plant discharges. These landscapes have a history of legacy contaminant use such as polychlorinated biphenyls (PCBs) resulting in impacts to sediment and water in these complex environments. Despite the ban of PCBs in new commercial use in 1979, PCB contamination is still widespread in the environment, with many fish consumption advisories throughout the Chesapeake Bay region based on elevated PCBs. Several watersheds in the Baltimore region have mandated reductions in PCBs per total maximum daily loads in tidal waters of the watersheds in order to promote compliance with water quality standards. Some of these mandated reductions (for example, regulated watershed runoff) specified in the total maximum daily loads are the responsibility of the local jurisdictions as part of their phase 1 National Pollutant Discharge Elimination System municipal separate storm sewer system permit. In cooperation with the Baltimore City Department of Public Works and Maryland Department of the Environment, the U.S. Geological Survey and University of Maryland, Baltimore County conducted a study from 2018 to 2020 to refine the sources of PCBs from the City of Baltimore into Back River and to use the results to improve the conceptual site model of PCBs in the Back River watershed. PCB concentrations in the water column of the nontidal streams in Back River watershed are relatively consistent throughout both tributaries, with greater concentrations detected in samples collected from Moores Run but greater loads estimated in samples collected from Herring Run. PCB concentrations measured in the bed sediments and analysis of the flux between sediment porewater (hereafter porewater) and surface water within the tributaries suggest that there are no stationary legacy sources within the stream channels. The bulk of PCB mass entering the system from these nontidal tributaries appears to be introduced primarily during storm events. While only one storm event was sampled and concentrations were quantified only in Herring Run, solids captured during the storm were characterized by increases in PCB mass and overall suspended solids concentrations. Although the bioavailability of the PCB-associated sediment is unknown, this mechanism appears to warrant additional attention to better understand how concentrations vary under different storm conditions and temporally. The importance of contaminated stormwater in loading to Herring Run is further supported by the PCB concentrations in storm drain sediments collected near the tributary, which were present in higher concentrations and were characterized by different homolog signatures compared to that in bed sediments. The observations in the tributaries differed from PCB concentrations and sediment characteristics downstream from the City of Baltimore boundary, in the upper tidal area of the main stem of Back River, particularly at the passive sampler locations BRT–1 and BRT–3. This depositional environment is characterized by higher organic content in sediments and higher concentrations of PCBs in porewater, which result in the possible flux of contaminants from sediment to the water column. This flux is generally opposite of that observed in the nontidal tributaries and the farthest upstream tidal site (BRT–2) and may be a result of the possible settling of sediment particles introduced via suspended solids in stormwater. Despite an observed considerable reduction in overall PCB mass loading to and from the Back River Wastewater Treatment Plant (BRWWTP) (and similar reductions observed in biosolids) compared to the estimates previously reported from 2015, effluent from the BRWWTP continues to be a primary source of PCBs to Back River. The current study confirmed the likeliness of fat, oil, and grease deposits within the miles of sewer pipe as a source of PCBs to the BRWWTP influent. The differences between PCB concentrations in fat, oil, and grease deposits found in pipes (during replacement) compared to that of the BRWWTP suggest that legacy deposits may contain higher PCB concentrations and may act as a source of PCBs to passing sewage, eventually entering the BRWWTP. Variation in freely dissolved concentrations in the sewer system was apparent through the analysis of PCBs in the primary pump stations using passive sampling, with the largest contribution to the influent attributed to a single pump station and associated piping. The contribution of PCBs to Herring Run and Moores Run via sanitary sewer overflows compared to the BRWWTP effluent is negligible, similar to reports from another large urban wastewater treatment plant. Therefore, decreased occurrence of sanitary sewer overflows is not expected to largely decrease PCB loads. Results of this study suggest that targeted, sediment-capture best management practices in Back River watershed could be an effective way to reduce PCB mass loading assuming that deposited contaminated sediments are effectively isolated. Recent studies of some common urban best management practices such as bioretention have shown removal of PCBs within the stormwater control structures. In addition, appropriately timed street sweeping practices with appropriate collection equipment may be an effective way to reduce contaminants such as PCBs from road runoff sources. Reductions in concentrations and mass loading within the sewer system measured in this study compared to that estimated 5 years prior reflect the possible success of ongoing gray infrastructure management actions. Reductions may be attributable to enhanced nutrient reduction upgrades to the BRWWTP and extensive capital improvements and maintenance to the sewer system. This study employed a combined sampling approach and a variety of sampling methods to include low-density polyethylene passive samplers, high-volume water samples, and grab samples of both water and sediment to characterize the PCB inputs to Herring Run, Moores Run, and Back River. Incorporating the passive samplers provided a time-weighted average of the freely dissolved concentration in the surface water, porewater, WWTP influent and effluent, and pump station influent over the deployment period with picogram per liter detection limits. A similar monitoring approach from this study could be implemented within other subwatersheds or municipal separate storm sewer system jurisdictions to assist in refining primary sources of PCBs in order to inform appropriate mitigation approaches.

Maryland↗
USGS2003

Spatial distribution and trends in trace elements, polycyclic aromatic hydrocarbons, organochlorine pesticides, and polychlorinated biphenyls in Lake Worth sediment, Fort Worth, Texas

In spring 2000, the Texas Department of Health issued a fish consumption advisory for Lake Worth in Fort Worth, Texas, because of elevated concentrations of polychlorinated biphenyls (PCBs) in fish. In response to the advisory and in cooperation with the U.S. Air Force, the U.S. Geological Survey collected 21 surficial sediment samples and three gravity core sediment samples to assess the spatial distribution and historical trends of selected hydrophobic contaminants, including PCBs, and to determine, to the extent possible, sources of hydrophobic contaminants to Lake Worth. Compared to reference (background) concentrations in the upper lake, elevated PCB concentrations were detected in the surficial sediment samples collected in Woods Inlet, which receives surface runoff from Air Force facilities and urban areas. Gravity cores from Woods Inlet and from the main part of the lake near the dam indicate that the concentrations of PCBs were three to five times higher in the 1960s than in 2000. A regression method was used to normalize sediment concentrations of trace elements for natural variations and to distinguish natural and anthropogenic contributions to sediments. Concentrations of several trace elements—cadmium, chromium, copper, lead, and zinc—were elevated in sediments in Woods Inlet, along the shoreline of Air Force facilities, and in the main lake near the dam. Concentrations of these five trace elements have decreased since 1970. Polycyclic aromatic hydrocarbons also were elevated in the same areas of the lake. Concentrations of total polycyclic aromatic hydrocarbons, normalized with organic carbon, were mostly stable in the upper lake but steadily increased near the dam, except for small decreases since 1980. The Woods Inlet gravity core showed the largest increase of the three core sites beginning about 1940; total polycyclic aromatic hydrocarbon concentrations in post-1940 sediments from the core showed three apparent peaks about 1960, 1984, and 2000. The concentrations of organochlorine pesticides were low relative to consensus-based sediment-quality guidelines and either decreased or remained constant since 1970. The two likely sources of hydrophobic contaminants to the lake are urban areas around the lake and the drainage area of Meandering Road Creek that contributes runoff to Woods Inlet and includes Air Force facilities.

Texas↗
USGS2017

Longshore water-current velocity and the potential for transport of contaminants—A pilot study in Lake Erie from Walnut Creek to Presque Isle State Park beaches, Erie, Pennsylvania, June and August 2015

Bacteria-driven restrictions and (or) advisories on swimming at beaches in Presque Isle State Park (PISP), Erie, Pennsylvania, can occur during the summer months. One of the suspected sources of bacteria is sediment. A terrestrial sediment source to the west of PISP is Walnut Creek, which discharges to Lake Erie about 8.5 kilometers southwest of PISP Beach 1. On June 24, June 25, August 18, and August 19, 2015, synoptic surveys were conducted by the U.S. Geological Survey, in cooperation with the Pennsylvania Sea Grant, in Lake Erie between Walnut Creek and PISP Beach 1 to characterize the water-current velocity and direction to determine whether sediment from Walnut Creek could be affecting the PISP beaches. Water-quality data (temperature, specific conductance, and turbidity) were collected in conjunction with the synoptic surveys in June. Water-quality data ( Escherichia coli [ E. coli ] bacteria, temperature, and turbidity) were collected about a meter from the shore (nearshore) on June 24, August 19, and after a precipitation event on August 11, 2015. Additionally, suspended sediment was collected nearshore on June 24 and August 11, 2015. Samples collected near Walnut Creek during all three bacterial sampling events contained higher counts than other samples. Counts steadily decreased from west to east, then increased about 1–2 kilometers from PISP Beach 1; however, this study was not focused on examining other potential sources of bacteria. The Velocity Mapping Toolbox (VMT) was used to process the water-current synoptic surveys, and the results were visualized within ArcMap. For the survey accomplished on June 24, 2015, potential paths a particle could take between Walnut Creek and PSIP Beach 1 if conditions remained steady over a number of hours were visualized. However, the water-current velocity and direction were variable from one day to the other, indicating this was likely an unrealistic assumption for the study area. This analysis was not accomplished for the other surveys due to unsteady lake conditions encountered on June 25 and August 18, and reduced quality of the survey on August 19.

Pennsylvania↗
USGS1999

Pesticides in streams in New Jersey and Long Island, New York, and relation to land use

Pesticide compounds were detected in all 50 water samples collected from streams in New Jersey and Long Island, New York, during June 9-18, 1997. Samples were analyzed for 47 compounds, of which 25 were detected. The number of pesticides detected at each site ranged from 1 to 14. The seven most frequently detected pesticides were atrazine (in 93 percent of samples), metolachlor (86 percent), prometon (84 percent), desethyl-atrazine (78 percent), simazine (78 percent), carbaryl (44 percent), and diazinon (44 percent). All pesticide concentrations were within both U.S. Environmental Protection Agency (USEPA) and State maximum contaminant levels (MCL?s) for drinking water and USEPA lifetime health advisory levels (HAL?s). Concentrations of dieldrin and methylazinphos at one or more sites, however, equaled or exceeded a Federal or State water-quality criterion for aquatic life. The pesticides detected in a stream were related to the land-use composition of the basin. Detection frequencies of 14 of the 25 pesticides detected were highest at agricultural sites; acetochlor, azinphos-methyl, carbofuran, and pebulate were detected only at agricultural sites. Seven compounds were detected most frequently at urban sites; trifluralin, dieldrin, napropamide, and benfluralin were detected only at urban sites. Four compounds were detected most frequently at sites draining areas of mixed land use. No pesticides were detected most frequently at sites draining forested areas. The median concentration and the detection frequency of a given pesticide always were highest in samples from sites in the same land-use category.The median concentrations of seven pesticides at the agricultural sites were at least twice as high as the median concentrations at sites in other land-use categories. The median concentrations of the seven compounds detected most frequently at urban sites were equal to or only slightly higher than the median concentrations at sites in other land-use categories. The median total-pesticide concentration was highest at agricultural sites (0.2 mg/L (micrograms per liter)) and lowest at forested sites (0.025 mg/L). Total-pesticide concentrations varied most at agricultural sites and least at forested sites. Total-pesticide concentration and number of pesticides detected at a site increased as the percentage of agricultural land in the basin increased and decreased as the percentage of undeveloped land increased. Only three of the seven most frequently detected compounds?atrazine, metolachlor, and carbaryl?are among the seven most heavily applied pesticides in New Jersey. This is because detection frequencies are the result of physical and chemical properties of the pesticide compounds as well as application rates. Water solubility and soil-adsorption coefficients appear to be the two physical properties of pesticides that most influence their presence in streams.

New Jersey, New York↗
USGS2025

Leveraging artificial intelligence and machine learning to advance Chesapeake Bay research and management: A review of status, challenges, and opportunities

The Chesapeake Bay and its watershed (hereafter “Chesapeake Bay region”) have been the focus of extensive restoration efforts for several decades. These restoration efforts are guided by the Chesapeake Bay Watershed Agreement (Chesapeake Executive Council 2014) which outlines 10 goals and 31 measurable outcomes. The Chesapeake Bay is globally recognized as a model for coastal restoration due to long-term investments in monitoring, modeling, implementation and research by the Chesapeake Bay Program (CBP) partnership. These monitoring network spans tidal and non-tidal regions and provides data across multiple scales. Artificial intelligence (AI), particularly machine-learning (ML) and deep learning (DL), has emerged as a powerful tool for analyzing large, complex datasets. These techniques have gained widespread adoption across various disciplines, including ecology, hydrology, and environmental science. In the Bay context, AI/ML is increasingly being used to explore drivers of environmental change, analyze system dynamics, and predict conditions in areas with limited monitoring. The CBP partnership, particularly its Scientific and Technical Advisory Committee (STAC), has increasingly recognized the growing role of AI/ML in watershed and estuarine management. Recent Chesapeake Community Research Symposium sessions and initiatives such as the Chesapeake Global Collaboratory highlight increasing regional momentum to apply big data and AI/ML for environmental solutions. Together, these developments underscore the timely need to explore how AI/ML can help advance Chesapeake Bay restoration and management. This STAC workshop, titled “Leveraging Artificial Intelligence and Machine learning to Advance Chesapeake Bay Research and Management: A review of status, challenges, and opportunities,” was held from February 24-25, 2025, in Edgewater, Maryland to bring together over 50 federal, state, and academic scientists and partners to synthesize the current state of AI/ML applications and identify research gaps in Chesapeake Bay research and management. The workshop focused on three main objectives: 1. Summarize recent AI/ML applications and lessons learned in both tidal and nontidal areas of the Chesapeake Bay region. 2. Identify challenges and gaps in applying AI/ML approaches to Chesapeake Bay data. Such challenges and gaps may include data limitations, harmonization issues, ineffective communication of AI/ML insights, and a lack of coordination among research and management institutions. 3. Develop recommendations and identify opportunities for leveraging AI/ML to address issues across the Chesapeake Bay region. Key areas of focus may include generating new information to support watershed management, delivering AI/MLgenerated insights to managers in a clear and actionable way, and fostering greater collaboration among stakeholders within the CBP Partnership. Workshop participants engaged in science presentations and breakout sessions to develop recommendations for advancing the integration of AI/ML techniques into research and management across the Chesapeake Bay region. By synthesizing current applications, identifying challenges, and exploring new opportunities, the workshop has provided valuable insights and recommendations for better leveraging AI/ML approaches to support the success of Bay restoration efforts. Together, these recommendations provide a roadmap for enhancing data-driven, science-based decision making aligned with the goals and outcomes of the Chesapeake Bay Watershed Agreement.

Delaware, Maryland, Virginia↗
USGS2001

Occurrence, distribution, and loads of selected pesticides in streams in the Lake Erie-Lake St. Clair basin, 1996–98

Thirty pesticides or their degradates were detected in 315 samples collected from 10 streams in the Lake Erie-Lake St. Clair Basin between March 1996 and February 1998 as part of the U.S. Geological Survey’s National Water-Quality Assessment (NAWQA) Program. Atrazine was detected in every sample, and deethylatrazine, metolachlor, and simazine were detected in more than 90 percent of all samples. Atrazine and metolachlor, the most heavily applied pesticides in the Basin, had the highest detected concentrations (85 and 78 micrograms per liter, respectively). No annual average concentrations exceeded the U.S. Environmental Protection Agency Maximum Contaminant Level or health advisory level at any of the surface-water-sampling sites. Seasonally elevated pesticide concentrations, however, have economic consequences on water-treatment facilities required to remove pesticides in water to meet drinking-water standards. From May through July, when most pesticides are transported by runoff into streams, time-weighted average concentrations of atrazine exceeded the Maximum Contaminant Level at five row-crop sites, and time-weighted average concentrations of atrazine and cyanazine frequently exceeded lifetime adult health advisories at these same sites. For some heavily used herbicides such as atrazine, metolachlor, cyanazine, and acetochlor, elevated concentrations persisted 4 to 6 weeks after the initial maximum concentration in the row-crop streams was measured. Land use and physical processes can affect the occurrence and distribution of pesticides. Pesticides were detected at greater frequency and at higher concentrations in samples from streams in basins dominated by row-crop agriculture than in samples from streams in urban or pasture/forest areas. Maximum measured concentrations were higher in 1997 than in 1996 and probably were related to greater precipitation in 1997. Generally, the number of pesticides detected in a basin increased with basin size. Pesticide concentrations showed strong seasonal trends related to the timing and amount of pesticide application. Row-crop herbicides applied in the spring, such as atrazine, had maximum measured concentrations in the spring; pesticides typically applied in late summer and early fall, such as diazinon, had maximum measured concentrations then. The increased number of detections and maximum measured concentrations of acetochlor and the corresponding decrease in the number of detections and concentrations of alachlor reflected changes in the amount of pesticides applied during the sampling period. The percentage of the applied atrazine that was detected in streams, in general, increased when the percentage of impermeable soils within each basin increased. Loads and yields of selected pesticides were calculated. The highest loads calculated were those for atrazine and metolachlor in the Maumee River at Waterville, Ohio, with 47,000 and 44,000 pounds per year, respectively. Of the row-crop basins, either the St. Joseph River near Newville, Ind., or the Auglaize River near Fort Jennings, Ohio, had the highest yields for the herbicides acetochlor, alachlor, atrazine, cyanazine, metolachlor, and simazine. The Cuyahoga River at Cleveland, Ohio, had the highest yields for diazinon and prometon—pesticides that typically are applied heavily in urban areas. The percentage of the applied atrazine that was calculated in the stream was determined for each basin in 1997. The export of atrazine ranged from 0.10 percent at the River Raisin near Manchester, Mich., to 10.6 percent at the St. Joseph River near Newville, Ind.

Indiana, Michigan, New York, Ohio, Pennsylania↗
USGS2021

Hydrogeologic framework, water levels, and selected contaminant concentrations at Valmont TCE Superfund Site, Luzerne County, Pennsylvania, 2020

The Valmont TCE Superfund Site, Luzerne County, Pennsylvania is underlain by fractured and folded sandstones and shales of the Pottsville and Mauch Chunk Formations, which form a fractured-rock aquifer recharged locally by precipitation. Industrial activities at the former Chromatex Plant resulted in trichloroethene (TCE) contamination of groundwater at and near the facility, which was identified in 1987 and led to listing as a Superfund site by the U.S. Environmental Protection Agency (EPA) in 1989. To address the problem of TCE concentrations in nearby residential wells that exceed the maximum contaminant level (MCL) of 5 micrograms per liter (μg/L), alternate water supplies were provided. A 2015 review of initial characterization and subsequent remediation by the EPA identified the need for an updated understanding of the complex hydrogeology and the conceptual site model. Additional contaminants present in groundwater at the site include some other volatile organic compounds (VOCs) and per- and polyfluoroalkyl substances (PFAS), predominantly consisting of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) present in concentrations that exceeded the EPA Health Advisory (HA) level of 5 nanograms per liter (ng/L) for combined PFOA and PFOS. In response to a request from the EPA in 2019, the U.S. Geological Survey (USGS) prepared cross sections and maps to provide more information about the hydrogeologic framework at and near the site and assist in improving the conceptual site model using water level and contaminant data collected by the EPA in 2020. The cross sections present lithologic correlations from available geophysical logs collected in wells from 2002 to 2014; they show alternating intervals of relatively elevated and reduced natural gamma activity that correspond to changes in lithology, with water-bearing zones and well screens commonly located at lithologic contacts, sometimes near thin coal seams. Water-bearing zones commonly are associated with fractures at or near lithologic contacts but also may be associated with fractures at or near apparent faulting. Recent (March 2020) water-level data shown on cross sections and maps indicate large downward vertical gradients and apparent radial gradients laterally to the northeast, northwest, and southwest that generally following topography. Recent (February to March 2020) data for TCE groundwater concentration shown on cross sections and maps indicate the highest TCE concentrations (greater than 3,000 μg/L and as much as 75,000 μg/L) and combined PFOA and PFOS concentrations (greater than 1,000 ng/L and up to at least 2,350 ng/L) are from shallow (less than 60 feet [ft] below land surface [bls]) and intermediate depth (60 to 100 ft bls) wells near the center of the former Chromatex Plant. TCE and PFAS (as combined PFOA and PFOS) contamination is present at greater depths, as much as 304 ft bls, as evidenced by samples collected from one well (a reconstructed former production well) near the plant, that contained concentrations of about 240 μg/L and 508 ng/L, respectively. The 2020 data also indicate that TCE and PFAS concentrations which exceed drinking-water MCL or HA levels are present in groundwater depths of less than 200 ft in an area that extends predominantly in a northeast direction from the former Chromatex Plant, and is apparently influenced by hydraulic gradients, lithology, and geologic structure.

Pennsylvania↗
USGS2015

Upstream factors affecting Tualatin River algae—Tracking the 2008 Anabaena algae bloom to Wapato Lake, Oregon

Significant Findings A large bloom that included floating mats of the blue-green algae Anabaena flos-aquae occurred in the lower 20 miles of the Tualatin River in northwestern Oregon between July 7 and July 17, 2008. The floating bloom was deemed a hazard to recreational users of the river due to the potential production of algal toxins (anatoxin- a and microcystin), and a public health advisory was posted for the lower 10.8 miles of the river by the Oregon Department of Human Services for July 12–25, 2008. The bloom caused nuisance taste and odor issues and required modified drinking-water treatment techniques where water was withdrawn for municipal uses in the upper reaches of the Tualatin River, some 46 miles upstream of the worst algae problems. Using water sample data from Clean Water Services and the Joint Water Commission, and continuous and discrete monitoring data from the U.S. Geological Survey, the source of the anomalous water-quality conditions and the likely source of the Anabaena bloom was traced upstream to discharges from the Wapato Lake agricultural area near Gaston, Oregon, in the upper part of the watershed near river mile 60. The Wapato Lake algae bloom occurred as standing water remained on the lakebed far longer than normal—into early summer. A failure of the levee on the edge of Wapato Lake in December 2007 caused by heavy rainfall and high water in the canal outside the levee inundated the lakebed to a depth of 7–9 feet, storing thousands of acre-feet more water than its normal winter volume. The water could not be pumped out until the levee was repaired or river levels receded, thus delaying drainage of the lake until summer and facilitating the bloom. In normal summers, the lower Tualatin River grows a moderate crop of algae that responds strongly to streamflow (residence time), light available for photosynthesis, and phosphorus concentrations. In 2008, however, inoculation of the river with phytoplankton and zooplankton discharged from Wapato Lake some 30 miles upstream of the lower, pooled reach of the river demonstrated the importance of upstream factors on plankton communities and water-quality conditions in the Tualatin River. The Wapato Lake algae bloom of July 2008 provided useful information and lessons for agencies managing public health, wetlands, agricultural activities, and water quality in the Tualatin River basin and similar river basins elsewhere. The results and insights derived from this study can be used to enhance future monitoring and data collection strategies designed to improve water quality and plankton models and better predict dissolved-oxygen concentrations in the lower Tualatin River.

Oregon↗
USGS1999

Relation of pesticide concentrations to season, streamflow, and land use in seven New Jersey streams

The presence and variability of pesticides in seven New Jersey streams was documented by analyzing 146 samples collected from the streams from April 1996 through June 1998. The samples were analyzed for 85 pesticides, including 50 herbicides, 28 insecticides, and 7 degradation products, at method detection limits that ranged from 0.001 to 0.018 μg/L (micrograms per liter). Pesticides were frequently detected; however, concentrations were generally low. The pesticides most frequently detected were atrazine, in 97 percent of the samples; prometon, 96 percent; metolachlor, 95 percent; desethyl-atrazine, 91 percent; simazine, 88 percent; diazinon, 58 percent; alachlor, 56 percent; and carbaryl, 54 percent. Detection frequencies were highest during the growing season (April-September). At least one pesticide was detected in all but one of these samples, and 49 percent of the samples contained 9 or more pesticides. The numbers of pesticides detected at a given site ranged from 13 to 29. Ten pesticides were detected at concentrations that exceeded established water-quality criteria. Thirty-one of these detections were in samples collected during the growing season and one during the nongrowing season. The pesticides that exceeded the U.S. Environmental Protection Agency (USEPA) maximum contaminant level for drinking water were atrazine, which exceeded 3 μg/L in four samples, and alachlor, 2 μg/L in two samples. Cyanazine exceeded the USEPA liftime health advisory level (HAL) of 1 μg/L in two samples. These eight detections occurred during runoff shortly after spring pesticide applications and represent a potential threat to municipal water supplies in the Raritan River basin. Concentrations of chlorpyrifos, chlorthalonil, diazinon, ethyl-parathion, and methyl-azinphos exceeded the chronic life criteria for the protection of aquatic life (ACQR) in 20 samples at four sites during the growing season. Dieldrin was detected in four samples and DDE in two samples at concentrations that exceeded New Jersey Department of Environmental Protection (NJDEP) human health criteria. Individual and total-pesticide concentrations and total numbers of pesticides detected in the samples varied with season and flow conditions. Median and maximum concentrations of most of the pesticides were highest during runoff in the growing season. Pesticide concentrations were typically lower and less variable in the nongrowing season than in the growing season, regardless of changes in hydrologic conditions; however, median concentrations of most pesticides were slightly lower during runoff than during base flow. The median total-pesticide concentration and median total number of pesticides detected were highest and most variable in runoff samples in the growing season. In the nongrowing season, the median total-pesticide concentration was lowest in runoff samples and least variable during base-flow conditions. Median total numbers of pesticides were lowest and least varibale in the nongrowing season during base-flow conditions at most sites. The highest total-pesticide concentrations were detected in samples from the two small agricultural basins (greater than 25 percent of land use is agricultural) during runoff in late spring and early summer. In general, insecticides were detected more frequently and in greater concentrations at urban sites. Concentrations of agricultural herbicides generally decreased with increasing flow at the four sites with less than 10 percent agriculture land use and increased with increasing flow at the three sites with more than 25 percent agricultural land use. Most of the pesticides that correlated positively with streamflow were detected at sites where land use in the basin would indicate the use of those particular pesticides. Most of the pesticides that correlated negatively with streamflow were present at the site in the Coastal Plain or at sites in which the land use in the basin would not indicate heavy u

New Jersey;New York↗
USGS2000

Effects of land use and hydrogeology on the water quality of alluvial aquifers in eastern Iowa and southern Minnesota, 1997

Ground-water samples were collected from monitoring wells at 31 agricultural and 30 urban sites in the Eastern Iowa Basins study unit during June–August 1997 to evaluate the effects of land use and hydrogeology on the water quality of alluvial aquifers. Ground-water samples were analyzed for common ions, nutrients, dissolved organic carbon, tritium, radon-222, pesticides and pesticide metabolites, volatile organic compounds, and environmental isotopes. Calcium, magnesium, and bicarbonate were the dominant ions in most samples and were likely derived from solution of carbonate minerals (calcite and dolomite) present in alluvial detrital deposits. Chloride and nitrate were dominant anions in samples from several wells. Sodium and chloride concentrations were significantly higher in samples from urban areas, where roads are more numerous and road salts may be more frequently applied, than in agricultural areas. Nitrate was detected in 94 percent of samples from agricultural areas and 77 percent of samples from urban areas. Nitrate concentrations were significantly higher in agricultural areas than in urban areas and exceeded the U.S. Environmental Protection Agency maximum ontaminant level for drinking water (10 milligrams per liter as N) in 39 percent of samples from agricultural areas. Nitrate concentrations in samples from urban areas did not exceed the maximum contaminant level. Greater use of fertilizers in agricultural areas most likely contributes to higher nitrate concentrations in samples from those areas. Tritium-based ages indicate ground water was most likely recharged after the 1950’s at all but one sampling site. Agricultural and urban land-use areas have remained relatively stable in the study area since the 1950’s; therefore, the effects of current land use should be reflected in ground water sampled during this study. Radon-222 was detected in all samples and exceeded the U.S. Environmental Protection Agency’s previously proposed maximum contaminant level for drinking water (300 picocuries per liter) in 71 percent of samples. Pesticides were detected in 84 percent of samples from agricultural areas and 70 percent from urban areas. Atrazine and metolachlor were the most frequently detected pesticides in samples from agricultural areas; atrazine and prometon were the most frequently detected pesticides in samples from urban areas. None of the pesticide oncentrations exceeded U.S. Environmental Protection Agency maximum contaminant levels or lifetime health advisories for drinking water. Pesticide metabolites were detected in 94 percent of samples from agricultural areas and 53 percent from urban areas. Metolachlor ethane sulfonic acid and deethylatrazine were the most frequently detected metabolites in samples from agricultural areas; metolachlor ethane sulfonic acid and alachlor ethane sulfonic acid were the most frequently detected metabolites in samples from urban areas. Total metabolite concentrations were significantly higher in samples from agricultural areas than in samples from urban areas. Total pesticide concentrations (parent compounds) tended to be higher in samples from agricultural areas; however, this difference was not statistically significant. Metabolites constituted the major portion of the total residue concentration in the alluvial aquifer. Volatile organic compounds were detected in 40 percent of samples from urban areas and 10 percent from agricultural areas. Methyl tertbutyl ether was the most commonly detected volatile organic compound and was present in 23 percent of samples from urban areas. Elevated concentrations (greater than 30 micrograms per liter) of methyl tert-butyl ether and BTEX compounds (benzene, toluene, ethylbenzene, and xylene) in two samples from urban areas suggest the possible presence of point-source gasoline leaks or spills. Factors other than land use may contribute to observed differences in water quality between and within agricultural and urban areas. Nitrate, atrazine, deethylatrazine, and deisopropylatrazine concentrations were significantly higher in shallow wells with sample intervals nearer the water table and in wells with thinner cumulative clay thickness above the sample intervals. These relations suggest that longer flow paths allow for greater residence time and increase opportunities for sorption, degradation, and dispersion, which may contribute to decreases in nutrient and pesticide concentrations with depth. Nitrogen speciation was influenced by redox conditions. Nitrate concentrations were significantly higher in ground water with dissolved-oxygen concentrations in excess of 0.5 milligram per liter. Ammonia concentrations were higher in ground water with dissolved-oxygen concentrations of 0.5 milligram per liter or less; however, this relation was not statistically significant. The amount of available organic matter may limit denitrification rates. Elevated nitrate concentrations (greater than 2.0 mg/L) were significantly related to lower dissolved organic carbon concentrations in water samples from both agricultural and urban areas. A similar relation between nitrate concentrations (in water) and organic carbon concentrations (in aquifer material) also was observed but was not statistically significant.

Iowa, Minnesota↗
USGS2024

The state of the science and practice of stream restoration in the Chesapeake: Lessons learned to inform better implementation, assessment and outcomes

The Chesapeake Bay Program’s (CBP) Science and Technical Advisory Committee (STAC) organized and led a workshop on the science and practice of stream restoration in order to summarize the state of knowledge in order to identify ways to improve stream restoration outcomes. The workshop identified a general framework for explaining the main factors leading to stream restoration outcomes: stream degradation has occurred, leading to regulatory and policy motivations that prioritize project goals, which leads to restoration approaches, assessment and monitoring efforts, and ultimately stream restoration outcomes. In the Chesapeake Bay watershed, stream restoration often occurs in response to Clean Water Act (CWA) mandates to reduce nitrogen, phosphorus, and sediment loads to the Bay. Reviews of stream restoration outcomes summarized at the workshop showed that, in general, stream restorations have led to minimal improvement to stream aquatic biota, effective ‘stabilization’ of channel form over time, moderate improvements to water quality, and short-term negative impacts to riparian vegetation. The fundamental finding of the workshop was that often the primary goal of stream restoration projects is to improve geomorphic stability in the restored reach and downstream water quality, and not to improve local ecological conditions through ‘uplift’ (improvement of one or more ecosystem functions through a restorative activity; a term defined in Appendix D), and therefore these projects often do not improve aquatic macroinvertebrate or fish communities. This conflict in goals is a shortcoming of the currently most common regulatory driver for stream restoration (reducing downstream loads of N, P, and sediment) that could be addressed directly through diversifying goals to include biotic uplift, as biological benefit is an assumed condition for the permitting and crediting of stream restoration projects. It is also likely that current understanding of stressors and drivers of stream ecosystem health is insufficient, and that reach-scale restoration focused on geomorphic restoration is not removing the actual sources of stream health impairment that may arise in the upstream watershed. More science could help to identify how to improve the ecological condition of streams through management. The outcome of stream restoration monitoring has revealed that while geomorphic and hydrodynamic functions of stream restoration projects may be achieved, biotic stream function improvements remain elusive. As such, ensuring uplift may be achieved by avoiding restoration projects that risk resources in higher-quality streams and riparian corridors. Reach-scale restoration often does not effectively mitigate the watershed-scale stressors of stream ecosystems. If a desired outcome of stream restoration includes ecological uplift, then focusing efforts on improving stream ecology could help meet that goal.

Chesapeake Bay watershed↗
USGS2003

Estimating the magnitude of the 100-year peak flow in the Big Lost River at the Idaho National Engineering and Environmental Laboratory, Idaho

Accurate estimates of peak flows in the Big Lost River at the Idaho National Engineering and Environmental Laboratory (INEEL) are needed to assist planners and managers with evaluating possible effects of flooding on facilities at the INEEL. A large difference of 4,350 cubic feet per second (ft 3 /s) between two previous estimates of the magnitude of the 100-year peak flow in the Big Lost River near the western boundary of the INEEL prompted the present study. Regression models that compared annual peak flows and attenuation of annual peak flows between successive gaging stations for the same flow event were used to estimate the magnitude of the 100-year peak flow in the Big Lost River. The 100-year peak flow of 4,790 ft 3 /s at the Howell Ranch gaging station was used as the starting point for this analysis. This estimate was determined by using a three-parameter log-Pearson Type III distribution as outlined in “Guidelines for Determining Flood Flow Frequency” (Bulletin 17B by the Interagency Advisory Committee on Water Data). The regression models indicated that, in the reach of the Big Lost River between Howell Ranch and Mackay Reservoir, downstream peak flows are lower than upstream peak flows. Peak-flow attenuation values for this reach of the river decreased nonlinearly as the magnitude of the peak flow increased. Extrapolation of the trend resulted in an attenuation estimate of 13 percent for this reach relative to the 100-year peak flow at the Howell Ranch gaging station. In the lower reach of the Big Lost River between Mackay Reservoir and Arco, downstream peak flows are also lower than upstream peak flows. However, in contrast to the upper reach, peak-flow attenuation values decreased linearly as the magnitude of the peak flow increased. Extrapolation of the data indicated that peak-flow attenuations in this reach of the river approach zero for flows approaching the 100-year peak-flow estimate immediately upstream and downstream from Mackay Reservoir. A regression model of annual maximum daily mean flows between Arco and the INEEL diversion dam indicated that the attenuation values in this reach of the river are nearly the same for all flows of record. Extrapolation of the linear regression of these values resulted in an attenuation estimate of 10 percent. Seepage measurements made during 1951–53 also resulted in a loss estimate of approximately 10 percent. This attenuation value, combined with the values from analyses of the upstream reaches, resulted in an estimate of the 100-year peak flow for the Big Lost River immediately upstream from the INEEL diversion dam of 3,750 ft 3 /s; upper and lower 95-percent confidence limits were 6,250 ft 3 /s and 1,300 ft 3 /s, respectively. Localized rainfall, even of high intensity, is not likely to produce large peak flows at the INEEL because of high loss rates (infiltration, bank storage, and channel storage) along much of the stream channel. The relatively short flow durations resulting from rainstorms historically have not provided sufficient volumes of water to satisfy local storage demands (bank and channel storage). Only after these storage demands are met do the loss rates decrease enough for significant peak flows to reach the INEEL site. An uncertain component of the present analysis is the effect of seismic activity on the 100-year peak-flow estimate. Analysis of the effect of the magnitude 7.3 Borah Peak earthquake in 1983 on normal flow conditions in the Big Lost River suggests that the joint occurrence of a large earthquake and a 100-year peak flow could significantly increase the magnitude of the peak flow at the INEEL.

Idaho↗
USGS2005

Submersed Aquatic Vegetation Modeling Output Online

Introduction The ability to predict the distribution of submersed aquatic vegetation in the Upper Mississippi River on the basis of physical or chemical variables is useful to resource managers. Wildlife managers have a keen interest in advanced estimates of food quantity such as American wildcelery (Vallisneria americana) population status to give out more informed advisories to hunters before the fall hunting season. Predictions for distribution of submerged aquatic vegetation beds can potentially increase hunter observance of voluntary avoidance zones where foraging birds are left alone to feed undisturbed. In years when submersed aquatic vegetation is predicted to be scarce in important wildlife habitats, managers can get the message out to hunters well before the hunting season (Jim Nissen, Upper Mississippi River National Wildlife and Fish Refuge, La Crosse District Manager, La Crosse, Wisconsin, personal communication). We developed a statistical model to predict the probability of occurrence of submersed aquatic vegetation in Pool 8 of the Upper Mississippi River on the basis of a few hydrological, physical, and geomorphic variables. Our model takes into consideration flow velocity, wind fetch, bathymetry, growing-season daily water level, and light extinction coefficient in the river (fig. 1) and calculates the probability of submersed aquatic vegetation existence in Pool 8 in individual 5- x 5-m grid cells. The model was calibrated using the data collected in 1998 (516 sites), 1999 (595 sites), and 2000 (649 sites) using a stratified random sampling protocol (Yin and others, 2000b). To validate the model, we chose the data from the Long Term Resource Monitoring Program (LTRMP) transect sampling in backwater areas (Rogers and Owens 1995; Yin and others, 2000a) and ran the model for each 5- x 5-m grid cell in every growing season from 1991 to 2001. We tallied all the cells and came up with an annual average percent frequency of submersed aquatic vegetation occurrence and compared the results with actual LTRMP survey data (fig. 2). Both a paired Student's test (P = 0.4620) and a Wilcoxon's two-sample test (P = 0.4738) did not contradict our null hypothesis that the model prediction and the sampling data are statistically the same. We have not found an effective statistical test to compare model-predicted spatial pattern with aerial photography geographic information, but we are satisfied with the model's outcome on the basis of visual inspection (fig. 3). A unique feature about this model is that a prediction can be made by the end of June each year; therefore, providing wildlife managers an assessment of current year vegetation growth condition 3 to 4 months ahead of the arrival of migrating waterfowl that feed on submersed aquatic vegetation. We are working with the LTRMP partnership to create a mechanism so that model predictions (fig. 4) can be updated annually and the results posted on the LTRMP Web site. Our model underestimated the prevalence of vegetation from 2001 to 2004. We speculate that the summer water level reduction conducted in 2001 and 2002 triggered vegetation responses that are outside the model's domain. Future enhancement of the model will incorporate the summer water level drawdown effects as well as the effects of growth conditions in previous years.

Open-File Report↗
USGS2010

Historical changes in annual peak flows in Maine and implications for flood-frequency analyses

Flood-frequency analyses use statistical methods to compute peak streamflows for selected recurrence intervals— the average number of years between peak flows that are equal to or greater than a specified peak flow. Analyses are based on annual peak flows at a stream. It has long been assumed that the annual peak streamflows used in these computations were stationary (non-changing) over very long periods of time, except in river basins subject to direct effects of human activities, such as urbanization and regulation. Because of the potential effects of global warming on peak flows, the assumption of peak-flow stationarity has recently been questioned. Maine has many streamgages with 50 to 105 years of recorded annual peak streamflows. In this study, this long-term record has been tested for historical flood-frequency stationarity, to provide some insight into future flood frequency. Changes over time in annual instantaneous peak streamflows at 28 U.S. Geological Survey streamgages with long-term data (50 or more years) and relatively complete records were investigated by examining linear trends for each streamgage’s period of record. None of the 28 streamgages had more than 5 years of missing data. Eight streamgages have substantial streamflow regulation. Because previous studies have suggested that changes over time may have occurred as a step change around 1970, step changes between each streamgage’s older record (start year to 1970) and newer record (1971 to 2006) also were computed. The median change over time for all 28 streamgages is an increase of 15.9 percent based on a linear change and an increase of 12.4 percent based on a step change. The median change for the 20 unregulated streamgages is slightly higher than for all 28 streamgages; it is 18.4 percent based on a linear change and 15.0 percent based on a step change. Peak flows with 100- and 5-year recurrence intervals were computed for the 28 streamgages using the full annual peak-flow record and multiple sub-periods of that record using the guidelines (Bulletin 17B) of the Interagency Advisory Committee on Water Data. Magnitudes of 100- and 5-year peak flows computed from sub-periods then were compared to those computed from the full period. Sub-periods of 30 years with starting years staggered by 10 years were evaluated (1907–36, 1917–46, 1927–56, 1937–66, 1947–76, 1957–86, 1967–96, and 1977–2006). Two other sub-periods were evaluated using older data (start-of-record to 1970) and newer data (1971 to 2006). The 5-year peak flow is used to represent small and relatively frequent flood flows in Maine, whereas the 100-year peak flow is used to represent large flood flows. The 1967–96 sub-period generated the highest 100- and 5-year peak flows overall when compared to peak flows based on the full period of record; the median difference for all 28 streamgages is 8 percent for 100- and 5-year peak flows. The 1977–2006 and 1971–2006 sub-periods also generated 100- and 5-year peak flows higher than peak flows based on the full period of record, but not as high as the peak flows based on the 1967–96 sub-period. The 1937–66 sub-period generated the lowest 100- and 5-year peak flows overall. The median difference from full-period peak flows is -11 percent for 100-year peak flows and -8 percent for 5-year peak flows. Overall, differences between peak flows based on the sub-periods and those based on the full periods, generated using the 20 unregulated streamgages, are similar to differences using all 28 streamgages. Increases in the 5- and 100-year peak flows based on recent years of record are, in general, modest when compared to peak flows based on complete periods of record. The highest peak flows are based on the 1967–96 sub-period rather than the most recent sub-period (1977-2006). Peak flows for selected recurrence intervals are sensitive to very high peak flows that may occur once in a century or even less frequently. It is difficult, therefore, to determine which approach will produce the most reliable future estimates of peak flows for selected recurrence intervals, using only recent years of record or the traditional method using the entire historical period. One possible conservative approach to computing peak flows of selected recurrence intervals would be to compute peak flows using recent annual peak flows and the entire period of record, then choose the higher computed value. Whether recent or entire periods of record are used to compute peak flows of selected recurrence intervals, the results of this study highlight the importance of using recent data in the computation of the peak flows. The use of older records alone could result in underestimation of peak flows, particularly peak flows with short recurrence intervals, such as the 5-year peak flows.

Maine↗
USGS2001

Shallow ground-water quality beneath rice areas in the Sacramento Valley, California, 1997

In 1997, the U.S. Geological Survey installed and sampled 28 wells in rice areas in the Sacramento Valley as part of the National Water-Quality Assessment Program. The purpose of the study was to assess the shallow ground-water quality and to determine whether any effects on water quality could be related to human activities and particularly rice agriculture. The wells installed and sampled were between 8.8 and 15.2 meters deep, and water levels were between 0.4 and 8.0 meters below land surface. Ground-water samples were analyzed for 6 field measurements, 29 inorganic constituents, 6 nutrient constituents, dissolved organic carbon, 86 pesticides, tritium (hydrogen- 3), deuterium (hydrogen-2), and oxygen-18. At least one health-related state or federal drinking-water standard (maximum contaminant or long-term health advisory level) was exceeded in 25 percent of the wells for barium, boron, cadmium, molybdenum, or sulfate. At least one state or federal secondary maximum contaminant level was exceeded in 79 percent of the wells for chloride, iron, manganese, specific conductance, or dissolved solids. Nitrate and nitrite were detected at concentrations below state and federal 2000 drinking-water standards; three wells had nitrate concentrations greater than 3 milligrams per liter, a level that may indicate impact from human activities. Ground-water redox conditions were anoxic in 26 out of 28 wells sampled (93 percent). Eleven pesticides and one pesticide degradation product were detected in ground-water samples. Four of the detected pesticides are or have been used on rice crops in the Sacramento Valley (bentazon, carbofuran, molinate, and thiobencarb). Pesticides were detected in 89 percent of the wells sampled, and rice pesticides were detected in 82 percent of the wells sampled. The most frequently detected pesticide was the rice herbicide bentazon, detected in 20 out of 28 wells (71 percent); the other pesticides detected have been used for rice, agricultural, and non-agricultural purposes. All pesticide concentrations were below state and federal 2000 drinking-water standards. The relation of the ground-water quality to natural processes and human activities was tested using statistical methods (Spearman rank correlation, Kruskal?Wallis, or rank-sum tests) to determine whether an influence from rice land-use or other human activities on ground-water chemistry could be identified. The detection of pesticides in 89 percent of the wells sampled indicates that human activities have affected shallow ground-water quality. Concentrations of dissolved solids and inorganic constituents that exceeded state or federal 2000 drinking-water standards showed a statistical relation to geomorphic unit. This is interpreted as a relation to natural processes and variations in geology in the Sacramento River Basin; the high concentrations of dissolved solids and most inorganic constituents did not appear to be related to rice land use. No correlation was found between nitrate concentration and pesticide occurrence, indicating that an absence of high nitrate concentrations is not a predictor of an absence of pesticide contamination in areas with reducing ground-water conditions in the Sacramento Valley. Tritium concentrations, pesticide detections, stable isotope data, and dissolved-solids concentrations suggest that shallow ground water in the ricegrowing areas of the Sacramento Valley is a mix of recently recharged ground water containing pesticides, nitrate, and tritium, and unknown sources of water that contains high concentrations of dissolved solids and some inorganic constituents and is enriched in oxygen-18. Evaporation of applied irrigation water, which leaves behind salt, accounts for some of the elevated concentrations of dissolved solids. More work needs to be done to understand the connections between the land surface, shallow ground water, deep ground water, and the drinking-water supplies in the Sacramento Valley.

Water-Resources Investigations Report↗
USGS2009

Comparison of the Immunomagnetic Separation/Adenosine Triphosphate Rapid Method and the Modified mTEC Membrane-Filtration Method for Enumeration of Escherichia coli

Water quality at beaches is monitored for fecal indicator bacteria by traditional, culture-based methods that can take 18 to 24 hours to obtain results. A rapid detection method that provides estimated concentrations of fecal indicator bacteria within 1 hour from the start of sample processing would allow beach managers to post advisories or close the beach when the conditions are actually considered unsafe instead of a day later, when conditions may have changed. A rapid method that couples immunomagnetic separation with adenosine triphosphate detection (IMS/ATP rapid method) was evaluated through monitoring of Escherichia coli (E. coli) at three Lake Erie beaches in Ohio (Edgewater and Villa Angela in Cleveland and Huntington in Bay Village). Beach water samples were collected between 4 and 5 days per week during the recreational seasons (May through September) of 2006 and 2007. Composite samples were created in the lab from two point samples collected at each beach and were shown to be comparable substitutes for analysis of two individual samples. E. coli concentrations in composite samples, as determined by the culture-based method, ranged from 4 to 24,000 colony-forming units per 100 milliliters during this study across all beaches. Turbidity also was measured for each sample and ranged from 0.8 to 260 neophelometric turbidity ratio units. Environmental variables were noted at the time of sampling, including number of birds at the beach and wave height. Rainfall amounts were measured at National Weather Service stations at local airports. Turbidity, rainfall, and wave height were significantly related to the culture-based method results each year and for both years combined at each beach. The number of birds at the beach was significantly related to the culture-based method results only at Edgewater during 2006 and during both years combined. Results of the IMS/ATP method were compared to results of the culture-based method for samples by year for each beach. The IMS/ATP method underwent several changes and refinements during the first year, including changes in reagents and antibodies and alterations to the method protocol. Because of the changes in the method, results from the two years of study could not be combined. Kendall's tau correlation coefficients for relations between the IMS/ATP and culture-based methods were significant except for samples collected during 2006 at Edgewater and for samples collected during 2007 at Villa Angela. Further, relations were stronger for samples collected in 2006 than for those collected in 2007, except at Edgewater where the reverse was observed. The 2007 dataset was examined to identify possible reasons for the observed difference in significance of relations by year. By dividing the 2007 data set into groups as a function of sampling date, relations (Kendall's tau) between methods were observed to be stronger for samples collected earlier in the season than for those collected later in the season. At Edgewater and Villa Angela, there were more birds at the beach at time of sampling later in the season compared to earlier in the season. (The number of birds was not examined at Huntington.) Also, more wet days (when rainfall during the 24 hours prior to sampling was greater than 0.05 inch) were sampled later in the season compared to earlier in the season. Differences in the dominant fecal source may explain the change in the relations between the culture-based and IMS/ATP methods.

Scientific Investigations Report↗
USGS2024

Using local monitoring results to inform the Chesapeake Bay Program’s Watershed Model

The Chesapeake Bay Program’s Watershed Model (CBWM) has been used as an accounting tool for the Chesapeake Bay Total Maximum Daily Load (TMDL). However, some of the fundamental parameters that underpin the watershed model may not represent local watershed characteristics at all scales. Significant investments have been made by state and local governments, and other local stakeholders, who are interested in validating loads and progress in implementing measures to achieve the pollutant reductions called for in the TMDL through local monitoring data. For the purposes of this STAC workshop, local monitoring is considered any relevant data collected by a local, regional, state, or federal organization that has not been used previously in the development, calibration, or validation of the CBWM. Some of these local monitoring efforts have been collecting data over the past 5-10 years, with some datasets extending back over more than two decades. However, the data and the CBWM are often not directly comparable due to differences in temporal and spatial scales or because the water quality parameters being monitored are not those estimated by the model. Therefore, a Scientific and Technical Advisory Committee (STAC) workshop was convened to bring together Chesapeake Bay Program (CBP) modelers, local and state government stakeholders, and scientists who are monitoring and analyzing local water quality data to recommend ways in which local monitoring data can be used to inform the CBWM, identify gaps between modeled and monitored data, and validate model predictions at the local scale. The workshop, “Using Local Monitoring Results to Inform the Chesapeake Bay Program’s Watershed Model”, was held in March 2023 to provide insight on the scope of local water quality monitoring efforts within and outside of the Bay watershed that could be used to inform the CBWM. Scientists and managers developed recommendations that could be used by modelers for either calibration or knowledge generation to inform the Phase 7 version of the CBWM currently under development for a 2027 decision by the CBP, recommendations for how local monitoring efforts could be designed or altered to better inform the CBWM, and recommendations for how monitored trends could be used in management. The preliminary presentations for the workshop provided essential background information on the CBWM and data used to parameterize it. This information was the foundation for discussions on existing data gaps, the importance of current local monitoring networks, and best practices for developing future monitoring networks. More information on this STAC-funded effort including workshop presentation slides and recordings can be accessed on the workshop webpage. Confidence in the loading estimates of the CBWM is critical because of its role as the accounting mechanism for measuring progress toward the Bay TMDL’s nutrient and sediment reduction goals. Those who are being asked or required to pay for these reductions, from state and local government managers to farmers, property owners and developers, must have confidence in the scientific validity of the CBWM’s loading estimates or trust in the restoration effort will dissipate. Toward that end, several local entities have invested in extensive urban, suburban, and agricultural monitoring programs to characterize nutrient and sediment loading (among other water quality parameters) at a relatively fine scale (from a few acres to 5 square miles). Monitoring networks outside of the Bay watershed were also included as their relevance and similarities to Bay watershed landscapes, hydrology, and climate conditions can help build the body of knowledge necessary for better parameterization of the CBWM. Local monitoring results could be analyzed for loads and trends for calibration of Phase 7, comparison against trends, informing the structure and parameterization of the model, and potentially in policy evaluation. The effectiveness of management practices at the small watershed scale is a primary question of watershed managers that could be addressed by local monitoring, but to do so study design and statistical techniques may need to be altered if these datasets are intended to inform parameterization of the Bay modeling tools. The partnership would benefit from the redesign of some existing monitoring programs so that they are hypothesis-driven, with fully described inputs, outputs, and practices. New statistical tools could be applied to evaluate the relative importance of various drivers affecting water quality and influenced by hydrogeologic setting and watershed condition.

Chesapeake Bay watershed↗
USGS2018

Concentrations of nutrients at the water table beneath forage fields receiving seasonal applications of manure, Whatcom County, Washington, autumn 2011–spring 2015

The U.S. Geological Survey, in cooperation with the Whatcom Conservation District (WCD), collected groundwater-quality data for roughly 3 years (October 2011–May 2015) from near the water table beneath forage fields receiving regular seasonal applications of liquid dairy manure in Whatcom County, Washington. The work was done as part of an evaluation of WCD’s prototypical Application Risk Management (ARM) decision support system. The ARM system uses a combination of field-specific hydrology, stage of crop-growth, manure management practices, soil conditions, and precipitation forecast to evaluate the timing of manure application via a set of decision support tools (Manure Spreading Advisory, ARM Worksheet, manure application setback distances) in order to reduce the risk of contamination of surface water and groundwater. The ARM system’s effectiveness in reducing leaching of nitrate to groundwater was evaluated by monitoring nitrate concentrations in recently recharged groundwater beneath paired test plots receiving manure application scheduled using either conventional (CON) manure scheduling procedures, which utilize fixed start and end dates for manure application along with projected crop nutrient requirements or ARM manure scheduling procedures using an approach to manure application timing based on projected crop nutrient needs, field conditions, and weather forecast. Water-quality samples from the surface of the water table were collected synoptically from paired test plots (2–5 monitoring wells per test plot) at approximately monthly intervals at three different dairy field sites. Water-quality samples from near the water table were isolated from the underlying aquifer using a combination of an inflatable packer and a fine-grained sand pack encompassing the well-screen interval. Concentrations of nitrate and chloride measured at the water table beneath test plots were highly variable. Concentrations of nitrate ranged from non-detectable to 116 milligrams nitrogen per liter (mg-N/L), and chloride ranged from 1.15 to 153 mg/L. In each test plot, seasonal variations were much greater than spatial variations. Differences in nitrate concentrations in groundwater between the two treatments were inconclusive. Nitrate concentrations in groundwater at paired treatment plots (Mann Whitney, p<0.05) were significantly lower beneath the ARM treatment plot at site B, yet significantly higher beneath the ARM treatment plot at site C. Nitrate concentrations in ground water varied significantly among individual wells at each site (Kruskal-Wallis, p<0.05), indicating that leaching of nitrates from soil following manure application is spatially variable at the field scale tested regardless of manure application strategy. At all three paired test plots, average concentrations of nitrate and chloride at the water table were lowest near the end of the growing season (September) and increased rapidly with the onset of autumn rains (October–December). Under both the conventional (calendar-based) and treatment (ARM-based) manure application scheduling systems, high soil nitrate concentrations in autumn were coincident with rising groundwater levels, suggesting that nitrate and chloride were flushed from soil to groundwater by recharge from the seasonal rains. Under both treatments, concentrations of nitrate in shallow (10–25 feet) groundwater beneath forage fields receiving manure applications were greater than the nitrate drinking water standard of 10 mg-N/L in approximately 85 percent of samples. Yearly mass loading of nitrogen to the groundwater system calculated from nitrate concentrations at the water table and estimates of recharge volume ranged from 86 to 196 pounds-N per acre, which was equivalent to approximately 16–37 percent of the recommended manure application rate for projected forage production yield of 7 dry tons per acre per year. Manure nitrogen applied in the autumn, when crop nutrient needs decrease due to reduced sunlight and cooler temperatures and commensurate with ongoing mineralization of soil organic-nitrogen and increased seasonal precipitation, are more likely to exceed the immediate plant nutritional requirements and hence be flushed to groundwater than manure applications occurring near the peak of the growing season.

Washington↗