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USGS2021

Characterization of groundwater quality and discharge with emphasis on selenium in an irrigated agricultural drainage near Delta, Colorado, 2017–19

Selenium is a water-quality constituent of concern for aquatic ecosystems in the lower Gunnison River Basin. Selenium is derived from bedrock of the Mancos Shale and is mobilized and transported to groundwater and surface water by application of irrigation water. Although it is recognized that groundwater contributes an appreciable amount of selenium to surface water, few studies have addressed interactions between the two. The U.S. Geological Survey in cooperation with the Colorado Water Conservation Board conducted a study during 2017–19 to characterize the quality and quantity of groundwater discharging to an agricultural drainage near Delta, Colorado, locally known as Sunflower Drain. Water quality in the study area is characterized by high dissolved solids with elevated concentrations of selenium and nitrate resulting from dissolution of soluble salts in the Mancos Shale. Selenium concentrations have decreased by 50 percent since the early 2000s, possibly in response to irrigation system improvements. Stable water isotopes indicate streamflow is dominated by canal water during the irrigation season (April to October) and, during the nonirrigation season (November to March), is dominated by groundwater that has undergone some degree of evaporation. Pesticide and pharmaceutical compounds were infrequently detected, and results indicate they were derived from sources outside the study area such that they do not appear to be useful as tracers of groundwater sources. Stable isotopes of nitrate indicate that nitrate originates from the Mancos Shale, and the isotopic composition is enriched by denitrification in the groundwater system. Using a mass-balance approach, estimated groundwater discharge rates to Sunflower Drain ranged from 0.15 to 0.27 cubic feet per second per mile with one losing reach identified. Selenium, sulfate, and nitrate concentrations in groundwater estimated by mass-balance calculations were similar to concentrations measured in the Poly 17 observation well, located in a largely irrigated area in east tributary. One tributary reach had higher concentrations of selenium, sulfate, and nitrate likely reflecting localized inputs of more concentrated groundwater, similar to the concentrations in the Poly 7 observation well, which is downgradient from a residential area in the west tributary. Three pilot studies were conducted, including fiber optic distributed temperature sensing to detect groundwater discharge zones in the stream channel, a passive seismic technique to estimate depth to bedrock, and use of radon-222 as a geochemical tracer of groundwater discharge. All three techniques show promise as additional approaches for investigating groundwater discharge surface-water systems in irrigated drainage areas on Mancos Shale. The factors that affect groundwater movement mainly include when and where irrigation water is transported and applied, and the distribution of bedrock of the Mancos Shale and overlying alluvial deposits. The average groundwater recharge rate for the study area was estimated at 8.1 inches per year, based on mass balance calculations from synoptic survey data. Along the western tributary of Sunflower Drain, there was evidence that spills from the East Canal may recharge the groundwater aquifer adjacent to the stream channel. Groundwater movement to the stream channel may be controlled by the topography of the alluvial/bedrock interface or focused along human-made features, such as tile drains and ditches constructed around irrigated fields. On larger scales, the top of bedrock was also important, creating a topographic constriction that caused a zone of groundwater discharge. The groundwater system is complex, and further study could better define the system, possibly through application of a groundwater flow model and more extensive studies using some of the exploratory methods evaluated in this study.

Colorado↗

USGS1976

Techniques for estimating flood depths for Oklahoma streams

Regional relations are defined for estimating the depths of floods having recurrence intervals ranging from 2 to 100 years for both natural and urban streams in Oklahoma. Contributing drainage area and the 2-year 24-hour rainfall are the only independent variables required for estimating flood depths for natural streams. For urban streams the percentage of the basin impervious and served by storm sewers is also required. The only limitations are that the stream be unregulated, that the main channels be unimproved, and that the contributing drainage area and the 2-year 24-hour rainfall be in the range of values used to derive the relations. The standard errors of estimate range from 24 percent for the 50- and 100-year floods to 33 percent for the 2-year flood for the natural streams. The estimation error for urban streams is not evaluated due to paucity of data. Although the flood depths estimated from techniques presented in this report are considered less reliable than those obtained from field surveys and hydraulic computations, the ease and simplicity of their determination are expected to make them useful for many purposes. Data on flood depths for 132 gaging stations are given in table 1.

Oklahoma↗

USGS1997

Water-quality assessment of the Rio Grande Valley, Colorado, New Mexico, and Texas: Summary and analysis of water-quality data for the basic-fixed-site network, 1993-95

The Rio Grande Valley study unit of the U.S. Geological Survey National Water-Quality Assessment Program collected monthly water- quality samples at a network of surface-water sites from April 1993 through September 1995. This basic-fixed-site network consisted of nine main-stem sites on the Rio Grande, five sites on tributaries of the Rio Grande, two sites on streams in the Rio Grande Valley study unit that are not directly tributary to the Rio Grande, and one site on a conveyance channel. During each monthly sampling, field properties were measured and samples were collected for the analysis of dissolved solids, major constituents, nutrients, selected trace elements, and suspended-sediment concentrations. During selected samplings, supplemental samples were collected for the analysis of additional trace elements, organic carbon, and/or pesticides. Spatial variations of dissolved-solids, major-constituent, and nutrient data were analyzed. The report presents summary statistics for the monthly water-quality data by sampling site and background information on the drainage basin upstream from each site. Regression equations are presented that relate dissolved-solids, major-constituent, and nutrient concentrations to streamflow, selected field properties, and time. Median instantaneous streamflow at each basic-fixed site ranged from 1.4 to 1,380 cubic feet per second. Median specific conductance at each basic-fixed site ranged from 84 to 1,680 microsiemens per centimeter at 25 degrees Celsius, and median pH values ranged from 7.8 to 8.5. The water sampled at the basic-fixed sites generally was well oxygenated and had a median dissolved-oxygen percent of saturation range from 89 to 108. With the exception of Rio Grande above mouth of Trinchera Creek, near Lasauses, Colorado, dissolved-solids concentrations in the main stem of the Rio Grande generally increased in a downstream direction. This increase is from natural sources such as ground-water inflow and evapotranspiration and from anthropogenic sources such as irrigation- return flows, urban runoff, and wastewater-treatment plant discharges. The smallest median dissolved-solids concentration detected at a basic- fixed site was 58 milligrams per liter and the largest was 1,240 milligrams per liter. The spatial distribution of calcium, magnesium, sodium, sulfate, chloride, and fluoride was similar to the spatial distribution of dissolved solids. The spatial distribution of potassium and bicarbonate varied slightly from that of dissolved solids. Median silica concentrations generally decreased in a downstream direction. Of all cations, calcium and sodium had the largest concentrations at most basic-fixed sites. Bicarbonate and sulfate were the anions having the largest concentrations at most sites. The largest median silica concentration was at Rito de los Frijoles in Bandelier National Monument, New Mexico, where silica composed approximately 50 percent of the dissolved solids. The largest concentrations and largest median concentrations of dissolved-nutrient analytes were detected at Santa Fe River above Cochiti Lake, New Mexico, and Rio Grande at Isleta, New Mexico. The relatively large dissolved-nutrient concentrations at these sites probably were due to discharges from wastewater-treatment plants and urban runoff. The largest concentrations and largest median concentrations of total ammonia plus organic nitrogen and total phosphorus were detected at Rio Puerco near Bernardo, New Mexico. The largest concentrations of these nutrients at this site were associated with runoff from summer thunderstorms. Dissolved-iron concentrations ranged from censored concentrations to 914 micrograms per liter. Median dissolved-iron concentrations ranged from 3 to 160 micrograms per liter.

Colorado, New Mexico, Texas↗

USGS2024

Prefabricated Zero Ascend Omnispecies (ZAO) modular fish passage modules using advanced manufacturing techniques

The Zero Ascend Omnispecies (ZAO) fish passage attraction module “ZAO Attractor” is a novel system designed to facilitate upstream passage for a broad spectrum of fish species, with a particular focus on American shad and river herring (alewife and/or blueback herring). Combining the use of prefabricated, modular components with advanced manufacturing, the ZAO aims to provide a cost-effective and scalable solution for fish passage attractions across various hydropower sites. The system features a surface level entry, so fish do not need to climb. In addition, it is designed to be adjusted and repositioned to create the most effective attraction flows by managing the outflows from hydropower turbines. Budget Period 1 (BP1) focused on the design and modeling of the ZAO Attractor and demonstrated the engineering feasibility of a modular, prefabricated, hydrodynamically efficient structure with surface level entry and passage. During BP1, the hypothesis was that certain structural adaptations, such as the addition of long fins, could direct turbine outflows to create a desirable downstream flow. Simulations, however, were inconclusive, revealing the complex nature of fish preferences for hydraulic conditions. It was discovered that there were limited published studies on the direct correlation between quantified flow patterns and fish attraction, emphasizing the need for controlled studies to observe and measure these effects. In Budget Period 2 (BP2), controlled studies with live fish were prioritized to address these complexities. A partially scaled ZAO Attractor was evaluated in laboratory conditions using native river water to assess its capability to attract and guide fish. Despite challenges with flume flow conditions and the impact of flume dimensions on flow directionality and velocity, the studies provided insights into fish behavior and preferences, particularly the requirement for a consistent flow stream for migration cues. Adjustments to the fin structure demonstrated potential effectiveness in guiding fish toward the module. However, the hydraulic conditions within the flume environment did not accurately reflect typical in-river scenarios, therefore the results were inconclusive with respect to the optimal system configuration for in-river use. In the future, conducting comprehensive field studies can enhance understanding of the interactions between fish behavior and flow conditions created by the ZAO Attractor. Additionally, a design review is advised, particularly regarding the load scenarios throughout the seasons and positioning of the ZAO Attractor. These studies should continue to refine the design to achieve its intended benefits: economical and effective fish attraction and passage that can be adapted to specific site conditions while allowing for continued energy generation at sites up for re-licensure and adding hydropower generation to previously untapped resources in non-powered dams and new stream reaches. In conclusion, the ZAO fish passage attraction module presents a promising approach to fish passage at hydropower stations, with the potential to balance environmental concerns with renewable energy development. However, further field validation and optimization are necessary to ensure its effectiveness and practicality in real-world applications.

Final Technical Report↗

USGS2012

Thresholds of flow-induced bed disturbances and their effects on stream metabolism in an agricultural river

Storm-driven flow pulses in rivers destroy and restructure sediment habitats that affect stream metabolism. This study examined thresholds of bed disturbances that affected patch- and reach-scale sediment conditions and metabolism rates. A 4 year record of discharge and diel changes in dissolved oxygen concentrations (ΔDO) was analyzed for disturbances and recovery periods of the ΔDO signal. Disturbances to the ΔDO signal were associated with flow pulses, and the recovery times for the ΔDO signal were found to be in two categories: less than 5 days (30% of the disturbances) or greater than 15 days (70% of the disturbances). A field study was performed during the fall of 2007, which included a storm event that increased discharge from 3.1 to 6.9 m 3 /s over a 7 h period. During stable flow conditions before the storm, variability in patch-scale stream metabolism values were associated with sediment texture classes with values ranging from −16.4 to 2.3 g O 2 2 /d (negative sign indicates net respiration) that bounded the reach-averaged rate of −5.6 g O 2 2 /d. Hydraulic modeling of bed shear stresses demonstrated a storm-induced flow pulse mobilized approximately 25% of the bed and reach-scale metabolism rates shifted from −5 to −40 g O 2 2 /d. These results suggest that storm-induced bed disturbances led to threshold behavior with respect to stream metabolism. Small flow pulses resulted in partial-bed mobilization that disrupted stream metabolism by increased turbidity with short recovery times. Large flow pulses resulted in full-bed mobilization that disrupted stream metabolism by destroying periphyton habitats with long recovery times.

Water Resources Research↗

USGS1998

Flow and geochemistry along shallow ground-water flowpaths in an agricultural area in southeastern Wisconsin

Water-quality and geohydrologic data were collected from 19 monitor wells and a stream in an agricultural area in southeastern Wisconsin. These sites were located along a 2,700-ft transect from a local ground-water high to the stream. The transect is approximately parallel to the horizontal direction of ground-water flow at the water table. Most of the wells were installed in unconsolidated deposits at five locations along the transect and include an upgradient well nest, a midgradient well nest, a downgradient well nest, wells in the lowland area near the stream, and wells installed in the stream bottom. The data collected from this study site were used to describe the water quality and geohydrology of the area and to explain and model the variations in water chemistry along selected ground-water flowpaths. Water samples from most wells and the stream were analyzed for major ions, nutrients, pesticides, dissolved organic carbon, aluminum, tritium, CFCs, 15N, 18O, and dissolved gases. Measurements of temperature, pH, specific conductance, and dissolved oxygen were made in the field. Concentrations of all dissolved constituents were below Wisconsin ground-water quality enforcement standards. The concentrations of both nitrate and ammonium in precipitation concentrated by evapotranspiration are roughly equal to the concentrations of either in the shallow ground waters. The nitrogen and oxygen isotope data, however, indicate that soil ammonium, ammonium fertilizer, and animal waste are possible nitrate sources. Concentrated precipitation can also supply dissolved sulfate to the shallow ground waters and may be a principal source of pesticides to the ground water. However, some input of dissolved chloride to the ground water from mineral or anthropogenic sources is necessary. X-ray diffraction analyses of samples from 2 cores show the most abundant mineral to be dolomite, with subordinate quartz, microclme, and plagioclase, and minor amounts of mica, hornblende, and chlorite. Hydraulic conductivities determined from slug tests at selected wells range from 0.006 to 55 feet per day, with most values between 0.4 and 12 feet per day. A cross-sectional ground-water flow model, representing the water-table flow system, was developed for the site and was used to identify possible ground-water flowpaths for geocli^mical modeling. The model was calibrated against measured water levels and was most sensitive to variation in recharge and hydraulic conductivity. The calibrated model shows that downward flow from shallow to deeper wells within a nest may occur at the upgradient and midgradient well nests, but that flow from each well nest travels beneath downgradient nests to the stream. Pathline and travel-time analysis performed on the calibrated flow-model output yielded travel times to well screens that range from 5.8 to 59 years with a recharge of 4 inches per yr. Recharge dates based on tritium and CFC concentrations range from pre-1955 to 1986 and are consistent with flowpaths1 and travel times in the calibrated flow model. Changes in water quality along ground-water flowpaths were evaluated using the geochemical model PHREEQC. Geochemical mole balance models of shallow ground-water formation show that the principal reaction, by an order of magnitude, is dissolution of dolomite with CO2 . Concentration factors in the mole-balance models range from 1 to 11, with most values between 5 and 10, which provides independent support for the concentration factor of 8 based on recharge estimates used in the flow model. Ground water recharging at mid- and downgradient wells is oxic and contains dissolved nitrate, whereas the ground water discharging to the stream is anoxic and contains dissolved ammonium. Redox environments were defined at each well on the basis of relative concentrations of various dissolved redox-active species. Chemically permissible flowpaths inferred from the observed sequence of redox environments at well sites are consistent with flowpaths in the ground-water flow model. The transition from nitrate in recharging ground water to ammonium in ground water discharging to the stream suggests the possibility of nitrate reduction along the flowpath. None of the techniques employed in this study, however, were able to prove the occurrence of this reaction.

Michigan, Wisconsin↗

USGS2005

Transport and fate of nitrate and pesticides: Hydrogeology and riparian zone processes

There is continuing concern over potential impacts of widespread application of nutrients and pesticides on ground- and surface-water quality. Transport and fate of nitrate and pesticides were investigated in a shallow aquifer and adjacent stream, Cow Castle Creek, in Orangeburg County, South Carolina. Pesticide and pesticide degradate concentrations were detected in ground water with greatest frequency and largest concentrations directly beneath and downgradient from the corn (Zea mays L.) field where they were applied. In almost all samples in which they were detected, concentrations of pesticide degradates greatly exceeded those of parent compounds, and were still present in ground waters that were recharged during the previous 18 yr. The absence of both parent and degradate compounds in samples collected from deeper in the aquifer suggests that this persistence is limited or that the ground water had recharged before use of the pesticide. Concentrations of NO3- in ground water decreased with increasing depth and age, but denitrification was not a dominant controlling factor. Hydrologic and chemical data indicated that ground water discharges to the creek and chemical exchange takes place within the upper 0.7 m of the streambed. Ground water had its greatest influence on surface-water chemistry during low-flow periods, causing a decrease in concentrations of Cl-, NO3-, pesticides, and pesticide degradates. Conversely, shallow subsurface drainage dominates stream chemistry during high-flow periods, increasing stream concentrations of Cl-, NO3-, pesticides, and pesticide degradates. These results point out the importance of understanding the hydrogeologic setting when investigating transport and fate of contaminants in ground water and surface water. ?? ASA, CSSA, SSSA.

Journal of Environmental Quality↗

USGS1978

Mass movement and storms in the drainage basin of Redwood Creek, Humboldt County, California — A progress report

Numerous active landslides are clearly significant contributors to high sediment loads in the Redwood Creek basin. Field and aerial-photograph inspections indicate that large mass-movement features, such as earthflows and massive streamside debris slides, occur primarily in terrain underlain by unmetamorphosed or slightly metamorphosed sedimentary rocks. These features cannot account for stream sediment derived from schist. Observed lithologic heterogeneity of stream sediment therefore suggests that large-scale mass movement is only one part of a complex suite of processes supplying sediment to streams in this basin. Other significant sediment contributors include various forms of fluvial erosion and small-scale discrete mass failures, particularly on oversteepened hillslopes adjacent to perennial streams. Photo-interpretive studies of landslide and timber-harvest history adjacent to Redwood Creek, together with analysis of regional precipitation and runoff records for six flood-producing storms between 1953 and 1975, indicate that loci and times of significant streamside landsliding are influenced by both local storm intensity and streamside logging. Analysis of rainfall records and historic accounts indicates that the individual storms comprising a late-19th-century series of storms in northwestern California were similar in magnitude and spacing to those of the past 25 years. The recent storms apparently initiated more streamside landslides than comparable earlier storms, which occurred prior to extensive road construction and timber harvest. Field observations and repeated surveys of stake arrays at 10 sites in the basin indicate that earthflows are especially active during prolonged periods of moderate rainfall; but that during brief intense storms, fluvial processes are the dominant erosion mechanism. Stake movement occurs mostly during wet winter months. Spring and summer movement was detected at some moist streamside sites. Surveys of stake arrays in two recently logged areas did not indicate exceptionally rapid rates of movement in three years following timber harvest.

California↗

USGS2021

Spring types and contributing aquifers from water-chemistry and multivariate statistical analyses for seeps and springs in Theodore Roosevelt National Park, North Dakota, 2018

Water resources in Theodore Roosevelt National Park, North Dakota, support wildlife, visitors, and staff, and play a vital role in supporting the native ecology of the park. The U.S. Geological Survey, in cooperation with the National Park Service, completed field work in 2018 for a study to address concerns about water availability and possible sources of groundwater contamination for seeps and springs in Theodore Roosevelt National Park. The objective of the study was to improve hydrologic knowledge and determine the water composition of 11 seeps and springs in the park by collecting water-chemistry data at springs, streams, wells, and rain collectors. Water samples were collected at 26 sites at springs, streams, wells, and rain collectors in the North and South Units of Theodore Roosevelt National Park. Samples in the North Unit were collected at 5 springs, 1 stream, 2 wells, and 1 rain collector. Samples in the South Unit were collected at 6 springs, 2 streams, 8 wells, and 1 rain collector. Samples from springs, streams, and wells were collected in May, July, and September 2018. Samples from rain collectors were collected when enough daily precipitation accumulated in the collectors. Sampled precipitation events during the study period were in May, June, July, August, and September 2018. Physical properties of sampled water—temperature, pH, and specific conductance—were measured in the field. Water samples were analyzed for stable isotopes of oxygen and hydrogen and for chloride concentration. Recharge rates for aquifers supplying springs were determined using precipitation volume and chloride concentrations for a 12-day period before the sample-collection date. Multivariate statistical analysis methods used on water-chemistry data included principal component analysis, cluster analysis, and end-member mixing analysis. Water composition was used to determine the spring type and contributing aquifers for 11 springs in the North and South Units of Theodore Roosevelt National Park from analyses of water-chemistry data between May and September 2018. In the North Unit, Achenbach Spring was classified as a filtration spring with water from an unconfined part of the upper Fort Union aquifer and infiltration of precipitation. Hagen Spring, Mandal Spring, and Stevens Spring were classified as contact springs supplied by semiconfined parts of the upper Fort Union aquifer. Overlook Spring at one time may have been a natural spring or seep but now is a developed spring that behaves like a flowing artesian well completed in a confined part of the upper Fort Union aquifer. In the South Unit, six springs were classified into two spring types: filtration and contact springs. Boicourt Spring and Sheep Butte Spring were classified as filtration springs that have water supplied by unconfined parts of the upper Fort Union aquifer and infiltrated precipitation. Big Plateau Spring, Lone Tree Spring, Sheep Pasture Spring, and Southeast Corner Spring were classified as contact springs that receive waters from a semiconfined part of the upper Fort Union aquifer.

North Dakota↗

USGS2003

Characterization of instream hydraulic and riparian habitat conditions and stream temperatures of the Upper White River Basin, Washington, using multispectral imaging systems

Instream hydraulic and riparian habitat conditions and stream temperatures were characterized for selected stream segments in the Upper White River Basin, Washington. An aerial multispectral imaging system used digital cameras to photograph the stream segments across multiple wavelengths to characterize fish habitat and temperature conditions. All imageries were georeferenced. Fish habitat features were photographed at a resolution of 0.5 meter and temperature imageries were photographed at a 1.0-meter resolution. The digital multispectral imageries were classified using commercially available software. Aerial photographs were taken on September 21, 1999. Field habitat data were collected from August 23 to October 12, 1999, to evaluate the measurement accuracy and effectiveness of the multispectral imaging in determining the extent of the instream habitat variables. Fish habitat types assessed by this method were the abundance of instream hydraulic features such as pool and riffle habitats, turbulent and non-turbulent habitats, riparian composition, the abundance of large woody debris in the stream and riparian zone, and stream temperatures. Factors such as the abundance of instream woody debris, the location and frequency of pools, and stream temperatures generally are known to have a significant impact on salmon. Instream woody debris creates the habitat complexity necessary to maintain a diverse and healthy salmon population. The abundance of pools is indicative of a stream's ability to support fish and other aquatic organisms. Changes in water temperature can affect aquatic organisms by altering metabolic rates and oxygen requirements, altering their sensitivity to toxic materials and affecting their ability to avoid predators. The specific objectives of this project were to evaluate the use of an aerial multispectral imaging system to accurately identify instream hydraulic features and surface-water temperatures in the Upper White River Basin, to use the multispectral system to help establish baseline instream/riparian habitat conditions in the study area, and to qualitatively assess the imaging system for possible use in other Puget Sound rivers. For the most part, all multispectral imagery-based estimates of total instream riffle and pool area were less than field measurements. The imagery-based estimates for riffle habitat area ranged from 35.5 to 83.3 percent less than field measurements. Pool habitat estimates ranged from 139.3 percent greater than field measurements to 94.0 percent less than field measurements. Multispectral imagery-based estimates of turbulent habitat conditions ranged from 9.3 percent greater than field measurements to 81.6 percent less than field measurements. Multispectral imagery-based estimates of non-turbulent habitat conditions ranged from 27.7 to 74.1 percent less than field measurements. The absolute average percentage of difference between field and imagery-based habitat type areas was less for the turbulent and non-turbulent habitat type categories than for pools and riffles. The estimate of woody debris by multispectral imaging was substantially different than field measurements; percentage of differences ranged from +373.1 to -100 percent. Although the total area of riffles, pools, and turbulent and non-turbulent habitat types measured in the field were all substantially higher than those estimated from the multispectral imagery, the percentage of composition of each habitat type was not substantially different between the imagery-based estimates and field measurements.

Water-Resources Investigations Report↗

USGS2013

Water quality in the Anacostia River, Maryland and Rock Creek, Washington, D.C.: Continuous and discrete monitoring with simulations to estimate concentrations and yields of nutrients, suspended sediment, and bacteria

Concentrations and loading estimates for nutrients, suspended sediment, and E. coli bacteria were summarized for three water-quality monitoring stations on the Anacostia River in Maryland and one station on Rock Creek in Washington, D.C. Both streams are tributaries to the Potomac River in the Washington, D.C. metropolitan area and contribute to the Chesapeake Bay estuary. Two stations on the Anacostia River, Northeast Branch at Riverdale, Maryland and Northwest Branch near Hyattsville, Maryland, have been monitored for water quality during the study period from 2003 to 2011 and are located near the shift from nontidal to tidal conditions near Bladensburg, Maryland. A station on Paint Branch is nested above the station on the Northeast Branch Anacostia River, and has slightly less developed land cover than the Northeast and Northwest Branch stations. The Rock Creek station is located in Rock Creek Park, but the land cover in the watershed surrounding the park is urbanized. Stepwise log-linear regression models were developed to estimate the concentrations of suspended sediment, total nitrogen, total phosphorus, and E. coli bacteria from continuous field monitors. Turbidity was the strongest predictor variable for all water-quality parameters. For bacteria, water temperature improved the models enough to be included as a second predictor variable due to the strong dependence of stream metabolism on temperature. Coefficients of determination (R 2 ) for the models were highest for log concentrations of suspended sediment (0.9) and total phosphorus (0.8 to 0.9), followed by E. coli bacteria (0.75 to 0.8), and total nitrogen (0.6). Water-quality data provided baselines for conditions prior to accelerated implementation of multiple stormwater controls in the watersheds. Counties are currently in the process of enhancing stormwater controls in both watersheds. Annual yields were estimated for suspended sediment, total nitrogen, total phosphorus, and E. coli bacteria using the U.S. Geological Survey model LOADEST with hourly time steps of turbidity, flow, and time. Yields of all four parameters were within ranges found in other urbanized watersheds in Chesapeake Bay. Annual yields for all four watersheds over the period of study were estimated for suspended sediment (65,500 – 166,000 kilograms per year per square kilometer; kg/yr/km 2 ), total nitrogen (465 - 911 kg/yr/km 2 ), total phosphorus (36 - 113 kg/yr/km 2 ), and E. coli bacteria (6.0 – 38 x 10 12 colony forming units/yr/km 2 ). The length of record was not sufficient to determine trends for any of the water-quality parameters; within confidence intervals of the models, results were similar to loads determined by previous studies for the Northeast and Northwest Branch stations of the Anacostia River.

Maryl↗

USGS1980