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At least 55 records · Page 3Linked to original sources
USGS2020

Trihalomethane precursors: Land use hot spots, persistence during transport, and management options

To meet drinking water regulations, rather than investing in costly treatment plant operations, managers can look for ways to improve source water quality; this requires understanding watershed sources and fates of constituents of concern. Trihalomethanes (THMs) are one of the major classes of regulated disinfection byproducts, formed when a specific fraction of the organic carbon pool—referred to as THM precursors—reacts with chorine and/or bromine during treatment. Understanding the source, fate, timing and duration of the organic compounds that react to form THMs will allow identification of targeted and effective management actions. In this study we evaluated THM precursor contributions from multiple land use categories and hydrologic contexts, including novel data for urban land uses that demonstrate strong potential to release water with high THM formation potential (THMFP; median 618 μg L −1 ): greater than storm runoff integrated across a mixed-use (1/3 natural, 2/3 agricultural) watershed (median 460 μg L −1 ), irrigation runoff from agricultural systems (357 μg L −1 ), or runoff from a natural forested (median 123 μg L −1 ) and shrubland/grassland (median 259 μg L −1 ) watersheds. While individual storm events released high THM precursor concentrations over short periods, dry season agricultural irrigation as well as urban landscapes have the potential to release water high in THM precursors for several months. Experimental bioassays and sampling along 333 miles of the California Aqueduct confirmed bioavailability and photooxidation potential of less than 10% for THM precursors, suggesting that rivers with residence times of days to weeks may act as THM precursor conduits, shuttling THM precursors from hundreds of miles away to drinking water intakes with minimal degradation. This finding has considerable implications for water managers, who may therefore consider THM precursor management strategies that target even sources located far upstream.

California↗
USGS2015

Sediment transport and evaluation of sediment surrogate ratings in the Kootenai River near Bonners Ferry, Idaho, Water Years 2011–14

The Kootenai River white sturgeon ( Acipenser transmontanus ) and other native fish species are culturally important to the Kootenai Tribe of Idaho, but their habitat and recruitment have been affected by anthropogenic changes to the river. Although the interconnections among anthropogenic changes and their impacts on fish are complex, the Kootenai Tribe of Idaho, in cooperation with other agencies, has been trying to understand and promote native fish recruitment through the development and implementation of the Kootenai River Habitat Restoration Program. As part of this effort, the U.S. Geological Survey collected sediment and streamflow information and evaluated use of acoustic backscatter as a sediment surrogate for estimating continuous suspended-sediment concentration at three sites in the Kootenai River white sturgeon critical habitat during water years 2011–14. During the study, total suspended-sediment and fines concentrations were driven primarily by contributions from tributaries flowing into the Kootenai River between Libby Dam and the study area and were highest during rain-on-snow events in those tributary watersheds. On average, the relative percentage of suspended-sediment concentration in equal-width-increment samples collected in water years 2011–14 composed of fines less than 0.0625 mm (called washload) was 73, 71, and 70 percent at the Below Moyie, Crossport, and Tribal Hatchery sites, respectively. Suspended sand transport often increased with high streamflows, typically but not always associated with releases from Libby Dam. Bedload measured at the Crossport site was about 5 percent, on average, of the total sediment load measured in samples collected in water years 2011–13 and was positively correlated with suspended-sediment load. Comparisons with regional regression and envelope lines for suspended-sediment and bedload transport in relation to unregulated drainage area (drainage area downstream of Libby Dam) show that sediment transport was substantially less in the Kootenai River than in selected, minimally regulated Rocky Mountain rivers. Acoustic surrogate ratings were developed between backscatter data collected using acoustic Doppler velocity meters (ADVMs) and results of suspended-sediment samples. Ratings were successfully fit to various sediment size classes (total, fines, and sands) using ADVMs of different frequencies (1.5 and 3 megahertz). Surrogate ratings also were developed using variations of streamflow and seasonal explanatory variables. The streamflow surrogate ratings produced average annual sediment load estimates that were 8–32 percent higher, depending on site and sediment type, than estimates produced using the acoustic surrogate ratings. The streamflow surrogate ratings tended to overestimate suspended-sediment concentrations and loads during periods of elevated releases from Libby Dam as well as on the falling limb of the streamflow hydrograph. Estimates from the acoustic surrogate ratings more closely matched suspended-sediment sample results than did estimates from the streamflow surrogate ratings during these periods as well as for rating validation samples collected in water year 2014. Acoustic surrogate technologies are an effective means to obtain continuous, accurate estimates of suspended-sediment concentrations and loads for general monitoring and sediment-transport modeling. In the Kootenai River, continued operation of the acoustic surrogate sites and use of the acoustic surrogate ratings to calculate continuous suspended-sediment concentrations and loads will allow for tracking changes in sediment transport over time.

Idaho↗
USGS2018

Before the storm: Antecedent conditions as regulators of hydrologic and biogeochemical response to extreme climate events

While the influence of antecedent conditions on watershed function is widely recognized under typical hydrologic regimes, gaps remain in the context of extreme climate events (ECEs). ECEs are those events that far exceed seasonal norms of intensity, duration, or impact upon the physical environment or ecosystem. In this synthesis, we discuss the role of source availability and hydrologic connectivity on antecedent conditions and propose a conceptual framework to characterize system response to ECEs at the watershed scale. We present four case studies in detail that span a range of types of antecedent conditions and type of ECE to highlight important controls and feedbacks. Because ECEs have the potential to export large amounts of water and materials, their occurrence in sequence can disproportionately amplify the response. In fact, multiple events may not be considered extreme in isolation, but when they occur in close sequence they may lead to extreme responses in terms of both supply and transport capacity. Therefore, to advance our understanding of these complexities, we need continued development of a mechanistic understanding of how antecedent conditions set the stage for ECE response across multiple regions and climates, particularly since monitoring of these rare events is costly and difficult to obtain. Through focused monitoring of critical ecosystems during rare events we will also be able to extend and validate modeling studies. Cross-regional comparisons are also needed to define characteristics of resilient systems. These monitoring, modeling, and synthesis efforts are more critical than ever in light of changing climate regimes, intensification of human modifications of the landscape, and the disproportionate impact of ECEs in highly populated regions.

Biogeochemistry↗
USGS1997

Water-quality assessment of part of the upper Mississippi River Basin, Minnesota and Wisconsin — Pesticides in streams, streambed sediment, and ground water, 1974-94

Available data on pesticides in streams, streambed sediment, and ground water from Federal, state, and local agencies are reviewed for part of the Upper Mississippi River Basin study unit of the National Water-Quality Assessment Program. The analysis focuses on a smaller study area encompassing 19,500 square miles that includes the Upper Mississippi River Basin from Lake Pepin upstream to sampling stations on the Mississippi River near Royalton, Minnesota, and the Minnesota River near Jordan, Minnesota, and the entire drainage basins of the St. Croix, Vermillion, and Cannon Rivers. Assessment is generally restricted to two groups of pesticides the most frequently detected herbicides and organochlorine insecticides although pesticides rarely or never detected are noted. Herbicides, including alachlor, atrazine, cyanazine, or metolachlor, were detected in every stream sampled except the Kettle River. Streams draining row-crop areas had the most herbicide detections. Atrazine was the most widely detected herbicide, with detections in all streams sampled except the Kettle River. Concentrations of atrazine, metolachlor, and cyanazine were greatest in July and detectable most of the year at very low (parts-per-trillion) concentrations. The herbicides EPTC and trifluralin were never detected, although they were used in amounts equal to or greater than those detected, reflecting the fact that some herbicides are less persistent than others. A small urban stream draining part of the Lake Harriet Watershed in Minneapolis, Minnesota, contained substantial concentrations of pesticides as well. Eighty-five percent of runoff events sampled in this entirely urbanized watershed had detections of herbicides commonly used for residential purposes, and 43 percent of the events had detections of alachlor, atrazine, cyanazine, or metolachlor herbicides used predominantly for agriculture. Pesticide concentrations in urban runoff remained well above detection limits throughout the summer, indicating repeated applications of pesticides. Selected organochlorine insecticides, banned since the 1970's, still were detected in recent streambed-sediment samples. Three insecticides, 4,4'-DDT, heptachlor, and lindane, and their metabolites account for almost two-thirds of the organochlorine insecticides detected. Organochlorine insecticides were detected more frequently in streambed sediment than in streamwater. Detections in both phases were most frequent within or downstream of the Twin Cities metropolitan area, indicating that most of these insecticides originated from the Twin Cities metropolitan area. The most frequently detected herbicides in ground water were the same as those frequently detected in streams. Most detections were found in the sand and gravel aquifers underlying agricultural areas, including the Anoka Sand Plain and Bonanza Valley. Atrazine, deethylatrazine, and deisopropylatrazine were detected most frequently. Detection frequencies of atrazine were extremely variable among the various agencies, ranging from 0 to 66.7 percent, probably as a result of different sampling purposes, well locations, and detection levels. Atrazine and atrazine metabolites were the only pesticides detected in bedrock aquifers, with detections found mainly in the agriculture-dominated southeastern part of the study area where bedrock commonly outcrops near the surface. Thus, most detections of herbicides in ground water were found in environmental settings where ground water is vulnerable to contamination. Atrazine was the only pesticide that equaled or exceeded a maximum contaminant level (of 3.0 micrograms per liter) for drinking water. Two stream samples from a small urban watershed in Minneapolis had atrazine concentrations of 3.6 and 3.8 micrograms per liter, and one ground-water sample had a concentration of 3.0 micrograms per liter. Trace concentrations (less than 0.06 micrograms per liter) of the organochlorine insecticides chlordane, dieldrin, endrin, and heptachlor exceeded chronic freshwater-quality criteria in stream samples from the Mississippi, Minnesota, St. Croix, and Vemillion Rivers in 1981 and 1990.

Minnesota, Wisconsin↗
USGS1985

Runoff and chemical loading in small watersheds in the Twin Cities Metropolitan Area, Minnesota

Flow, rainfall, and water-quality data were collected during 1980 for 15 to 30 rainfall and snowmelt events on 6 rural and 11 urban watersheds in the Twin Cities Metropolitan Area. Event or daily flow and load models (for seven constituents) were developed and used with runoff and rainfall data for 1963-80 to compute 2-year frequency annual and seasonal flows and loads for each watershed. In models of storm-sewered watersheds, total storm rainfall proved to be the most significant factor controlling runoff and loads. Depending on the watershed type, antecedent soil-moisture indices and rainfall intensity also were important factors in estimating runoff. Annual runoff from storm-sewered watersheds averaged about 27 percent of annual precipitation, ranging from 13 to 57 percent. Runoff in urban main-stem streams ranged from 13 to 20 percent and was related to the percent of urbanization in the watershed. Annual runoff in rural watersheds ranged from 6 to 20 percent of annual precipitation. Runoff responses were highest in the snowmelt season for all watersheds and declined through the rest of the year. Rural watersheds showed a considerable decrease in runoff response during late summer and fall. Urban-watershed response from season to season was more consistent than rural watersheds because of the impervious area and storm sewers in urban watersheds. (USGS)

Minneosta↗
USGS2019

Changes in event‐based streamflow magnitude and timing after suburban development with infiltration‐based stormwater management

Green stormwater infrastructure implementation in urban watersheds has outpaced our understanding of practice effectiveness on streamflow response to precipitation events. Long‐term monitoring of experimental urban watersheds in Clarksburg, Maryland, USA, provided an opportunity to examine changes in event‐based streamflow metrics in two treatment watersheds that transitioned from agriculture to suburban development with a high density of infiltration‐focused stormwater control measures (SCMs). Urban Treatment 1 has predominantly single family detached housing with 33% impervious cover and 126 SCMs. Urban Treatment 2 has a mix of single family detached and attached housing with 44% impervious cover and 219 SCMs. Differences in streamflow‐event magnitude and timing were assessed using a before‐after‐control‐reference‐impact design to compare urban treatment watersheds to a forested control and an urban control with detention‐focused SCMs. Streamflow and precipitation events were identified from 14 years of sub‐daily monitoring data with an automated approach to characterize peak streamflow, runoff yield, runoff ratio, streamflow duration, time to peak, rise rate, and precipitation depth for each event. Results indicated that streamflow magnitude and timing were altered by urbanization in the urban treatment watersheds, even with SCMs treating 100% of the impervious area. The largest hydrologic changes were observed in streamflow magnitude metrics, with greater hydrologic change in Urban Treatment 2 compared to Urban Treatment 1. While streamflow changes were observed in both urban treatment watersheds, SCMs were able to mitigate peak flows and runoff volumes compared to the urban control. The urban control had similar impervious cover to Urban Treatment 2, but Urban Treatment 2 had more than twice the precipitation depth needed to initiate a flow response and lower median peak flow and runoff yield for events less than 20 mm. Differences in impervious cover between the Urban Treatment watersheds appeared to be a large driver of differences in streamflow response, rather than SCM density. Overall, use of infiltration‐focused SCMs implemented at a watershed‐scale did provide enhanced attenuation of peak flow and runoff volumes compared to centralized‐detention SCMs.

Maryland↗
USGS2023

Evaluating drivers of hydrology, water quality, and benthic macroinvertebrates in streams of Fairfax County, Virginia, 2007–18

In 2007, the U.S. Geological Survey partnered with Fairfax County, Virginia, to establish a long-term water-resources monitoring program to evaluate the hydrology, water quality, and ecology of Fairfax County streams and the watershed-scale effects of management practices. Fairfax County uses a variety of management practices, policies, and programs to protect and restore its water resources, but the effects of such strategies are not well understood. This report used streamflow, water-quality, and ecological monitoring data collected from 20 Fairfax County watersheds from 2007 through 2018 to assess the effects of management practices, landscape factors, and climatic conditions on observed nutrient, sediment, salinity, and benthic-macroinvertebrate community responses. Urbanization, climatic variability, and an increase in management practices occurred within Fairfax County during the study period. Impervious cover, housing units, wastewater infrastructure, and (or) stormwater infrastructure increased in most study watersheds. Climatic conditions varied among study years; countywide estimates of average-annual air temperature differed by about 3 degrees Celsius, and total precipitation ranged from about 34 to 63 inches per year. The effects of the management practices, implemented to reduce nitrogen, phosphorus, and (or) sediment loads, are considered in this study. These management practices primarily consist of stormwater retrofits and stream restorations; however, stream restorations account for most of the financial investment and expected load reductions. Management practices were implemented in half of the study watersheds, and most practices were installed and reductions credited late in the study period. Changes in hydrologic response during storm events were evaluated over the study period because many management practices that were implemented were designed to achieve nutrient and sediment reductions by slowing or intercepting runoff. The average number and length of storm events was mostly unchanged throughout the monitoring network. Four watersheds with 10 years of streamflow data showed a mixture of trends in stormflow peak, volume, and rate-of-change. Event-mean nutrient and sediment concentrations from these watersheds were evaluated during storm events and generally showed increases in total phosphorus (TP) and suspended sediment and reductions or no changes in total nitrogen (TN). Landscape inputs of nitrogen and phosphorus and the percentage of inputs delivered to streams were estimated for the study watersheds. Estimated phosphorus from fertilizer and nitrogen from atmospheric deposition represented large nutrient inputs in most watersheds; amounts of other nonpoint sources varied based on land use. Estimated nitrogen inputs declined throughout Fairfax County and in most study watersheds from 2008 through 2018; in comparison, phosphorus input changes were relatively small. Most nonpoint-nutrient inputs were retained on the landscape and did not reach streams, with slightly more nitrogen retention than phosphorus, on average. Retention rates were lower for years with more precipitation and streamflow. After adjusting for streamflow, TN and TP loads were generally higher for years with more nutrient inputs. Calculated as a function of flow-adjusted loads, TP retention declined at most stations from 2009 through 2018, in comparison, TN retention was relatively unchanged. Landscape and climatic conditions affected spatial differences and changes in Fairfax County stream conditions from 2009 through 2018. TN concentrations were higher and increases over time were larger in watersheds with elevated septic-system density. TP concentrations were higher in watersheds with more turfgrass; concentrations were lower, but had larger increases over time, in watersheds with deeper soils. Suspended-sediment concentrations were higher in watersheds with greater stream densities. Specific conductance was higher in watersheds with more developed land use and shallower soils. Benthic-macroinvertebrate index of biotic integrity (IBI) scores were lower in watersheds with high road density and had larger increases over time in bigger, more developed watersheds. Annual variability in TN and TP concentrations and benthic-macroinvertebrate IBI scores was affected by precipitation; annual variability in suspended sediment concentrations and specific conductance was affected by air temperature. After accounting for influences from landscape and climatic conditions, expected management-practice effects were not consistently observed in monitored stream responses. These effects were assessed by comparing expected management-practice load reductions with the timing, direction, and magnitude of changes in storm-event hydrology, nutrient and sediment loads, median-annual water-quality conditions, and benthic-macroinvertebrate IBI scores. An important consideration for future investigations of management-practice effects is how to control for water-quality and ecological variability caused by geologic properties, the urban environment, precipitation, and (or) air temperature. The interpretation of management-practice effects in this report was likely influenced by a combination of factors, including (1) the amount, timing, and location of management-practice implementation; (2) unmeasured landscape and climatic factors; (3) uncertain management-practice expectations; (4) hydrologic variability; and (5) analytical assumptions. Through continued data-collection efforts, particularly after management practices have been completed, many of these factors may become less influential in the future.

Virginia↗
USGS2025

Predicting aquatic habitat connectivity across watershed boundaries: Implications for interbasin spread of nonindigenous aquatic species.

Understanding habitat connectivity is critical for managing nonindigenous aquatic species (NAS) spread. Dams and watershed boundaries can be impassable to NAS during typical conditions but may become temporarily passable during flooding. The goal of our project was to develop an approach for identifying locations of aquatic connectivity at a fine spatial scale along watershed boundaries using readily available data. To develop this approach, we focused on the potential for range expansion of invasive fish in the United States via possible cross-boundary habitat connections. First, we developed an index using metrics of elevation, watershed size, and geology at regular points along a watershed boundary to stratify points by likelihood of connectivity during high precipitation (>20 mm of precipitation in a 3-day period). We then used a subset of points across a gradient of connectivity likelihoods to gather Landsat-derived observed surface water data and developed a statistical model to predict surface water presence from landscape characteristics. We applied the model throughout the entire watershed boundary to identify locations of hydrologic connectivity during high-water events. The presence of surface water on watershed boundaries was predicted by the interactions between watershed boundary point elevation relative to the minimum adjacent HUC-12 elevations and watershed boundary point elevation relative to neighboring point elevations (marginal R 2 = 0.94). Our approach can be used to identify potential areas of surface water connectivity between watersheds quickly and easily at a fine spatial scale using readily available, remotely sensed data that can inform conservation and management actions across disciplines.

North Dakota, South Dakota↗
USGS2007

Occurrence of pesticides in water, sediment, and soil from the Yolo Bypass, California

The objective of this study was to evaluate the potential sources of pesticides to the Yolo Bypass, including those that could potentially impact critical life stages of resident fish. To assess direct inputs during inundation, pesticide concentrations were analyzed in water and suspended and bed sediment samples collected from source watersheds during high-flow events. To understand inputs from direct application on fields, pesticides were also measured in soils collected from several sites within the Bypass. Thirteen current-use pesticides were detected in water samples collected in 2004 with the highest pesticide concentrations observed at the input sites to the Bypass during high-flow. Hexazinone and simazine were detected at all sites and at some of the highest concentrations. In bed and suspended sediments collected in 2004 and 2005, thirteen current-use pesticides were detected along with DDT and its metabolites. Trifluralin, DDE, and DDT were highest in the bed sediments, whereas oxyfluorfen and thiobencarb were highest in the suspended sediments. With the exception of the three organochlorine insecticides, suspended sediments had higher pesticide concentrations compared to bed sediments, indicating the potential for pesticide transport especially during high-flow events. Soil samples were dominated by DDT and its degradates but also contained a variety of current-use pesticides typically at lower concentrations. The types of pesticides detected in water and sediments were correlated with agricultural application in each watershed. Understanding the distribution of pesticides between the water and sediment is important in assessing their fate and transport within the Bypass, and in evaluating the exposure and potential effects to resident fish.

California↗
USGS2015

Observational changes to the natural flow regime in Lee Creek in relation to altered precipitation patterns and its implication for fishes

The natural flow regime is important for structuring streams and their resident ichthyofauna and alterations to this regime can have cascading consequences. We sought to determine if changes in hydrology could be attributed to changes in precipitation in a minimally altered watershed (Lee Creek). The stream flow regime was analyzed using Indicators of Hydrologic Alteration (IHA) software, and data from a nearby climate station were used to summarize concurrent precipitation patterns. We discovered that Lee Creek hydrology had become flashier (i.e., increased frequency of extreme events of shorter duration) since 1992 coincident with changes in precipitation patterns. Specifically, our results show fewer but more intense rain events within the Lee Creek watershed. Our research provides evidence that climate-induced changes to the natural flow regime are currently underway and additional research on its effects on the fish community is warranted.

Arkansas, Oklahoma↗
USGS2014

Human and bovine viruses in the Milwaukee River Watershed: hydrologically relevant representation and relations with environmental variables

To examine the occurrence, hydrologic variability, and seasonal variability of human and bovine viruses in surface water, three stream locations were monitored in the Milwaukee River watershed in Wisconsin, USA, from February 2007 through June 2008. Monitoring sites included an urban subwatershed, a rural subwatershed, and the Milwaukee River at the mouth. To collect samples that characterize variability throughout changing hydrologic periods, a process control system was developed for unattended, large-volume (56–2800 L) filtration over extended durations. This system provided flow-weighted mean concentrations during runoff and extended (24-h) low-flow periods. Human viruses and bovine viruses were detected by real-time qPCR in 49% and 41% of samples (n = 63), respectively. All human viruses analyzed were detected at least once including adenovirus (40% of samples), GI norovirus (10%), enterovirus (8%), rotavirus (6%), GII norovirus (1.6%) and hepatitis A virus (1.6%). Three of seven bovine viruses analyzed were detected including bovine polyomavirus (32%), bovine rotavirus (19%), and bovine viral diarrhea virus type 1 (5%). Human viruses were present in 63% of runoff samples resulting from precipitation and snowmelt, and 20% of low-flow samples. Maximum human virus concentrations exceeded 300 genomic copies/L. Bovine viruses were present in 46% of runoff samples resulting from precipitation and snowmelt and 14% of low-flow samples. The maximum bovine virus concentration was 11 genomic copies/L. Statistical modeling indicated that stream flow, precipitation, and season explained the variability of human viruses in the watershed, and hydrologic condition (runoff event or low-flow) and season explained the variability of the sum of human and bovine viruses; however, no model was identified that could explain the variability of bovine viruses alone. Understanding the factors that affect virus fate and transport in rivers will aid watershed management for minimizing human exposure and disease transmission.

Wisconsin↗
USGS2024

Post-wildfire curve number estimates for the southern Rocky Mountains in Colorado, USA

The curve number method first developed by the US Department of Agriculture Soil Conservation Service (now the Natural Resources Conservation Service) is often used for post-wildfire runoff assessments. These assessments are critical for land and emergency managers making decisions on life and property risks following a wildfire event. Three approaches (i.e., historical event observations, linear regression model, and regression tree model) were used to help estimate a post-wildfire curve number from watershed and wildfire parameters. For the first method, we used runoff events from 102 burned watersheds in Colorado, southern Wyoming, northern New Mexico, and eastern Utah to quantify changes in curve number values from pre- to post-wildfire conditions. The curve number changes from the measured runoff events vary substantially between positive and negative values. The measured curve number changes were then associated with watershed characteristics (e.g., slope, elevation, northness, and eastness) and land cover type to develop prediction models that provide estimates of post-wildfire curve number changes. Finally, we used a regression tree method to demonstrate that accurate predications can be developed using the measured curve number changes from our study domain. These models can be used for future post-wildfire assessments within the region.

Colorado, New Mexico, Utah, Wyoming↗
USGS2025

Hysteretic response of suspended-sediment in wildfire affected watersheds of the Pacific Northwest and Southern Rocky Mountains

Wildfires can have a profound impact on hydrosedimentary interactions, or the relationship between sediment and runoff, in forested headwater streams. Quantification of sediment-runoff dynamics at the event scale is integral for understanding source areas and transport of suspended-sediment through a watershed following wildfire. Here we used high-frequency turbidity and stream discharge data, coupled with discrete suspended-sediment measurements, in burned and unburned watersheds in the Southern Rocky Mountains and the western Cascades Range to evaluate the response of fine-grained (clay- and silt-sized particles) suspended-sediment. Hysteresis analysis was conducted on estimated suspended-sediment concentrations (using turbidity as a proxy) and streamflow through measurement of the difference in sediment concentration on the rising and falling limbs of the event hydrograph. All burned watersheds exhibited elevated fine suspended-sediment concentrations relative to concentrations found in pre-fire conditions. Changes to hysteretic response vary and may depend on a watershed's sediment connectivity limitations. Results suggest a watershed's inherent hillslope-to-channel (or lateral) connectivity is the primary factor controlling the relative magnitude of event-driven fine sediment fluxes in watersheds affected by wildfire. While wildfire did promote lateral connectivity through activation of hillslope sources, snowmelt, precipitation characteristics and antecedent conditions were more important drivers of hysteretic response than wildfire. For watersheds influenced by annual snowpack, we identified a predominantly clockwise hysteretic response during snowmelt and counterclockwise events during the late spring and summer months. There were also proportionally more counterclockwise events after wildfire in watersheds with high sediment connectivity. Results suggest contrasting wildfire-related sediment risk potential. Rivers in burned watersheds with high sediment connectivity may pose a higher risk to receiving waterbodies, such as larger tributaries or reservoirs, while rivers with low sediment connectivity may experience long-term sediment-related risk within the watershed above the outlet.

Oregon↗
USGS2002

Hydrologic conditions and quality of rainfall and storm runoff in agricultural and rangeland areas in San Patricio County, Texas, 2000-2001

During 2000–2001, rainfall and runoff were monitored in one mixed agricultural watershed and two rangeland watersheds in San Patricio County, located in the Coastal Bend area of South Texas. During this period, five rainfall samples were collected and analyzed for selected nutrients. Ten runoff samples from nine runoff events were collected at the three watershed monitoring stations. Runoff samples were analyzed for selected nutrients, major ions, trace elements, pesticides, and bacteria. Study area rainfall during 2000 and 2001 was 33.27 and 28.20 inches, respectively, less than the long-term average annual of 36.31 inches. Total runoff from the study area watersheds during 2000–2001 was 2.46 inches; the regional average is about 2 inches per year. Rainfall and runoff during the study period was typical of historical patterns, with periods of below average rainfall interspersed with extreme events. Three individual storm events accounted for about 29 percent of the total rainfall and 86 percent of the total runoff during 2000– 2001. Runoff concentrations of nutrients, major ions, and trace elements generally were larger in the mixed agricultural watershed than runoff concentrations in the rangeland watersheds. Pesticides were detected in two of eight runoff samples. Three pesticides (atrazine, deethylatrazine, and trifluralin) were detected in very small concentrations; only deethylatrazine was detected in a concentration greater than the laboratory minimum reporting level. Bacteria in agricultural and rangeland runoff is a potential water-quality concern as all fecal coliform and E. coli densities in the runoff samples exceeded Texas Surface Water Quality Standards for receiving waters. However, runoff and relatively large bacteria densities represent very brief and infrequent conditions, and the effect on downstream water is not known. Rainfall deposition is a major source of nitrogen delivered to the study area. Rainfall nitrogen (mostly ammonia and nitrate) exceeded the runoff yield. The average annual rainfall deposition of total nitrogen on the study area watersheds was 1.3 pounds per acre. In contrast, an average annual yield of 0.57 and 0.21 pound per acre of total nitrogen in runoff exited the mixed agricultural watershed and the rangeland watersheds, respectively.

Texas↗
USGS2000

Chemical data and lead isotopic compositions of geochemical baseline samples from streambed sediments and smelter slag, lead isotopic compositions in fluvial tailings, and dendrochronology results from the Boulder River watershed, Jefferson County, Montana

Introduction As a part of the U.S. Geological Survey Abandoned Mine Lands Initiative, metal-mining related wastes in the Boulder River study area in northern Jefferson County, Montana, have been evaluated for their environmental effects. The study area includes a 24-km segment of the Boulder River in and around Basin, Montana and three principal tributaries to the Boulder River: Basin Creek, Cataract Creek, and High Ore Creek. Mine and prospect waste dumps and mill wastes are located throughout the drainage basins of these tributaries and in the Boulder River. Mine-waste material has been transported into and down streams, where it has mixed with and become incorporated into the streambed sediments. In some localities, mine waste material was placed directly in stream channels and was transported downstream forming fluvial tailings deposits along the stream banks. Water quality and aquatic habitat have been affected by trace-element-contaminated sediment that moves from mine wastes into and down streams during snowmelt and storm runoff events within the Boulder River watershed. Present-day trace element concentrations in the streambed sediments and fluvial tailings have been extensively studied. However, in order to accurately evaluate the impact of mining on the stream environments, it is also necessary to evaluate the pre-mining trace-element concentrations in the streambed sediments. Three types of samples have been collected for estimation of pre-mining concentrations: 1) streambed sediment samples from the Boulder River and its tributaries located upstream from historical mining activity, 2) stream terrace deposits located both upstream and downstream of the major tributaries along the Boulder River, and 3) cores through sediment in overbank deposits, in abandoned stream channels, or beneath fluvial tailings deposits. In this report, we present geochemical data for six stream-terrace samples and twelve sediment-core samples and lead isotopic data for six terrace and thirteen core samples. Sample localities are in table 1 and figures 1 and 2, and site and sample descriptions are in table 2. Geochemical data have been presented for cores through fluvial tailings on High Ore Creek, on upper Basin Creek, and on Jack Creek and Uncle Sam Gulch. Geochemical and lead isotopic data for modern streambed-sediment samples have been presented by Fey and others. Lead isotopic determinations in bed sediments have been shown to be an effective tool for evaluating the contributions from various sources to the metals in bed sediments. However, in order to make these calculations, the lead isotopic compositions of the contaminant sources must also be known. Consequently, we have determined the lead isotopic compositions of five streambed-sediment samples heavily contaminated with fluvial mine waste immediately downstream from large mines in the Boulder River watershed in order to determine the lead isotopic signatures of the contaminants. Summary geochemical data for the contaminants are presented here and geochemical data for the streambed-sediment samples are given by Fey and others. Downstream from the Katie mill site and Jib tailings, fluvial deposits of mill tailings are present on a 10-m by 50-m bar in the Boulder River below the confluence with Basin Creek. The source of these tailings is not known, but fluvial tailings are also present immediately downstream from the Katie mill site, which is immediately upstream from the confluence with Basin Creek. Nine cores of fluvial tailings from this bar were analyzed. Dendrochronology samples were taken at several stream terrace localities to provide age control on the stream terrace deposits. Trees growing on the surfaces of stream terraces provide a minimum age for the terrace deposits, although floods subsequent to the trees' growth could have deposited post-mining overbank deposits around the trees. Historical data were also used to provide estimates of minimum ages of cultural features and to bracket the age of events.

Montana↗
USGS2022

Contributing areas to domestic wells in dipping sedimentary rocks under extreme recharge events

We use particle tracking to determine contributing areas (CAs) to wells for transient flow models that simulate cyclic domestic pumping and extreme recharge events in a small synthetic watershed underlain by dipping sedimentary rocks. The CAs consist of strike-oriented bands at locations where the water table intersects high-hydraulic conductivity beds, and from which groundwater flows to the pumping well. Factors that affect the size and location of the CAs include topographic flow directions, rock dip direction, cross-bed fracture density, and position of the well relative to streams. For an effective fracture porosity (n e ) of 10 -4 , the fastest advective travel times from CAs to wells are only a few hours. These results indicate that wells in this type of geologic setting can be highly vulnerable to contaminants or pathogens flushed into the subsurface during extreme recharge events. Increasing n e to 10 -3 results in modestly smaller CAs and delayed well vulnerability due to slower travel times. CAs determined for steady-state models of the same setting, but with long-term average recharge and pumping rates, are smaller than CAs in the models with extreme recharge. Also, the earliest-arriving particles arrive at the wells later in the steady-state models than in the extreme-recharge models. The results highlight the importance of characterizing geologic structure, simulating plausible effective porosities, and simulating pumping and recharge transience when determining CAs in fractured rock aquifers to assess well vulnerability under extreme precipitation events.

Groundwater↗
USGS2025

Invasive African clawed frogs ( Xenopus laevis ) in Washington State: Status, response efforts, and lessons learned

The African clawed frog (ACF, Xenopus laevis ), which is indigenous to sub-Saharan Africa, is an aquatic invasive species known to have severe ecological impacts on native fauna when introduced into non-endemic regions. In 2015, ACFs were detected in Washington State, U.S. for the first time, and the species is now documented at three cities across western Washington: Lacey, Bothell, and Issaquah. We cataloged the known ACF occurrences, early management efforts, biological data about the frogs, and status of these invasive populations at the three sites from 2015–2023. The ACFs appear to be established in at least three watersheds in the Puget Sound region despite substantial effort at eradicating them at one site. Presence of ACFs in watersheds that lack surface connectivity implies independent introduction events, and the capture of frogs in multiple subbasins in the same watershed may reflect the potential for further spread. Because the ACF is nocturnal and otherwise behaviorally and visually highly cryptic, other established populations may go undetected. Where the ACFs are largely confined to stormwater ponds — as many of our current observations suggest — eradication may still be possible, though a substantial, focused effort would be required. In addition, significant refinement of eradication approaches will be needed to ensure effectiveness in topographically and vegetatively complex Pacific Northwest aquatic environments.

Washington↗
USGS2025

Near-channel erosion as a driver of watershed-scale sediment and phosphorus loading in a forested sub-watershed of Lake of the Woods

The Little Fork River, a forested watershed in northern Minnesota, United States, is a disproportionate contributor of sediment and phosphorus to Rainy River and Lake of the Woods. Sources of sediment and sediment-bound phosphorus to the Little Fork were investigated using complementary lines of evidence in the form of geochemical sediment fingerprinting and a stream-corridor sediment budget that included harvested forest and ravines, in addition to upland forest and agriculture, roads, and streambanks. Near-channel ravine and streambank sources comprised 95–100 % of streambed sediment and 79–100 % of suspended sediment at the river mouth, while tributaries had up to 50% of suspended sediment from upland sources including harvested forest, agriculture, and roads. Repeat suspended-sediment sampling at eight sites showed more source variability among sites than across events. Ravine erosion was the watershed’s largest contributor to downstream sediment and sediment-bound phosphorus loading, while streambed sediment had a larger streambank source. Near-channel erosion also contributed phosphorus, though with less labile and redox-sensitive forms than forest and agricultural soils. In contrast to observations from agricultural settings, suspended-sediment phosphorus concentrations were elevated above some, but not all sources. The effects of watershed size, glacial history, land cover, and variable temperature and precipitation on runoff generation and peak streamflow are important considerations for mitigating near-channel loss of sediment and phosphorus in the Little Fork. These results suggest that management of sediment and phosphorus export from the Little Fork could incorporate context for location in the watershed, geomorphic setting, and runoff characteristics.

Minnesota↗