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At least 325 records · Page 18Linked to original sources

USGS1986

Hydrologic conditions in Connors Bog Area, Anchorage, Alaska

Connors Bog is a wetland in Anchorage, Alaska, which provides a habitat for many wildlife species and is a popular area for driving off-road vehicles. A landfill, and residential and commercial developments are present in areas which were once wetland. The main source of water is precipitation, which averages about 15 in/yr. Estimates of evapotranspiration, which is the main component of water outflow, range from 10 to 20 in/yr. Minor amounts of groundwater and surface runoff flow into the area from the northeast and southwest and flow out of the area to the northwest and south. Within the wetland, water in peat and sand is unconfined and becomes more mineralized with depth. A leachate beneath and near an abandoned landfill is characterized by concentrations of dissolved solids, dissolved chloride, and total organics that are higher than those of the area 's natural water. The maximum lateral extent of detectable contamination in 1984 was < 500 ft from the landfill 's edge. Water in glacial deposits that underlie a poorly permeable layer of silt and clay is confined. A well completed in this confined aquifer yielded water that had a low concentration of dissolved solids, 150 mg/L. The potentiometric surface of this aquifer was about 20 ft lower than the water table during 1984. Connors Lake occupies a depression that extends below adjacent groundwater levels. The 40-acre lake has a maximum depth of about 9 ft and a low rate of biological production. The quality of water in the lake has not been adversely impacted by nearby residential development or landfill operations. Lake levels appear to be influenced by precipitation and adjacent groundwater levels. (Author 's abstract)

Water-Resources Investigations Report↗

USGS2010

Investigation of submarine groundwater discharge along the tidal reach of the Caloosahatchee River, southwest Florida

The tidal reach of the Caloosahatchee River is an estuarine habitat that supports a diverse assemblage of biota including aquatic vegetation, shellfish, and finfish. The system has been highly modified by anthropogenic activity over the last 150 years (South Florida Water Management District (SFWMD), 2009). For example, the river was channelized and connected to Lake Okeechobee in 1881 (via canal C-43). Subsequently, three control structures (spillway and locks) were installed for flood protection (S-77 and S-78 in the 1930s) and for saltwater-intrusion prevention (S-79, W.P. Franklin Lock and Dam in 1966). The emplacement of these structures and their impact to natural water flow have been blamed for water-quality problems downstream within the estuary (Flaig and Capece, 1998; SFWMD, 2009). Doering and Chamberlain (1999) found that the operation of these control structures caused large and often rapid variations in salinity during various times of the year. Variable salinities could have deleterious impacts on the health of organisms in the Caloosahatchee River estuary. Flow restriction along the Caloosahatchee has also been linked to surface-water eutrophication problems (Doering and Chamberlain, 1999; SFWMD, 2009) and bottom-sediment contamination (Fernandez and others, 1999). Sources of nutrients (nitrogen and phosphorous) that cause eutrophication are primarily from residential sources and agriculture, though wastewater-treatment-plant discharges can also play a major role (SFWMD, 2009). The pathway for many of these nutrients is by land runoff and direct discharge from stormwater drains. An often overlooked source of nutrients and other chemical constituents is from submarine groundwater discharge (SGD). SGD can be either a diffuse or point source (for example, submarine springs) of nutrients and other chemical constituents to coastal waters (Valiela and others, 1990; Swarzenski and others, 2001; 2006; 2007; 2008). SGD can be composed of either fresh or marine water or various mixed ratios of fresh and marine water (Martin and others, 2007). In coastal areas where water-table elevations (hydraulic gradients) are steep, such as in Hood Canal, Washington (Swarzenski and others, 2007; Simonds and others, 2008), groundwater entering the coastal marine waters can be fresh (~1-4 parts per thousand, ppt). SGD in coastal locations that have low relief (low hydraulic gradients) such as the study area or other locations in Florida are typically driven by tidal pumping (Reich and others, 2002; 2008; Swarzenski and others, 2008), and water advecting into surface water is composed of recirculated marine water mixed with either fresh or brackish groundwaters. The importance of SGD in the delivery of nutrients and trace elements to coastal environments has been shown to be both beneficial and deleterious to ecosystem health (Valiela and others, 1990). The logical step in studying SGD is to map areas where SGD occurs. Methods such as continuous surface-water radon-222 ( 222 Rn) mapping and electrical resistivity (continuous resistivity profiles, CRP) have been developed and used to identify potential SGD sites (Dulaiova and others, 2005; Swarzenski and others 2004; 2006; 2007; 2008; Reich and others, 2008). CRP data record subsurface, bulk-resistivity measurements to depths up to 25 meters (m). The bulk resistivity can be representative of changes in porewater salinity or in lithology (Reich and others, 2008; Swarzenski and others, 2008). Radon-222 (half-life = 3.28 days) is a natural tracer of groundwater, because sediments and rocks, containing uranium-bearing materials such as limestone and phosphatic material, continually produce 222 Rn. Rn-222 (also referred to simply as radon) is an ideal tracer, because there is a constant source. Since radon is a gas, 222 Rn does not build up in the surface water but rather evades directly to the atmosphere (Burnett and Dulaiova, 2003; Burnett and others, 2003; Dulaiova and Burnett, 2006).

Florida↗

USGS2014

Understanding thermodynamic relationships and geochemical mass balances from catchment to coast: A tribute to the life and career of Owen P. Bricker III

This special volume of aquatic geochemistry is dedicated to the memory of Owen Peterson Bricker III (1936–2011) and serves as a tribute to his life and career. Owen had a distinguished and productive research career in both academics at Johns Hopkins University (Fig. 1) and as a public servant with the Maryland Geological Survey, the US Environmental Protection Agency, and the US Geological Survey. He was a pioneer and leader in aqueous geochemistry, who applied a study approach that quantified mineral weathering reactions and equilibrium thermodynamic relations to better understand the chemical evolution of stream water in small watersheds. He will be especially remembered for his efforts to establish rigorous field studies in small catchments around the United States as a means of quantifying the sources of acid-neutralizing capacity that affect the chemical status and biological health of natural waters.

Aquatic Geochemistry↗

USGS1993

Toxicity and bioaccumulation of waterborne and dietary selenium in juvenile bluegill ( Lepomis macrochirus )

Juvenile bluegill ( Lepomis macrochirus ) were exposed to waterborne selenium as a 6:1 mixture of selenate to selenite (as Se) for 60 d and to dietary seleno- l -methionine for 90 d. Measured concentrations of total selenium in the waterborne exposure ranged from 0.16 to 2.8 mg/l, and concentrations of seleno- l -methionine in the test diet ranged from 2.3 to 25.0 mg/kg wet weight. Mortality, body weight, condition factor, swimming and feeding behavior, aggression, and selenium tissue residues were monitored during the tests. Increased mortality at measured concentrations of 0.64 mg Se/l and greater was the primary adverse effect of waterborne selenium on the juvenile bluegill. Bluegill exposed to 2.8 mg/l of waterborne Se for 30 d exhibited a significant reduction in condition factor ( K ), whereas dietary exposure of bluegill to 25 mg Se/kg for 30 d and 13 mg Se/kg or greater for 90 d elicited significant reductions in K . Mortality and swimming activity of bluegill were not affected in the dietary exposure. Net accumulation of Se from both water and diet was directly related to exposure concentration. Bioconcentration factors ranged from 5 to 7 for bluegill exposed to waterborne Se and from 0.5 to 1.0 for fish exposed to dietary Se. Results of these laboratory tests indicate that survival of bluegill may be impaired in natural waters with elevated Se concentrations.

Aquatic Toxicology↗

USGS1983

Geohydrologic data for test well USW H-5, Yucca Mountain area, Nye County, Nevada

This report presents data on drilling operations, lithology, borehole geophysics, water-level monitoring, core analysis, ground-water chemistry, pumping tests, and packer-injection tests for test well USW H-5. The well is one of a series of test wells drilled in and near the southwestern part of the Nevada Test Site, Nye County, Nevada, in cooperation with the U.S. Department of Energy. These test wells are part of the Nevada Nuclear Waste Storage Investigations to identify suitable sites for storage of high-level radioactive wastes. Test well USW H-5 was drilled to a total depth of 1,219 meters through volcanic rocks consisting mostly of ash-flow tuff. Depth to water in the well ranged between 703.8 and 707.2 meters below land surface, at an approximate altitude of 704 meters above sea level. Drawdown in the well exceeded 6 meters after test pumping more than 3,000 minutes at a rate of 10 liters per second. Borehole-flow surveys showed that about 90 percent of the water in the well is contributed by the zone between 707 and about 820 meters below land surface. Two composite water samples collected after well completion contained 206 and 220 milligrams per liter of dissolved solids. Sodium and bicarbonate were the predominant dissolved anion and cation. The concentration of dissolved silica was 48 milligrams per liter in both samples, which is a relatively large concentration for most natural waters.

Nevada↗

USGS1972

Water for cranberry culture in the Cranmoor area of central Wisconsin

The Cranmoor area of central Wisconsin is the principal cranberry producing area of the State. Cranberries are grown in only about 2.5 square miles of an 80-square-mile marsh and swamp in the Cranberry Creek basin. Cranberry growers have built reservoirs and ditches throughout 25 square miles of marsh for better management of the area's natural water supply. Additional water is diverted into the basin to supplement the cranberry needs. In the 1966-67 hydrologic budget for Cranberry Creek basin, annual inputs were 27.8 inches of precipitation, 3.8 inches of surface-water diversion into the basin, and 1.1 inches decrease in stored water. Annual outputs were. 20.8 inches of evapotranspiration, 11.7 inches of runoff, and 0.2 inch of groundwater outflow. During the 1966-67 period, precipitation averaged about 3 inches per year below normal. The water used for cranberry culture is almost exclusively surface water. Efficient management of the basin's water supply, plus intermittent diversions of about 100 cubic feet per second from outside the basin, provide cranberry growers with a sufficient quantity of water. Although the quantity of surface water is adequate, the pH (generally 5.7-6.7) is slightly high for optimum use. Dissolved oxygen is slightly low, generally between 4 and 10 milligrams per liter. The water is soft; iron and manganese contents vary seasonally, being high in winter and summer and low in spring. Additional supplies of surface water can be obtained by increasing diversions from outside the basin and by increasing reservoir capacity within the basin. Ground water, although not presently used for cranberries, is available in the central, southern, and eastern parts of the basin, where the thickness of the saturated alluvium exceeds 50 feet. Well yields in these areas might be as much as 1,000 gpm (gallons per minute). Additionally, well yields of as much as 1,000 gpm may be expected from saturated alluvium southeast of Cranberry Creek basin. Where saturated alluvium is less than 50 feet thick, in the northern and western parts of the basin, well yields generally are less than 50 gpm. Ground water is also available from sandstone in the western part of the basin. Where the sandstone is thickest (about 60 ft.), well yields may be as much as 200 gpm. The quality of ground water is similar to that of surface water. The pH of water from the shallow alluvium ranges between 6.0 and 6,6; the pH of water from the deep alluvium is about 7.0. Ground water is soft to moderately hard, 22 to 88 milligrams per liter, and contains excessive amounts of iron and manganese.

Wisconsin↗

USGS2004

Compound-specific carbon and hydrogen isotope analysis of sub-parts per billion level waterborne petroleum hydrocarbons

Compound-specific carbon and hydrogen isotope analysis (CSCIA and CSHIA) has been increasingly used to study the source, transport, and bioremediation of organic contaminants such as petroleum hydrocarbons. In natural aquatic systems, dissolved contaminants represent the bioavailable fraction that generally is of the greatest toxicological significance. However, determining the isotopic ratios of waterborne hydrophobic contaminants in natural waters is very challenging because of their extremely low concentrations (often at sub-parts ber billion, or even lower). To acquire sufficient quantities of polycyclic aromatic hydrocarbons with 10 ng/L concentration for CSHIA, more than 1000 L of water must be extracted. Conventional liquid/liquid or solid-phase extraction is not suitable for such large volume extractions. We have developed a new approach that is capable of efficiently sampling sub-parts per billion level waterborne petroleum hydrocarbons for CSIA. We use semipermeable membrane devices (SPMDs) to accumulate hydrophobic contaminants from polluted waters and then recover the compounds in the laboratory for CSIA. In this study, we demonstrate, under a variety of experimental conditions (different concentrations, temperatures, and turbulence levels), that SPMD-associated processes do not induce C and H isotopic fractionations. The applicability of SPMD-CSIA technology to natural systems is further demonstrated by determining the ??13C and ??D values of petroleum hydrocarbons present in the Pawtuxet River, RI. Our results show that the combined SPMD-CSIA is an effective tool to investigate the source and fate of hydrophobic contaminants in the aquatic environments.

Environmental Science & Technology↗

USGS2023

Bioavailability and toxicity models of copper to freshwater life: The state of regulatory science

Efforts to incorporate bioavailability adjustments into regulatory water quality criteria in the United States have included four major procedures: hardness-based single-linear regression equations, water-effect ratios (WERs), biotic ligand models (BLMs), and multiple-linear regression models (MLRs) that use dissolved organic carbon, hardness, and pH. The performance of each with copper (Cu) is evaluated, emphasizing the relative performance of hardness-based versus MLR-based criteria equations. The WER approach was shown to be inherently highly biased. The hardness-based model is in widest use, and the MLR approach is the US Environmental Protection Agency's (USEPA's) present recommended approach for developing aquatic life criteria for metals. The performance of criteria versions was evaluated with numerous toxicity datasets that were independent of those used to develop the MLR models, including olfactory and behavioral toxicity, and field and ecosystem studies. Within the range of water conditions used to develop the Cu MLR criteria equations, the MLR performed well in terms of predicting toxicity and protecting sensitive species and ecosystems. In soft waters, the MLR outperformed both the BLM and hardness models. In atypical waters with pH <5.5 or >9, neither the MLR nor BLM predictions were reliable, suggesting that site-specific testing would be needed to determine reliable Cu criteria for such settings. The hardness-based criteria performed poorly with all toxicity datasets, showing no or weak ability to predict observed toxicity. In natural waters, MLR and BLM criteria versions were strongly correlated. In contrast, the hardness-criteria version was often out of phase with the MLR and, depending on waterbody and season, could be either strongly overprotective or underprotective. The MLR-based USEPA-style chronic criterion appears to be more generally protective of ecosystems than other models.

Environmental Toxicology and Chemistry↗

USGS2006

Aspects of the biology of Salicornia bigelovii torr. In relation to a proposed restoration of a wind-tidal flat system on the South Texas, USA Coast

Wind-tidal flats are the dominant coastal wetland type in southern Texas USA. Succulent vascular plants are colonizing the flats in some locations, often where past dredge disposal along navigation channels and other activities have interrupted natural water communication between hypersaline bays and large areas of wind-tidal flats. The objective of this study was to test the feasibility of proposed removal of a causeway at Laguna Atascosa National Wildlife Refuge to restore the historic hydrologic regime and eradicate encroaching vascular plants, mostly Salicornia bigelovii, on the assumption that high sediment salt excluded these vascular plants under natural conditions. Assessment in spring 1998 of the density of Salicornia in relation to elevation and sediment salt of bare and vegetated zones on the vegetated flats on one side of the causeway and entirely barren flats with unimpaired connection to Laguna Madre on the other side of the causeway suggested that sediment salt >0.1 g ml-1 excluded vascular plants. However, bimonthly sampling in 1999-2000 revealed that sediment salt concentrations were >0.1 g ml-1 throughout the vegetated zone in July and more locally in the period of winter low water, with little impairment to established plants. This indicates that if control is desired, it must be exerted at germination and early establishment during and after fall high water. Continuous monitoring of water levels on either side of the causeway suggests that, even with removal of the causeway, flooding with hypersaline lagoon water will be too infrequent to counteract the freshening effect of a permanent hydraulic connection to the main agricultural drain of the lower Rio Grande Valley that has developed at the other end of the salt flat. Monitoring Salicornia distribution over six years documented huge variation between years but no trend toward increasing dominance of the flats. The results of this study illustrate that the most obvious alterations to a site may not be the most influential on function and that the scale of analysis may have to extend far beyond the site in space and time to evaluate a proposed restoration properly. ?? 2006, The Society of Wetland Scientists.

Wetlands↗

USGS2002

Historical patterns of river stage and fish communities as criteria for operations of dams on the Illinois river

The hydrologic regime of the Illinois River has been altered over the past 100 years. Locks and dams regulate water surface elevations and flow, enabling commercial navigation to continue year round. This study relates changes in water surface elevation to fish abundance in the river, and establishes target criteria for operating locks and dams. Using long-term records of daily river stage, we identified ecologically meaningful hydrological parameters for eight gage locations along the Illinois River. Inter-annual variability of a long-term fisheries dataset beginning in 1957 was related to variability in stage, flood and recession duration, frequency, timing, and rate of change of water levels. Reversals in water surface elevation, maximum stage levels, and length of the spring flood were the most important parameters influencing abundance of age-zero fishes in annual collections. Smallmouth buffalo ( Ictiobus bubalus ), black crappie ( Pomoxis nigromaculatus ), freshwater drum ( Aplodinotus grunneins ), and white bass ( Morone chrysops ) were most abundant in samples during years that approximated the natural water level regime. Of the 33 hydrologic parameters evaluated for the entire water year from an Illinois River gage site on La Grange Reach, all except average stage in January and Julian date (JD) of maximum stage had moderate or high hydrologic alteration based on the historical range of variation (RVA). The highest degree of hydrologic alteration was for minimum stage levels (1-day, 3-day, and 7-day), rate-of-rise, and rate-of-fall. Other parameters that have been severely altered were 30-day minimum stage, 90-day maximum stage, and the annual number of water level reversals. Operations of the La Grange and Peoria locks and dams could be modified so water level variability would approximate that of the late 1800s, when fish and wildlife resources were abundant. The water regime could be regulated to maintain navigation and improve conditions for native plants and animals without increasing flood damages.

Illinois River↗

USGS2021

Export of photolabile and photoprimable dissolved organic carbon from the Connecticut River

Dissolved organic carbon (DOC) impacts water quality, the carbon cycle, and the ecology of aquatic systems. Understanding what controls DOC is therefore critical for improving large-scale models and best management practices for aquatic ecosystems. The two main processes of DOC transformation and removal, photochemical and microbial DOC degradation, work in tandem to modify and remineralize DOC within natural waters. Here, we examined both the photo- and microbial remineralization of DOC (photolability and biolability), and the indirect phototransformation of DOC into biolabile DOC (photoprimed biolability) for samples that capture the spatiotemporal and hydrological gradients of the Connecticut River watershed. The majority of DOC exported from this temperate watershed was photolabile and the concentration of photolabile DOC correlated with UV absorbance at 254 nm ( r 2 = 0.86). Phototransformation of DOC also increased biolability, and the total photolabile DOC (sum of photolabile and photoprimed biolabile DOC) showed a stronger correlation with UV absorbance at 254 nm (r 2 = 0.92). We estimate that as much as 49% (SD = 3.3%) and 10% (SD = 1.1%) of annual DOC export from the Connecticut River is directly photolabile and photoprimable, respectively. Thus, 2.82 Gg C year −1 (SD = 0.67 Gg C year −1 ) or 1.13 Mg C km −2 year −1 (SD = 0.27 km −2 year −1 ) of total photolabile DOC escapes photochemical degradation within the river network to be exported from the Connecticut River each year.

Connecticut River↗

USGS2023

Use of multiparameter instruments for routine field measurements

The “National Field Manual for the Collection of Water-Quality Data” (NFM) provides guidelines and procedures for U.S. Geological Survey (USGS) personnel who collect data used to assess the quality of the Nation’s surface-water and groundwater resources. This chapter, NFM A6.8, provides guidance and protocols for the use of multiparameter instruments for routine field measurements, which includes storage and maintenance of equipment, calibration, troubleshooting, and procedures for measurement and reporting. It updates and supersedes USGS Techniques of Water-Resources Investigations, book 9, chapter A6.8, version 1.1, by Jacob Gibs, Franceska D. Wilde, and Heather A. Heckathorn. The use of multiparameter instruments for conducting field measurements has become routine. The methods described here are specific to the use of multiparameter instruments. The field methods described in this chapter are applicable to most natural waters. Before 2017, the NFM chapters were released in the USGS Techniques of Water-Resources Investigations series. Effective in 2018, new and revised NFM chapters are being released in the USGS Techniques and Methods series; this series change does not affect the content and format of the NFM. More information is in the general introduction to the NFM (USGS Techniques and Methods, book 9, chapter A0) at https://doi.org/10.3133/tm9A0 . The authoritative current versions of NFM chapters are available in the USGS Publications Warehouse at https://pubs.er.usgs.gov/ . Comments, questions, and suggestions related to the NFM can be addressed to nfm@usgs.gov .

Techniques and Methods↗

USGS1986

Natural flow and water consumption in the Milk River basin, Montana and Alberta, Canada

A study was conducted to determine the differences between natural and nonnatural Milk River streamflow, to delineate and quantify the types and effects of water consumption on streamflow, and to refine the current computation procedure into one which computes and apportions natural flow. Water consumption consists principally of irrigated agriculture, municipal use, and evapotranspiration. Mean daily water consumption by irrigation ranged from 10 cu ft/sec to 26 cu ft/sec in the Canada part and from 6 cu ft/sec to 41 cu ft/sec in the US part. Two Canadian municipalities consume about 320 acre-ft and one US municipality consumes about 20 acre-ft yearly. Evaporation from the water surface comprises 80% 0 90% of the flow reduction in the Milk River attributed to total evapotranspiration. The current water-budget approach for computing natural flow of the Milk River where it reenters the US was refined into an interim procedure which includes allowances for man-induced consumption and a method for apportioning computed natural flow between the US and Canada. The refined procedure is considered interim because further study of flow routing, tributary inflow, and man-induced consumption is needed before a more accurate procedure for computing natural flow can be developed. (Author 's abstract)

Water-Resources Investigations Report↗

USGS2026

Decoding the oxidative digestion mechanism for polystyrene nanoplastic detection in the Great Lakes using a customizable Raman spectral processing algorithm

Despite the concerns surging around nanoplastics (NPs) regarding their prevalence and bioavailability in freshwater systems, robust detection of NPs in complex environmental matrices is hindered by the lack of standardized sample pretreatment and a mechanistic understanding of oxidative digestion. Here, we systematically investigate the interaction between hydrogen peroxide (H 2 O 2 ) and polystyrene (PS) NPs during digestion in deionized (DI) water and four environmental matrices from in and around the Great Lakes Basin. To facilitate high-throughput analysis, we develop Pre_peak, a customizable Raman spectral processing algorithm that achieves >99% accuracy for both NP identification and interference rejection, allowing reliable NP quantification via pixel counting and systematic decoding of the oxidative digestion mechanisms. In DI water, varying H 2 O 2 doses from 0 to 30% has negligible effects on the recovery and Raman signal intensity of PS NPs over 24 hours of digestion. However, morphological changes and aggregation of PS NPs are observed when the H 2 O 2 dose exceeds 20%. Prolonged digestion further leads to progressive NP loss. In natural waters, the optimal dosage and digestion duration depend on matrix characteristics, including dissolved organic matter (DOM) and ion composition. This study provides mechanistic insights into NP–oxidant interactions and underscores the need for matrix-tailored digestion protocols to advance standardized NP detection in freshwater environments.

Great Lakes↗

USGS1988

Recharge to the Eagle Valley ground-water basin by streamflow in Vicee Canyon, west-central Nevada

Recharge to groundwater could be increased by adding imported water to natural surface water flow in Vicee Canyon, in Eagle Valley, Nevada, where municipal pumping has caused as much as 50 ft of water level decline since 1972. Measurements of infiltration rates, percolation rates, and hydraulic conductivity indicate that the area could be conducive to artificial recharge from infiltration of augmented streamflow. Runoff creates natural infiltration beds on the floor of Vicee Canyon, but baseflow causes channelization and armoring of the stream channel, reducing infiltration rates from about 4 inches to 1 inch/hour. A water balance of the streamflow in Vicee Canyon indicates that 60 to 70% becomes recharge, and the remainder is lost to evaporation from a nearby gravel pit and evapotranspiration on the canyon floor. Estimates of recharge from measurements in the unsaturated and saturated zones account for about 45% of the total streamflow. Application of a groundwater flow model indicates that at present pumping rates, water levels below Vicee Canyon and at a nearby municipal well may rise about 15-30 ft after 5 years as a result of about 1 cu ft/sec of augmented streamflow infiltration. (USGS)

Water-Resources Investigations Report↗

USGS2014

Report of the committee on underground waters, 1936–37

In accordance with the by‐laws of the Section, the Committee on Underground Waters has been reconstituted during the past year. With their research interests turning to other subjects, several members have dropped out, and four new men have been appointed. In order to maintain contact with the work of related committees, Charles H. Lee, Chairman of the Committee on Absorption and Transpiration, and C. S. Howard, Chairman of the Committee on Cnemistry of Natural Waters, have become members of the Committee on Underground Waters. The personnel of the Committee is as follows: H. F. Blaney C. S. Howard M. M. Leighton H. E. Simpson G. M. Fair F. H. Lahee O. E. Meinzer A. C. Swinnerton Willard Gardner C. H. Lee A. M. Piper D. G. Thompson, Chairman.

Eos, Transactions, American Geophysical Union↗

USGS2013

Optical techniques for the determination of nitrate in environmental waters: Guidelines for instrument selection, operation, deployment, maintenance, quality assurance, and data reporting

The recent commercial availability of in situ optical sensors, together with new techniques for data collection and analysis, provides the opportunity to monitor a wide range of water-quality constituents on time scales in which environmental conditions actually change. Of particular interest is the application of ultraviolet (UV) photometers for in situ determination of nitrate concentrations in rivers and streams. The variety of UV nitrate sensors currently available differ in several important ways related to instrument design that affect the accuracy of their nitrate concentration measurements in different types of natural waters. This report provides information about selection and use of UV nitrate sensors by the U.S. Geological Survey to facilitate the collection of high-quality data across studies, sites, and instrument types. For those in need of technical background and information about sensor selection, this report addresses the operating principles, key features and sensor design, sensor characterization techniques and typical interferences, and approaches for sensor deployment. For those needing information about maintaining sensor performance in the field, key sections in this report address maintenance and calibration protocols, quality-assurance techniques, and data formats and reporting. Although the focus of this report is UV nitrate sensors, many of the principles can be applied to other in situ optical sensors for water-quality studies.

Techniques and Methods↗

USGS1999

Estimating Concentrations of Road-Salt Constituents in Highway-Runoff from Measurements of Specific Conductance

Discrete or composite samples of highway runoff may not adequately represent in-storm water-quality fluctuations because continuous records of water stage, specific conductance, pH, and temperature of the runoff indicate that these properties fluctuate substantially during a storm. Continuous records of water-quality properties can be used to maximize the information obtained about the stormwater runoff system being studied and can provide the context needed to interpret analyses of water samples. Concentrations of the road-salt constituents calcium, sodium, and chloride in highway runoff were estimated from theoretical and empirical relations between specific conductance and the concentrations of these ions. These relations were examined using the analysis of 233 highwayrunoff samples collected from August 1988 through March 1995 at four highway-drainage monitoring stations along State Route 25 in southeastern Massachusetts. Theoretically, the specific conductance of a water sample is the sum of the individual conductances attributed to each ionic species in solution-the product of the concentrations of each ion in milliequivalents per liter (meq/L) multiplied by the equivalent ionic conductance at infinite dilution-thereby establishing the principle of superposition. Superposition provides an estimate of actual specific conductance that is within measurement error throughout the conductance range of many natural waters, with errors of less than ?5 percent below 1,000 microsiemens per centimeter (?S/cm) and ?10 percent between 1,000 and 4,000 ?S/cm if all major ionic constituents are accounted for. A semi-empirical method (adjusted superposition) was used to adjust for concentration effects-superposition-method prediction errors at high and low concentrations-and to relate measured specific conductance to that calculated using superposition. The adjusted superposition method, which was developed to interpret the State Route 25 highway-runoff records, accounts for contributions of constituents other than calcium, sodium, and chloride in dilute waters. The adjusted superposition method also accounts for the attenuation of each constituent's contribution to conductance as ionic strength increases. Use of the adjusted superposition method generally reduced predictive error to within measurement error throughout the range of specific conductance (from 37 to 51,500 ?S/cm) in the highway runoff samples. The effects of pH, temperature, and organic constituents on the relation between concentrations of dissolved constituents and measured specific conductance were examined but these properties did not substantially affect interpretation of the Route 25 data set. Predictive abilities of the adjusted superposition method were similar to results obtained by standard regression techniques, but the adjusted superposition method has several advantages. Adjusted superposition can be applied using available published data about the constituents in precipitation, highway runoff, and the deicing chemicals applied to a highway. This semi-empirical method can be used as a predictive and diagnostic tool before a substantial number of samples are collected, but the power of the regression method is based upon a large number of water-quality analyses that may be affected by a bias in the data.

Water-Resources Investigations Report↗