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At least 1,369 records · Page 76Linked to original sources

Travel time for solutes, upper Sabine River basin, Texas, April 16-30, 1972

The U.S. Geological Survey, in cooperation with the Sabine River Compact Administration, conducted time-of-travel studies in the Sabine River Basin on April 16-30, 1972. One study was made on the main stem of the Sabine River in four reaches from Lake Tawakoni to Toledo Bend Reservoir, a distance of 219 miles. Two other studies were made on reaches of Lake Fork Creek and Big Sandy Creek. The purpose of these studies was to provide travel-rate data to be used by the Sabine River Authority of Texas in constructing a hydrologic model of the basin.

Texas↗

Physicochemical and analytical data for tributary water, lake water, and lake sediment, Lake Arrowhead, Clay and Archer Counties, Texas, 2006

Lake Arrowhead is a reservoir about 24 kilometers southeast of Wichita Falls, Texas, that provides drinking water for the city of Wichita Falls and surrounding areas. The U.S. Geological Survey, in cooperation with the City of Wichita Falls, did a study in 2006 to assess conditions contributing to elevated arsenic concentrations in Lake Arrowhead. This report describes the sampling and analytical methods, quality assurance, and physicochemical and analytical data. Physiochemical properties were measured in and water samples were collected from five tributaries to Lake Arrowhead (Little Wichita River, West Little Post Oak Creek, East Little Post Oak Creek, Deer Creek, and an unnamed tributary) immediately after storms. Lake water measuring and sampling were done approximately monthly from January through September 2006 at three deep-water sites and seasonally, in January and August 2006, at three shallow-water sites. Cores of lake bottom sediment were collected from five sites on August 30, 2006. Arsenic concentrations in tributary water samples ranged from 1.5 to 6.3 and 0.5 to 4.8 micrograms per liter for unfiltered and filtered samples, respectively. The highest arsenic concentrations were in samples collected from the West Little Post Oak Creek sampling site. Physicochemical properties in lake water varied with depth and season. Dissolved arsenite plus arsenate concentrations in lake water samples generally were between 3 and 5 micrograms per liter. Arsenite concentrations typically were below the laboratory reporting level of 0.6 microgram per liter. There were no detections of monomethylarsonate or dimethylarsinate. The concentration of arsenic in lake sediment samples ranged from 4.4 to 11.2 milligrams per kilogram, with a median of 6.4 milligrams per kilogram. The median arsenic concentration of the five top-interval sediment samples was 8.8 milligrams per kilogram, which generally is higher than the concentrations estimated to be on suspended sediment in the tributaries. Sediment concentrations of seven trace elements were compared to two consensus-based sediment quality guidelines for each: the threshold effect concentration and the probable effect concentration. Arsenic concentration exceeded the threshold effect concentration in one top-interval sediment sample.

Data Series↗

Environmental impacts of petroleum production: Fate of inorganic and organic chemicals in produced water from the Osage-Skiatook Petroleum Environmental Research sites, Osage County, Oklahoma

About 15 scientists from the U. S. Geological Survey, other Federal agencies and academia are involved in a multidisciplinary investigation to study the transport, fate, and natural attenuation of inorganic salts, trace metals, radionuclides and organic compounds present in produced water, and their impacts on soil, surface and ground water and the local ecosystem at the Osage-Skiatook Petroleum Environmental Research (OSPER) A and B sites, located in Osage County, OK. The Branstetter lease, OSPER B site, is typical of many aging petroleum fields in Osage County, which ranks among the top oil and gas producing counties in Oklahoma with close to 40,000 wells. Current production in Osage County is mainly from stripper wells (averaging ~2.8 bbls/d oil and >30 bbls/d brine) that are shallow, mostly 300-700 m in depth, and produce from several sandstones of Pennsylvanian age. About one hectare of land at the OSPER B site is affected by salt scarring, soil salinization and brine and petroleum contamination due to the leakage of produced water and associated hydrocarbons from two brine pits and due to accidental releases from active tank batteries. Eventually, the bulk of inorganic salts and some dissolved organic species in the released brine reach, directly or via the two local streams, the adjacent Skiatook Lake, a 4250-hectare reservoir that provides drinking water to the local communities and is a major recreational fishery. About 40 water samples were obtained from several oil wells at the B site and adjoining areas, the two brine pits, several brine pools and seeps in the impacted area, local streams, Skiatook Lake, and from about 20 boreholes (1-71 m deep), recently drilled and completed with slotted PVC tubing. Water level monitoring and additional sampling is continuing. Results to date show that the produced water is a high-salinity (~150,000 mg/L total dissolved solids) Na-Ca-Cl brine, with relatively high concentrations of Sr, Mg and NH4, but low amounts of SO4 and H2S. With the exception of Fe and Mn, the concentrations of trace metals are low, and the values of dissolved organics are relatively low. As the brine flows from the brine pits through the shallow eolian sand, colluvial and alluvial deposits to the streams and Skiatook Lake, it is diluted by infiltrating water from precipitation. Its chemical composition is modified by sorption, mineral precipitation/dissolution, transpiration, volatilization and oxidation/reduction reactions. Bacteria likely play an important role in many of these reactions.

Oklahoma↗

A rare Uroglena bloom in Beaver Lake, Arkansas, spring 2015

A combination of factors triggered a Uroglena volvox bloom and taste and odor event in Beaver Lake, a water-supply reservoir in northwest Arkansas, in late April 2015. Factors contributing to the bloom included increased rainfall and runoff containing increased concentrations of dissolved organic carbon, followed by a stable pool, low nutrient concentrations, and an expansion of lake surface area and littoral zone. This was the first time U. volvox was identified in Beaver Lake and the first time it was recognized as a source of taste and odor. Routine water quality samples happened to be collected by the US Geological Survey and the Beaver Water District throughout the reservoir during the bloom—. Higher than normal rainfall in March 2015 increased the pool elevation in Beaver Lake by 2.3 m (by early April), increased the surface area by 10%, and increased the littoral zone by 1214 ha; these conditions persisted for 38 days, resulting from flood water being retained behind the dam. Monitoring programs that cover a wide range of reservoir features, including dissolved organic carbon, zooplankton, and phytoplankton, are valuable in explaining unusual events such as this Uroglena bloom.

Arkansas↗

Introduction and summary of findings

Lakes Mead and Mohave, which are the centerpieces of Lake Mead National Recreation Area (LMNRA), provide many significant benefits that have made the modern development of the Southwestern United States possible. Lake Mead is the largest reservoir by volume in the nation and it supplies critical storage of water supplies for more than 25 million people in three Western States (California, Arizona, and Nevada). Storage within Lake Mead supplies drinking water and the hydropower to provide electricity for major cities including Las Vegas, Phoenix, Los Angeles, Tucson, and San Diego, and irrigation of more than 2.5 million acres of croplands (National Park Service, 2010). Lake Mead is arguably the most important reservoir in the nation because of its size and the services it delivers to the Western United States (Holdren and Turner, 2010).

Arizona, Nevada↗

Suspended-sediment loads, reservoir sediment trap efficiency, and upstream and downstream channel stability for Kanopolis and Tuttle Creek Lakes, Kansas, 2008-10

Continuous streamflow and turbidity data collected from October 1, 2008, to September 30, 2010, at streamgage sites upstream and downstream from Kanopolis and Tuttle Creek Lakes, Kansas, were used to compute the total suspended-sediment load delivered to and released from each reservoir as well as the sediment trap efficiency for each reservoir. Ongoing sedimentation is decreasing the ability of the reservoirs to serve several purposes including flood control, water supply, and recreation. River channel stability upstream and downstream from the reservoirs was assessed using historical streamgage information. For Kanopolis Lake, the total 2-year inflow suspended-sediment load was computed to be 600 million pounds. Most of the suspended-sediment load was delivered during short-term, high-discharge periods. The total 2-year outflow suspended-sediment load was computed to be 31 million pounds. Sediment trap efficiency for the reservoir was estimated to be 95 percent. The mean annual suspended-sediment yield from the upstream basin was estimated to be 129,000 pounds per square mile per year. No pronounced changes in channel width were evident at five streamgage sites located upstream from the reservoir. At the Ellsworth streamgage site, located upstream from the reservoir, long-term channel-bed aggradation was followed by a period of stability. Current (2010) conditions at five streamgages located upstream from the reservoir were typified by channel-bed stability. At the Langley streamgage site, located immediately downstream from the reservoir, the channel bed degraded 6.15 feet from 1948 to 2010. For Tuttle Creek Lake, the total 2-year inflow suspended-sediment load was computed to be 13.3 billion pounds. Most of the suspended-sediment load was delivered during short-term, high-discharge periods. The total 2-year outflow suspended-sediment load was computed to be 327 million pounds. Sediment trap efficiency for the reservoir was estimated to be 98 percent. The mean annual suspended-sediment yield from the upstream basin was estimated to be 691,000 pounds per square mile per year. In general, no pronounced changes in channel width were evident at six streamgage sites located upstream from the reservoir. At the Barnes and Marysville streamgage sites, located upstream from the reservoir, long-term channel-bed degradation followed by stability was indicated. At the Frankfort streamgage site, located upstream from the reservoir, channel-bed aggradation of 1.65 feet from 1969 to 1989 followed by channel-bed degradation of 2.4 feet from 1989 to 2010 was indicated and may represent the passage of a sediment pulse caused by historical disturbances (for example, channelization) in the upstream basin. With the exception of the Frankfort streamgage site, current (2010) conditions at four streamgages located upstream from the reservoir were typified by channel-bed stability. At the Manhattan streamgage site, located downstream from the reservoir, high-flow releases associated with the 1993 flood widened the channel about 60 feet (30 percent). The channel bed at this site degraded 4.2 feet from 1960 to 1998 and since has been relatively stable. For the purpose of computing suspended-sediment concentration and load, the use of turbidity data in a regression model can provide more reliable and reproducible estimates than a regression model that uses discharge as the sole independent variable. Moreover, the use of discharge only to compute suspended-sediment concentration and load may result in overprediction. Stream channel banks, compared to channel beds, likely are a more important source of sediment to Kanopolis and Tuttle Creek Lakes from the upstream basins. Other sediment sources include surface-soil erosion in the basins and shoreline erosion in the reservoirs.

Kansas↗

Hydrographic surveys of four narrows within the Namakan reservoir system, Voyageurs National Park, Minnesota, 2011

The U.S. Geological Survey performed multibeam echosounder hydrographic surveys of four narrows in the Namakan reservoir system in August 2011, in cooperation with the International Joint Commission and Environment Canada. The data-collection effort was completed to provide updated and detailed hydrographic data to Environment Canada for inclusion in a Hydrologic Engineering Centers River Analysis System hydraulic model. The Namakan reservoir system is composed of Namakan, Kabetogama, Sand Point, Crane, and Little Vermilion Lakes. Water elevations in the Namakan reservoir system are regulated according to rule curves, or guidelines for water-level management based on the time of year, established by the International Joint Commission. Water levels are monitored by established gages on Crane Lake and the outlet of Namakan Lake at Kettle Falls, but water elevations throughout the system may deviate from these measured values by as much as 0.3 meters, according to lake managers and residents. Deviations from expected water elevations may be caused by between-lake constrictions (narrows). According to the 2000 Rule Curve Assessment Workgroup, hydrologic models of the reservoir system are needed to better understand the system and to evaluate the recent changes made to rule curves in 2000. Hydrographic surveys were performed using a RESON SeaBat™7125 multibeam echosounder system. Surveys were completed at Namakan Narrows, Harrison Narrows, King Williams Narrows, and Little Vermilion Narrows. Hydrographic survey data were processed using Caris HIPS TM and SIPS TM software that interpolated a combined uncertainty and bathymetric estimator (CUBE) surface. Quality of the survey results was evaluated in relation to standards set by the International Hydrographic Organization (IHO) for describing the uncertainty of hydrographic surveys. More than 90 percent of the surveyed areas at the four narrows have resulting bed elevations that meet the IHO “Special Order” quality. Survey datasets published in this report are formatted as text files of x-y-z coordinates and as CARIS Spatial Archive TM (CSAR TM ) files with corresponding metadata.

Minnesota↗

Floods in the Canadian and Pecos River basins of New Mexico, May and June 1937

In May and June floods occurred in the Canadian and Pecos River Basins of New Mexico that were unusually high and in many places were record breaking. The floods were caused by heavy rains that occurred over the eastern part of the State from May 23 to June 4 in a series of intense and intermittent storms. During these storms of the cloudburst type as much as 12 inches of rain fell in the 13-day period, and a fall of 7 inches in 2 hours and 40 minutes was reported from the vicinity of Clayton. Heavy rains also fell in the mountainous region west of Roswell, amounting to as much as l0 inches at some places. Much of the region that had excessive rainfall is relatively flat and has no well-defined drainage system. From these areas there was very little run-off and practically no water was contributed to the major streams. Hail fell at many places in eastern New Mexico, causing damage to crops, livestock, and other property. Hail fell somewhere in the Canadian and Pecos River Basins almost every day during the storm period, but the duration of the fall was generally short. The largest hailstones were reported from Clayton, where one stone measured 8 inches in circumference and weighed 9 ounces; at Centerville, where reports state that some stones were 9 to 10 inches in circumference; and near Roswell, where it was reported that six stones would fill a gallon bucket. The Canadian River flood reached a peak at Logan of 110,000 second-feet, which has been exceeded in this century only by the floods of 1904, 1909, and 1914. The total run-off at Logan for the flood period has been computed as 653,800 acre-feet. At Santa Rosa the Pecos River reached a maximum discharge of 88,200 second-feet, which is greater than any previously recorded. This flood was partly stored in the Alamogordo Reservoir; the peak below the reservoir was only 25,200 second-feet. The Pecos River flood at Roswell reached a maximum discharge of more than 80,000 second-feet. This water came mostly from tributaries that have .their sources in the mountainous area west of Roswell. The Cienaga del Macho, ordinarily a small dry creek, discharged about 49,800 second-feet at its peak. The Rio Hondo experienced several flood peaks, the largest at Roswell probably being near 20,000 second-feet. Berrendo Creek, which enters the Rio Hondo near Roswell, had a computed peak discharge of 37,700 second-feet. Roswell was subjected to several floods that inundated large areas of the town. Considerable damage was done by the water, which covered nearly all the area occupied by the town. Lake McMillan, an artificial reservoir on the Pecos River about 12 miles above Carlsbad, was put to a severe strain by the large quantity of water passing through it, but no serious damage resulted. The capacity of the lake at spillway level is about 39,000 acre-feet, but at the peak of the flood the lake held about 86,000 acre-feet. The total quantity of water passing through the lake during the flood period was more than 440,000 acre-feet. This report presents data pertinent to the floods of May and June 1937, including results of peak discharge determinations made at about 14 miscellaneous places, records of peak stages and discharges and of mean daily discharges during the flood period at 23 regular river-measurement stations, records of rainfall at about 190 places, an isohyetal map showing rainfall over the entire State and two isohyetal maps showing rainfall over the Canadian and Pecos River Basins, and a discussion of the weather conditions during the flood period, including an upper-air wind and pressure chart of the United States for May 28, 1937. In addition to the information listed above the report includes a summary of records of past floods at all places in New Mexico at which authentic records were available.

New Mexico↗

Phytoplankton, taste-and-odor compounds, and cyanotoxin occurrence in four water-supply reservoirs in the Triangle area of North Carolina, April–October 2014

Prior to 2014, local utilities and State agencies monitored for cyanotoxins and taste-and-odor (T&O) compounds and reported occasional detections in three water-supply reservoirs in Wake County, North Carolina. Comparable data for cyanotoxins and T&O compounds were lacking for other water-supply reservoirs in the Triangle area of North Carolina. This report assesses whether cyanotoxins and T&O compounds occurred in four previously unmonitored North Carolina Triangle area water-supply reservoirs at levels that exceed existing North Carolina and U.S. Environmental Protection Agency recreational and drinking water health advisory, guidance, and criterion levels based on data collected during the peak phytoplankton growth period in 2014. Samples were collected from five sites across the study reservoirs (Cane Creek Reservoir, West Fork Eno River Reservoir, B. Everett Jordan Lake, and University Lake) between April and October 2014 and analyzed for physical characteristics, chemical constituents, phytoplankton communities, cyanotoxins, and T&O compounds. Lake stratification during the sampling period in 2014 could indicate that the deep zones of the water column, during stratified anoxic conditions, may serve as possible sources of nutrients and metals for algal growth and other biogeochemical processes. Differences in phytoplankton communities were attributed to variability in environmental conditions across the sites and sampling events. Differences generally were greater among sites than among sampling events for phytoplankton communities and environmental conditions. Phytoplankton community assemblages, within reservoirs, often were dominated by cyanobacteria that contained genera capable of producing T&O compounds and cyanotoxins during summer and fall months. The occurrence and associated biovolumes of potential producers of cyanotoxins and T&O compounds varied across the sites and sampling events. Of 20 samples collected during the study, the T&O compound geosmin and the cyanotoxin microcystin were present in 19 and 18 samples, respectively. While not harmful, the aesthetically displeasing geosmin concentrations periodically exceeded the human detection threshold of 15 nanograms per liter at most sites. The T&O compound 2-methylisoborneol (MIB) was detected in 11 of 20 samples, with concentrations below the human detection threshold of 15 nanograms per liter in all but one sample. The cyanotoxin anatoxin-a was detected in two of the samples. No other cyanotoxins were detected during the study. In general, results did not indicate the biovolume of any given phytoplankton genera in the study was correlated with increased concentrations of MIB, geosmin, or microcystin. Results from this study indicated that microcystin concentrations in the water-supply reservoirs in the Triangle area were below EPA-recommended recreational level of 8 micrograms per liter, but periodically exceeded the EPA finished-water 10-day health advisory level of 0.3 microgram per liter for bottle-fed infants and preschool-age children. This suggests longer term data collection may be necessary to better understand the magnitude and frequency of cyanotoxin concentrations in these four water-supply reservoirs, particularly those with an elevated risk of exceeding the EPA 10-day health advisory levels in the finished drinking water or those with a higher frequency of T&O compound occurrence.

North Carolina↗

A method for improving predictions of bed-load discharges to reservoirs

Effective management options for mitigating the loss of reservoir water storage capacity to sedimentation depend on improved predictions of bed-load discharges into the reservoirs. Most predictions of bed-load discharges, however, are based on the assumption that the rates of bed-load sediment availability equal the transport capacity of the flow, ignoring the spatio-temporal variability of the sediment supply. This paper develops a semiquantitative method to characterize bed-load sediment transport in alluvial channels, assuming a channel reach is non-supply limited when the bed-load discharge of a given sediment particle-size class is functionally related to the energy that is available to transport that fraction of the total bed-load. The method was applied to 22 alluvial stream channels in the USA to determine whether a channel reach had a supply-limited or non-supply-limited bed-load transport regime. The non-supply-limited transport regime was further subdivided into two groups on the basis of statistical tests. The results indicated the pattern of bed-load sediment transport in alluvial channels depends on the complete spectrum of sediment particle sizes available for transport rather than individual particle-size fractions represented by one characteristic particle size. The application of the method developed in this paper should assist reservoir managers in selecting bed-load sediment transport equations to improve predictions of bed-load discharge in alluvial streams, thereby significantly increasing the efficiency of management options for maintaining the storage capacity of waterbodies. ?? 2007 Blackwell Publishing Asia Pty Ltd.

Lakes and Reservoirs: Research and Management↗

How reservoirs alter drinking water quality: Organic matter sources, sinks, and transformations

Within reservoirs, production, transformation, and loss of dissolved organic matter (DOM) occur simultaneously. While the balance between production and loss determines whether a reservoir is a net sink or source of DOM, changes in chemical composition are also important because they affect DOM reactivity with respect to disinfection by-product (DBP) formation. The composition of the DOM pool also provides insight into DOM sources and processing, which can inform reservoir management. We examined the concentration and composition of DOM in San Luis Reservoir, a large off-stream impoundment of the California State Water Project. We used a wide array of DOM chemical tracers including dissolved organic carbon (DOC) concentration, trihalomethane and haloacetic acid formation potentials (THMFP and HAAFP, respectively), absorbance properties, isotopic composition, lignin phenol content, and structural groupings determined by 13 C nuclear magnetic resonance (NMR). There were periods when the reservoir was a net source of DOC due to the predominance of algal production (summer), a net sink due to the predominance of degradation (fall–winter), and balanced between production and consumption (spring). Despite only moderate variation in bulk DOC concentration (3.0–3.6 mg C/L), changes in DOM composition indicated that terrestrial-derived material entering the reservoir was being degraded and replaced by aquatic-derived DOM produced within the reservoir. Substantial changes in the propensity of the DOM pool to form THMs and HAAs illustrate that the DBP precursor pool was not directly coupled to bulk DOC concentration and indicate that algal production is an important source of DBP precursors. Results suggest reservoirs have the potential to attenuate DOM amount and reactivity with respect to DBP precursors via degradative processes; however, these benefits can be decreased or even negated by the production of algal-derived DOM.

California↗

Rhodhiss Lake, North Carolina: Analysis of ambient conditions and simulation of hydrodynamics, constituent transport, and water-quality characteristics, 1993-94

From January 1993 through March 1994, the U.S. Geological Survey conducted an investigation of Rhodhiss Lake in cooperation with the Western Piedmont Council of Governments. Objectives of the investigation were to describe ambient hydrologic and water-quality conditions, to estimate loadings of nutrients and suspended solids from selected tributaries and point sources, and to simulate hydraulic circulation and water-quality characteristics in Rhodhiss Lake using a hydrodynamic computer model. The riverine headwaters of Rhodhiss Lake were unstratified, well oxygenated, and contained relatively high concentrations of suspended solids and nutrients throughout the study period. In general, concentrations of suspended solids, nitrate, orthophosphate, and total phosphorus decreased in a downstream direction from the headwaters to the Rhodhiss Dam. However, increases in specific conductance frequently were observed downstream from a wastewater discharge near mid-reservoir. From mid-reservoir to the dam, Rhodhiss Lake thermally stratified during the summer of 1993. In this reach, dissolved oxygen was rapidly depleted from the bottom waters beginning in May 1993, and anoxic conditions persisted in the hypolimnion through the summer. During summer stratification, concentrations of nitrite plus nitrate, ammonia, and orthophosphate were low in the epilimnion, but concentrations of ammonia, orthophosphate, and total phosphorus increased in the hypolimnion. During fall and winter, Rhodhiss Lake was characterized by alternating periods of stratification and mixing. A maximum chlorophyll-a concentration of 52 micrograms per liter was observed at mid-reservoir on November 17, 1993, and was the only value that exceeded the North Carolina water-quality standard of 40 micrograms per liter. Concentrations of fecal coliform bacteria exceeded 200 colonies per 100 milliliters in the headwaters of Rhodhiss Lake 37 percent of the time, and at mid-reservoir and in the forebay 16 percent of the time. In Lower Creek, a tributary to Rhodhiss Lake, concentrations of fecal coliform bacteria exceeded 200 colonies per 100 milliliters in 76 percent of the samples. This stream also contained elevated concentrations of nitrite plus nitrate, phosphorus, and specific conductance. Loading estimates showed that almost all of the suspended solids and the majority of the nitrogen and phosphorus entering the headwaters of Rhodhiss Lake originated from nonpoint sources. During the investigation, point sources accounted for less than 1 percent of the suspended solids load to the reservoir headwaters, but point sources accounted for up to 27 and 22 percent of the total nitrogen and total phosphorus loads, respectively. Additional loadings of nitrogen and phosphorus entered Rhodhiss Lake by municipal wastewater discharge near mid-reservoir. The U.S. Army Corps of Engineers CE-QUAL-W2 model is a two-dimensional, laterally averaged model that simulates hydrodynamics and water quality. The model was applied to Rhodhiss Lake from Huffman Bridge to Rhodhiss Dam--a distance of 18.5 kilometers--and was calibrated using data collected from April 1993 through March 1994. During the simulation period, measured water levels varied a total of 1.32 meters, and water temperatures ranged from 4 to 30 degrees Celsius. The calibrated model provided good agreement between measured and simu- lated water levels at Rhodhiss Dam. Likewise, simulated water temperatures were generally within 2 degrees Celsius of measured values; however, the model tended to overpredict temperatures near the bottom of the reservoir by 1 to 3 degrees Celsius during warm months. This suggests that the model, as calibrated, overpredicts vertical mixing. Simulated dissolved oxygen concentrations followed the same general patterns and magnitudes as measured values, and there was good agreement between simulated and measured frequency of occurrence of dissolved oxygen concentrations less than 5 milligra

North Carolina↗

Water quality of Lake Arlington on Village Creek, north-central Texas; 1973 to 1981

Water in Lake Arlington on Village Creek in north-central Texas had volume-weighted average concentrations of less than 240 milligrams per liter of dissolved solids, less than 30 milligrams per liter of dissolved chloride, and less than 40 milligrams per liter of dissolved sulfate between January 29, 1973, and August 20, 1981. The water was moderately hard (hardness greater than 60 but less than 120 milligrams per liter as calcium carbonate). The concentrations of each of these constituents were usually greatest during winter, especially during the first few years of the study, but decreased significantly as discharges of municipal wastes were systematically and progressively diverted to treatment facilities downstream from the reservoir. Thermal stratification in Lake Arlington usually begins during March or April and persists until October. Thermal stratification has resulted in significant seasonal and areal variations in the concentration of dissolved oxygen, dissolved iron, dissolved manganese, total inorganic nitrogen, and total phosphorus. Oxygen utilized in the decay of organic matter is not replenished during periods of summer stagnation, and water below depths of 30 to 40 feet usually contains less than 2 milligrams per liter of dissolved oxygen during stagnation. Even though heated effluent from an electrical generating plant is returned to the reservoir at site GC and causes an elevation of water temperature, average dissolved oxygen levels at this site are not significantly different from levels at other sites. During summer stagnation, reducing conditions result in the dissolution of iron and manganese from bottom deposits at deep sites in the reservoir. At site AQ, a deep site near Arlington Dam, dissolved iron concentrations in water near the bottom during summer stagnation ranged from less than 10 to 1,100 micrograms per liter and averaged about 640 micrograms per liter. Dissolved manganese concentrations near the bottom at site AC during summer staynation ranged from 20 to 2,700 micrograms per liter and averaged about 1,500 micrograms per liter. The concentrations of dissolved iron and dissolved manganese in water throughout the reservoir during winter circulation and in water near the reservoir surface during summer stagnation averaged less than 50 micrograms per liter. Seasonal temperature and dissolved oxygen cycles resulted in the recycling of dissolved iron and dissolved manganese between the water and bottom sediments. However, no significant accumulation of these constituents within the reservoir was detected during the study. The concentrations of total inorganic nitrogen and total phosphorus are greatest during summer stagnation in water near the bottom at deep sites. At site AC during the summer, the concentrations of total inorganic nitrogen in the hypolimnion averaged about 0.9 milligram per liter, and the concentration of total phosphorus near the bottom averaged about 0.2 milligram per liter. The concentrations of total inorganic nitrogen in the epilimnion at site AC averaged about 0.1 milligram per liter; the concentrations of total phosphorus averaged less than 0.1 milligram per liter. The densities and composition of algal populations varied seasonally. At site AC, total algae counts ranged from 200 to 240,000 cells per mi Hi liter and averaged about 50,000 cells per milliliter. At site FC, total algae counts ranged from 1,000 to 290,000 cells per milliliter and averaged about 56,000 cells per milliliter. Algal densities were greatest during the summer with blue-green algae being the predominant phyla.

Texas↗

Are walleye from Lake Roosevelt contaminated with mercury?

To find out, scientists from the U. S. Geological Survey (USGS) tested walleye and other sport fish from the upper Columbia River and Franklin D. Roosevelt Lake (Lake Roosevelt), the largest reservoir in Washington and a popular fishing spot. Findings: Walleye had higher concentrations of mercury than other sport fish. Larger walleye had higher mercury concentrations than smaller walleye. Mercury concentrations in walleye fillets ranged from 0.11 to 0.44 parts per million (ppm). These concentrations do not exceed the current Federal standard (1.0 ppm of mercury) designed to protect the health of people who eat small amounts of fish. After reviewing these findings, the Washington State Department of Health concluded that people who regularly consume large amounts of Lake Roosevelt walleye may be at risk of adverse health effects from mercury and should limit their consumption of these fish.

Washington↗

Role of edaphic, hydrologic, and land cover variables in determining dissolved organic carbon in Missouri (USA) reservoirs and streams

In Missouri, distinct geophysical gradients influence statewide patterns in water quality. Here, we quantify the spatiotemporal variability of dissolved organic carbon (DOC) in reservoirs and streams and the edaphic, hydrologic, and land cover variables that account for cross-system variation. Datasets included statewide inventories collected over decades and studies with greater temporal resolution ( n = >6350 DOC measurements). Among reservoirs, the smallest DOC concentration was measured in a spring-fed system within a forested watershed, and the largest was where agricultural biosolids were applied to the land (range 1.0–15.9 mg/L, overall mean 5.8 mg/L). Reservoir values increased from the southern forested Highlands (mean 4.7 mg/L) to the northern agricultural Plains (mean 7.0 mg/L). Stream DOC was similar to reservoir values (overall mean in streams 6.3 mg/L; Highlands mean 4.0 mg/L; Plains mean 6.6 mg/L), despite differences in study design and collection period. Reservoir DOC increased in spring, indicative of allochthonous loading, with small autochthonous additions during a broad summer peak. Temporal variability in DOC was low relative to macronutrients and chlorophyll in both reservoirs and streams, indicating DOC may be a sensitive and readily detected indicator of temporal change in these systems. In regression analyses, watershed features accounted for more than 60% of overall cross-system variability in DOC in both reservoirs and streams. Driver-response relations, however, differed between regions. This analysis extends our understanding of environmental influences on surface water chemistry in Missouri and indicates DOC is nearly as predictable as macronutrients using landscape-level features.

Missouri↗

Hydrologic characterization for Spring Creek and hydrologic budget and model scenarios for Sheridan Lake, South Dakota, 1962-2007

The U.S. Geological Survey cooperated with South Dakota Game, Fish and Parks to characterize hydrologic information relevant to management of water resources associated with Sheridan Lake, which is formed by a dam on Spring Creek. This effort consisted primarily of characterization of hydrologic data for a base period of 1962 through 2006, development of a hydrologic budget for Sheridan Lake for this timeframe, and development of an associated model for simulation of storage deficits and drawdown in Sheridan Lake for hypothetical release scenarios from the lake. Historically, the dam has been operated primarily as a 'pass-through' system, in which unregulated outflows pass over the spillway; however, the dam recently was retrofitted with an improved control valve system that would allow controlled releases of about 7 cubic feet per second (ft3/s) or less from a fixed depth of about 60 feet (ft). Development of a hydrologic budget for Sheridan Lake involved compilation, estimation, and characterization of data sets for streamflow, precipitation, and evaporation. The most critical data need was for extrapolation of available short-term streamflow records for Spring Creek to be used as the long-term inflow to Sheridan Lake. Available short-term records for water years (WY) 1991-2004 for a gaging station upstream from Sheridan Lake were extrapolated to WY 1962-2006 on the basis of correlations with streamflow records for a downstream station and for stations located along two adjacent streams. Comparisons of data for the two streamflow-gaging stations along Spring Creek indicated that tributary inflow is approximately proportional to the intervening drainage area, which was used as a means of estimating tributary inflow for the hydrologic budget. Analysis of evaporation data shows that sustained daily rates may exceed maximum monthly rates by a factor of about two. A long-term (1962-2006) hydrologic budget was developed for computation of reservoir outflow from Sheridan Lake for the historical pass-through operating system. Two inflow components (stream inflow and precipitation) and one outflow component (evaporation) were considered. The hydrologic budget uses monthly time steps within a computational year that includes two 6-month periods - May through October, for which evaporation is accounted for, and November through April, when evaporation is considered negligible. Results indicate that monthly evaporation rates can substantially exceed inflow during low-flow periods, and potential exists for outflows to begin approaching zero-flow conditions substantially prior to the onset of zero-inflow conditions, especially when daily inflow and evaporation are considered. Results also indicate that September may be the month for greatest potential benefit for enhancing fish habitat and other ecosystem values in downstream reaches of Spring Creek with managed releases of cool water. Computed monthly outflows from Sheridan Lake for September are less than 1.0 ft3/s for 8 of the 44 years (18 percent) and are less than 2.0 ft3/s for 14 of the 44 years (32 percent). Conversely, none of the computed outflows for May are less than 2.0 ft3/s. A short-term (July through September 2007) data set was used to calculate daily evaporation from Sheridan Lake and to evaluate the applicability of published pan coefficients. Computed values of pan coefficients of approximately 1.0 and 1.1 for two low-flow periods are larger than the mean annual pan coefficient of 0.74 for the area that is reported in the literature; however, the computed values are consistent with pan coefficients reported elsewhere for similar late summer and early fall periods. Thus, these results supported the use of variable monthly pan coefficients for the long-term hydrologic budget. A hydrologic model was developed using the primary components of the hydrologic budget and was used to simulate monthly storage deficits and drawdown for Sheridan Lake using hypothetical

South Dakota↗

Effects of capture depth on walleye hooking mortality during ice fishing

Length-based regulations are a common tool used to limit fishing mortality by controlling the size of fish harvested. While such regulations are helpful in managing fish populations, mortality associated with catch-and-release fishing may negatively impact a fishery. We evaluated factors affecting hooking mortality of walleye ( Sander vitreus ) in 2 mainstem Missouri River reservoirs in South Dakota. Winter walleye hooking mortality was evaluated during the ice fishing season in February and March 2020. After capture, walleye ( n = 55) were placed into holding pens for 12 to 72 h to monitor postrelease mortality. Hooking mortality was found to be 20% following angling. Capture depth, landing time, and time in pen were the most influential variables on probability of hooking mortality ( p m ). We observed a sharp increase in p m for walleye captured at depths from 10 to 12 m, where the probability of mortality for fish increased appreciably from 5 to 37%, respectively. Our findings indicate that hooking mortality during the ice fishing season can be substantial in lakes where walleye angling occurs at depths greater than 10 m.

South Dakota↗

Understanding and documenting the scientific basis of selenium ecological protection in support of site-specific guidelines development for Lake Koocanusa, Montana, U.S.A., and British Columbia, Canada

Modeling of ecosystems is a part of the U.S. Environmental Protection Agency’s protocol for developing site-specific selenium guidelines for protection of aquatic life. Selenium as an environmental contaminant is known to bioaccumulate and cause reproductive effects in fish and wildlife. Here we apply a modeling methodology—ecosystem-scale selenium modeling—to understand and document the scientific basis for predicting and validating ecological protection for Lake Koocanusa, a transboundary reservoir between Montana and British Columbia. A comprehensive set of site-specific data compiled from public databases (Federal, State, and Provincial) and reports by Teck Coal Ltd., is available in a companion U.S. Geological Survey data release. The tissue guideline used within modeling here to assess protection is the U.S. Environmental Protection Agency’s national selenium guideline for whole-body fish (dry weight); however, other numeric values for a whole-body guideline or other tissue types may be assumed if applicable tissue-to-tissue conversion factors are available. We consider the report assembled here as a working document that presents a model that can effectively address and structure the needs of (1) scientific understanding in representing the lake’s ecosystem and selenium biodynamics and (2) policy and management development during a decision-making process, but it is open to modification and updating as more ecologically detailed data become available. The approach brings together the main concerns involved in selenium toxicity: likelihood of high exposure, inherent species sensitivity, and close connectivity of ecosystem characteristics and behavioral ecology of predators. Detailed site-specific modeling equations are provided to document the linked factors that determine the responses of ecosystems to selenium. A series of scenarios quantifies the implications of choices of site-specific variables including food-web species, bioavailability of particulate material, and partitioning between the dissolved and particulate phases at the base of food webs. A gradient mapping tool applied to Lake Koocanusa provides a precedent for ecosystem-scale modeling of lakes by recognizing the importance of lake strata and hydrodynamics as components of modeling. Data requirements for ecosystem modeling, including ecological and hydrological process information fundamental to the dietary biodynamics of selenium in site-specific food webs, were assessed as a precursor to model validation for Lake Koocanusa. Understanding these relationships is necessary to connect modeling outcomes to reproductive effects and establish boundaries, in the case of Lake Koocanusa, for the influences of dam operation, fish-community viability, and its Clean Water Act impaired 303(d)-listing status on ecosystem function. We find that an assemblage of conditions affects the representation of Lake Koocanusa’s ecosystem within modeling scenarios but that the constructed gradient maps, mechanistic model, and associated bioaccumulation potentials portray and quantify the variables that are determinative to protection of predator species. Ecological and hydrological sorting of compiled individual data points on a site- and species-specific basis helps identify and address model uncertainties. Sources of uncertainty include (1) the scarcity of data for some environmental media compartments across time and locations, (2) the complexity of hydrodynamic conditions that can lead to seasonal ecological disconnects such as in selenium partitioning from water into particulates, and (3) the functional status of Lake Koocanusa’s ecosystem because of cumulative effects of various environmental stresses (for example, fish-community changes, flow regime changes, parasites, gonadal dysfunction, and increasing mining input-selenium concentrations since 1984). To this last point, it is important to determine where Lake Koocanusa is in an impairment-restoration cycle so as not to base protection on survivor bias, the maintenance of a currently degraded ecosystem, or normalized toxicity. In a broader context, one of the overall consequences of revised selenium regulations is that their derivation is now dependent on being able to define and understand the status of the ecosystem on which protection is based.

Montana, British Columbia↗