Geology Reports⌕ Search

SEARCH · Geology Reports

Results for “Lakes & Reservoirs”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,477 records · Page 82Linked to original sources
USGS1983

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↗
USGS1997

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↗
USGS2024

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↗
USGS2009

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↗
USGS2022

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↗
USGS2020

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↗
USGS2013

Estimation of sediment inflows to Lake Tuscaloosa, Alabama, 2009-11

The U.S. Geological Survey, in cooperation with the City of Tuscaloosa, evaluated the concentrations, loads, and yields of suspended sediment in the tributaries to Lake Tuscaloosa in west-central Alabama, from October 1, 2008, to January 31, 2012. The collection and analysis of these data will facilitate the comparison with historical data, serve as a baseline for future sediment-collection efforts, and help to identify areas of concern. Lake Tuscaloosa, at the reservoir dam, receives runoff from a drainage area of 423 square miles (mi 2 ). Basinwide in 2006, forested land was the primary land cover (68 percent). Comparison of historical imagery with the National Land Cover Database (2001 and 2006) indicated that the greatest temporal land-use change was timber harvest. The land cover in 2006 was indicative of this change, with shrub/scrub land (12 percent) being the secondary land use in the basin. Agricultural land use (10 percent) was represented predominantly by hay and pasture or grasslands. Urban land use was minimal, accounting for 4 percent of the entire basin. The remaining 6 percent of the basin has a land use of open water or wetlands. Storm and monthly suspended-sediment samples were collected from seven tributaries to Lake Tuscaloosa: North River, Turkey Creek, Binion Creek, Pole Bridge Creek, Tierce Creek, Carroll Creek, and Brush Creek. Suspended-sediment concentrations and streamflow measurements were statistically analyzed to estimate annual suspended-sediment loads and yields from each of these contributing watersheds. Estimated annual suspended-sediment yields in 2009 were 360, 540, and 840 tons per square mile (tons/mi 2 ) at the North River, Turkey Creek, and Carroll Creek streamflow-gaging stations, respectively. Estimated annual suspended-sediment yields in 2010 were 120 and 86 tons/mi 2 at the Binion Creek and Pole Bridge Creek streamflow-gaging stations, respectively. Estimated annual suspended-sediment yields in 2011 were 190 and 300 tons/mi 2 at the Tierce Creek and Brush Creek streamflow-gaging stations, respectively. The North River watershed at the streamflow-gaging station contributes 53 percent of the drainage area for Lake Tuscaloosa. A previous study in the 1970s analyzed streamflow and historical suspended-sediment samples to estimate a long-term average suspended-sediment yield of 300 tons per year per square mile in the North River watershed. Analysis of data collected in the North River watershed during the 2009 water year (October 2008 to September 2009) estimated a sediment yield of 360 tons/mi 2 . The North River watershed, a major portion of the Lake Tuscaloosa drainage basin, has not experienced a substantial increase in sedimentation rates. During the 2009 water year, the Turkey Creek watershed (6.16 mi 2 ) and the Carroll Creek watershed (20.9 mi 2 ) produced greater suspended-sediment yields than the North River watershed but contribute a much smaller drainage area to Lake Tuscaloosa. Aerial photography and bathymetric surveys indicate that Carroll Creek has experienced increased sediment deposition in the upstream portions of the channel. Carroll Creek is also the only watershed in the current study that has a substantial percentage (11 percent) of urban

Alabama↗
USGS2003

Hydrothermal and tectonic activity in northern Yellowstone Lake, Wyoming

Yellowstone National Park is the site of one of the world's largest calderas. The abundance of geothermal and tectonic activity in and around the caldera, including historic uplift and subsidence, makes it necessary to understand active geologic processes and their associated hazards. To that end, we here use an extensive grid of high-resolution seismic reflection profiles (∼450 km) to document hydrothermal and tectonic features and deposits in northern Yellowstone Lake. Sublacustrine geothermal features in northern Yellowstone Lake include two of the largest known hydrothermal explosion craters, Mary Bay and Elliott's. Mary Bay explosion breccia is distributed uniformly around the crater, whereas Elliott's crater breccia has an asymmetric distribution and forms a distinctive, ∼2-km-long, hummocky lobe on the lake floor. Hydrothermal vents and low-relief domes are abundant on the lake floor; their greatest abundance is in and near explosion craters and along linear fissures. Domed areas on the lake floor that are relatively unbreached (by vents) are considered the most likely sites of future large hydrothermal explosions. Four submerged shoreline terraces along the margins of northern Yellowstone Lake add to the Holocene record of postglacial lake-level fluctuations attributed to “heavy breathing” of the Yellowstone magma reservoir and associated geothermal system. The Lake Hotel fault cuts through northwestern Yellowstone Lake and represents part of a 25-km-long distributed extensional deformation zone. Three postglacial ruptures indicate a slip rate of ∼0.27 to 0.34 mm/yr. The largest (3.0 m slip) and most recent event occurred in the past ∼2100 yr. Although high heat flow in the crust limits the rupture area of this fault zone, future earthquakes of magnitude ∼5.3 to 6.5 are possible. Earthquakes and hydrothermal explosions have probably triggered landslides, common features around the lake margins. Few high-resolution seismic reflection surveys have been conducted in lakes in active volcanic areas. Our data reveal active geothermal features with unprecedented resolution and provide important analogues for recognition of comparable features and potential hazards in other subaqueous geothermal environments.

Wyoming↗
USGS2016

Behavior patterns and fates of adult steelhead, Chinook salmon, and coho salmon released into the upper Cowlitz River Basin, 2005–09 and 2012, Washington

A multiyear radiotelemetry evaluation was conducted to monitor adult steelhead ( Oncorhynchus mykiss ), Chinook salmon ( O. tshawytscha ), and coho salmon ( O. kisutch ) behavior and movement patterns in the upper Cowlitz River Basin. Volitional passage to this area was eliminated by dam construction in the mid-1960s, and a reintroduction program began in the mid-1990s. Fish are transported around the dams using a trap-and-haul program, and adult release sites are located in Lake Scanewa, the uppermost reservoir in the system, and in the Cowlitz and Cispus Rivers. Our goal was to estimate the proportion of tagged fish that fell back downstream of Cowlitz Falls Dam before the spawning period and to determine the proportion that were present in the Cowlitz and Cispus Rivers during the spawning period. Fallback is important because Cowlitz Falls Dam does not have upstream fish passage, so fish that pass the dam are unable to move back upstream and spawn. A total of 2,051 steelhead and salmon were tagged for the study, which was conducted during 2005–09 and 2012, and 173 (8.4 percent) of these regurgitated their transmitter prior to, or shortly after release. Once these fish were removed from the dataset, the final number of fish that was monitored totaled 1,878 fish, including 647 steelhead, 770 Chinook salmon, and 461 coho salmon. Hatchery-origin (HOR) and natural-origin (NOR) steelhead, Chinook salmon, and coho salmon behaved differently following release into Lake Scanewa. Detection records showed that the percentage of HOR fish that moved upstream and entered the Cowlitz River or Cispus River after release was relatively low (steelhead = 38 percent; Chinook salmon = 67 percent; coho salmon = 41 percent) compared to NOR fish (steelhead = 84 percent; Chinook salmon = 82 percent; coho salmon = 76 percent). The elapsed time from release to river entry was significantly lower for NOR fish than for HOR fish for all three species. Tagged fish entered the Cowlitz River in greater proportions than the Cispus River, regardless of origin. We found that 23–47 percent of the HOR fish entered the Cowlitz River and 12–38 percent entered the Cispus River. Similarly, 67–70 percent of the NOR fish entered the Cowlitz River and 38–66 percent entered the Cispus River. These behavioral differences translated into similar differences in fates during the spawning periods as higher percentages of tagged fish were assigned Cowlitz River fates than Cispus River fates. Fallback rates were affected by fish origin and release site. Overall, 12 percent of steelhead, 19 percent of Chinook salmon, and 8 percent of coho salmon fell back downstream of Cowlitz Falls Dam prior to spawning. Fallback rates were lower for fish that were released in the Cowlitz River or the Cispus River than for reservoir-released fish, but statistical comparisons were not robust because of small sample sizes at the river release sites. Fallback rates for fish released at the river release sites were 10 percent lower for steelhead, 4 percent lower for Chinook salmon, and 9 percent lower for coho salmon than for reservoir-released fish. However, fallback rates also were different between HOR and NOR fish. Fallback rates were significantly higher for HOR reservoir-released fish than for NOR reservoir-released fish. This study provided data that were insightful for understanding behavior and movement patterns in the upper Cowlitz River Basin and yielded estimates of fallback rates and fish fates that may be useful for fishery managers in the years to come. Studies from other systems have shown that factors such as prespawn mortality and fallback have resulted in substantial losses to spawning populations where trap-and-haul programs are being used as a restoration tool. Future research in the upper Cowlitz River Basin may use additional telemetry studies, genetic analyses, and spawning ground surveys to provide answers for new questions and to continue to monitor the progress of the reintroduction effort.

Washington↗
USGS1976

History of irrigation and characteristics of streamflow in Nebraska, part of the North and South Platte River basins

More than 80 years of streamflow records have been collected in Nebraska. Such records are essential in planning water developments and managing water resources. Their value can be enhanced if the records are analyzed statistically. This report presents statistics on the flow of streams in the North and South Platte River basins. Major irrigation projects have been constructed in the basins since gaging of streams was begun, and the records of stream discharge at gaging stations show the effects on streamflow of those developments. Streamflow records presented in this report were computed from data that represent 1973 conditions. All reservoirs on the North Platte River above Lake McConaughy are in Wyoming. The operation of those reservoirs and irrigation projects has a direct effect on the characteristics of streamflow in the Nebraska part of the basin. A brief description of the present river system is presented.

Nebraska↗
USGS2001

Assessment of water-quality conditions in the J.B. Converse Lake watershed, Mobile County, Alabama, 1990-98

J.B. Converse (Converse) Lake is a 3,600-acre, tributary-storage reservoir in Mobile County, southwestern Alabama. The lake serves as the primary drinking-water supply for the city of Mobile. The Converse Lake watershed lies within the Coastal Plain Physiographic Province. Semiconsolidated to unconsolidated sediments of sand, silt, gravel, and clay underlie the watershed, and are covered by acidic soils. Land use in the watershed is mainly forest (64 percent) and agriculture (31 percent). Residential and commercial development account for only 1 percent of the total land use in the watershed. Converse Lake receives inflow from seven major tributaries. The greatest inflows are from Big Creek, Crooked Creek, and Hamilton Creek that had mean annual streamflows of 72.2, 19.4, and 25.0 cubic feet per second, respectively, for the period 1990 to 1998, which represents about 72 percent of the total annual streamflow to the lake. The total mean annual inflow to the lake is estimated to be about 163 cubic feet per second. In general, water quality in Converse Lake and its tributaries meets the criteria established by the Alabama Department of Environmental Management (ADEM) for drinking-water supplies, whole-body contact, and aquatic life. The exceptions include acidic pH levels, iron and manganese levels above secondary or aesthetic criteria, and fecal bacterial levels in some tributaries above whole-body contact (swimmable) criteria. The pH levels throughout the watershed were commonly below the criteria level of 6.0, but this appears to have been a naturally occurring phenomenon caused by poorly buffered soil types, resistant sediments, and forested land use. Median iron and manganese levels were above aesthetic criteria levels of 300 and 50 micrograms per liter, respectively, in some tributaries. All tributary sites in the Converse Lake watershed had median and minimum dissolved-oxygen concentrations above the ADEM criteria level of 5 milligrams per liter except for Boggy Branch, which had a minimum dissolved-oxygen concentration of 3.7 milligrams per liter. The degree to which nutrient contributions from tributaries were causing nutrient enrichment and eutrophication in Converse Lake was assessed. Trend analysis detected little or no change in nutrient concentrations at the tributary and lake sites in the Converse Lake watershed from the 1991 to 1998 water years. Nutrient concentrations at most tributary sites exhibited a significant, positive relation with streamflow that indicated the dominant source of nutrient input to the watershed is from nonpoint contributions. From 1990 to 1998, computed mean annual loads of 75,400 kilograms of total nitrogen, 36,950 kilograms of total Kjeldahl nitrogen, 28,870 kilograms of total inorganic nitrogen, and 3,480 kilograms of total phosphorus were contributed to the lake by Big Creek, Hamilton Creek, and Crooked Creek combined. These mean annual loads of nutrients corresponded to borderline eutrophic/mesotrophic conditions in the lake. Of the combined loads, 62 percent of the total nitrogen, 70 percent of the total Kjeldahl nitrogen, 54 percent of the total inorganic nitrogen, and 47 percent of the total phosphorus originated from the forested subbasin of Big Creek. The more residential and agricultural subbasins of Crooked Creek and Hamilton Creek, however, yielded over twice the total phosphorus load per hectare of land use. Crooked and Hamilton Creek subbasins also had higher yields of the more bioavailable total inorganic nitrogen. A simplistic empirical model could not explain the relation between year-to-year nutrient contributions to Converse Lake from the tributaries and the lake's ability to assimilate those contributions. The potential presence of pathogens in the lake and its tributaries was assessed based on fecal bacterial concentrations. Fecal bacterial concentrations at some tributary sites were above existing criteria for swimmable uses. Contributions of fecal bacte

Water-Resources Investigations Report↗
USGS2003

Monitoring instream turbidity to estimate continuous suspended-sediment loads and yields and clay-water volumes in the upper North Santiam River Basin, Oregon, 1998-2000

Three real-time, instream water-quality and turbidity-monitoring sites were established in October 1998 in the upper North Santiam River Basin on the North Santiam River, the Breitenbush River, and Blowout Creek, the main tributary inputs to Detroit Lake, a large, controlled reservoir that extends from river mile 61 to 70. Suspended-sediment samples were collected biweekly to monthly at each station. Rating curves provided estimated suspended-sediment concentration in 30-minute increments from log transformations of the instream turbidity monitoring data. Turbidity was found to be a better surrogate than discharge for estimating suspended-sediment concentration. Daily and annual mean suspended-sediment loads were estimated using the estimated suspended-sediment concentrations and corresponding streamflow data. A laboratory method for estimating persistent (residual) turbidity from separate turbidity samples was developed. Turbidity was measured over time for each sample. Turbidity decay curves were derived as the suspended sediment settled. Each curve was used to estimate a turbidity value for a given settling time. Medium to fine clay particle (< 0.002 mm [millimeter] diameter) settling times of 8.5 hours were computed using Stokes Law. An average of 30 persistent turbidity samples was collected from each of the 3 sites. These samples were used to estimate the 0.002-mm-size clay particle persistent turbidity for each site. The monitored instream 30-minute turbidity values were converted to a calculated persistent turbidity value that would have resulted after 8.5 hours of settling in the laboratory. Persistent turbidities of 10 NTU and above were tabulated for each site. (Water of 10 NTU and above can interfere with or damage treatment filters and result in intake closures at drinking-water facilities.) A method was developed that used the persistent turbidity experiments, turbidity decay curves, and stream discharge to estimate the volume of water containing suspended clay that entered Detroit Lake from the three main tributaries. 'Suspended-clay water' was defined as water having a value of at least 10 NTU after settling the required 8.5 hours. The suspended-clay concentrations of 10 NTU or higher were paired with the corresponding stream discharge in the continuous record. These summed discharges represent the annual volume of water containing suspended clay that entered Detroit Lake from the three main tributaries. Higher yields (load per unit area) of suspended sediment and suspended-clay water were observed from the smaller Breitenbush River and Blowout Creek subbasins than from the main-stem North Santiam River for water years 1999 and 2000. The 3-day peak streamflow and turbidity events in 1999 and 2000 carried two-thirds of the annual suspended-sediment load for the three subbasins. Turbidity and suspended-sediment concentration relations within the upper North Santiam River Basin are basin specific and can change annually within a single subbasin. Techniques developed during this study will assist water resource planners in understanding and managing water quality in their watersheds, particularly those in which there are persistent-turbidity problems.

Water-Resources Investigations Report↗
USGS2007

Use of the Delphi method in resolving complex water resources issues

The tri-state river basins, shared by Georgia, Alabama, and Florida, are being modeled by the U.S. Fish and Wildlife Service and the U.S. Army Corps of Engineers to help facilitate agreement in an acrimonious water dispute among these different state governments. Modeling of such basin reservoir operations requires parallel understanding of several river system components: hydropower production, flood control, municipal and industrial water use, navigation, and reservoir fisheries requirements. The Delphi method, using repetitive surveying of experts, was applied to determine fisheries' water and lake-level requirements on 25 reservoirs in these interstate basins. The Delphi technique allowed the needs and requirements of fish populations to be brought into the modeling effort on equal footing with other water supply and demand components. When the subject matter is concisely defined and limited, this technique can rapidly assess expert opinion on any natural resource issue, and even move expert opinion toward greater agreement.

Journal of the American Water Resources Associatio↗
USGS2025

Non-native prey availability and over-compensatory density dependence drive population dynamics of a native fish predator

Understanding the factors that regulate population dynamics is crucial for conserving imperiled species. Bull trout ( Salvelinus confluentus ), a piscivorous salmonid and one of North America's most threatened cold-water species, has declined significantly due to habitat loss, overfishing, invasive species, and climate change. While recovery efforts have primarily targeted these threats, the role of prey availability in influencing bull trout population dynamics under multiple stressors remains poorly understood. Using a stage-based integrated population model, we quantified the effects of non-native prey availability (kokanee; Oncorhynchus nerka ), angling pressure, climatic variation, and density-dependent processes on bull trout population dynamics in Lake Koocanusa, a transboundary reservoir and river system (United States and Canada), over a 40-year period (1980–2023). Our results show that bull trout populations are regulated by density-dependent processes, including over-compensation in sub-adult recruitment and reduced adult survival at high densities. Increased kokanee biomass and restricted harvest significantly enhanced bull trout survival and abundance, whereas reduced water availability had a limited negative effect on sub-adult production. Model simulations indicate that as kokanee biomass availability increases, the number of bull trout that can be sustainably harvested also increases. In fact, a modest annual fishery (300 individuals) can be sustained, especially under moderate to high kokanee biomass conditions. These results underscore the importance of prey availability, including non-native species, in supporting bull trout populations. Effective management of threatened apex fish predators like bull trout requires addressing the complex interplay between environmental threats, prey dynamics, and density-dependent mechanisms across all life stages.

British Columbia, Montana↗
USGS2016

Evidence of estrogenic endocrine disruption in smallmouth and largemouth bass inhabiting Northeast U.S. National Wildlife Refuge waters: A reconnaissance study

Intersex as the manifestation of testicular oocytes (TO) in male gonochoristic fishes has been used as an indicator of estrogenic exposure. Here we evaluated largemouth bass ( Micropterus salmoides ) or smallmouth bass ( Micropterus dolomieu ) form 19 National Wildlife Refuges (NWRs) in the Northeast U.S. inhabiting waters on or near NWR lands for evidence of estrogenic endocrine disruption. Waterbodies sampled included rivers, lakes, impoundments, ponds, and reservoirs. Here we focus on evidence of endocrine disruption in male bass evidenced by gonad histopathology including intersex or abnormal plasma vitellogenin (Vtg) concentrations. During the fall seasons of 2008&ndash;2010, we collected male smallmouth bass ( n =118) from 12 sites and largemouth bass ( n =173) from 27 sites. Intersex in male smallmouth bass was observed at all sites and ranged from 60% to 100%; in male largemouth bass the range was 0&ndash;100%. Estrogenicity, as measured using a bioluminescent yeast reporter, was detected above the probable no effects concentration (0.73 ng/L) in ambient water samples from 79% of the NWR sites. Additionally, the presence of androgen receptor and glucocorticoid receptor ligands were noted as measured via novel nuclear receptor translocation assays. Mean plasma Vtg was elevated (>0.2 mg/ml) in male smallmouth bass at four sites and in male largemouth bass at one site. This is the first reconnaissance survey of this scope conducted on US National Wildlife Refuges. The baseline data collected here provide a necessary benchmark for future monitoring and justify more comprehensive NWR-specific studies.

Maine, Maryland, Massachusetts, New Hampshire, New↗
USGS2001

Enantiomeric composition of chiral polychlorinated biphenyl atropisomers in aquatic and riparian biota

The enantiomeric composition of polychlorinated biphenyl (PCB) atropisomers was measured in river and riparian biota (fish, bivalves, crayfish, water snakes, barn swallows) from selected sites throughout the United States by using chiral gas chromatography/mass spectrometry. Nonracemic enantiomeric fractions (EFs) were observed for PCBs 91, 95, 136, and 149 for aquatic and riparian biota from Lake Hartwell, SC, a reservoir heavily contaminated with PCBs, and for these congeners and PCBs 132, 174, 176, and 183 in river fish and bivalves nationwide. Fish and bivalves showed marked differences in EFs as compared to sediment found at the same sampling sites, thus suggesting that PCBs are bioprocessed in biota in a different manner from those found in sediment (e.g., reductive dechlorination). Species-dependent patterns in PCB EFs were observed, which suggest differences in the ability of different species to bioprocess PCBs enantioselectively, most likely by metabolism. The presence of nonracemic PCBs in fish and bivalves suggests greater metabolic degradation of PCBs in these organisms than indicated from previous achiral studies and underscores the powerful potential of chiral analysis as a tracer of environmental bioprocesses.

Environmental Science & Technology↗
USGS2000

Growth and diet of fish in Waldo Lake, Oregon

Waldo Lake, located in the Oregon Cascades, is considered to be one of the most dilute lakes in the world. Even with low nutrient concentrations and sparse populations of zooplankton, introduced fish in the lake are large in size and in good condition when compared to fish from other lakes. This apparent anomaly is due to the availability of benthic macroinvertebrates. Taxa found in the stomach contents offish captured in Waldo Lake consist primarily of Chironomidae larvae and pupae, Trichoptera larvae and pupae, amphipods, Ephemeroptera larvae, and Odonata larvae.

Oregon↗
USGS2000

Chlorophyll maxima in mountain ponds and lakes, Mount Rainier National Park, Washington State, USA

Hypolimnetic chlorophyll maxima are common in clear lakes and often occur at depths with between 1 and 0.1% of the surface incident light. Little is known, however, about the concentrations of chlorophyll in thermally unstratified mountain ponds and how these concentrations compare to epilimnetic and hypolimnetic concentrations in mountain lakes. The objectives of this study were to document the concentrations of chlorophyll in thermally unstratified ponds and stratified lakes in Mount Rainier National Park (MORA) and to compare the results with concentrations and distributions of chlorophyll in clear-deep lakes in the Oregon Cascade Range and the Sierra Nevada Range. Thirty-two ponds (<2.5 m deep) and 14 lakes(>9.9 m deep) were sampled primarily during the summers of 1992 to 1996 at MORA. Water samples from near the surface (0.1–0.5 m) of ponds and near the surface and near the bottom of lakes were collected over the deepest part of each system. One exception, Mowich Lake, was sampled at seven depths between the surface and 50 m (Z=58.6 m). Chlorophyll concentrations were low in all systems, but higher in ponds (average 1.8 μg·L −1 ) than in lakes. Chlorophyll concentrations were higher in hypolimnetic lake samples (average 0.7 μg·L −1 ) than in epilimnetic lake samples (average 0.2 μg·L −1 ). Elevated concentrations of chlorophyll in mountain ponds, relative to those in hypolimnetic lake samples, may have been influenced by increased nutrient availability from interactions at the mud-water interface and, in this park, defecation by elk that used many of the ponds as wallows. Mowich Lake showed a chlorophyll maximum (~1.5 μg·L −1 ) near the lake bottom. Based on Secchi disk clarity readings, the depth of 1.0% incident surface solar radiation was greater than the maximum depths of the ponds and lakes. Comparative data from other clear-deep lakes in the Oregon Cascade Range and Sierra Nevada Range suggested that deep-chlorophyll maxima (~1.5 μg·L −1 ) occurred at <1.0% and > 0.1% of the incident surface solar radiation, and that the typical maximum depths ranged between 75 and 140 m during thermal stratification.

Washington↗