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At least 307 records · Page 17Linked to original sources
USGS2018

Assessment of dissolved-selenium concentrations and loads in the lower Gunnison River Basin, Colorado, as part of the Selenium Management Program, from 2011 to 2016

The Gunnison Basin Selenium Management Program implemented a water-quality monitoring network in 2011 in the lower Gunnison River Basin in Colorado. Selenium is a trace element that bioaccumulates in aquatic food chains and can cause reproductive failure, deformities, and other harmful effects. This report presents the percentile values of selenium because regulatory agencies in Colorado make decisions based on the U.S. Environmental Protection Agency (EPA) Clean Water Act Section 303(d) that uses percentile values of concentration. Also presented are dissolved-selenium loads at 18 sites in the lower Gunnison River Basin for water years (WYs) 2011–2016 (October 1, 2010, through September 30, 2016). Annual dissolved-selenium loads were calculated for five sites with continuous U.S. Geological Survey (USGS) streamflow-gaging stations. Annual dissolved-selenium loads for WY 2011 through WY 2016 ranged from 179 and 391 pounds (lb) at Uncompahgre River at Colona to 11,100 and 17,300 lb at Gunnison River near Grand Junction (herein called Whitewater), respectively. Instantaneous loads were calculated for five sites with continuous U.S. Geological Survey (USGS) streamflow-gaging stations and 13 ancillary sites where discrete water-quality sampling also took place, using discrete water-quality samples and the associated discharge measurements collected during the period. Median instantaneous loads ranged from 0.01 pound per day (lb/d) at Smith Fork near Lazear to 33.0 lb/d at Whitewater. Mean instantaneous loads ranged from 0.06 lb/d at Smith Fork near Lazear to 36.2 lb/d at Whitewater. Most tributary sites in the basin had a median instantaneous dissolved-selenium load of less than 20.0 lb/day. In general, dissolved-selenium loads at Gunnison River main-stem sites showed an increase from upstream to downstream. The State of Colorado water-quality standard for dissolved selenium of 4.6 micrograms per liter (µg/L) was compared to the 85th percentiles for dissolved selenium at selected sites. Annual 85th percentiles for dissolved selenium were calculated for the five core sites having USGS streamflow-gaging stations using estimated dissolved-selenium concentrations from linear regression models. The 85th-percentile concentrations for WYs 2011–2016 based on this method ranged from 0.62 µg/L and 1.1µg/L at Uncompahgre River at Colona to 12.1 µg/L and 18.7 µg/L at Uncompahgre River at Delta. The 85th percentiles for dissolved selenium also were calculated for sites with sufficient data using water-quality samples collected during WYs 2011–2016. The annual 85th-percentile concentrations based on the discrete samples ranged from 0.16 µg/L and 0.17 µg/L at Gunnison River below Gunnison Tunnel to 62.2 µg/L and 170 µg/L at Loutzenhizer Arroyo at North River Road. A trend analysis was completed for Whitewater to determine if dissolved-selenium loads are increasing or decreasing. The trend analysis indicates a decrease of 9,100 lb from WY 1986 to WY 2016, a 40.8 percent reduction during the time period. The trend analysis for the annual dissolved-selenium load for WY 1994 to WY 2016 indicates a decrease of 6,300 lb per year, or 33.3 percent.

Colorado↗
USGS2021

Characterization of water resources in the Big Lost River Basin, south-central Idaho

Water resources in the Big Lost River Basin, Idaho are vital to irrigated agriculture, domestic, municipal and other uses but declining groundwater levels, diminished streamflows, and concern about drought motivated an evaluation of water resources in the basin. This multichapter volume documents the findings of a hydrogeologic investigation of the Big Lost River Basin that was jointly conducted by the U.S. Geological Survey, Idaho Department of Water Resources, and Idaho Geological Survey from 2018 through 2021. Chapter A (Zinsser, 2021) describes the hydrogeologic framework of the Big Lost River Basin. The framework presents a conceptual definition of four hydrogeologic units, a three-dimensional hydrogeologic framework model representing the spatial occurrence of the hydrogeologic units, and a description of groundwater occurrence and movement. Chapter B (Dudunake and Zinsser, 2021) describes streamflow gains from and losses to groundwater in the Big Lost River between Mackay Reservoir and south of Arco. Streamflow losses and gains were estimated from a series of four measurement events completed during spring and fall conditions from 2019 to 2021. Chapter C (Clark, 2022) describes budgets for the Big Lost River Basin from 2000 to 2019. The groundwater budgets provide annual estimates for aquifer inflows and outflows and include representations of average, wet, and dry conditions. Collectively, these reports present a characterization of water resources in the Big Lost River Basin that will help address current challenges in water-resources management.

Idaho↗
USGS2021

Estimating flow-duration statistics and low-flow frequencies for selected streams and the implementation of a StreamStats web-based tool in Puerto Rico

Daily mean streamflow data from 28 U.S. Geological Survey streamflow-gaging stations in Puerto Rico with 10 or more years of unregulated or minimally affected flow record through water year 2018 were used to develop regression equations for flow duration and annual n -day low-flow statistics. Ordinary least-squares and generalized least-squares regression techniques were used to develop regional regression equations for flow-duration statistics at the 99th, 98th, 95th, 90th, 80th, 70th, 60th, and 50th percent exceedance probabilities and annual n -day low-flow frequency statistics for the 1-, 7-, 14-, and 30-day mean low flows with the 2-year (0.5 nonexceedance probability), 5-year (0.2 nonexceedance probability), and 10-year (0.1 nonexceedance probability) recurrence intervals. A StreamStats web application was developed to estimate basin and climatic characteristics for the regional regression equation analysis. Basin and climatic characteristics determined to be significant explanatory variables in one or more regression equations included drainage area, mean total annual reference evapotranspiration, and minimum basin elevation. The adjusted coefficient of determination for the flow-duration regression equations ranged from 57.7 to 81.4 percent. The pseudo coefficient of determination for the annual n -day low-flow regression equations ranged from 64.6 to 70.7 percent. The StreamStats web application incorporates the flow duration, and annual n -day low-flow regression equations and can provide streamflow estimates for most ungaged sites in the island.

Puerto Rico↗
USGS1987

Ground-water hydrology of the Toppenish Creek basin, Yakima Indian Reservation, Washington

A groundwater flow model was constructed for the Toppenish Creek basin aquifer system in eastern Washington. Flow was simulated in three aquifer units: (1) the confined old valley fill and shallow basalt (unit 2); (2) the underlying primary basalt (unit 3); and (3) the deep basalt (unit 4). Water levels in the overlying unconfined alluvial aquifer (unit 1) were held fixed. Calibrated transmissivities ranged from 0.01 to 0.48 foot squared per second. Calibrated storage coefficients were 0.0004 to 0.006. The confining-bed leakance ranged from 2.0 x 10 to the minus 11th power to 2.5 x 10 to the minus 10th power feet per second per foot. Under steady-state conditions (1954) annual natural recharge was about 29,000 acre-ft underflow from adjacent basins. Annual pumpage increased from less than 500 acre-ft in 1954 to an average of 19,600 acre-ft for 1971 and 1972. Pumpage caused simulated declines in unit 3 of up to 95 ft for 1955-72. Projected annual declines from 1973-77 using 1971-72 pumpage were about 0.5-1.5 ft in unit 2 and 0.2-1.5 ft in unit 3. The corresponding declines from 1978-82 were 0.2-1.2 ft and 0.2-0.8 ft, respectively. Using 1971-72 pumpage plus 12 ,400 acre-ft per year from unit 3, the calculated annual declines from 1978-82 were 1-36 ft in unit 2 and 4-20 ft in unit 3. (USGS)

Water-Resources Investigations Report↗
USGS1986

Suspended sediment in Minnesota streams

Suspended-sediment samples have been collected by the U.S. Geological Survey from 115 sites on Minnesota streams since October 1960. Data from 42 sites were sufficient for characterizing sediment concentrations and yields. Average concentrations ranged from 4.4 milligrams per liter on the Baptism River in northeastern Minnesota to 190 milligrams per liter on the Root River in the southeast. Log-linear equations that describe the sediment-transport curve were developed for 33 daily sediment stations and used to estimate long-term sediment yields. Average annual yields ranged from less than 1.0 ton per square mile on the Pelican River, to more than 200 tons per square mile on the Root and Whitewater Rivers and Deer Creek. Estimates indicated that under extreme circumstances the average annual sediment load for 2 years could be transported in slightly more than one day. Analysis showed that more than 90 percent of the annual sediment load was carried during 3 to 9 months of the year. On the average, almost 25 percent of the annual sediment load was transported during April. Generally, it was found that less than 4 percent of the average annual load was transported during December, January, and February, which indicates that sampling frequency could be reduced during winter.

Minnesota↗
USGS2008

Quantifying Ground-Water and Surface-Water Discharge from Evapotranspiration Processes in 12 Hydrographic Areas of the Colorado Regional Ground-Water Flow System, Nevada, Utah, and Arizona

Rapid population growth in southern Nevada has increased the demand for additional water supplies from rural areas of northern Clark and southern Lincoln counties to meet projected water-supply needs. Springs and rivers in these undeveloped areas sustain fragile riparian habitat and may be susceptible to ground-water withdrawals. Most natural ground-water and surface-water discharge from these basins occurs by evapotranspiration (ET) along narrow riparian corridors that encompassed about 45,000 acres or about 1 percent of the study area. This report presents estimates of ground- and surface-water discharge from ET across 3.5 million acres in 12 hydrographic areas of the Colorado Regional Ground-Water Flow System. Ground-and surface-water discharge from ET were determined by identifying areas of ground- and surface-water ET, delineating areas of similar vegetation and soil conditions (ET units), and computing ET rates for each of these ET units. Eight ET units were identified using spectral-reflectance characteristics determined from 2003 satellite imagery, high-resolution aerial photography, and land classification cover. These ET units are dense meadowland vegetation (200 acres), dense woodland vegetation (7,200 acres), moderate woodland vegetation (6,100 acres), dense shrubland vegetation (5,800 acres), moderate shrubland vegetation (22,600 acres), agricultural fields (3,100 acres), non-phreatophytic areas (3,400,000 acres), and open water (300 acres). ET from diffuse ground-water and channelized surface-water is expressed as ETgs and is equal to the difference between total annual ET and precipitation. Total annual ET rates were calculated by the Bowen ratio and eddy covariance methods using micrometeorological data collected from four sites and estimated at 3.9 ft at a dense woodland site (February 2003 to March 2005), 3.6 ft at a moderate woodland site (July 2003 to October 2006), 2.8 ft at a dense shrubland site (June 2005 to October 2006), and 1.5 ft at a moderate shrubland site (April 2006 to October 2006). Annual ETgs rates were 3.4 ft for dense woodland vegetation, 3.2 ft for moderate woodland vegetation, 2.2 ft for dense shrubland vegetation, and 1.0 ft for moderate shrubland vegetation. Published annual rates of ETgs were used for the other ET units found in the study area. These rates were 3.4 ft for dense meadowland vegetation, 5.2 ft for agricultural fields, and 4.9 ft for open water. For the non-phreatophytic ET unit, ETgs was assumed to be zero. Estimated ground- and surface-water discharge from ET was calculated by multiplying the ETgs by the ET-unit acreage and equaled 24,480 acre-ft for dense woodland vegetation, 19,520 acre-ft for moderate woodland vegetation, 12,760 acre-ft for dense shrubland vegetation, 22,600 acre-ft for moderate shrubland vegetation, 680 acre-ft for dense meadowland vegetation, 16,120 acre-ft for agricultural fields, 1,440 acre-ft for open water, and 0 acre-ft for the non-phreatophytic ET unit. Estimated ground-water and surface-water discharge from ET from each hydrographic area was calculated by summing the total annual ETgs rate for ET units found within each hydrographic area and equaled 1,952 acre-ft for the Black Mountains Area, 6,080 acre-ft for California Wash, 4,090 acre-ft for the Muddy River Springs Area, 11,510 acre-ft for Lower Moapa Valley, 51,960 acre-ft for the Virgin River Valley, 16,168 acre-ft for Lower Meadow Valley Wash, 5,840 acre-ft for Clover Valley, and 0 acre-ft for Coyote Spring Valley, Kane Springs Valley, Tule Desert, Hidden Valley (North), and Garnet Valley. The annual discharge from ETgs for the study area totals about 98,000 acre-ft.

Scientific Investigations Report↗
USGS1999

Water resources of Monroe County, New York, water years 1989-93, with emphasis on water quality in the Irondequoit Creek basin: Part 2. Atmospheric deposition, ground water, streamflow, trends in water quality, and chemical loads to Irondequoit Bay

Irondequoit Creek, which drains 169 square miles in the eastern part of Monroe County, has been recognized as a source of contaminants that contribute to the eutrophication of Irondequoit Bay on Lake Ontario. The discharge from sewage-treatment plants to the creek and its tributaries was eliminated in 1979 by diversion to another wastewater-treatment facility, but sediment and nonpoint-source pollution remain a concern. This report presents data from five surface-water sites in the Irondequoit Creek basin. Irondequoit Creek at Railroad Mills, East Branch Allen Creek, Allen Creek near Rochester, Irondequoit Creek at Blossom Road, and Irondequoit Creek at Empire Boulevard, to supplement published data from 1984-88. Data from Northrup Creek, which drains 11.7 square miles in western Monroe County, provide information on surface-water quality west of the Genesee River. Also presented are water-level and water-quality data from 12 observation-well sites in Ellison and Powdermill Parks and atmospheric-deposition data from 1 site (Mendon Ponds). Concentrations of several chemical constituents in streams of the Irondequoit Creek basin showed statistically significant trends during 1989-93. Concentrations of total suspended-solids and volatile suspended-solids in Irondequoit Creek at Blossom Road decreased 13.5 and 12.5 percent per year, respectively, and those at Empire Boulevard decreased 33.5 and 22 percent per year, respectively. Concentrations of ammonia plus organic nitrogen increased 17.6 percent per year at one site in the basin, but decreased 8.5 and 22.3 percent per year at two sites. Nitrite plus nitrate decreased at only one site (3.5 percent per year). Concentrations of total phosphorus increased at two sites (about 7 percent per year) and decreased at two other sites (7.6 and 29.9 percent per year), and orthophosphate concentrations increased at one site (10.8 percent per year). Dissolved chloride increased at three sites (1.7 to 10.9 percent per year), and dissolved sulfate decreased at one site (2.1 percent per year) and increased at one site (6.8 percent per year). Median concentrations of constituents were significantly lower in atmospheric deposition than in streamflow, although annual deposition of ammonia nitrogen, nitrite plus nitrate, total phosphorus, and orthophosphate in the basin exceeded the amounts removed by streamflow. Atmospheric deposition of chloride and sulfate, by contrast, represented only 1 and 12 percent, respectively, of the loads transported by Irondequoit Creek (Blossom Road site). Comparison of water-quality data from the Allen Creek site and Irondequoit Creek at Blossom Road from water years 1989-93 with corresponding data from 1984-88 indicates significant changes in median concentrations of several constituents. The concentration of dissolved chloride increased at Blossom Road and was unchanged at Allen Creek, whereas sulfate decreased at both sites. Concentrations of ammonia plus organic nitrogen, and nitrite plus nitrate, were significantly lower during 1989-93 than during 1984-88 at both sites. Total phosphorus concentration was lower during 1984-88 than during 1989-93 at Blossom Road but showed no change at Allen Creek, and orthophosphate concentration for 1989-93 was lower than in 1984-88 at both sites. Comparison of chemical loads in atmospheric deposition also indicates significant changes in many constituents. Five-year-mean loads of sodium, sulfate, and lead in atmospheric deposition for 1989-93 exceeded those for 1984-88, whereas 5-year-mean loads of calcium, magnesium, potassium, chloride, nitrite plus nitrate, ammonia nitrogen, and orthophosphate for 1989-93 were lower than in 1984-88. The changes in surface-water quality resulted from several factors within the basin, including land-use changes, annual and seasonal variations in streamflow, and year-to-year variations in the application of deicing salts on area roads. Statistical analyses of long-term (9 years or more) flow records of three unregulated streams in Monroe County indicate that annual mean flows for water years 1989- 93 were in the normal range (20th- to 80th-percentile). The greatest mean annual flow in this period-about 140 percent of normal at Irondequoit Creek and Black Creek-occurred in 1993, but the annual mean flow for that water year at Allen Creek was only 98 percent of normal. The lowest annual mean flows of these streams-ranging from 75 percent of normal to 93 percent of normal-occurred in 1989. The average annual mean flows for these streams for 1989-93 was 104 percent of normal, and that for 1984-88 was normal.

New York↗
USGS2000

Hydrology, water quality, and phosphorus loading of Little St. Germain Lake, Vilas County, Wisconsin

Little St. Germain Lake, which is in Vilas County. Wisconsin, just northeast of St. Germain (fig. 1), is one of 21 impoundments operated by Wisconsin Valley Improvement Company (WVIC) to provide storage for power and recreational use. The level of the lake, which was originally dammed in 1882, has been maintained by the WVIC at about 5 feet above its natural level since 1929, and it is annually drawn down about 1.5 feet from December through March. In the interest of protecting and improving the water quality of the lake, the Little St. Germain Lake Improvement Association was established in 1959. Later, the I .ittle St. Germain Lake District was formed. The Wisconsin Department of Natural Resources (WDNR), in collaboration with the Lake District, did a study during 1983-85 to document the water quality of the lake and examine management alternatives (Wisconsin Department of Natural Resources, 1985). Results of the study indicated that, because of relatively high phosphorus loading to the lake, most of the lake was eutrophic (relatively productive), with the possible exception of the West Bay. The results also indicated monitoring of the lake should continue, and that actions should be taken to decrease nutrient loading to the lake by controlling erosion, fertilizer runoff, and leakage from septic systems. The lake was monitored in detail again during 1991-94 by the U.S. Geological Survey (USGS) as part of a cooperative study with the Lake District. This study demonstrated water-quality variation among the basins of Little St. Germain Lake and extensive areas of winter anoxia (absence of oxygen). Further in-depth studies were then conducted during 1994-2000 to define the extent of winter anoxia, refine the hydrologic and phosphorus budgets of the lake, quantify the effects of annual drawdowns, and provide information needed to develop a comprehensive lake-management plan. This report presents the results of the studies since 1991.

Wisconsin↗
USGS1889

Eighth annual report of the United States Geological Survey to the Secretary of the Interior, 1886-1887: Part 1

The Geological Survey was organized, with Mr. Clarence King as Director, in March, 1879. In March, 1881, Mr. King resigned and the present Director was appointed. From its organization to the present time the Survey has steadily grown as Congress has enlarged its functions and increased its appropriations. During this time the scientific organization has gradually developed to the condition set forth in the last annual report. It seems advisable now to describe fully the business organization and methods of the Survey, which has heretofore been done only in part. Under the act of July 7, 1884, a joint commission was created to consider the organization of certain scientific bureaus. In the volume of testimony prepared by that commission the business operations of the Geological Survey were in part set forth; but this partial presentation was unsystematic, the facts recorded being elicited in irregular order by interrogatories arising in the course of a long investigation. It is designed here to make a more thorough exposition oi the subject. The business system of the Geological Survey is subordinate to the scientific organization and its character is dependent thereon. The development of the divisions of the Survey whose function is the transaction of business has therefore followed the development of the purely scientific divisions, and overy modification of plan for the scientific work may carry with it some modification of the business organization.

Annual Report↗
USGS2001

Phosphorus and nitrogen concentrations and loads at Illinois River south of Siloam Springs, Arkansas, 1997-1999

Water-quality sampling consisting of every other month (bimonthly) routine sampling and storm event sampling (six storms annually) is used to estimate annual phosphorus and nitrogen loads at Illinois River south of Siloam Springs, Arkansas. Hydrograph separation allowed assessment of base-flow and surfacerunoff nutrient relations and yield. Discharge and nutrient relations indicate that water quality at Illinois River south of Siloam Springs, Arkansas, is affected by both point and nonpoint sources of contamination. Base-flow phosphorus concentrations decreased with increasing base-flow discharge indicating the dilution of phosphorus in water from point sources. Nitrogen concentrations increased with increasing base-flow discharge, indicating a predominant ground-water source. Nitrogen concentrations at higher base-flow discharges often were greater than median concentrations reported for ground water (from wells and springs) in the Springfield Plateau aquifer. Total estimated phosphorus and nitrogen annual loads for calendar year 1997-1999 using the regression techniques presented in this paper (35 samples) were similar to estimated loads derived from integration techniques (1,033 samples). Flow-weighted nutrient concentrations and nutrient yields at the Illinois River site were about 10 to 100 times greater than national averages for undeveloped basins and at North Sylamore Creek and Cossatot River (considered to be undeveloped basins in Arkansas). Total phosphorus and soluble reactive phosphorus were greater than 10 times and total nitrogen and dissolved nitrite plus nitrate were greater than 10 to 100 times the national and regional averages for undeveloped basins. These results demonstrate the utility of a strategy whereby samples are collected every other month and during selected storm events annually, with use of regression models to estimate nutrient loads. Annual loads of phosphorus and nitrogen estimated using regression techniques could provide similar results to estimates using integration techniques, with much less investment.

Water-Resources Investigations Report↗
USGS2004

Distribution, migration behavior, habitat use, and species interactions of fall-released juvenile hatchery spring Chinook salmon on the Deschutes River, Oregon, 2002, Annual report 2002

In a review of National Fish Hatcheries (NFH), the U.S. Fish and Wildlife Service (USFWS) identified the need to assess the fate of hatchery-reared fish and their potential effect on the aquatic community (USFWS 1998). Additionally, in the Columbia River Biological Opinion, the National Marine Fisheries Service (NMFS) recommended monitoring and evaluating ecological interactions between hatchery and wild fish (NMFS 1999). In 2002, a study was designed to investigate the fate of hatchery-reared fish and to assess habitat use and fish interactions in the Deschutes River, Oregon.

Oregon↗
USGS2001

Concentrations and annual fluxes for selected water-quality constituents from the USGS National Stream Quality Accounting Network (NASQAN) 1996-2000

This report contains concentrations and annual mass fluxes (loadings) for a broad range of water-quality constituents measured during 1996-2000 as part of the U.S. Geological Survey National Stream Quality Accounting Network (NASQAN). During this period, NASQAN operated a network of 40-42 stations in four of the largest river basins of the USA: the Colorado, the Columbia, the Mississippi (including the Missouri and Ohio), and the Rio Grande. The report contains surface-water quality data, streamflow data, field measurements (e.g. water temperature and pH), sediment-chemistry data, and quality-assurance data; interpretive products include annual and average loads, regression parameters for models used to estimate loads, sub-basin yield maps, maps depicting percent detections for censored constituents, and diagrams depicting flow-weighted average concentrations. Where possible, a regression model relating concentration to discharge and season was used for flux estimation. The interpretive context provided by annual loads includes identifying source and sink areas for constituents and estimating the loadings to receiving waters, such as reservoirs or the ocean.

Water-Resources Investigations Report↗
USGS2010

Changes in streamflow and the flux of nutrients in the Mississippi-Atchafalaya River Basin, USA, 1980-2007

Nutrients and freshwater delivered by the Mississippi and Atchafalaya Rivers drive algal production in the northern Gulf of Mexico, which eventually results in the widespread occurrence of hypoxic bottom waters along the Louisiana and Texas coast. Researchers have demonstrated a relation between the extent of the hypoxic zone and the magnitude of streamflow, nutrient fluxes, and nutrient concentrations in the Mississippi River, with springtime streamflows and fluxes being the most predictive. In 1999 the U.S. Geological Survey (USGS) estimated the flux of nitrogen, phosphorus, and silica at selected sites in the Mississippi Basin and to the Gulf of Mexico for 1980-1996. These flux estimates provided the baseline information used by the Mississippi River/Gulf of Mexico Watershed Nutrient Task Force to develop an Action Plan for reducing hypoxia in the northern Gulf of Mexico. The primary goal of the Action Plan was to achieve a reduction in the size (areal extent) of the hypoxic zone from an average of approximately 14,000 square kilometers in 1996-2000 to a 5-year moving average of less than 5,000 square kilometers by 2015. Improved statistical models and adjusted maximum likelihood estimation using USGS Load Estimator (LOADEST) software were used to estimate annual and seasonal nutrient fluxes for 1980-2007 at selected sites on the Mississippi River and its tributaries. These data provide a means to evaluate the influence of natural and anthropogenic effects on delivery of water and nutrients to the Gulf of Mexico; to define subbasins that are the most important contributors of nutrients to the gulf; and to investigate the relations among streamflow, nutrient fluxes, and the size and duration of the Gulf of Mexico hypoxic zone. A comparative analysis between the baseline period of 1980-1996 and 5-year moving averages thereafter indicate that the average annual streamflow and fluxes of total nitrogen, nitrate, orthophosphate, and silica to the Gulf of Mexico have decreased. However, the flux of total phosphorus between the baseline period and subsequent 5-year periods has increased. The average spring (April, May, and June) streamflow and fluxes of silica, total nitrogen, nitrate, and orthophosphate to the Gulf of Mexico also decreased, whereas the spring flux of total phosphorus has increased. Similar changes in streamflow and nutrient flux were observed at many sites Buxtonwithin the basin. The inputs of water, total nitrogen, and total phosphorus from the major subbasins of the Mississippi-Atchafalaya River Basin as a percentage of the to-the-gulf totals have increased from the Ohio River Basin, decreased from the Missouri River Basin, and remained relatively unchanged from the Upper Mississippi, Red, and Arkansas River Basins. Changes in streamflow and nutrient fluxes are related, but short-term variations in sources of streamflow and nutrients complicate the interpretation of factors that affect nutrient delivery to the Gulf of Mexico. Parametric time-series models are used to try and separate natural variability in nutrient flux from changes due to other causes. Results indicate that the decrease in annual nutrient fluxes that has occurred between the 1980-1996 baseline period and more recent years can be largely attributed to natural causes (climate and streamflow) and not management actions or other human controlled activities in the Mississippi-Atchafalaya River Basin. The downward trends in total nitrogen, nitrate, ammonium, and orthophosphate that were detected at either the Mississippi River near St. Francisville, La., or the Atchafalaya River at Melville, La., occurred prior to 1995. In spite of the general decrease in nutrient flux, the average size of the Gulf of Mexico hypoxic zone has increased between 1997 and 2007. The reasons for this are not clear but could be due to the type or nature of nutrient delivery. Whereas the annual flux of total nitrogen to the Gulf of Mexico has decreased, the proporti

Scientific Investigations Report↗
USGS1974

Flood profiles and inundated areas along the Lower Nisqually River, Washington

Nisqually River flood profiles, covering the reach from near the river mouth to river mile 6.4, were developed in a 2-year field study (1970-72) as part of a continuing program with the State of Washington Department of Ecology. The main channel of the reach will convey without overflow discharges as large as about 21,000 cubic feet per second, which have a 6-year recurrence interval. The banks in some areas will be overtopped at 25,500 cubic feet per second, which has a 13-year recurrence interval. The areas where overbank flooding will first occur, and water-surface profiles of a 3.4-year and 100-year flood were determined for six flood-profile stations. The largest flood for which data are available was that of December 1933; the approximate area that would be presently inundated by such a flood is shown. Alder and La Grande Reservoirs can reduce the magnitude of lower annual flood peaks downstream to some extent, but insufficient data are available to predict their effects on very large floods.

Washington↗
USGS1997

Analysis of bottom sediment to estimate nonpoint-source phosphorus loads for 1981-96 in Hillsdale Lake, northeast Kansas

Bottom sediment in Hillsdale Lake, northeast Kansas, was analyzed as a means of estimating the annual load of total phosphorus deposited in the lake from nonpoint sources. Topographic, bathymetric, and sediment-core data were used to estimate the total mass of phosphorus in the lake-bottom sediment. Available streamflow and water-quality data were used to compute the mean annual mass of phosphorus (dissolved plus suspended) exiting the lake as well as the mean annual load of phosphorus added to the lake from point sources. A simple mass balance then was used to compute the mean annual load of phosphorus from nonpoint sources. Mean annual sediment deposition from 1981 through 1996 was estimated to be 265 million pounds (120 million kilograms). The total mass of phosphorus in the lake-bottom sediment was estimated to be 924,000 kilograms, with a mean annual load of 62,000 kilograms. The mean annual mass of phosphorus exiting in the lake out-flow was estimated to be about 8,000 kilograms. The mean annual loads of phosphorus added to the lake from point and nonpoint sources were estimated to be 5,000 and 65,000 kilograms, respectively. Thus, the contribution to the total mean annual phosphorus load in Hillsdale Lake from point sources is about 7 percent and from nonpoint sources, about 93 percent.

Kansas↗
USGS1962

Glacier observations, Glacier National Park, Montana, 1961

This report records the results obtained during the 1961 season in the continuing program of glacier observations in Glacier National Park. The investigations currently in progress relate to the Grinnell and Sperry Glaciers. This program is carried on cooperatively by the Geological Survey, the National Park Service and the Weather Bureau. The program includes the determination of annual changes in the surface elevation of the glaciers by the measurement of profiles, and changes during the summer months by the establishment of and observations at ablation stakes; rapping the glacier termini in selected years to record advance or recession; determination of annual movement by the location of marked rocks; the operation of two storage-precipitation gages in the immediate vicinity of the Grinnell Glacier to record annual precipitation; the operation of two gaging stations, one just below the Grinnell Glacier during the summer months and one Just below the outlet of Grinnell Lake on a year round basis; temperature data near the Grinnell Glacier and temperature and precipitation data at the Sperry Chalet near the Sperry Glacier during the summer months. The results of the work are described in the following sections.

Montana↗
USGS2020

Magnitude and frequency of floods in Alabama, 2015

To improve flood-frequency estimates at rural streams in Alabama, annual exceedance probability flows at gaged locations and regional regression equations used to estimate annual exceedance probability flows at ungaged locations were developed by using current geospatial data, new analytical methods, and annual peak-flow data through September 2015 at 242 streamgages in Alabama and surrounding States. The regional regression equations were derived from statistical analyses of annual peak-flow data and basin characteristics for a subset of 217 streamgages. Four flood regions were identified based on residuals from the regional regression analyses and contain sites with similar basin characteristics. A separate set of equations was derived for estimating flood frequency and magnitude for small rural streams using a subset of 40 small basin streamgages. A large river analysis was also completed for 14 selected large-river streamgages in Alabama. Annual exceedance probability flows presented in this report reflect additional streamflow data collected since the previous study of flood magnitude and frequency in Alabama, which included streamflow through September 2003.

Alabama↗