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At least 1,081 records · Page 60Linked to original sources
USGS1983

Hydraulic conductivity, specific yield, and pumpage — High Plains aquifer system, Nebraska

Hydrologic data used to evalute the ground-water potential of the High Plains aquifer system in Nebraska are presented on maps showing the hydraulic conductivity and specific yield of the aquifer system and the volume and distribution of water pumped for irrigation from the aquifer system during 1980. The High Plains aquifer system underlies 177,000 square miles in parts of eight states, including 64,770 square miles in Nebraska. It consists of the Ogallala Formation and Tertiary and Quaternary deposits that are saturated and hydraulically connected to the Ogallala. The hydraulic conductivity of the aquifer system varies from greater than 200 feet per day in parts of the North Platte, Platte, Elkhorn, and Republican River valleys to less than 25 feet per day in the northwestern part of the state. Specific yield of the aquifer system ranges from 10 to 20 percent in most of the state and averages 16 percent. The estimated volume of water recoverable from the aquifer system in Nebraska is 2,237 million acre-feet. Inches of water withdrawn from the aquifer system during 1980 varied from less than 1.5 in the sandhills of north-central Nebraska to more than 12 in the Platte River and Blue River basins. This withdrawal represents about 6,703,000 acre-feet of ground water.

Nebraska↗
USGS1982

Hydrologic-information needs for oil-shale development, northwestern Colorado

Hydrologic information is not adequate for proper development of the large oil-shale reserves of Piceance basin in northwestern Colorado. Exploratory drilling and aquifer testing are needed to define the hydrologic system, to provide wells for aquifer testing, to design mine-drainage techniques, and to explore for additional water supplies. Sampling networks are needed to supply hydrologic data on the quantity and quality of surface water, ground water, and springs. A detailed sampling network is proposed for the White River basin because of expected impacts related to water supplies and waste disposal. Emissions from oil-shale retorts to the atmosphere need additional study because of possible resulting corrosion problems and the destruction of fisheries. Studies of the leachate materials and the stability of disposed retorted shale piles are needed to insure that these materials will not cause problems. Hazards related to in-situ retorts, and the wastes related to oil-shale development in general also need further investigation. (USGS)

Water-Resources Investigations Report↗
USGS1983

Potential effects of surface coal mining on the hydrology of the Greenleaf-Miller area, Ashland coal field, southeastern Montana

The Greenleaf-Miller area of the Ashland coal field contains reserves of Federal coal that have been identified for potential lease sale. A hydrologic study was conducted in the potential lease area in 1981 to describe the existing hydrologic system and to assess potential impacts of surface coal mining on local water resources. The hydrologic data collected from wells, test holes, and springs were used to identify aquifers in the alluvium (Pleistocene and Holocene age) and the Tongue River member of the Fort Union Formation (Paleocene age). Coal, clinker, and sandstone beds comprise the aquifers in the Tongue River Member. Most streams are ephemeral and flow only as a result of precipitation. The only perennial surface-water flow in the study area is along short reaches downstream from springs. A mine plan for the area is not available; thus, the location of mine cuts, direction and rate of the mine expansion, and duration of mining are unknown. The mining of the Sawyer and Knoblock coal beds in the Tonge River Member would effect ground-water flow in the area. Declines in the potentiometric surface would be caused by dewatering where the mine pits intersect the water table. Wells and springs would be removed in the mine area; however, deeper aquifers are available as replacement sources of water. The chemical quality of the ground water would change after moving through the spoils. The change would be an increase in the concentration of dissolved solids. (USGS)

Montana↗
USGS1983

Magnitude and frequency of flooding on small urban watersheds in the Tampa Bay area, west-central Florida

Hydrologic data collected on nine small urban watersheds in the Tampa Bay area of west-central Florida and a method for estimating peak discharges in the study area are described. The watersheds have mixed land use and range in size from 0.34 to 3.45 square miles. Watershed soils, land use, and storm-drainage system data are described. Urban development ranged from a sparsely populated area with open-ditch storm sewers and 19% impervious area to a completely sewered watershed with 61% impervious cover. The U.S. Geological Survey natural-basin and urban-watershed models were calibrated for the nine watersheds using 5-minute interval rainfall data from the Tampa, Florida, National Weather Service rain gage to simulate annual peak discharge for the period 1906-52. A log-Pearson Type III frequency analysis of the simulated annual maximum discharge was used to determine the 2-, 5-, 10-, 25-, 50-, and 100-year flood discharges for each watershed. Flood discharges were related in a multiple-linear regression to drainage area, channel slope, detention storage area, and an urban-development factor determined by the extent of curb and gutter street drainage and storm-sewer system. The average standard error for the regional relations ranged from + or - 32 to + or - 42%. (USGS)

Florida↗
USGS1984

Channel changes of Powder River between Moorhead and Broadus, Montana, 1939-1978

Bank erosion and changes in channel width, length, and pattern were determined for the Powder River between Moorhead and Broadus, Montana using maps of the bankfull channel made from aerial photographs taken during 1939, 1954, 1967, 1973, and 1978. Contemporaneous daily mean and peak discharge records from Moorhead provide the hydrologic data used to interpret the measurements. Magnitudes and frequency of flows were determined for each interval of time delimited by photographs. Bank erosion is related to the number of days that mean discharge was equal to or greater than bankfull (1.5-year flood). Mean channel width ranged between 264 ft (1973) and 415 ft (1967). The channel was wider after periods of higher annual peak flows. The channel lengthened between 1939 and 1978, although at least 12 meanders cut off between Moorhead and Broadus. Variable rates of lengthening in the reach reflect the degree of bedrock control in the valley and local variations in valley slope. Data from the Powder River verify the concept of thresholds of channel pattern stability that were demonstrated experimentally. (USGS)

Water-Resources Investigations Report↗
USGS1984

Water resources of Ponape, Caroline Islands

Ponape is the third largest island in the western Pacific, with a land area of 129 square miles. The island is volcanic, nearly circular in shape, and covered with lush tropical vegetation. The mountainous interior has the highest peaks in the western Pacific. Annual rainfall at Kolonia and other coastal areas is 191 inches. Inland at higher elevations, the rainfall is considerably higher. The upper Nanpil River basin averages about 340 inches annually. Runoff-to-rainfall ratios for Ponapean streams show that about two thirds of the rain falling on the island runs off. Flow-duration curves show the similarity of the geology, vegetation, and rainfall of the drainage basins and indicate little ground-water contribution to surface runoff. Surface-water quality is excellent as shown by 53 chemical anlyses of water from 19 streams. Water of the Nanpil River, the source of water for the central water system, is especially low in dissolved elements and solids. This report summarizes in one volume all the hydrologic data collected and provides analyses that may be used by planning and public works officials as a basis for making decisions on the development and management of their water resources. (USGS)

Water-Resources Investigations Report↗
USGS1984

Water resources of the Palau Islands

The Palau Islands are a group of 350 islands, ranging in size from a few hundred square feet to the 153-square-mile island of Babelthuap. Babelthuap is the second largest island in the Western Pacific and comprises more than 80 percent of the total land area of the Palau Islands. Most of the islands are uninhabited limestone ridges covered with dense vegetation. These islands have no freshwater resources and are not included in this report. The island of Koror with an area of 3.6 square miles is the administrative, commercial, and population center of Palau and has an annual average rainfall of 148 inches. Short-term rainfall records at other locations in the islands indicate little variation in annual rainfall throughout the Palau Islands. Runoff-to-rainfall ratios for streams on Babelthuap show that about 70 percent of the rain falling on the island runs off to the ocean. The uniformity of rainfall and basin characteristics is shown by the excellent correlation between mean annual rainfall on Koror and streamflow on Babelthuap and by the close correlations between discharge at gaging stations and partial-record sites. Surface water quality is generally very good as shown by 55 chemical analyses of water from 18 sources. The dissolved solids concentration of water samples did not exceed 66 milligrams per liter. This report summarizes in one volume hydrologic data collection in a 14-year period of study and provides interpretations of the data than can be used by planners and public works officials as a basis for making decisions on the development and management of the islands' water resources.

Water-Resources Investigations Report↗
USGS1984

Water resources of Kosrae, Caroline Islands

Kosrae is a high volcanic island about 42 square miles in area and the easternmost of the Caroline Islands. Mount Finkol (Mt. Crozer), at 2,065 feet, is the highest point on the island. Mountainous ridges descend sharply to narrow coastal strips which support a population of 5,500 people. Many streams, some quite large relative to the size of the island, drain radially from the interior. The average annual discharge of surface water amounts to almost 7 million gallons per square mile per day. Annual rainfall for coastal areas on Kosrae averages about 200 inches, and is similar to the rainfall for coastal areas on the island of Ponape, about 340 statute miles to the northwest. Rainfall in the interior was estimated at 225 inches per year of which about two thirds runs off as streamflow. Surface-water quality is very good as shown by 42 chemical analyses of water from 12 streams. This report summarizes in one volume the hydrologic data collected and provides interpretations that can be used by planning and public works officials as a basis for making decisions on the development and management of their water resources. (USGS)

Water-Resources Investigations Report↗
USGS1984

Floods of March 1982, Indiana, Michigan, and Ohio

Rapid melting of a snowpack containing 2 to 6 inches of water equivalent coinciding with moderate rainfall caused flooding in March 1982 across northern Indiana, southern Michigan, and northwestern Ohio. Millions of dollars in property damage and the loss of four lives resulted from the flooding. Peak discharges at several gaging stations in each of the following river basins have recurrence intervals of 50 to greater than 100 years: Wabash, St. Joseph, River Raisin, Maumee, and Kankakee. Flooding in the Wabash River basin was confined to major tributaries draining from the north. The St. Joseph River experienced flooding having a recurrence interval of about 50 years. Peak discharges having recurrence intervals of 50 to greater than 100 years were recorded on the River Raisin. Flooding on most large streams in the Maumee River basin was the worst since 1913. The Kankakee River and its major tributary, Yellow River, recorded peak discharges having recurrence intervals greater than 100 years. Hydrologic data have been tabulated for 83 gaging stations and partial-record sites. Maps are presented to emphasize the severity and untimely sequence of meteorological conditions that provided the potential and triggered the floods. Hydrographs are shown for 32 gaging stations.

Indiana, Michigan, Ohio↗
USGS1984

Hydrology of Area 62, Northern Great Plains and Rocky Mountain Coal Provinces, New Mexico and Arizona

This report summarizes available hydrologic data for Area 62 and will aid leasing decisions, and the preparation and appraisal of environmental impact studies and mine-permit applications. Area 62 is located at the southern end of the Rocky Mountain Coal Province in parts of New Mexico and Arizona and includes approximately 9,500 square miles. Surface mining alters, at least temporarily, the environment; if the areas are unreclaimed, there can be long-term environmental consequences. The land-ownership pattern in Area 62 is complicated. The checkerboard pattern created by several types of ownership makes effective management of these lands difficult. The climate generally is semiarid with average annual precipitation ranging from 10 to 20 inches. Pinons, junipers, and grasslands cover most of the area, and much of it is used for grazing by livestock. Soils vary with landscape, differing from flood plains and hillslopes to mountain slopes. The major structural features of this area were largely developed during middle Tertiary time. The main structural features are the southern San Juan Basin and the Mogollon slope. Coal-bearing rocks are present in four Cretaceous rock units of the Mesaverde Group: the Gallup Sandstone, the Dileo Coal Member, and the Gibson Coal Member of the Crevasse Canyon Formation, and the Cleary Coal Member of the Menefee Formation. Area 62 is drained by Black Creek, the Puerco River, the Zuni River, Carrizo Wash-Largo Creek, and the Rio San Jose. Only at the headwaters of the Zuni River is the flow perennial. The streamflow-gaging station network consists of 25 stations operated for a variety of needs. Streamflow changes throughout the year with variation related directly to rainfall and snowmelt. Base flow in Area 62 is zero indicating no significant ground-water discharge. Mountainous areas contribute the highest mean annual runoff of 1.0 inch. Very few water-quality data are available for the surface-water stations. Of the nine surface-water stations that have water-quality data, only one has chemical analyses from more than 10 samples. Therefore, sufficient data to characterize the area in detail are not available. Suspended sediment data are available only for a few surface- water stations in the area. Erosion rates generally are less than 1 acre-foot per square mile per year. Greater erosion rates are found within the badland areas. Water levels are periodically measured at 21 selected wells in Area 62. These observation wells are located mostly along the Rio San Jose and northeast of Gallup, New Mexico. The recharge to ground-water aquifers generally coincide with areas of greater precipitation in the mountainous areas. Depth to water below land surface is generally less than 200 feet. Well yields of 100 gallons per minute are common in most of the area. Ground-water quality is variable both within each aquifer and between aquifers. Water quality generally is best near recharge areas. Historical and current data related to stream discharge, water quality, and suspended sediment are available from computer files in the U.S. Geological Survey's National Water Data Storage and Retrieval System (WATSTORE) and through the National Water Data Exchange (NAWDEX).

Water-Resources Investigations Report↗
USGS1986

Ground-water availability and water quality at Southbury and Woodbury, Connecticut

Increases in population and commercial and industrial development during the past 20 years have increased the demand for water in the Towns of Southbury and Woodbury, Connecticut. The stratified-drift aquifer, underlying much of the Pomperaug River valley, is the most practical source for additional large supplies. The yield of the aquifer was evaluated with a two-dimensional, digital flow model. The model was constructed with hydrologic data from previous studies, and test boring logs , seismic profiles, water-level measurements, and other information collected during the present study. Simulations made with the calibrated model indicate that, with no pumpage, groundwater levels in the aquifer will fall about 4.6 ft below average during low-recharge (least-favorable) periods, and rise about 0.6 ft above average during high-recharge (most-favorable) periods. Simulated withdrawals from 10 wells indicate that from 5.0 to 8.8 million gallons/day are available as total recharge rates range from 21.4 to 36.1 inches/year. If these pumpages were consumed or exported from the basin, estimated average flow reductions of the Pomperaug River would range from 7.7 to 12.9 cu ft/sec. The quality of the water from the stratified-drift aquifer is generally excellent in most areas and meets State drinking-water standards. Chemical analyses of groundwater from 11 wells in the Middle Quarter area of Woodbury indicate that organohalide compounds are present. A maximum trichloroethane concentration of 260 micrograms/L has been reported and groundwater in the area is presently being monitored for organohalides. The water meets standards established by the State. Surface water samples collected at 7 sites in the study area meet the Connecticut drinking water standards for all constituents except coliform bacteria. Complete conventional treatment of surface water from some wells will be required to meet State drinking water standards relative to coliforms. (USGS)

Water-Resources Investigations Report↗
USGS1984

Geohydrologic conditions in the Vekol Valley, Pinal and Maricopa Counties, Arizona-1983

Vekol Valley is a north-trending valley in south-central Arizona. The valley includes 270 mi 2 and is bounded by the Table Top and Vekol Mountains on the east, the Sand Tank and Maricopa Mountains and the White Hills on the west, and the Both and Haley Hills on the north. The climate is semiarid and precipitation occurs as local summer thunderstorms and regional winter storms. The average annual precipitation is 7 to 8 in., and the potential evaporation rate is about 10 times that of the average annual rainfall (Sells and Hill, 1974, p. 7, 44). Storm runoff occurs mainly as sheetflow and floods of short duration. Although some runoff is diverted into catchment tanks for use by livestock, runoff is not used for irrigation or public supply. Vekol Valley is underlain by a thick sequence of basin sediments, sedimentary rocks, and volcanic rocks. The surrounding mountains are composed of crystalline and volcanic rocks, which also underlie the basin sediments to form the sides and bottom of the basin. The valley is divided into a northern part and a southern part by a bedrock outcrop of crystalline rocks between the White Hills on the west and the Table Top Mountains on the east (R. P. Wilson, 1979, p. 8). The northern part is about 90 mi 2 (J. R. Marie and K. J. Hollett, U.S. Geological Survey, written commun., 1984) and the southern part is about 180 mi 2 . The hydrologic data on which this map is based are available, for the most part, in computer-printout form and may be consulted at the Arizona Department of Water Resources, 99 East Virginia, Phoenix, and the U.S. Geological Survey offices in: Federal Building, 301 West Congress Street, Tucson , and 3788 North 16th Street, Suite E, Phoenix. Material from which copies can be made at private expense is available at the Tuscon and Phoenix offices of the U.S. Geological Survey.

Arizona↗
USGS1985

Summary of northern Atlantic Coastal Plain hydrology and its relation to disposal of high-level radioactive waste in buried crystalline rock – A preliminary appraisal

Interpretation of available hydrologic data suggests that some areas beneath the Coastal Plain in the States of Delaware, Maryland, New Jersey, North Carolina, and Virginia might have some potential for the disposal of nuclear waste in crystalline rock that is buried beneath the Coastal Plain sediments. The areas of major interest occur where the top of the basement rock lies between 1,000 and 4,000 feet below sea level, the aquifer(s) immediately above the basement rock are saturated with saline water, confining material overlies the saline water bearing aquifer(s), and groundwater flow in the saline water aquifer(s) can be established. Preliminary data on (1) the distribution and thickness of the lowermost aquifers and confining beds, (2) the distribution of hydraulic conductivity in the lowermost aquifers, (3) estimated hydraulic heads and inferred direction of lateral groundwater flow for 1980, and (4) the distribution of saline water and brine, indicate eastern parts of the study area relatively best meet most of the criteria proposed for sediments that would overlie any potential buried crystalline-rock disposal site.

Delaware, Maryland, New Jersey, North Carolina, Vi↗
USGS1986

Preliminary evaluation of the basal sandstone in Tennessee for receiving injected wastes

The U.S. Environmental Protection Agency is authorized, under the Safe Drinking Water Act, to administer the Underground Injection Control program. This program allows for the regulation of deep-well disposal of wastes and establishes criteria to protect underground sources of drinking water from contamination. The basal sandstone in Tennessee occurs west of the Valley and Ridge province at depths of 5,000 to 9,000 feet below land surface. The basal sandstone consists of about 30 to 750 feet of Cambrian sandstone overlying the crystalline basement complex. The basal sandstone is overlain and confined by shale and carbonate rocks of the Middle and Upper Cambrian Conasauga Group. Hydrologic data for the basal sandstone, available from only three sites (four wells) in Tennessee, indicate that the basal sandstone generally has low porosity and permeability with a few zones having enough permeability to accept injected fluids. Limited water-quality data indicate the basal sandstone contains water with dissolved-solids concentrations exceeding 10,000 milligrams per liter. Since the dissolved-solids conce ntrations exceed 10,000 milligrams per liter, the basal sandstone is not classified as an underground source of drinking water according to U.S. Environmental Protection Agency regulations.

Tennessee↗
USGS1986

Hydraulic properties of rock units and chemical quality of water for INEL-1 — A 10,365-foot deep test hole drilled at the Idaho National Engineering Laboratory, Idaho

A 10,365-ft deep test hole drilled at the INEL (Idaho National Engineering Laboratory) in southeastern Idaho provided hydraulic information for rock units underlying the Snake River Plain aquifer. Four aquifer tests showed that the hydraulic conductivity decreased with depth--from an average of 0.03 ft/day for the interval from 1,511 to 2,206 ft below land surface to an average of 0.002 ft/day for the interval from 4 ,210 to 10,365 ft. In contrast the hydraulic conductivity of the Snake River Plain aquifer ranges from 1 to 100 ft/day. The hydraulic head increased with depth; the head at depth was about 115 ft greater than that for the Snake River Plain aquifer. Water temperature in the test hole increased from 26 C at 600 ft below land surface to 146 C at 9,985 ft. The gradient was nearly linear and averaged about 1.3 C/100 ft of depth. Water from the Snake River Plain aquifer contained 381 mg/L of dissolved solids and had a calcium bicarbonate chemical composition. The dissolved solids concentration in underlying rock units ranged from 350 to 1,020 mg/L and the water had a sodium bicarbonate composition. Hydrologic data for the test hole suggest that the effective base of the Snake River Plain aquifer near the test hole is between 840 and 1,220 ft below land surface. The upward vertical movement of water into the Snake River Plain aquifer from underlying rock units could be on the order of 15,000 acre-ft/year at INEL. (Author 's abstract)

Idaho↗
USGS1989

Suspended-sediment yields from an unmined area and from mined areas before and after reclamation in Pennsylvania, June 1978-September 1983

The U.S. Geological Survey, in cooperation with the Pennsylvania Department of Environmental Resources, has collected hydrologic data from areas in Tioga, Clearfield, and Fayette Counties to determine the effects of surface coal mining on sediment yields. The data were collected from June 1978 through September 1983. Rainfall, streamflow and suspended-sediment data were collected with automatic recording and sampling equipment. Data were collected in Tioga County from an agricultural area that was unaffected by mining and from a forested area prior to surface mining. Data were collected from two areas affected by active surface mining in Tioga County and from an area in Clearfield County being mined by the contour-surface method. Data also were collected from three areas, Tioga, Clearfield, and Fayette Counties, during and after reclamation. The efficiencies of sediment-control pounds in Clearfield and Fayette Counties also were determined. The average annual sediment yield from the agricultural area in Tioga County, which was 35 percent forested, was 0.48 ton per acre per year, and the yield from the forested area prior to mining was 0.0036 ton per acre per year. The average annual sediment yields from the areas affected by active surface mining were 22 tons per acre from the improved haul road and 148 tons per acre from the unimproved haul road. The average annual sediment yield from the site in Clearfield County that had been prepared for mining was 6.3 tons per acre. The average annual sediment yield from the same site while it was being mined by the contour method was 5.5 tons per acre per year. The sediment-control pond reduced the average annual sediment yield to 0.50 ton per acre while the site was prepared for mining and to 0.14 ton per acre while the site was being mined. Because the active surface mining reduced the effective drainage area to the pond, the sediment yield decreased from 0.50 to 0.14 ton per acre. Average annual suspended-sediment yields from the reclaimed site in Tioga County were 1.0 ton per acre during the first year, when vegetation was becoming established, and 0.037 ton per acre during the second year, when vegetation was well established. The average annual sediment yield below a 21.2-acre, reclaimed, surface mine in Clearfield County that had been mined by the contour method was 15 tons per acre during the first year when vegetation was becoming established. However, the average annual sediment yield below a sediment-control pond at this reclaimed site in Clearfield County was 0.30 ton per acre. Data collected from a 4.2-acre reclaimed area that had been surface mined by the block-cut method in Fayette County showed that annual sediment yields from the area were 77 tons per acre in 1981 (no vegetation), 32 tons per acre in 1982 (sparse vegetation), and 1.0 ton per acre in 1983 (well-esatablished vegetation). The average annual yield below a sediment-control pond at the mine site in Fayette County was 0.19 ton per acre during the 27 months of data collection.

Water-Resources Investigations Report↗
USGS1989

Water resources of Sedgwick County, Kansas

Hydrologic data from streams, impoundments, and wells are interpreted to: (1) document water resources characteristics; (2) describe causes and extent of changes in water resources characteristics; and (3) evaluate water resources as sources of supply. During 1985, about 134,200 acre-ft of water (84% groundwater) were used for public (42%), irrigation, (40%), industrial (14%), and domestic (4%) supplies. Streamflow and groundwater levels are related directly to precipitation, and major rivers are sustained by groundwater inflow. Significant groundwater level declines have occurred only in the Wichita well field. The Arkansas and Ninnescah Rivers have sodium chloride type water; the Little Arkansas River, calcium bicarbonate type water. Water quality characteristics of water in small streams and wells depend primarily on local geology. The Wellington Formation commonly yields calcium sulfate type water; Ninnescah Shale and unconsolidated deposits generally yield calcium bicarbonate type water. Sodium chloride and calcium sulfate type water in the area often have dissolved-solids concentrations exceeding 1,000 mg/L. Water contamination by treated sewage effluent was detected inparts of the Arkansas River, Little Arkansas River, and Cowskin Creek. Nitrite plus nitrate as nitrogen contamination was detected in 11 of 101 wells; oilfield brine was detected in the Wichita-Valley Center Floodway, Prairie Creek, Whitewater Creek, and 16 of 101 wells; and agricultural pesticides were detected in 8 of 14 impoundments and 5 of 19 wells. Generally, the water is acceptable for most uses. (USGS)

Water-Resources Investigations Report↗
USGS1990

Water quality characteristics of inflow to and outflow from B. Everett Jordan Lake, North Carolina, 1982-86

B. Everett Jordan Lake, a 13,900-acre reservoir in the north-central Piedmont of North Carolina, was completed in February 1982. Hydrologic data were collected at four inflow sites and one outflow site to define water-quality characteristics. Data include streamflow data and 56 physical and chemical characteristics of streamwater. Concentrations of some constituents at inflow sites were as much as 83-times greater than background concentrations in streams relatively unaffected by man. At the outflow site, however, some of these constituents were only as much as 6-times greater. The minimum dissolved-oxygen concentration measured at an inflow site was 1.0 mg/L, whereas the minimum concentration measured at the outflow site was 4.9 mg/L. Significant differences in other physical characteristics between inflow and outflow sites include a reduction in maximum concentration of suspended sediment from 2,360 mg/L in an inflow sample to 130 mg/L at the outflow site and a reduction of maximum specific conductance values from more than 1,100 microsiemens/centimeter in an inflow sample to 301 microsiemens/centimeter in outflow. The maximum concentration of total nitrogen at inflow sites was 27.0 mg/L compared with 3.2 mg/L at the outflow site. The maximum total phosphorus concentration at inflow sites was 13.0 mg/L compared with 0.6 mg/L at the outflow site. Average annual loads of total nitrogen and total phosphorus in the outflow were as much as 67% and 40% of inflow loads, respectively. Maximum yields at an inflow site were 5.8 t/sq mi (tons per square mile) for nitrogen and 1.4 t/sq mi for phosphorus. Yields of these constituents at the outflow site were 1.5 and 0.2 t/mi, respectively.

North Carolina↗