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Flood hydrographs for 26 gaging stations and rainfall data were used together with a rainfall-runoff simulation model to derive unit hydrographs and important unit-hydrograph variables. Methods were developed for estimating unit hydrographs at ungaged sites using either the Clark or dimensionless unit-hydrograph methods. The 26 derived unit hydrographs were compared...

Operating Criteria and Procedures for Newlands Project irrigation and Public Law 101-618 could result in reductions in surface water used for agriculture in the Carson Desert, potentially affecting ground-water supplies from shallow, intermediate, and basalt aquifers. A near-surface zone could exist at the top of the shallow aquifer near the...

Currently (1993), about 170 kg/yr of phosphorus discharges into Ashumet Pond on Cape Cod from a plume of sewage-contaminated ground water. Phosphorus in the plume is mobile in two distinct geochemical environments--an anoxic zone containing dissolved iron and a suboxic zone containing dissolved oxygen. Phosphorus mobility in the suboxic zone...

Suspended-sediment concentration and discharge data were collected at 7 daily record stations and 70 partial-record stations during 1952- 84. Median suspended-sediment concentrations ranged from 24 to 61 milligrams per liter at daily record stations; concentrations ranged from 6 to 539 milligrams per liter at partial-record stations. Most suspended sediment transported...

An accounting system for estimating and distributing consumptive use of water by vegetation to water users was developed for the Colorado River to meet the requirements of a U.S. Supreme Court decree and used with data from calendar year 1984. The system is based on a water-budget method to estimate...

Analysis of surface-water-quality data has enabled an assessment of water-quality conditions and trends and their relation to human and natural factors in the lower Kansas River basin, Kansas and Nebraska. This basin drains 15,300 square miles of predominantly agricultural land and is one of seven pilot studies completed as part...

In sedimentary deposits beneath arid Las Vegas Valley, ground-water levels have declined as much as 280 feet since 1912 in deeper aquifers due to pumping associated with urban development. Accompanying land subsidence has been as great as 5 feet. Predictive simulations show that by maintaining pumpage and recharge at 1980...

The source of water to wells is ultimately the location where the water flowing to a well enters the boundary surface of the ground-water system . In ground-water systems that receive most of their water from areal recharge, the location of the water entering the system is at the water...

As part of the National Water-Quality Assessment program (NAWQA), existing water-quality data and ancillary information from the Kentucky River basin study unit were compiled and evaluated to provide a description of existing conditions and long-term trends in water quality. The data and evaluations were used to develop a conceptual understanding...

Disposal of munitions and chemical-warfare substances has introduced inorganic and organic contaminants to the ground water, surface water, and bottom sediment at O-Field, in the Edgewood area of Aberdeen Proving Ground, Maryland. Contaminants include chloride, arsenic, transition metals, chlorinated aliphatic hydrocarbons, aromatic compounds, and organosulfur and organophosphorus compounds. The hydrologic...

Major ions, unstable field constitutents, and the environmental isotopes tritium, deuterium, and oxygen-18 were measured in water from 112 wells that are open to the uppermost producing zones of the upper Floridan Aquifer. Tritium analyses indicate that the unconfined aquifer in northern areas contains relatively young water that has entered...

Median monthly atrazine concentrations detected in surface-water samples from the Big Blue River basin (1977-86) exceeded the U.S. Environmental Protection Agency health-advisory level (3.0 micrograms per liter) during May through September. Herbicide loads transported from the basin in 1986, expressed in tons and in percentage of amount applied, were alachlor...

Available surface water-quality data were used to provide an initial assessment of current water-quality conditions for 1978-86, define long-term trends in constituent concentrations, and relate current water-quality conditions and trends to human and natural factors in the lower Kansas River basin, Kansas and Nebraska. This basin drains 15,300 square miles...

The Santa Cruz River in southeastern Arizona has a long history of channel instability. Since the late 19th century, lateral channel erosion has caused extensive property damage, particularly in Pima County. The dominant mechanism of channel change in a reach depends on channel morphology and flood magnitude. The timing and...

The effects of selected agricultural land-management practices on water quality were assessed in a comparative study of four small basins in the Piedmont province of North Carolina. Agricultural practices, such as tillage and applications of fertilizer and pesticides, are major sources of sediment, nutrients, and pesticides in surface water, and...

No abstract available....

Ground water is the sole freshwater supply for the Eastern Shore Peninsula in Virginia. The fresh ground-water-flow system consists of a water-table aquifer underlain by three confined aquifers separated by intervening confining units. Results of simulations using a sharp-interface, ground-water-flow model indicate that current levels of withdrawal have not caused...

Methods and step-by-step examples are presented to estimate (1) peak-frequency relations, (2) flood hydrographs and volumes, and (3) volume-duration frequency relations of small urban streams in Ohio. The methods were developed to assist planners in the design of hydraulic structures for which hydrograph routing is required or where the temporary...

Equations for estimating the 95-, 98-, and 99-percent duration discharges for streams in Massachusetts with natural flow conditions were developed by use of weighted-least-squares regression analyses. Record extension methods were used to estimate the low-flow statistics for sites used in the regression analyses that were lacking complete record during the...

Humification, the process whereby biomass consisting of dead plant and animal remains is converted into soil organic matter (humus), is one of the basic processes of the carbon cycle. The organic compounds that make up plant and animal tissue are thermodynamically unstable in the oxidizing atmosphere at the surface of...

Freshwater for Hilton Head Island, South Carolina, is supplied by withdrawals from the Upper Floridan aquifer. Freshwater for the nearby city of Savannah, Georgia, and for the industry that has grown adjacent to the city, has also been supplied, in part, by withdrawal from the Upper Floridan aquifer since 1885....

No abstract available....

Ground-water quality was assessed in a 5,000-square-mile area of the High Plains aquifer in south-central Kansas that is susceptible to nonpoint-source contamination from agricultural and petroleum-production activities. Of particular interest was the presence of agricultural chemicals and petroleum-derived hydrocarbons that might have been associated with brines that formerly were disposed...