Publications

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No abstract available.

A MODular Finite-Element, digital-computer program (MODFE) was developed to simulate steady or unsteady-state, two-dimensional or axisymmetric ground-water-flow. The modular structure of MODFE places the computationally independent tasks that are performed routinely by digital-computer programs simulating ground-water flow into separate subroutines, which are executed from the main program by cont

A MODular, Finite-Element digital-computer program (MODFE) was developed to simulate steady or unsteady-state, two-dimensional or axisymmetric ground-water flow. Geometric- and hydrologic-aquifer characteristics in two spatial dimensions are represented by triangular finite elements and linear basis functions; one-dimensional finite elements and linear basis functions represent time. Finite-elemen

Soluble tracers can be used to simulate the transport and dispersion of soluble wastes that might have been introduced or are planned for introduction into surface waters. Measured tracer-response curves produced from the injection of a known quantity of soluble tracer can be used in conjunction with the superposition principle to simulate potential waste buildup in streams, lakes, and estuaries.

Modifications to the computer code for nonlinear regression solution of steady-state ground-water flow problems in "Regression Modeling of Ground-Water Flow", by R.L. Cooley and R.L. Naff (U.S. Geological Survey, Techniques of Water Resources Investigations, book 3, chap. B4, 1990), improve the performance of the code. The changes 1) allow any model parameters to be transformed to natural logarith

Excessive precipitation produced severe flooding in a nine-State area in the upper Mississippi River Basin during spring and summer 1993. Following a spring that was wetter than average, weather patterns that persisted from early June through July caused the upper Midwest to be deluged with an unusually large amount of rainfall. Monthly precipitation data were examined at 10 weather-station locati

Heavy rainfall and severe flooding in the upper Mississippi River Basin from mid-June through early August 1993 flushed extraordinarily large amounts of agricultural chemicals (herbicides and nitrate) into the Mississippi River, many of its tributaries, and, ultimately, the Gulf of Mexico. Even though extremely high streamflows were recorded during the flood in 1993, concentrations of herbicides,

From mid-June through early August 1993, flooding was severe in the upper Mississippi River Basin following a wet-weather pattern that persisted over the area for at least 6 months before the flood. The magnitude and timing of several intense rainstorms in late June and July, combined with wet antecedent climatic conditions, were the principal causes of the flooding. Flood-peak discharges that equ

Water withdrawals in the United States during 1990 were estimated to average 408,000 million gallons per day (Mgal/d) of freshwater and saline water for offstream uses--2 percent more than the 1985 estimate. Total freshwater withdrawals were an estimated 339,000 Mgal/d during 1990, about the same as during 1985. Average per-capita use for all offstream uses was 1,620 gallons per day (gal/d) of fre

Data collected at 152 sampling sites during 1970-79 were used to characterize fluvial sediment in North Carolina streams. On the basis of predominant land use in individual basins, sites were categorized into one of five groups: forested (7 sites), forested and affected by minor development (7 sites), rural affected by agriculture (83 sites), rural affected by nonagricultural activities (38 sites)

Accurate delineation of recharge areas for wells is an important requisite to protecting ground-water quality. Zones of transport and zones of contribution are two types of recharge areas that can be delineated. Analytical-calculation, numerical-modeling, and hydrogeologic-mapping methods were used to delineate recharge areas for two high-capacity wells (greater than about 200 gallons per minute d