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An increasing dependence on ground-water resources in the Portland Basin has made it necessary for State and local governments to evaluate the capability of the ground-water system to meet present and future demands for water. This report describes the regional ground-water system and provides a conceptualization of the aquifer system....

The Charlotte Harbor estuarine system, having a surface area of about 270 square miles, averages about 7 feet in depth and is connected to deep water of the Gulf of Mexico through several passes and inlets between barrier islands. Three major rivers flow into the estuary--the Peace, the Myakka, and...

A one-dimensional numerical model was developed to simulate the soil water balance of a densely vegetated prairie site in west-central Florida. Transient simulations of the soil water balance were performed using field-measured soil and vegetation properties. Simulated and measured soil water content generally agreed to within 0.04; however, simulated water...

A study was made to examine the near-surface water balance of a dry prairie site in west-central Florida. The water balance, which was defined on a unit area basis and for a depth of 5.5 meters, was described for the period June 1991 to October 1992. Precipitation during the 498...

Statistical operations termed model-adjustment procedures can be used to incorporate local data into existing regression modes to improve the predication of urban-runoff quality. Each procedure is a form of regression analysis in which the local data base is used as a calibration data set; the resulting adjusted regression models can...

MODFLOW and MODPATH numerical models were used to generate areas of contribution to public supply wells for simulated hypothetical anisotropy and heterogeneous carbonate aquifer systems. The simulations incorporated, to varying degrees, the anisotropy and heterogeneity observed in a karst carbonate aquifer system. These include: isotropic and homogeneous single-layer system, doubly-porous...

This volume contains 50 articles describing severe, widespread, or unusual flooding in 28 of the 50 States during 1990 and 1991. Each flood is described to an extent commensurate with its significance and the availability of data on the hydrology and the damages. Each article includes one or more maps...

Available data through 1992 on aquatic biota in the San Joaquin-Tulare Basins study unit of the National Water-Quality Assessment Program were analyzed to provide a conceptual framework to guide study design. The analysis included information on the biology of fish, aquatic macroinvertebrates, aquatic algae, and concentrations of trace elements and...

A three-dimensional model was developed through a parameter-estimation method based on nonlinear regression to simulate ground-water flow in the Lockport Group, a fractured dolomite aquifer near Niagara Falls, N.Y. Horizontal fracture zones within the Lockport Group were represented by model layers, and connections between the zones were represented by vertical...

Water-quality data were collected from the Fountain Creek alluvial aquifer in 1988 and 1989 as part of the Toxic-Waste Ground-Water Contamination Program. These data indicate that dissolved solids, most major ions, fluoride, ammonium, boron, lithium, selenium, and strontium were more concentrated in the agricultural land-use area than in the upgradient...

Two approaches were used to estimate future lake-level probabilities for Devils Lake. The first approach is based on an annual lake-volume model, and the second approach is based on a statistical water mass-balance model that generates seasonal lake volumes on the basis of seasonal precipitation, evaporation, and inflow. Autoregressive moving...

Investigations were conducted in Arizona during the early 1980's to obtain hydrologic data in order to deliver 30,000 acre-feet of water annually to the Ak-Chin Indian Reservation. A recharge experiment produced infiltration rates for an ephemeral stream channel that ranged from 0.64 to 1.09 cubic feet per second per 1,000...

The lower Apalachicola-Chattahoochee-Flint River Basin is underlain by Coastal Plain sediments of pre-Cretaceous to Quaternary age consisting of alternating units of sand, clay, sandstone, dolomite, and limestone that gradually thicken and dip gently to the southeast. The stream-aquifer system consists of carbonate (limestone and dolomite) and elastic sediments, which define...

The micrometeorological methods of energy-balance Bowen ratio and eddy correlation probably are suitable for determining evapotranspiration from unforested sites, but the aerodynamic effects of tall tree canopies need to be considered when the methods are used for forested sites. Potential evapotranspiration methods might not yield reliable estimates of evapotranspiration for...

A numerical model was developed to simulate ground-water flow in the Tri-County region, which consists of Clinton, Eaton, and Ingham Counties, Michigan. This region includes a nine-township area surrounding Lansing, Michigan. The model simulates the regional response of the Saginaw aquifer to major groundwater withdrawals associated with public-supply wells. The...

A model based on de Sant-Venant equations for dynamic flow in open channels was calibrated and verified for a 0.75-mile urbanized reach of Spring Brook, a tributary to the West Branch Du Page River. The model was used to simulate flow in the reach, which passes through two short culverts,...

Hydrologic and geochemical research has identified and characterized the physical and chemical processes that control the evolution and movement of metal contaminants in ground water beneath Miami Wash and lower Pinal Creek. The dissolution of calcite in the alluvial aquifer has slowed and neutralized part of the acidic plume, and...

A computer model that simulates a plume of brackish water in the Biscayne Aquifer has been developed. Simulations showed the remnant plume moving generally south-southeastward after 1985 and gradually dissipating. The plume of brackish water (originating from a well drilled in 1944) will be completely dispersed between 1994 and 2003....

Samples collected at streamflow-gaging stations in the Puerco and Little Colorado rivers show that radioactivity of suspended sediment at gaging stations downstream from inactive uranium mines was not significantly higher than at gaging stations where no mining has occurred upstream. Drinking-water standards for many constituents, however, commonly are exceeded during...

Physical, chemical, and microbial processes controlled transport of a nitrogen-rich ground-water plume through a glacial aquifer. Lithologic heterogeneity and vertical head gradients influenced plume movement and geometry. Nitrate was the predominant nitrogen form and oxygen was depleted in the ground-water plume. However, denitrification transformed only 2 percent of plume nitrogen...

Movement of agricultural chemicals alachlor, atrazine, cyanazine, deethylatrazine, deisopropylatrazine, and metolachlor between surface water and ground water is documented by data collected from May 1989 through July 1991 at an unfarmed study site adjacent to the Cedar River in Iowa. During periods of runoff, these chemicals moved from the Cedar...

Over 120 publications that describe the 1980 eruption effects of Mount St. Helens on rivers, lakes, and the Columbia River estuary are reviewed. Water-quality changes ranged from minor, short-lived effects, to totally altered drainage basins and newly created lakes. Turbidity increased; concentrations of cations, anions, and dissolved organic carbon increased....

Local and regional patterns in the organic content of sediments in the surficial aquifer, as reflected in topography and land use, control dissolved oxygen and nitrate concentrations in ground water that recharged through agricultural fields and flowed beneath riparian woodlands. Dissolved oxygen and nitrate concentrations decreased beneath the woodlands as...

Ground-water samples, core samples, and hydrologic measurements were obtained in the Central Oklahoma Aquifer as part of the pilot National Water-Quality Assessment Program. This report examines ground-water recharge and discharge, the potentiometric surface, the chemical and isotopic composition of ground water, and the abundances and textures of minerals in core...

A dynamical-systems approach was developed and evaluated for computing ice-affected streamflow. The approach provides for dynamic simulation and parameter estimation of site-specific equations relating ice effects to routinely measured environmental variables. Comparison indicates that results from the dynamical-systems approach ranked higher than results from 11 analytical methods previously investigated on...