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Groundwater quality observation networks are examples of discontinuous sampling on variables presenting spatial continuity and highly skewed frequency distributions. Anywhere in the aquifer, lognormal kriging provides estimates of the variable being sampled and a standard error of the estimate. The average and the maximum standard error within the network can...

Exploration for natural resources is accomplished through partial sampling of extensive domains. Such imperfect knowledge is subject to sampling error. Complex systems of equations resulting from modelling based on the theory of correlated random fields are reduced to simple analytical expressions providing global indices of estimation variance. The indices are...

Recursive algorithms for estimating the states of nonlinear physical systems are developed. This requires some key hypotheses regarding the structure of the underlying processes. Members of this class of random processes have several desirable properties for the nonlinear estimation of random signals. An assumption is made about the form of...

In April 1979 and April 1980, major flooding along the lower Pearl River caused extensive damage to homes located on the flood plain in the Slidell, Louisiana, area. In response to questions about causes of these floods and means of mitigating future floods, the U.S. Geological Survey, in cooperation with...

The program named PHRQPITZ is a computer code capable of making geochemical calculations in brines and other electrolyte solutions to high concentrations using the Pitzer virial-coefficient approach for activity-coefficient corrections. Reaction-modeling capabilities include calculation of (1) aqueous speciation and mineral-saturation index, (2) mineral solubility, (3) mixing and titration of aqueous...

During 1979-81, the U.S. Geological Survey conducted a large-scale study of the Apalachicola River in northwest Florida, the largest and one of the most economically important rivers in the State. Termed the Apalachicola River Quality Assessment, the study emphasized interrelations among hydrodynamics, the flood-plain forest, and the nutrient-detritus flow through...

No abstract available. ...

Ground water in the 3,458-square-mile lower Susquehanna River basin occupies secondary openings in bedrock. The distribution of openings is a function of lithology, depth, and topography. Local flow systems account for most of the total ground-water flow. Average annual recharge for the lower basin is 1,857 million gallons per day,...

Aquifers in Island County, Washington, that are intruded by seawater from Puget Sound contain chloride concentrations that exceed 100 mg/L. Chloride concentrations exceeded 100 mg/L in 24 % of the wells that were drilled below sea level and sampled in August 1981, but most of the chloride concentrations did not...

A modification of the one-sixth order semi-quantitative emission spectrographic method for the analysis of 30 elements in geologic materials (Grimes and Marranzino 1968) improves the limits of determination of some volatile to moderately volatile elements. The modification uses a compound-pendulum-mounted filter to regulate the amount of emitted light passing into...

The distribution and abundance of phytoplankton in the fresh, tidal Potomac River, Md., was different during 1979-81 from that observed in the 1960's and 1970's. Concentrations of phytoplankton in the 1960's and 1970's reached maximum attainable levels that were limited only by self-shading. A sag in phytoplankton abundance, apparent during...

The characteristics and distributions of near-surface bottom sediments and of nutrients in the sediments provide information on modern sediment and nutrient sources, sedimentation environments, and geochemical reactions in the tidal Potomac system, Maryland and Virginia. This information is fundamental to an improved understanding of sedimentation and eutrophication problems in the...

Hydrogeologic factors influencing leachate movement from an in-situ oil-shale retort near Rock Springs, Wyoming, were investigated through models of ground-water flow and solute transport. Leachate, indicated by the conservative ion thiocyanate, has been observed ? mile downgradient from the retort. The contaminated aquifer is part of the Green River Formation...

A finite-difference model that simulates three-dimensional flow of groundwater was modified to simulate steady flow of freshwater in a multiple-aquifer system containing freshwater and static saltwater. The two fluids are assumed to be immiscible, with constant but different densities, and are separated by a sharp interface. The interface position computed...

This manual describes the U.S. Geological Survey Minimonitor Water Quality Data Measuring and Recording System. Instructions for calibrating, servicing, maintaining, and operating the system are provided. The Survey Minimonitor is a battery-powered , multiparameter water quality monitoring instrument designed for field use. A watertight can containing signal conditioners is connected...

Freshwater to supply Hilton Head Island, S.C., is obtained from the upper permeable zone of the Upper Floridan aquifer. Long-term pumping at Savannah, Ga., and the steadily increasing pumping on Hilton Head Island, have lowered Upper Floridan heads near the center of the island from about 10 feet above sea...

The northern divide of the Susquehanna River basin crosses 29 broad valleys that contain thick glacial deposits but are drained only by small headwater streams. Much groundwater could be withdrawn from sand and gravel deposits in these valleys with little immediate effect on streamflow. A digital model of the headwater...

The interpretation of geochemical data from a regional survey of the Aban al Ahmar quadrangle resulted in the selection of areas for follow-up studies. The results of detailed geochemical studies of these areas, combined with field observation, resulted in the selection of areas of moderate to high mineral resource potential....

RIV2 is a package for the U.S. Geological Survey 's modular, three-dimensional, finite-difference, groundwater flow model developed by M. G. McDonald and A. W. Harbaugh that simulates river-discharge routing. RIV2 replaces RIVI, the original river package used in the model. RIV2 preserves the basic logic of RIV1, but better represents...

Because of the imbalance between recharge and pumpage, groundwater levels declined as much as 100 ft in some areas of Borrego Valley, California during drinking 1945-80. As an aid to analyzing the effects of pumping on the groundwater system, a three-dimensional finite-element groundwater flow model was developed. The model was...

An existing groundwater model was used to simulate changes in groundwater flow caused by hypothetical pumping in an area near the south-eastern part of Carson City, Nevada. A total of five hypothetical pumping patterns were used in the model simulations. The simulations assumed two pumping rates: total annual average pumpage...

An existing groundwater model of Carson Valley was used to simulate changes in groundwater flow on the east side of Carson Valley, Nevada, in response to hypothetical increases in groundwater pumpage. Pumpage scenarios that reflect State groundwater permits and pending applications were used in four different simulations to estimate the...

This report presents a finite-difference model and its associated modular computer program. The model simulates flow in three dimensions. The report includes detailed explanations of physical and mathematical concepts on which the model is based and an explanation of how those concepts are incorporated in the modular structure of the...