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Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

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At least 181 records · Page 10Linked to original sources
USGS1995

Nonpoint sources of pesticides in the San Joaquin River, California; input from winter storms, 1992-93

Organophosphate insecticides, including chlor- pyrifos, diazinon, and methidathion, are applied to dormant orchards in the San Joaquin Valley, California, during late December through January. This time frame coincides with the period of heaviest rainfall in the valley, and rainfall mobilizes a portion of these pesticides from the orchards. The pesticides enter the San Joaquin River and have been detected along the perennial reach of the river. A storm on the evening of February 7 and the morning of February 8, 1993, deposited more than an inch and a half of rain in the San Joaquin Valley. Two distinct peaks of organophosphate pesticide concentrations were measured at the mouth of the San Joaquin River during a single rise in discharge. Both peaks were attributed to contrasts between the soil texture and hydrology of the eastern and western valley. The fine soil texture and small size of the western tributary basins contributed to rapid runoff. Diazinon concentrations peaked within hours after rainfall ended and then decreased because of a combination of dilution with pesticide-free runoff from the nearby Coast Ranges and decreased pesticide concentrations in the agricultural runoff. Data for the Merced River, a large tributary of the eastern San Joaquin Valley, are sparse, but indicate that peak concentrations occurred at least a day after those of the western tributary streams. That delay may be due to the presence of well-drained soils, the larger size of the drainage basins, and the management of surface-water drainage networks. Runoff from a subsequent storm, on February 18 and 19, contained significantly lower concentrations of most organophosphate pesticides, indicating that runoff from the first storm had already removed most of the pesticides available for rainfall-induced transport.

Open-File Report↗
USGS1996

Documentation of model input and output values for the simulation of the ground-water flow system in the Cretaceous-age Coastal Plain aquifers of South Carolina

This report and the attached 3 1/2-inch diskette contain, in compressed format, the data sets for the model of ground-water flow in the Cretaceous-age Coastal Plain aquifers of South Carolina. The data sets can be uncompressed using a program provided with this report. The uncompressed files require approximately 3.7 megabytes of disk space on an IBM-compatible microcomputer1 using the MS-DOS operating system. All files are in American Standard Code for Information Interchange format.

South Carolina↗
USGS2007

U.S. Geological Survey input-data form and operational procedure for the assessment of conventional petroleum accumulations: Chapter 25 in Petroleum systems and geologic assessment of oil and gas in the San Joaquin Basin Province, California

The U.S. Geological Survey model for undiscovered conventional accumulations is designed to aid in the assessment of crude oil, natural gas, and natural gas liquids (collectively called petroleum) resources. Conventional accumulations may be described in terms of discrete fields or pools localized in structural and stratigraphic traps by the buoyancy of oil or natural gas in water. Conventional accumulations are commonly bounded by a down-dip water contact. The assessment model requires estimates of the number and sizes of undiscovered conventional accumulations. Technically recoverable petroleum resources from undiscovered conventional accumulations are calculated by statistically combining probability distributions of the estimated number and sizes of undiscovered accumulations, along with associated risks and coproduct ratios. Probabilistic estimates of petroleum resources are given for oil in oil accumulations, gas (associated/dissolved) in oil accumulations, natural gas liquids in oil accumulations, gas (nonassociated) in gas accumulations, and total liquids (oil and natural gas liquids) in gas accumulations.

Professional Paper↗
USGS2005

Water quality, hydrology, and phosphorus loading to Little St. Germain Lake, Wisconsin, with special emphasis on the effects of winter aeration and ground-water inputs

Little St. Germain Lake is a 978-acre, multibasin lake in Vilas County, Wisconsin. In the interest of protecting and improving the water quality of the lake, the Little St. Germain Lake District initiated several cooperative studies with the U.S. Geological Survey between 1991 and 2004 to (1) document the water quality and the extent of winter anoxia in the lake, (2) evaluate the success of aerators at eliminating winter anoxia, (3) develop water and nutrient budgets for the lake, and (4) assess how the water quality of the lake should respond to changes in phosphorus loading. This report presents the results of these cooperative studies with special emphasis on the water quality in the lake since 2000, including the effects of winter aeration and the importance of ground-water contributions of phosphorus to the productivity of the lake. Measurements collected during these studies indicate that the water quality in Little St. Germain Lake was consistently different among basins. The West Bay consistently had the best water quality, the South Bay had intermediate water quality, and the East and Upper East Bays consistently had the worst water quality. The water quality in each of the basins was relatively stable from 1991 to 2000; however, since 2001, the West Bay has changed from oligotrophic to mesotrophic, the South Bay has changed from mesotrophic to eutrophic, and the East and Upper East Bays have changed from eutrophic to eutrophic/hypereutrophic. Winter anoxia frequently occurred throughout most of the lake, except in the West Bay and just below the ice in the East Bay. To eliminate winter anoxia, coarse-bubble line aerators were installed and operated in the Upper East, East, and South Bays. The aerators in the Upper East and South Bays were very successful at eliminating winter anoxia; however, the aerator in the East Bay had little impact on the dissolved oxygen concentrations throughout its basin. Detailed water and phosphorus budgets computed for the lake indicated that inflow from Muskellunge Creek was the major source of phosphorus to the lake and that ground water was the secondary source. Results from a detailed ground-water-flow model indicated that ground water flows into the lake from all sides, except the south sides of the West and Second South Bays. Most of the phosphorus appears to come from natural sources, such as ground water and surface water flowing through relatively undeveloped areas surrounding Little St. Germain Lake and Muskellunge Lake. Several empirical water-quality models were used to simulate how the East and Upper East Bays of the lake should respond to reductions in phosphorus loading from Muskellunge Creek. Simulation results indicated that reductions in tributary loading could improve the water quality of the East and Upper East Bays. Improving the water quality of these bays would also improve the water quality of the South and Second South Bays because of the flow of water through the lake. However, even with phosphorus loading from Muskellunge Creek completely eliminated, most of the lake would remain borderline mesotrophic/eutrophic because of the contributions of phosphorus from ground water.

Wisconsin↗
USGS2011

Hydrography of and biogeochemical inputs to Liberty Bay, a small urban embayment in Puget Sound, Washington

This multi-chapter report describes scientific and logistic understanding gained from a 2 year proof-of-concept study in Liberty Bay, a small urban embayment in central Puget Sound, Washington. The introductory chapter describes the regional and local setting, the high-level study goals, the site-specific urban stressors, and the interdisciplinary study approach. Subsequent data chapters describe detailed studies of various components of the Liberty Bay ecosystem: the aquatic environment (Chapter 2), surface and groundwater quantity and quality (Chapter 3), sediment quality (Chapter 4), eelgrass habitat (Chapter 5), carbon and nitrogen sources (Chapter 6), and a statistical model relating herring spawn probability to shoreline attributes (Chapter 7). The final chapter synthesizes knowledge about individual components into a system-wide understanding of how urbanization may affect the Liberty Bay ecosystem. The Liberty Bay study was conducted as part of the U.S. Geological Survey's Coastal Habitats in Puget Sound project, an interdisciplinary collaboration to understand physical and biological processes that affect nearshore ecosystems.

Scientific Investigations Report↗
USGS2020

Updating data inputs, assessing trends, and evaluating a method to estimate probable high groundwater levels in selected areas of Massachusetts

A method to estimate the probable high groundwater level in Massachusetts, excluding Cape Cod and the islands, was developed in 1981. The method uses a groundwater measurement from a test site, groundwater measurements from an index well, and a distribution of high groundwater levels from wells in similar geologic and topographic settings. The U.S. Geological Survey, in cooperation with the Massachusetts Department of Environmental Protection, conducted an update to the Frimpter method for estimating the probable high groundwater levels in Massachusetts. The study evaluated the potential changes to the method resulting from four decades of additional groundwater-level data and the expansion of the network of wells for monitoring groundwater levels. The differences and potential benefits of daily, as opposed to monthly, measurements in the application of the method were examined because of the increased availability of high-frequency (subdaily) groundwater-level data. The study also considered long-term trends in groundwater levels that may alter the accuracy of the method. Finally, the accuracy of the estimated high groundwater levels was evaluated, and improved implementation guidance was prepared. For this study, groundwater levels in 153 wells in Massachusetts and surrounding States with records with lengths of 16 to 78 years were analyzed. The highest recorded groundwater levels ranged from 1.2 feet (ft) above land surface (flooded conditions) to 45.8 ft below land surface, with a median of 4.6 ft below land surface. The maximum annual groundwater-level range was 1.4 to 17.9 ft, with a median of 5.5 ft. The within-month variation, maximum annual groundwater-level range, and highest recorded groundwater level were computed using daily mean groundwater-level values from 28 wells with continuous records. The use of daily data resulted in larger maximum annual groundwater-level ranges (0.02 to 2.94 ft larger, with a median of 0.58 ft larger) and shallower highest-recorded groundwater levels (0.0 to 1.60 ft shallower, with a median of 0.18 ft shallower) than computations based on monthly measurements in the same wells. Statistical tests showed moderate to strong evidence of trends in measurements of both high and low groundwater levels within most of the periods during which water levels were analyzed. High groundwater levels rose beneath the land surface at most sites during four of the six periods used for analysis (1966–2015, 1986–2015, 1991–2010, and 1981–2010). Low groundwater levels also increased at many sites during most of the periods evaluated, but this trend was less widespread than the similar trends in high groundwater levels, and the trend was to deeper low groundwater levels at more sites than the trend to deeper high groundwater levels. There was no clear trend in annual groundwater-level ranges at most sites during the six periods analyzed. In general, the Frimpter method predicted shallower (higher) high groundwater levels than were observed but correctly classified sites according to their suitabilities for unmounded septic systems. The mean error of the predictions (difference between the estimated and observed groundwater levels) ranged from −3.23 ft to −1.40 ft for various approaches to estimating the groundwater-level range and selecting an index well. The method correctly classified 83 to 86 percent of monitoring-well sites according to their suitability for an unmounded septic system for many approaches to estimating the annual groundwater-level range and selecting an index well. The approach selected for estimating the annual groundwater-level range and selecting an index well will depend upon the importance of an accurate estimate of the high groundwater level as compared to the importance of an estimated high groundwater level that is less likely to be exceeded.

Connecticut, Massachusetts, New Hampshire, Rhode I↗
USGS2015

Inaccuracies in sediment budgets arising from estimations of tributary sediment inputs: an example from a monitoring network on the southern Colorado plateau

Sediment budgets are an important tool for understanding how riverine ecosystems respond to perturbations. Changes in the quantity and grain-size distribution of sediment within river systems affect the channel morphology and related habitat resources. It is therefore important for resource managers to know if a channel reach is in a state of sediment accumulation, deficit or stasis. Many studies have estimated sediment loads from ungaged tributaries using regional sediment-yield equations or other similar techniques. While these approaches may be valid in regions where rainfall and geology are uniform over large areas, use of sediment-yield equations may lead to poor estimations of sediment loads in semi-arid climates, where rainfall events, contributing geology, and vegetation have large spatial variability.

Arizona↗
USGS2017

Investigation of input reduction techniques for morphodynamic modeling of complex inlets with baroclinic forcing

The Mouth of the Columbia River (MCR) is a complex estuary inlet system characterized by a buoyant plume created by high freshwater flows from the Columbia River into the Pacific Ocean. Data obtained during two major field campaigns have resulted in a comprehensive dataset of hydrodynamics and sediment transport under high (2013) and low (2005) river flow conditions. Through the analysis of this data and model simulations obtained with the Delft3D (MCR) model application we explored the importance and effect of stratification on sand-sized sediment for short- and long-term sediment transport simulations. Stratification influences the sediment transport through much of the estuary, and significantly reduces sediment export at the MCR. A correlation analysis reveals that a similar representative tide that best approximates the spring-neap averaged transport can be selected for both stratified and non-stratified flow. This correspondence implies that standard morphodynamic tide schematizations (e.g. Lesser, 2009) may also be valid in the stratified conditions found at MCR and other highly stratified estuaries.

Columbia River↗