Geology topics

C. A. Thompson

Publications and source records attributed to C. A. Thompson.

4 recordsLinked to original sources

USGS2010

Reconciling uncertain costs and benefits in bayes nets for invasive species management

Bayes nets are used increasingly to characterize environmental systems and formalize probabilistic reasoning to support decision making. These networks treat probabilities as exact quantities. Sensitivity analysis can be used to evaluate the importance of assumptions and parameter estimates. Here, we outline an application of info-gap theory to Bayes nets that evaluates the sensitivity of decisions to possibly large errors in the underlying probability estimates and utilities. We apply it to an example of management and eradication of Red Imported Fire Ants in Southern Queensland, Australia and show how changes in management decisions can be justified when uncertainty is considered. ?? 2009 Society for Risk Analysis.

Risk Analysis↗

USGS2007

Walnut creek watershed monitoring project, Iowa: Monitoring water quality in response to prairie restoration

Land use and surface water data for nitrogen and pesticides (1995 to 1997) are reported for the Walnut Creek Watershed Monitoring Project, Jasper County Iowa. The Walnut Creek project was established in 1995 as a nonpoint source monitoring program in relation to watershed habitat restoration and agricultural management changes implemented at the Neal Smith National Wildlife Refuge by the U.S. Fish and Wildlife Service. The monitoring project utilizes a paired-watershed approach (Walnut and Squaw creeks) as well as upstream/downstream comparisons on Walnut for analysis and tracking of trends. From 1992 to 1997, 13.4 percent of the watershed was converted from row crop to native prairie in the Walnut Creek watershed. Including another 6 percent of watershed farmed on a cash-rent basis, land use changes have been implemented on 19.4 percent of the watershed by the USFWS. Nitrogen and pesticide applications were reduced an estimated 18 percent and 28 percent in the watershed from land use changes. Atrazine was detected most often in surface water with frequencies of detection ranging from 76-86 percent. No significant differences were noted in atrazine concentrations between Walnut and Squaw Creek. Nitrate-N concentrations measured in both watersheds were similar; both basins showed a similar pattern of detection and an overall reduction in nitrate-N concentrations from upstream to downstream monitoring sites. Water quality improvements are suggested by nitrate-N and chloride ratios less than one in the Walnut Creek watershed and low nitrate-N concentrations measured in the subbasin of Walnut Creek containing the greatest amount of land use changes. Atrazine and nitrate-N concentrations from the lower portion of the Walnut Creek watershed (including the prairie restoration area) may be decreasing in relation to the upstream untreated component of the watershed. The frequencies of pesticide detections and mean nitrate-N concentrations appear related to the percentage of row crop in the basins and subbasins. Although some results are encouraging, definitive water quality improvements have not been observed during the first three years of monitoring. Possible reasons include: (1) more time is needed to adequately detect changes; (2) the size of the watershed is too large to detect improvements; (3) land use changes are not located in the area of the watershed where they would have greatest effect; or (4) water quality improvements have occurred but have been missed by the project monitoring design. Longer-term monitoring will allow better evaluation of the impact of restoration activities on water quality.An overview is given on the Walnut Creek Watershed Monitoring Project established as a nonpoint source monitoring program in relation to watershed habitat restoration and agricultural management changes implemented at the Neal Smith National Wildlife Refuge by the U.S. Fish and Wildlife Services. Focus is on land use and surface water data for nitrogen and pesticides. Initial results obtained for the first three years of monitoring are discussed.

Iowa↗

USGS2002

Temperate zone fens of the glaciated Midwestern USA

A study of more than 70 fens in the Midwestern United States and a review of the literature indicates that these temperate zone wetlands may differ from fens of the boreal zone and are not adequately differentiated from the by present classification systems. Fens of the Midwestern temperate zone 1) are wetlands with high botanical diversity, 2) are supported in part by ground water with conductivity > 100mS/cm and circumneutral pH, 3) contain water in the root zone during most of the growing season yet are not usually innudated, and 4) accumulate organic and/or carbonate substrates. Individually, none of these descriptors is adequate to distinguish fens from other wetland communities of the Midwest such as marshes, sedge meadows, and wet prairies; yet, when they are taken together, such discrimination is possible. While fens of this zone share many species, our study does not support using indicator species because too few are both faithfully represented and geographically widespread. Midwestern temperate fens are sustained by forces of climate, landscape, and geology, which permit ground water to seep continuously into the root zone in a focused location. Since water availability in the temperate Midwest is less than in the boreal zone, continuous discharge is needed to maintain the saturation conducive to peat formation.

Illinois, Indiana, Iowa, Michigan, Minnesota, Miss↗

USGS1992

Availability and quality of water from the alluvial, glacial-drift, and Dakota aquifers and water use in southwest Iowa

A ground-water resources investigation was conducted in southwest Iowa to describe the availability, quality, and use of water from the alluvial, glacial-drift, and Dakota aquifers in a nine-county area. Historical water quality was examined for each aquifer, and water samples were collected for major ions, trace metals, radionuclides, and selected pesticides. Selected aspects of surface-water resources in the study area also were examined to more fully evaluate alluvial aquifers. The flood plain of the Missouri River valley was not included except for the accounting of the water use in the area. Four principal alluvial aquifers consisting of sand and gravel deposits in the valleys of the Nishnabotna, Tarkio, Nodaway, and One Hundred and Two Rivers are present. Yields to wells have been reported as large as 2,000 gallons per minute; however, most yields are less than 100 gallons per minute. Nitrate concentrations greater than the drinking-water regulation and agricultural herbicides have been detected in 6 of 27 samples from municipal water supplies. Four types of glacial-drift aquifers are present-loess, inter-till sand and gravel, basal sand and gravel, and buried-channel aquifers. The glacial-drift aquifers are most commonly used by rural water users or users that do not have access to alluvial aquifers. These aquifers are discontinuous and unpredictable in location. Hydraulic and water-quality data generally are unavailable for these aquifers. Wells completed in loess commonly yield less than 10 gallons per minute, although there are reports of yields as large as 20 gallons per minute. Yields of 10 to 120 gallons per minute appear to be possible for inter-till and basal sand and gravel aquifers. Yields of more than 150 gallons per minute are possible from some buried-channel aquifers. The Dakota aquifer is comprised of bedrock of Cretaceous age and is present as erosional remnants and outliers in several counties, mainly Cass and Montgomery. Yields of more than 150 gallons per minute to wells completed in the Dakota aquifer have been reported, although yields of 20 gallons per minute or less are more typical. The drinking-water regulation for nitrate has been exceeded in some samples from the Dakota aquifer. The quantity of water withdrawn for municipal, rural-domestic, livestock, and other permitted water users was determined for each of the three principal aquifer types. The total water use within the study area was about 91.8 million gallons per day; 35.3 percent was from alluvial ground-water sources. Alluvial aquifers supplied most of the water from ground-water sources. The largest use of water is for permitted irrigation purposes, mostly from the Missouri River alluvial aquifer.

Iowa↗