Geology topics

Bruce D. Lindsey

Publications and source records attributed to Bruce D. Lindsey.

60 records · Page 4Linked to original sources

USGS1998

Ground-water discharge and base-flow nitrate loads of nontidal streams, and their relation to a hydrogeomorphic classification of the Chesapeake Bay watershed, middle Atlantic Coast

Existing data on base-flow and groundwater nitrate loads were compiled and analyzed to assess the significance of groundwater discharge as a source of the nitrate load to nontidal streams of the Chesapeake Bay watershed. These estimates were then related to hydrogeomorphic settings based on lithology and physiographic province to provide insight on the areal distribution of ground-water discharge. Base-flow nitrate load accounted for 26 to about 100 percent of total-flow nitrate load, with a median value of 56 percent, and it accounted for 17 to 80 percent of total-flow total-nitrogen load, with a median value of 48 percent. Hydrograph separations were conducted on continuous streamflow records from 276 gaging stations within the watershed. The values for base flow thus calculated were considered an estimate of ground-water discharge. The ratio of base flow to total flow provided an estimate of the relative importance of ground-water discharge within a basin. Base-flow nitrate loads, total-flow nitrate loads, and total-flow total-nitrogen loads were previously computed from water-quality and discharge measurements by use of a regression model. Base-flow nitrate loads were available from 78 stations, total-flow nitrate loads were available from 86 stations, and total-flow total-nitrogen loads were available for 48 stations. The percentage of base-flow nitrate load to total-flow nitrate load could be computed for 57 stations, whereas the percentage of base-flow nitrate load to totalflow total-nitrogen load could be computed for 36 stations. These loads were divided by the basin area to obtain yields, which were used to compare the nitrate discharge from basins of different sizes. The results indicate that ground-water discharge is a significant source of water and nitrate to the total streamflow and nitrate load. Base flow accounted for 16 to 92 percent of total streamflow at the 276 sampling sites, with a median value of 54 percent. It is estimated that of the 50 billion gallons of water that reaches the Chesapeake Bay each day, nearly 27 billion gallons is base flow. Generalized lithology (siliciclastic, carbonate, crystalline, and unconsolidated) was combined with physiographic province (the Appalachian Plateau, the Valley and Ridge, the Blue Ridge, the Piedmont, including the Mesozoic Lowland section, and the Coastal Plain) to delineate 11 hydrogeomorphic regions. Areal variation of base flow and base-flow nitrate yield were assessed by means of nonparametric, one-way analysis of variance on basins grouped by the dominant hydrogeomorphic region and by correlation analysis of base flow or base-flow nitrate yield with the percentage of land area of a given hydrogeomorphic region within a basin. Base flow appeared to have a significant relation to the hydrogeomorphic regions. The highest percentages of base flow were found in areas underlain by carbonate rock, crystalline rock with relatively low relief, and unconsolidated sediments. Lower percentages were found in areas underlain by siliclastic rocks and crystalline rocks with relatively high relief. The relation between base-flow nitrate yield and hydrogeomorphic region is less clear. Although there is a relation between low nitrate yields and areas underlain by highrelief siliciclastic rocks, and a relation between high yields and carbonate rocks, much of this relation can be explained by the strong association between the hydrogeomorphic units and land use. In addition, most basins are mixtures of several hydrogeomorphic regions, so the nitrate yield from a basin depends on a large number of complex interacting factors. These unclear results indicate that the sample of available data used here may not be adequate to fully assess the relation between base-flow nitrate yield and the hydrogeomorphic setting of the basin. The results appear to show, however, that ground-water discharge is an important component of the total nontidal streamflow, and that ground-water discharge varies according to the hydrogeomorphic regions. Environmental management of the nontidal streams in the Chesapeake Bay watershed will thus have to consider the prevention of nutrient infiltration into aquifers as well as prevention of overland runoff of high-nitrogen waters.

Chesapeake Bay watershed↗

USGS1997

Water-quality assessment of the Lower Susquehanna River Basin, Pennsylvania and Maryland: Design and implementation of water-quality studies, 1992-95

From 1992 through 1995, nearly 1,200 water-quality samples from about 500 sites were collected, processed, and analyzed for the U.S. Geological Survey's (USGS) National Water-Quality Assessment (NAWQA) Program in the Lower Susquehanna River Basin in Pennsylvania and Maryland. Sites were selected and samples were collected for 28 integrated water-quality studies designed to provide a comprehensive and nationally consistent description of current water-quality conditions, to begin to identify trends in water quality, and to determine the major factors that affect observed water quality. To achieve this, stream-water, ground-water, streambed-sediment, and biota samples were collected, and habitat assessments were conducted at selected data-collection sites. This report discusses the water-quality study design, site-selection strategy, and implementation steps used to obtain water-quality and related data. Methods employed to collect, process, and analyze samples, characterize sites, and assess habitat are described. A comprehensive list of all sites employed in these studies and their characteristics is provided. Sample analyses conducted for the water-quality studies described in this report, including nutrients, pesticides, major ions, volatile organic compounds (VOC's), and trace elements, as well as measured or observed physical properties and habitat characteristics, also are listed.

Maryland, Pennsylvania↗

USGS1997

Nitrate in ground water and stream base flow in the lower Susquehanna River Basin, Pennsylvania and Maryland

High concentrations of nitrate in both ground and surface water have been identified as a significant water-quality issue in the Lower Susquehanna River Basin. This report uses data collected by the National Water Quality Assessment (NAWQA) Program in the basin and compares nitrate concentrations found in ground water and surface water on both a spatial and temporal basis and relates nitrate concentrations to land use. Nitrate concentrations in the Lower Susquehanna River Basin in Pennsylvania and Maryland were higher in ground water than in surface water in agricultural areas underlain by carbonate bedrock and agricultural areas underlain by crystalline bedrock. Nitrate concentrations were higher in surface water than in ground water in urban areas underlain by carbonate bedrock. Nitrate concentrations also were higher in surface water than ground water in both agricultural and forested areas underlain by sandstone and shale. Nitrate concentrations in ground water vary in areas with different land use and bedrock type. Ground-water nitrate concentrations were highest in agricultural areas underlain by carbonate bedrock, where 45 percent of the samples exceeded the U.S. Environmental Protection Agency (USEPA) Maximum Contaminant Level (MCL) of 10 mg/L (milligrams per liter as N). Waters from 36 percent of the wells in agricultural areas underlain by crystalline bedrock also had nitrate concentrations greater than 10 mg/L. Nitrate concentrations in water from wells in urban areas underlain by carbonate bedrock and in forested and agricultural areas underlain by sandstone and shale seldom exceeded the MCL. Nitrate concentrations were generally higher in surface water in areas underlain by carbonate bedrock than in areas underlain by noncarbonate bedrock; however, when an agricultural area underlain by carbonate bedrock and an agricultural area underlain by sandstone and shale with similar manure application rates were compared, nitrate concentrations in surface water were not significantly different. A comparison of three agricultural areas underlain by carbonate bedrock shows that the manure application rate is strongly correlated with nitrate concentration. Nitrate concentrations in stream base flow at seven sites where samples were collected throughout the year were commonly higher in the winter months than in the summer months. A statistically significant correlation between streamflow and nitrate concentration existed for six of the seven sites, indicating that seasonal variability in precipitation may be the cause of some of the seasonal variation in concentration. Other possible explanations for this variation include the seasonal cycle in plant uptake of nitrogen and seasonal fluctuations in uptake of nitrate by algae in streams. Because no information was available about the traveltime for ground water, interpretation of this temporal variation was not conclusive. Estimates of base-flow loads and yields of nitrate showed that agricultural areas underlain by carbonate bedrock provide the highest yield of nitrate when compared with the other areas studied. Agricultural areas underlain by sandstone and shale and crystalline bedrock also provide large amounts of nitrate to the river. The large amount of nitrate in the water from these areas cause a significant increase in nitrate loads transported by the Susquehanna River to the Chesapeake Bay. Urban areas underlain by carbonate bedrock had a high yield of nitrate but comprise such a small part of the basin that the nitrate load from these areas was small. In contrast, forested areas underlain by sandstone and shale bedrock had low base-flow nitrate yields, but these areas comprise a large percentage of the basin, making the overall nitrate load from these areas high.

Maryland, Pennsylvania↗

USGS1996

Occurrence and concentrations of volatile organic compounds in shallow ground water in the Lower Susquehanna River Basin, Pennsylvania and Maryland

This report presents the results of a regional assessment of volatile organic compounds (VOC's) in ground water from six sampling areas within the Lower Susquehanna River Basin. The sampling areas, selected to represent aquifers where ground water is used as a drinking water supply, include four areas underlain by limestone, one area underlain by crystalline bedrock, and one area underlain by interbedded sandstone and shale. The land use is rural in five areas and urban in one area. Samples were collected in 1993-95 from 118 wells ranging from 30 to 226 feet deep. Analyses for 60 VOC's at detection levels ranging from 0.05 to 0.2 mg/L (micrograms per liter) reveal the presence of 24 compounds. The compounds were present in water from 32 of the 118 wells. Methyl tert-butyl ether was the most commonly detected compound. Concentrations of methyl tert-butyl ether, found in 16 of the 118 wells, ranged from 0.11 to 51 mg/L. Chloroform was the second most commonly detected compound. The highest concentration detected in a water sample was 61 mg/L of chloroform. None of the detections in samples from wells used as drinking water supplies exceeded the Maximum Contaminant Levels or Lifetime Health Advisory Levels established by the U.S. Environmental Protection Agency. However, the 51 mg/L of methyl tert-butyl ether, detected in water from a monitoring well, is in the 20 to 200 mg/L range proposed for a Lifetime Health Advisory Level. The occurrence of VOC's in limestone aquifers in the Great Valley near Harrisburg, Pa., is influenced by land use. VOC's occur more frequently in the urban area than in the agricultural area. Within the urban area, analyses of samples from wells, springs, and a spring-fed stream show contaminated ground water discharging from springs and flowing into the stream.

Maryland, Pennsylvania↗

USGS1996

Radon in ground water of the lower Susquehanna and Potomac River basins

Ground-water samples collected from 267 wells were analyzed for radon as part of a water-quality reconnaissance of subunits of the Lower Susquehanna and Potomac River Basins conducted by the United States Geological Survey (USGS) as part of the National Water-Quality Assessment (NAWQA) program. Radon is a product of the radioactive decay of uranium. Airborne radon has been cited by the Surgeon General of the United States as the second-leading cause of lung cancer and the United States Environmental Protection Agency (USEPA) has identified ground-water supplies as possible contributing sources of indoor radon. Eighty percent of ground-water samples collected for this study were found to contain radon at activities greater than 300 pCi/L (picocuries per liter), the USEPA's proposed Maximum Contaminant Level for radon in drinking water, and 31 percent of samples contained radon at activities greater than 1,000 pCi/L. The 10 subunits where samples were collected were grouped into three classes - median ground-water radon activity less than 300 pCi/L, between 300 pCi/L and 1,000 pCi/L, and greater than 1,000 pCi/L. Subunits underlain by igneous and metamorphic rocks of the Piedmont Physiographic Province typically have the highest median ground-water radon activities (greater than 1,000 pCi/L); although there is a large variation in radon activities within most of the subunits. Lower median radon activities (between 300 pCi/L and 1,000 pCi/L) were found in ground water in subunits underlain by limestone and dolomite. Of three subunits underlain by sandstone and shale, one fell into each of the three radon-activity classes. The large variability within these subunits may be attributed to the fact that the uranium content of sandstone and shale is related to the uranium content of the sediments from which they formed.

lower Susquehanna and Potomac River basins↗

USGS1996

Bacteriological quality of ground water used for household supply, Lower Susquehanna River basin, Pennsylvania and Maryland

This report describes the bacteriological results of a ground-water study conducted from 1993 to 1995 as part of the U.S. Geological Survey's National Water-Quality Assessment Program in the Lower Susquehanna River Basin study unit. Water samples collected from 146 household supply wells were analyzed for fecal-indicator organisms including total coliform, fecal coliform, Escherichia coli ( E. coli ), and fecal streptococcus concentrations. Supporting data used in the interpretations are selected water-quality constituents, well-construction information, and the environmental setting at the well site including land use, physiography, and bedrock type. Water from nearly 70 percent of the wells sampled had total coliform present and thus was not suitable for drinking without treatment. Fecal coliforms were found in water from approximately 25 percent of the sampled wells. E. coli testing was not conducted in 1993. Approximately 30 percent of the 88 sampled wells had waters with E. coli . Fecal streptococcus bacteria was present in water from about 65 percent of the wells sampled. Bacteriological contamination was more likely to occur in water from wells in agricultural areas than in water from wells in forested areas. Water from wells sampled in the Ridge and Valley Physiographic Province was more likely to have bacteria than water from wells in the Piedmont Physiographic Province. Differences in bacterial concentrations among bedrock types are only statistically significant for E. coli . Bacterial concentrations are weakly related to well-age but not to other well characteristics such as the total well depth or the casing length. Relations exist between bacterial concentrations and selected water-quality constituents. Most wells from which water was sampled did not have sanitary seals and very few were grouted. This may have contributed to the number of detections of bacteria. It is uncertain whether the bacteria detected are the result of widespread aquifer contamination or site-specific factors.

Maryland, Pennsylvania↗