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USGS2000

Regional water table (1998) and ground-water-level changes in the Mojave River and the Morongo ground-water basins, San Bernardino County, California

The Mojave River and the Morongo ground-water basins are in the southwestern part of the Mojave Desert in southern California. Ground water from these basins supplies a major part of the water requirements for the region. The rapid and continuous population growth in this area has resulted in ever-increasing demands on local ground-water resources. The continuing collection and interpretation of ground-water data helps local water districts, military bases, and private citizens gain a better understanding of the ground-water systems and, consequently, water availability. During 1998 the U.S. Geological Survey and other agencies made approximately 2,370 water-level measurements in the Mojave River and the Morongo ground-water basins. These data document recent conditions and changes in ground-water levels. A water-level contour map was drawn using data from 450 wells, providing coverage for most of both basins. Twenty-three hydrographs show long-term (as much as 70 years) water-level trends throughout the basins. To help show effects of late seasonal recharge along the Mojave River, 14 short-term (13 years) hydrographs were created. A water-level change map was compiled to enable comparison of 1996 and 1998 water levels. The Mojave River and the Morongo ground-water basins had little change in water levels between 1996 and 1998 - with the exception of the areas of the Yucca Valley affected by artificial recharge. Other water-level changes were localized and reflected pumping or measurements made before seasonal recharge. Three areas of perched ground water were identified: El Mirage Lake (dry), Adelanto, and Lucerne Valley.

California↗

USGS2000

Characterization of rainfall-runoff response and estimation of the effect of wetland restoration on runoff, Heron Lake Basin, southwestern Minnesota, 1991-97

The U.S. Geological Survey (USGS), in cooperation with the Minnesota Department of Natural Resources and the Heron Lake Watershed District, conducted a study to characterize the rainfall-runoff response and to examine the effects of wetland restoration on the rainfall-runoff response within the Heron Lake Basin in southwestern Minnesota. About 93 percent of the land cover in the Heron Lake Basin consists of agricultural lands, consisting almost entirely of row crops, with less than one percent consisting of wetlands. The Hydrological Simulation Program – Fortran (HSPF), Version 10, was calibrated to continuous discharge data and used to characterize rainfall-runoff responses in the Heron Lake Basin between May 1991 and August 1997. Simulation of the Heron Lake Basin was done as a two-step process: (1) simulations of five small subbasins using data from August 1995 through August 1997, and (2) simulations of the two large basins, Jack and Okabena Creek Basins, using data from May 1991 through September 1996. Simulations of the five small subbasins was done to determine basin parameters for the land segments and assess rainfall-runoff response variability in the basin. Simulations of the two larger basins were done to verify the basin parameters and assess rainfall-runoff responses over a larger area and for a longer time period. Best-fit calibrations of the five subbasin simulations indicate that the rainfall-runoff response is uniform throughout the Heron Lake Basin, and 48 percent of the total rainfall for storms becomes direct (surface and interflow) runoff. Rainfall-runoff response variations result from variations in the distribution, intensity, timing, and duration of rainfall; soil moisture; evapotranspiration rates; and the presence of lakes in the basin. In the spring, the amount and distribution of rainfall tends to govern the runoff response. High evapotranspiration rates in the summer result in a depletion of moisture from the soils, substantially affecting the rainfall-runoff relation. Five wetland restoration simulations were run for each of five subbasins using data from August 1995 through August 1997, and for the two larger basins, Jack and Okabena Creek Basins, using data from May 1991 through September 1996. Results from linear regression analysis of total simulated direct runoff and total rainfall data for simulated storms in the wetland-restoration simulations indicate that the portion of total rainfall that becomes runoff will be reduced by 46 percent if 45 percent of current cropland is converted to wetland. The addition of wetlands reduced peak runoff in most of the simulations, but the reduction varied with antecedent soil moisture, the magnitude of the peak flow, and the presence of current wetlands and lakes. Reductions in the simulated total and peak runoff from the Jack Creek Basin for most of the simulated storms were greatest when additional wetlands were simulated in the North Branch Jack Creek or the Upper Jack Creek Subbasins. In the Okabena Creek Basin, reductions in simulated peak runoff for most of the storms were greatest when additional wetlands were simulated in the Lower Okabena Creek Subbasin.

Minnesota↗

USGS2000

Suspended sediment in the Indiana Harbor Canal and the Grand Calumet River, northwestern Indiana, May 1996-June 1998

Suspended-sediment samples and streamflow data were collected from May 1996 through June 1998 at three sites in the Grand Calumet River Basin - Indiana Harbor Canal at East Chicago, the east branch of the Grand Calumet River at Gary, and the west branch of the Grand Calumet River at Hammond. Sample analysis allowed for retention of sediments of 0.0015 millimeters or larger.

Indiana↗

USGS2000

Water-quality assessment of part of the Upper Mississippi River Basin, Minnesota and Wisconsin - Ground-water quality in an agricultural area of Sherburne County, Minnesota, 1998

The quality of shallow ground water in a 75-mi 2 agricultural area of the Anoka Sand Plain aquifer in central Minnesota is described as part of the National Water Quality Assessment (NAWQA) Program - a national-scale assessment of the quality of water resources within large study units in various hydrologic settings. Data were collected during 1998 from 29 wells completed in the aquifer, which predominantly consists of surficial glacial sand and gravel sediments. The depth below land surface to the water table ranged from 3.3 to 44 ft (median of 15.5 ft). Ground water was of the calciummagnesium bicarbonate type. Ionic constituents also included sodium, sulfate, and chloride. Iron and manganese concentrations generally were not greater than their U.S. Environmental Protection Agency (USEPA) Secondary Maximum Contaminant Levels (300 and 50 ug/L, respectively). About 38 percent of 29 samples had nitrate-N (nitrogen) concentrations greater than the USEPA Maximum Contaminant Level (MCL) of 10 mg/L. About 72 percent of the samples had nitrate-N concentrations greater than the presumed natural background level of 3 mg/L. The maximum nitrate-N concentration was 47 mg/L. The median nitrate-N concentration of 7.1 mg/L, although not greater than the MCL, exceeded the natural background level. Nitrogen isotope ratios indicate that the sources of nitrate were commercial fertilizer and soil organic matter. Concentrations of total dissolved phosphorus and orthophosphate were generally less than 1 mg/L. About 86 percent of 29 samples had detectable concentrations of at least 1 of 13 pesticide compounds. The samples were analyzed for 83 pesticide compounds. Frequencies of detection of these compounds were: deethylatrazine-79 percent; atrazine-76 percent; metolachlor-41 percent; metribuzin and bentazon-21 percent; prometon-10 percent; tebuthiuron-7 percent; and alachlor, 2,6-diethylaniline, dicamba, dinoseb, malathion, and simazine-3 percent. The detected pesticide compounds had concentrations less than 1 ug/L. Detected compounds with USEPA MCLs (atrazine, bentazon, alachlor, dinoseb, and simazine) had concentrations less than their respective MCLs. About 50 percent of 20 samples analyzed for 86 volatile organic compounds (VOCs) had detectable concentrations of at least 1 of 7 VOCs. Frequencies of detection of these 7 VOCs were: 1,2,3,4-tetramethylbenzene-40 percent; and trichlorofluoromethane, styrene, chloromethane, benzene, methylbenzene, and trichloromethane-5 percent. The detected VOCs had concentrations less than 0.120 ug/L. Detected VOCs with USEPA MCLs - styrene, benzene, methylbenzene, and trichloromethane - were present at concentrations 2-4 orders of magnitude less than their respective MCLs. Tritium concentrations had a range of from 7.5 to 18.8 tritium units (TUs) and a median of 12.5 TUs. These concentrations indicate that the ground water predominantly recharged after testing of thermonuclear weapons during the early 1950's.

Minnesota↗

USGS2000

Water-quality assessment of part of the Upper Mississippi River Basin, Minnesota and Wisconsin - Ground-water quality in three different land-use areas, 1996-98

The surficial sand and gravel aquifer is susceptible to effects from land-use in the Upper Mississippi River Basin study unit of the National Water-Quality Assessment (NAWQA) Program. The purpose of this report is to describe the ground-water quality and the assessment of how different land-uses affect the shallow ground-water quality in the surficial sand and gravel aquifer. Ground-water quality was compared in three different land-use areas; an urban residential/commercial area on the edge of the Anoka Sand Plain in a portion of the Twin Cities metropolitan area (urban study), an intensive agricultural area in the Anoka Sand Plain (agricultural study), and a forested area in the Bemidji-Bagley Sand Plain (forested study). Ground water was sampled and analyzed for about 200 constituents, including physical parameters, major ions, selected trace elements, nutrients, dissolved organic carbon, selected pesticides, selected volatile organic compounds (VOCs), and tritium. The urban study wells were sampled during June and July 1996. The agricultural study wells were sampled during May and September 1998. The forested study wells were sampled during June 1998. The depth to water below the land surface generally was less than 20 ft in all three land-use studies. The median pH value in the urban study was 7.2, with medians in the agricultural and forested studies at 7.4 and 7.5, respectively. The median specific conductance was significantly greater in the urban study than in the agricultural and forested studies (914, 553, and 487 µS/cm respectively). The median dissolved oxygen concentration in the urban study (0.9 mg/L) was significantly less than the median in the agricultural or forested studies (5.3 and 2.3 mg/L respectively). Alkalinities in the agricultural study, with a median of 178 mg/L as CaCO 3 , were significantly less than medians in the urban or forested studies (261 and 246 mg/L as CaCO 3 , respectively). The water composition in the surficial aquifer in all three land-use studies is dominated by calcium, magnesium, and bicarbonate. Sulfate and chloride concentrations in water samples were significantly greater in the urban study than in the agricultural or forested studies, and concentrations in the forested study were least. Most of the water samples in all three land-use studies were very hard (greater than 180 mg/L as CaCO 3 ). Nitrate-nitrogen concentrations were greatest in the agricultural study, in which 38 percent of water samples exceeded the U.S. Environmental Protection Agency’s maximum contaminant level (MCL) for nitrate-nitrogen. Nitrate-nitrogen was greater than the MCL in 3 percent of urban study samples. None of the forested study samples exceeded the MCL for nitrate-nitrogen. Concentrations of phosphorus generally were less than 0.05 mg/ L, with no significant differences between the land-uses. A total of 19 pesticides were detected in water samples from one or more land-use study wells, with 11 pesticides detected in the urban study, 14 detected in the agricultural study, and 4 detected in the forested study. Atrazine, deethylatrazine, and simazine were the only pesticides detected in all three land-use studies. A significantly greater percentage of pesticide detections were present in water samples from the agricultural study than from the urban or forested studies (86.2, 56.7, and 46.7 percent, respectively). Prometon was the most frequently detected pesticide in the urban study. Atrazine and deethylatrazine were the most frequently detected pesticides in the agricultural and forested studies. Twenty-one VOCs were detected in water samples from one or more land-use study wells, with 19 detected in the urban study, 7 detected in the agricultural study, and none detected in the forested study. Chloromethane, trichloromethane, methylbenzene, trichlorofluoromethane, and benzene were all detected in both the urban and agricultural studies. A significantly greater percentage of VOC detections were present in water samples from the urban study than from the agricultural study (90 and 50 percent, respectively). Carbon disulfide was the most frequently detected VOC in the urban study. The compound 1,2,3,4-tetramethyl benzene was the most frequently detected VOC in the agricultural study. Tritium concentrations indicate that the water in the surficial sand and gravel aquifer has been recharged since 1953. Median tritium concentrations ranged from 11.6 to 12.8 tritium units. No significant difference in tritium concentrations was present between the three land-use studies. Comparisons of previous land-use studies in Minnesota with the three NAWQA land-use studies generally indicated the same patterns. Ground-water quality in surficial sand and gravel aquifers is affected by land-use practices. Ground water in urban studies has greater specific conductances, alkalinities, chloride, sodium, sulfate, and dissolved solid concentrations than agricultural or forested/undeveloped studies. Nitrate-nitrogen was detected in greater concentrations in agricultural studies than in urban studies, with concentrations in the forested/undeveloped studies less than in the agricultural or the urban studies. Agricultural studies have the greatest detection rates, numbers, and total concentrations of pesticides. Pesticide detection rates and total pesticide concentrations in the urban studies were less than in the agricultural studies, with the most frequently detected pesticides (prometon and dicamba) different than those in the agricultural studies (atrazine and deethylatrazine). A greater number of VOCs were detected in urban studies and at greater concentrations than in agricultural studies. Few pesticides or VOCs were detected in forested/undeveloped studies.

Minnesota↗

USGS2000

Fecal-coliform bacteria concentrations in streams of the Chattahoochee River National Recreation Area, Metropolitan Atlanta, Georgia, May–October 1994 and 1995

The Metropolitan Atlanta area has been undergoing a period of rapid growth and development. The population in the 10-county metropolitan area almost doubled from about 1.5 million people in 1970 to 2.9 million people in 1995 (Atlanta Regional Commission, written commun., 2000). Residential, commercial, and other urban land uses more than tripled during the same period (Frick and others, 1998). The Chattahoochee River is the most utilized water resource in Georgia. The rapid growth of Metropolitan Atlanta and its location downstream of the headwaters of the drainage basin make the Chattahoochee River a vital resource for drinking-water supplies, recreational opportunities, and wastewater assimilation. In 1978, the U.S. Congress declared the natural, scenic, recreation, and other values of 48 miles of the Chattahoochee River from Buford Dam to Peachtree Creek to be of special national significance. To preserve this reach of the Chattahoochee River, the U.S. Congress created the Chattahoochee River National Recreational Area (CRNRA), which includes the Chattahoochee River downstream from Buford Dam to the mouth of Peachtree Creek and a series of park areas adjacent to the river in northern Metropolitan Atlanta Even with this protection, waters of the Chattahoochee River and many of its tributaries in Metropolitan Atlanta did not meet water-quality standards set for designated uses during 1994 and 1995 (fig. 1 and table 1). Much of the degradation of water quality has been associated with areas undergoing rapid urban growth and sprawling suburban development. The resulting conversion of mostly forested land to urban land has multiple adverse effects on water quality. Degradation of water quality may be caused by a number of factors including an increase in nutrient concentrations, sediment and sedimentbound contaminant concentrations (e.g., metals and pesticides) (Frick and others, 1998), and fecal-coliform bacteria concentrations (Center for Watershed Protection, 1999). The presence of fecal-coliform bacteria in streams and rivers indicates that contamination by fecal material from human or animal sources has occurred and contact with these waters can result in exposure to pathogenic bacteria often associated with fecal contamination. During 1994 and 1995, elevated concentrations of fecal-coliform bacteria were the most common reason that the Chattahoochee River and tributaries did not meet their designated uses of drinking-water supply, recreation, and fishing. According to the Georgia Department of Natural Resources (1997), during 1994 and 1995, 67 of 77 stream reaches assessed in Metropolitan Atlanta did not meet or only partially met water-quality requirements for designated uses. Excessive concentrations of fecal-coliform bacteria were a contributing factor in 63 of the 67 streams that did not meet or only partially met designated uses. High concentrations of fecal-coliform bacteria have the potential to reduce the recreational value of the river and pose a continued threat, with unknown health risks, to humans that come in contact with the water while fishing, boating, rafting, wading, and swimming.

Georgia↗

USGS2000

Use of borehole geophysical logs for improved site characterization at Naval Weapons Industrial Reserve Plant, Dallas, Texas

A shallow alluvial aquifer at the Naval Weapons Industrial Reserve Plant near Dallas, Texas, has been contaminated by organic solvents used in the fabrication and assembly of aircraft and aircraft parts. Natural gamma-ray and electromagnetic-induction log data collected during 1997 from 162 wells were integrated with existing lithologic and cone-penetrometer test log data to improve characterization of the subsurface alluvium at the site. The alluvium, consisting of mostly fine-grained, low-permeability sediments, was classified into low, intermediate, and high clay-content sediments on the basis of the gamma-ray logs. Low clay-content sediments were interpreted as being relatively permeable, whereas high clay-content sediments were interpreted as being relatively impermeable. Gamma-ray logs, cone-penetrometer test logs, and electromagnetic-induction logs were used to develop a series of intersecting sections to delineate the spatial distribution of low, intermediate, and high clay-content sediments and to delineate zones of potentially contaminated sediments. The sections indicate three major sedimentary units in the shallow alluvial aquifer at NWIRP. The lower unit consists of relatively permeable, low clay-content sediments and is absent over the southeastern and northwestern part of the site. Permeable zones in the complex, discontinuous middle unit are present mostly in the western part of the site. In the eastern and southeastern part of the site, the upper unit has been eroded away and replaced by fill material. Zones of potentially contaminated sediments are generally within the uppermost clay layer or fill material. In addition, the zones tend to be local occurrences.

Texas↗

USGS2000

Delineation and Analysis of Uncertainty of Contributing Areas to Wells at the Southbury Training School, Southbury, Connecticut

Contributing areas to public-supply wells at the Southbury Training School in Southbury, Connecticut, were mapped by simulating ground-water flow in stratified glacial deposits in the lower Transylvania Brook watershed. The simulation used nonlinear regression methods and informational statistics to estimate parameters of a ground-water flow model using drawdown data from an aquifer test. The goodness of fit of the model and the uncertainty associated with model predictions were statistically measured. A watershed-scale model, depicting large-scale ground-water flow in the Transylvania Brook watershed, was used to estimate the distribution of groundwater recharge. Estimates of recharge from 10 small basins in the watershed differed on the basis of the drainage characteristics of each basin. Small basins having well-defined stream channels contributed less ground-water recharge than basins having no defined channels because potential ground-water recharge was carried away in the stream channel. Estimates of ground-water recharge were used in an aquifer-scale parameter-estimation model. Seven variations of the ground-water-flow system were posed, each representing the ground-water-flow system in slightly different but realistic ways. The model that most closely reproduced measured hydraulic heads and flows with realistic parameter values was selected as the most representative of the ground-water-flow system and was used to delineate boundaries of the contributing areas. The model fit revealed no systematic model error, which indicates that the model is likely to represent the major characteristics of the actual system. Parameter values estimated during the simulation are as follows: horizontal hydraulic conductivity of coarse-grained deposits, 154 feet per day; vertical hydraulic conductivity of coarse-grained deposits, 0.83 feet per day; horizontal hydraulic conductivity of fine-grained deposits, 29 feet per day; specific yield, 0.007; specific storage, 1.6E-05. Average annual recharge was estimated using the watershed-scale model with no parameter estimation and was determined to be 24 inches per year in the valley areas and 9 inches per year in the upland areas. The parameter estimates produced in the model are similar to expected values, with two exceptions. The estimated specific yield of the stratified glacial deposits is lower than expected, which could be caused by the layered nature of the deposits. The recharge estimate produced by the model was also lower?about 32 percent of the average annual rate. This could be caused by the timing of the aquifer test with respect to the annual cycle of ground-water recharge, and by some of the expected recharge going to parts of the flow system that were not simulated. The data used in the calibration were collected during an aquifer test from October 30 to November 4, 1996. The model fit was very good, as indicated by the correlation coefficient (0.999) between the weighted simulated values and weighted observed values. The model also reproduced the general rise in ground-water levels caused by ground-water recharge and the cyclic fluctuations caused by pumping prior to the aquifer test. Contributing areas were delineated using a particle-tracking procedure. Hypothetical particles of water were introduced at each model cell in the top layer and were tracked to determine whether or not they reached the pumped well. A deterministic contributing area was calculated using the calibrated model, and a probabilistic contributing area was calculated using a Monte Carlo approach along with the calibrated model. The Monte Carlo simulation was done, using the parameter variance/covariance matrix generated by the regression model, to estimate probabilities associated with the contributing area to the wells. The probabilities arise from uncertainty in the estimated parameter values, which in turn arise from the adequacy of the data available to comprehensively describe the groundwater-flow sy

Water-Resources Investigations Report↗

USGS2001

Ground-Water Hydrology of the Upper Deschutes Basin, Oregon

The upper Deschutes Basin is among the fastest growing regions in Oregon. The rapid population growth has been accompanied by increased demand for water. Surface streams, however, have been administratively closed to additional appropriation for many years, and surface water is not generally available to support new development. Consequently, ground water is being relied upon to satisfy the growth in water demand. Oregon water law requires that the potential effects of ground-water development on streamflow be evaluated when considering applications for new ground-water rights. Prior to this study, hydrologic understanding has been insufficient to quantitatively evaluate the connection between ground water and streamflow, and the behavior of the regional ground-water flow system in general. This report describes the results of a hydrologic investigation undertaken to provide that understanding. The investigation encompasses about 4,500 square miles of the upper Deschutes River drainage basin.A large proportion of the precipitation in the upper Deschutes Basin falls in the Cascade Range, making it the principal ground-water recharge area for the basin. Water-balance calculations indicate that the average annual rate of ground- water recharge from precipitation is about 3,500 ft3/s (cubic feet per second). Water-budget calculations indicate that in addition to recharge from precipitation, water enters the ground-water system through interbasin flow. Approximately 800 ft3/s flows into the Metolius River drainage from the west and about 50 ft3/s flows into the southeastern part of the study area from the Fort Rock Basin. East of the Cascade Range, there is little or no ground-water recharge from precipitation, but leaking irrigation canals are a significant source of artificial recharge north of Bend. The average annual rate of canal leakage during 1994 was estimated to be about 490 ft3/s. Ground water flows from the Cascade Range through permeable volcanic rocks eastward out into the basin and then generally northward. About one-half the ground water flowing from the Cascade Range discharges to spring-fed streams along the margins of the range, including the upper Metolius River and its tributaries. The remaining ground water flows through the subsurface, primarily through rocks of the Deschutes Formation, and eventually discharges to streams near the confluence of the Deschutes, Crooked, and Metolius Rivers. Substantial ground-water discharge occurs along the lower 2 miles of Squaw Creek, the Deschutes River between Lower Bridge and Pelton Dam, the lower Crooked River between Osborne Canyon and the mouth, and in Lake Billy Chinook (a reservoir that inundates the confluence of the Deschutes, Crooked, and Metolius Rivers).The large amount of ground-water discharge in the confluence area is primarily caused by geologic factors. North (downstream) of the confluence area, the upper Deschutes Basin is transected by a broad region of low-permeability rock of the John Day Formation. The Deschutes River flows north across the low-permeability region, but the permeable Deschutes Formation, through which most of the regional ground water flows, ends against this rampart of low-permeability rock. The northward-flowing ground water discharges to the streams in this area because the permeable strata through which it flows terminate, forcing the water to discharge to the surface. Virtually all of the regional ground water in the upper Deschutes Basin discharges to surface streams south of the area where the Deschutes River enters this low-permeability terrane, at roughly the location of Pelton Dam.The effects of ground-water withdrawal on streamflow cannot presently be measured because of measurement error and the large amount of natural variability in ground-water discharge. The summer streamflow near Madras, which is made up largely of ground-water discharge, is approximately 4,000 ft3/s. Estimated consumptive ground-water use in the basin i

Water-Resources Investigations Report↗

USGS2000

Nutrients and suspended sediment in snowmelt runoff from part of the Upper Mississippi River Basin, Minnesota and Wisconsin, 1997

The U.S. Geological Survey sampled snowmelt runoff from 42 stream sites during March and April 1997 in part of the Upper Mississippi River Basin, Minnesota and Wisconsin, to characterize nutrient and suspended-sediment concentrations, yields, and loads. Ancillary data from 12 sites provided data to estimate constituent loads delivered during snowmelt and 1997. The snowmelt period contributed from 1 to 50 percent of 1997 annual loads of total nitrogen, total phosphorus, and suspended sediment at small stream sites, and 17 to 70 percent of annual loads at mainstem river sites. Small streams in agricultural areas transported the greatest proportions of annual loads during snowmelt. Snowmelt from urban streams transported the least proportions of annual loads. Agricultural streams had significantly greater median yields (p < 0.025) of dissolved nitrite, nitrate, phosphorus, orthophosphate, total nitrogen, and total phosphorus than forested sites, and significantly greater median yields (p < 0.025) of dissolved nitrate and orthophosphate than all other land uses. In forested areas, yields of suspended sediment and all nutrient forms were significantly greater (p < 0.05) for streams draining impermeable deposits than permeable deposits.

Minnesota, Wisconsin↗

USGS2000

Quality-assurance results for routine water analyses in U.S. Geological Survey laboratories, water year 1998

The U.S. Geological Survey operates a quality-assurance program based on the analyses of reference samples for two laboratories: the National Water Quality Laboratory and the Quality of Water Service Unit. Reference samples that contain selected inorganic, nutrient, and low-level constituents are prepared and submitted to the laboratory as disguised routine samples. The program goal is to estimate precision and bias for as many analytical methods offered by the participating laboratories as possible. Blind reference samples typically are submitted at a rate of 2 to 5 percent of the annual environmental-sample load for each constituent. The samples are distributed to the laboratories throughout the year. The reference samples are subject to the identical laboratory handling, processing, and analytical procedures as those applied to environmental samples and, therefore, have been used as an independent source to verify bias and precision of laboratory analytical methods and ambient water-quality measurements. The results are stored permanently in the National Water Information System and the Blind Sample Project's data base. During water year 1998, 95 analytical procedures were evaluated at the National Water Quality Laboratory and 63 analytical procedures were evaluated at the Quality of Water Service Unit. An overall evaluation of the inorganic and low-level constituent data for water year 1998 indicated 77 of 78 analytical procedures at the National Water Quality Laboratory met the criteria for precision. Silver (dissolved, inductively coupled plasma-mass spectrometry) was determined to be imprecise. Five of 78 analytical procedures showed bias throughout the range of reference samples: chromium (dissolved, inductively coupled plasma-atomic emission spectrometry), dissolved solids (dissolved, gravimetric), lithium (dissolved, inductively coupled plasma-atomic emission spectrometry), silver (dissolved, inductively coupled plasma-mass spectrometry), and zinc (dissolved, inductively coupled plasma-mass spectrometry). At the National Water Quality Laboratory during water year 1998, lack of precision was indicated for 2 of 17 nutrient procedures: ammonia as nitrogen (dissolved, colorimetric) and orthophosphate as phosphorus (dissolved, colorimetric). Bias was indicated throughout the reference sample range for ammonia as nitrogen (dissolved, colorimetric, low level) and nitrate plus nitrite as nitrogen (dissolved, colorimetric, low level). All analytical procedures tested at the Quality of Water Service Unit during water year 1998 met the criteria for precision. One of the 63 analytical procedures indicated a bias throughout the range of reference samples: aluminum (whole-water recoverable, inductively coupled plasma-atomic emission spectrometry, trace).

Water-Resources Investigations Report↗

USGS2000

Diffusion sampler testing at Naval Air Station North Island, San Diego County, California, November 1999 to January 2000

Volatile organic compound concentrations in water from diffusion samplers were compared to concentrations in water obtained by low-flow purging at 15 observation wells at the Naval Air Station North Island, San Diego, California. Multiple diffusion samplers were installed in the wells. In general, comparisons using bladder pumps and diffusion samplers showed similar volatile organic carbon concentrations. In some wells, sharp concentration gradients were observed, such as an increase in cis-1,2-dichloroethene concentration from 100 to 2,600 micrograms per liter over a vertical distance of only 3.4 feet. In areas where such sharp gradients were observed, concentrations in water obtained by low-flow sampling at times reflected an average concentration over the area of influence; however, concentrations obtained by using the diffusion sampler seemed to represent the immediate vicinity of the sampler. When peristaltic pumps were used to collect ground-water samples by low-flow purging, the volatile organic compound concentrations commonly were lower than concentrations obtained by using diffusion samplers. This difference may be due to loss of volatiles by degassing under negative pressures in the sampling lines induced while using the peristaltic pump, mixing in the well screen, or possible short-circuiting of water from an adjacent depth. Diffusion samplers placed in buckets of freephase jet fuel (JP-5) and Stoddard solvent from observation wells did not show evidence of structural integrity loss during the 2 months of equilibration, and volatile organic compounds detected in the free-phase fuel also were detected in the water from the diffusion samplers.

California↗

USGS2000

Use of biological characteristics of common carp ( Cyprinus carpio ) to indicate exposure to hormonally active agents in selected Minnesota streams, 1999

The presence of hormonally active agents (HAAs) was determined in selected Minnesota streams using biological characteristics (measures of endocrine disruption) of common carp ( Cyprinus carpio ) exposed to wastewater treatment plant (WWTP) effluent and runoff from agricultural and forested land. Four biological characteristics of common carp were used as indicators of HAAs in the streams selected for this study: (1) high concentrations of vitellogenin in male fish and low concentrations in female fish, (2) high or low plasma concentrations of the sex steroid hormones (17β-estradiol and 11-ketotestosterone), (3) low gonado-somatic index (GSI) (gonad weight divided by total body weight multiplied by 100) values, and (4) abnormal gonad histopathology (high percent of atretic oocytes in female ovaries and high percent ceroid/lipofuscin tissue in male or female gonads). The study design was a paired site approach targeting sites downstream and upstream of WWTP discharges on different streams. Male (221 individuals) and female (201 individuals) common carp were collected using electrofishing techniques from seven streams with sites at two locations (upstream and downstream of WWTPs), and eight sites located downstream of WWTPs with no upstream-paired sites. Samples were collected between August 3 and September 13, 1999. The presence of HAAs in selected Minnesota streams was indicated by biological characteristics in common carp. Biological characteristics used in this study identified WWTP effluent as a potential source of HAAs. Additionally, fish located at sites upstream of WWTP effluent primarily draining agricultural land show indications of HAAs, which may be the result of agricultural runoff or other sources of HAAs. There was variability among all sites and among sites within each site group. Differences among sites may be due to differences in water chemistry or fish exposure time. Natural variation in the biological characteristics may account for some of the differences observed in this study. This study and others indicate the presence of HAAs in surface water and the potential signs of endocrine disruption in resident fish populations. Detailed controlled studies could confirm the effects of particular chemicals such as pesticides or components of WWTPs on fish reproduction and population structure.

Minnesota↗

USGS2000

Hydrology of the Helena area bedrock, west-central Montana, 1993-98

The Generalized Bedrock Geologic Map of the Helena Area, West-Central Montana (plate 1 in the report) provides an intermediate-scale overview of bedrock in the Helena area. The geologic map has been compiled at a scale of 1:100,000 from the most widely available sources of geologic map information (see index to geologic mapping on pl. 1). That information has been updated by M.W. Reynolds for this report with more recent geologic mapping and field revision of published maps. All well locations and all bedrock units penetrated during drilling have been confirmed on geologic maps at the largest scale available. Source geologic maps are all at scales larger than 1:100,000 scale. Care has been taken to ensure accurate representation of the original geology at the compilation scale. However, positional accuracy of some features might be somewhat diminished at the smaller scale of the base map when compared with the original data source. Also, line thicknesses for contacts and faults necessarily assume a greater width, relative to the real geologic feature, at the scale of the generalized map than on any original map. The map is not intended for large-scale, site-specific detailed planning. Bedrock units throughout the Helena area are generally covered by young surficial deposits such as alluvium, colluvium, glacial debris, or windblown sediment. Thickness of such deposits varies from veneers through which the underlying bedrock is clearly discernible to major thicknesses that conceal all underlying bedrock and structure. Boundaries of major accumulations of surficial deposits are attributed separately from bedrock contacts. These boundaries should not be considered precise at the map scale or at larger scales. Boundaries shown may be less accurate positionally than bedrock contacts and faults because (1) surficial deposits commonly thin to a knife edge; (2) different mappers will interpret the edge differently when drawing a boundary; or (3) the original geologic map maker was concerned principally with bedrock units and structure and thus overlooked, or did not originally map as consistently, some surficial deposits. Veneers of surficial sediment, when saturated, can be local sources of recharge to underlying bedrock. Use of the generalized map to define their distribution does not substitute for site specific mapping of such deposits. Specific knowledge is needed to determine the water-bearing properties of the geologic units at and surrounding a site because the units, including the igneous and metamorphic rocks, have internal differences in stratigraphy, composition, mineralogy and grain size or crystallinity. These differences, together with structural imprints such as faults, folds, and the spacing, orientation, degree of openness of fractures, and extent and type of mineral filling in fractures and faults, all affect the ability of rocks to store and transmit water.

Montana↗

USGS2001

Water-Quality Assessment of part of the Upper Mississippi River Basin, Minnesota and Wisconsin— Organochlorine compounds in streambed sediment and fish tissues, 1995-97

Streambed sediments and fish tissues were collected in part of the Upper Mississippi River Basin to assess the presence and distribution of organochlorine compounds (OCs) including PCBs. A total of 13 OCs were detected among 14 of 27 streambed sediment sampling locations. In fish tissues analyzed, 9 OCs were detected among 17 of 24 sites sampled. Eight OCs were detected in both fish and streambed sediment samples, they were: cis-chlordane, o,p'-DDD; p,p'-DDD; p,p'-DDE; p,p'-DDT; hexachlorobenzene; transnonachlor; and PCBs. The most frequently detected OCs were: p,p'-DDE; and p,p'-DDD in streambed sediment and p,p'-DDE and PCBs in fish tissues. No OCs were detected in streambed sediment at agricultural sites; however, the agricultural sites had 17 detections of OCs in fish tissue. Urban streams had concentrations of total DDT and metabolites in streambed sediment that exceed guidelines for classification of sites with high probabilities of adverse effects to aquatic organisms. Total DDT was the only OC within an urban land use that exceeded guidelines for piscivorous wildlife.

Minnesota, Wisconsin↗

USGS1999

Fecal coliform and Escherichia coli bacteria in the St. Croix National Scenic Riverway, Summer 1999

Fecal coliform and Escherichia coli ( E. coli ) concentrations were determined in the St. Croix National Scenic Riverway to assess whether pathogenic organisms pose a potential problem for recreational use. Samples were collected from May through September 1999 at 22 locations on the St. Croix and Namekagon Rivers. No concentrations exceeded water-quality criteria or standards set by the U.S. Environmental Protection Agency or the states of Minnesota and Wisconsin. Maximum fecal coliform and E. coli concentrations were measured in the St. Croix River at St. Croix Falls, Wisconsin. Median fecal coliform and E. coli concentrations were greater in the St. Croix River near Woodland Corner, Wisconsin, and at Marine on St. Croix, Minnesota than at other locations sampled. There were no consistent short-term variations in fecal coliform or E. coli concentrations during the summer period or any significant relations between concentrations and stream discharge, based on these results.

Minnesota, Wisconsin↗

USGS2001

Ground-water recharge and flowpaths near the edge of the Decorah-Platteville-Glenwood confining unit, Rochester, Minnesota

The primary source of ground water for the city of Rochester, Olmsted County, southeastern Minnesota is the St. Peter-Prairie du Chien-Jordan aquifer. Based on results of a previous U.S. Geological Survey investigation in the Rochester area, relatively high rates of areal recharge to the St. Peter-Prairie du Chien-Jordan aquifer occur along the edge of the overlying Decorah-Platteville-Glenwood confining unit. The primary source of water to the zone of increased recharge along the edge of the confining unit is the upper carbonate aquifer. Ground-water recharge rates to the St. Peter-Prairie du Chien-Jordan aquifer during all of 1998 ranged from 1.9 to 25.5 in./yr (inches per year). Recharge rates were greatest near the edge of the Decorah-Platteville-Glenwood confining unit and least where the confining unit is thick and is overlain by the upper carbonate aquifer (mean of 2.0 in./yr). Recharge rates downslope from the edge of the confining unit were greatest to the St. Peter on the slope entering the main South Fork Zumbro River Valley. Results of groundwater age dating using chlorofluorocarbons (CFCs) indicated recharge dates ranging from (1) the mid-1950’s to the early 1990’s for the St. Peter, (2) the late 1960’s to approximately 1990 for the Prairie du Chien, and (3) the early to mid-1950’s for the Jordan. Cross-sectional model simulations indicated that most of the areal recharge entering the aquifer system through the upper carbonate aquifer discharges from springs and seeps. Of the 2.28 ft3/s (cubic feet per second) of areal recharge that enters the upper carbonate aquifer, 2.23 ft3/s is discharged from the aquifer by springs and seeps. Results indicate that areal recharge to the upper Prairie du Chien moves primarily westward and discharges to Bear Creek. Areal recharge rates derived from hydrograph analysis, CFC age-dating, and cross-sectional model analysis were much greater to the St. Peter downslope from the edge of the Decorah-Platteville-Glenwood confining unit (25.5, 35.3, and 23.75 in./yr, respectively) than occurs to the Prairie du Chien in any hydrogeologic setting. The model-simulated discharge from springs and seeps in the lower part of the upper carbonate aquifer represents a potential source of water of 33 in./yr to the St. Peter unit, similar to the estimated areal recharge rates derived from hydrograph analysis and CFC age-dating. The water withdrawn by pumped wells or discharged to Bear Creek is derived predominantly from areal recharge near the edge of the Decorah-Platteville-Glenwood confining unit (0.47 ft 3 /s), rather than from water that has leaked downward through the Decorah unit (0.03 ft 3 /s). Model simulated discharge through springs and seeps in the lower part of the upper carbonate aquifer (0.21 ft 3 /s) represents a potential source of water to the St. Peter-Prairie du Chien-Jordan aquifer.

Minnesota↗

USGS2001

The response of the Iao aquifer to ground-water development, rainfall, and land-use practices between 1940 and 1998, Island of Maui, Hawaii

Ground water pumped from the Iao aquifer has been used for agricultural purposes since 1948, and domestic purposes since 1955. In 1990, the Hawaii State Commission on Water Resource Management established a value of 20 million gallons per day for the sustainable yield of the aquifer. Water-level data from observation wells throughout the aquifer and information on the depth to and thickness of the transition zone between freshwater and saltwater at the Waiehu deep monitor well indicate that pumping rates near the sustainable yield value of 20 million gallons per day could result in saltwater intrusion in some pumped wells. Since the introduction of pumpage in 1948 and the reduction of recharge in 1980, water levels have declined, chloride concentrations of the pumped water have increased, and the transition zone between freshwater and saltwater has risen. Water levels declined by about 18 feet between 1940 and 1998 in the area near Iao Stream, and by as much as 6 feet between 1977 and 1997 in the vicinity of the major well fields near Waiehu Stream. Chloride concentrations of pumped water have risen at all the well fields, but are presently below the U.S. Environmental Protection Agency recommended standard of 250 milligrams per liter. The chloride concentration of water pumped from Mokuhau 2, however, was 460 milligrams per liter in late 1996 when pumping was halted at this well. The midpoint of the transition zone, as measured at the Waiehu deep monitor well, rose by about 108 feet between 1985 and 1998.

Hawaii↗