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At least 1,531 records · Page 85Linked to original sources
USGS2001

Diurnal variations in metal concentrations in the Alamosa River and Wightman Fork, southwestern Colorado, 1995-97

A comprehensive sampling network was implemented in the Alamosa River Basin from 1995 to 1997 to address data gaps identified as part of the ecological risk assessment of the Summitville Superfund site. Aluminum, copper, iron, and zinc were identified as the constituents of concern for the risk assessment. Water-quality samples were collected at six sites on the Alamosa River and Wightman Fork by automatic samplers. Several discrete (instantaneous) samples were collected over 24 hours at each site during periods of high diurnal variations in streamflow (May through September). The discrete samples were analyzed individually and duplicate samples were composited to produce a single sample that represented the daily-mean concentration. The diurnal variations in concentration with respect to the theoretical daily-mean concentration (maximum minus minimum divided by daily mean) are presented. Diurnal metal concentrations were highly variable in the Alamosa River and Wightman Fork. The concentration of a metal at a single site could change by several hundred percent during one diurnal cycle. The largest percent change in metal concentrations was observed for aluminum and iron. Zinc concentrations varied the least of the four metals. No discernible or predictable pattern was indicated in the timing of the daily mean, maximum, or minimum concentrations. The percentage of discrete sample concentrations that varied from the daily-mean concentration by thresholds of plus or minus 10, 25, and 50 percent was evaluated. Between 50 and 75 percent of discrete-sample concentrations varied from the daily-mean concentration by more than plus or minus 10 percent. The percentage of samples exceeding given thresholds generally was smaller during the summer period than the snowmelt period. Sampling strategies are critical to accurately define variability in constituent concentration, and conversely, understanding constituent variability is important in determining appropriate sampling strategies. During nonsteady-state periods, considerable errors in estimates of daily-mean concentration are possible if based on one discrete sample. Flow-weighting multiple discrete samples collected over a diurnal cycle provides a better estimate of daily-mean concentrations during nonsteady-state periods.

Colorado↗
USGS2000

Documentation of a computer program to simulate lake-aquifer interaction using the MODFLOW ground water flow model and the MOC3D solute-transport model

Heads and flow patterns in surficial aquifers can be strongly influenced by the presence of stationary surface-water bodies (lakes) that are in direct contact, vertically and laterally, with the aquifer. Conversely, lake stages can be significantly affected by the volume of water that seeps through the lakebed that separates the lake from the aquifer. For these reasons, a set of computer subroutines called the Lake Package (LAK3) was developed to represent lake/aquifer interaction in numerical simulations using the U.S. Geological Survey three-dimensional, finite-difference, modular ground-water flow model MODFLOW and the U.S. Geological Survey three-dimensional method-of-characteristics solute-transport model MOC3D. In the Lake Package described in this report, a lake is represented as a volume of space within the model grid which consists of inactive cells extending downward from the upper surface of the grid. Active model grid cells bordering this space, representing the adjacent aquifer, exchange water with the lake at a rate determined by the relative heads and by conductances that are based on grid cell dimensions, hydraulic conductivities of the aquifer material, and user-specified leakance distributions that represent the resistance to flow through the material of the lakebed. Parts of the lake may become "dry" as upper layers of the model are dewatered, with a concomitant reduction in lake surface area, and may subsequently rewet when aquifer heads rise. An empirical approximation has been encoded to simulate the rewetting of a lake that becomes completely dry. The variations of lake stages are determined by independent water budgets computed for each lake in the model grid. This lake budget process makes the package a simulator of the response of lake stage to hydraulic stresses applied to the aquifer. Implementation of a lake water budget requires input of parameters including those representing the rate of lake atmospheric recharge and evaporation, overland runoff, and the rate of any direct withdrawal from, or augmentation of, the lake volume. The lake/aquifer interaction may be simulated in both transient and steady-state flow conditions, and the user may specify that lake stages be computed explicitly, semi-implicitly, or fully-implicitly in transient simulations. The lakes, and all sources of water entering the lakes, may have solute concentrations associated with them for use in solute-transport simulations using MOC3D. The Stream Package of MODFLOW-2000 and MOC3D represents stream connections to lakes, either as inflows or outflows. Because lakes with irregular bathymetry can exist as separate pools of water at lower stages, that coalesce to become a single body of water at higher stages, logic was added to the Lake Package to allow the representation of this process as a user option. If this option is selected, a system of linked pools (sublakes) is identified in each time step and stages are equalized based on current relative sublake surface areas.

Water-Resources Investigations Report↗
USGS2000

Reconnaissance of the hydrology, water quality, and sources of bacterial and nutrient contamination in the Ozark Plateaus aquifer system and Cave Springs Branch of Honey Creek, Delaware County, Oklahoma, March 1999-March 2000

A reconnaissance investigation of hydrology and water quality was conducted to evaluate possible sources of bacteria and nutrient contamination in the Cave Springs Branch basin and the underlying karstic Ozark Plateau aquifer system. Objectives were to: (1) determine the directions of ground-water flow in the basin and determine whether Cave Springs Branch interacts with ground water, (2) compare water quality in Cave Springs Branch with water quality in nearby wells to determine whether the stream is contaminating nearby wells, and (3) determine sources of fecal coliform bacteria and nitrate contamination in Cave Springs Branch and ground water. Potential sources of bacteria and nitrate in the area include cultivated agriculture, cow and horse on pasture, poultry production, households, and wildlife. Presence of fecal coliform and fecal streptococcal bacteria directly indicate fecal contamination and the potential for the presence of other pathogenic organisms in a water supply. Nitrate in drinking water poses health risks and may indicate the presence of additional contaminants. Fecal coliform bacteria colony counts were least in wells, intermediate in the poultry-processing plant wastewater outfall and Honey Creek above the confluence with Cave Springs Branch, and greatest in Cave Springs Branch. Bacteria strains and resistance to antibiotics by some bacteria indicate that livestock may have been sources of some bacteria in the water samples. Multiple antibiotic resistances were not present in the isolates from the water samples, indicating that the bacteria may not be from human or poultry sources. Ribotyping indicates that Escherichia coli bacteria in water samples from the basin were from bird, cow, horse, dog, deer, and human sources. The presence of multiple ribotypes from each type of animal source except bird indicates that most of the bacteria are from multiple populations of source animals. Identifiable sources of bacteria in Cave Springs Branch at the state line were dominantly cow and horse with one ribotype from bird. Escherichia coli was detected in only one well sample. Bacterial ribotypes in water from that upgradient well indicated human and dog feces as sources for bacteria, and that on site wastewater treatment may not always be adequate in these highly permeable soils. Greater concentrations of nitrate in Cave Springs Branch and O'Brien Spring relative to the poultry-processing plant wastewater outfall may be due, in part, to conversion of ammonia from poultry processing plant wastewater. The poultry-processing plant wastewater outfall sample collected in March 2000 contained greater concentrations of ammonia and total organic nitrogen plus ammonia than the spring, stream, and well samples collected during August 1999. Cave Springs Branch and Honey Creek contributed approximately equal loads of nitrogen to Honey Creek below the confluence and the greatest loads of nitrogen were introduced to Cave Springs Branch by the poultry processing plant wastewater outfall and O'Brien Spring. Nitrate concentrations in upgradient well samples ranged from 0.38 to 4.60 milligrams per liter, indicating that there are sources of ground-water nitrogen other than Cave Springs Branch, such as animal waste, fertilizer, or human waste. Nitrogen compounds in water from wells downgradient of Cave Springs Branch may be from Cave Springs Branch, fertilizers, animal waste, or human waste.

Oklahoma↗
USGS2001

Hydrologic and salinity characteristics of Currituck Sound and selected tributaries in North Carolina and Virginia, 1998–99

Data collected at three sites in Currituck Sound and three tributary sites between March 1, 1998, and February 28, 1999, were used to describe hydrologic and salinity characteristics of Currituck Sound. Water levels and salinity were measured at West Neck Creek at Pungo and at Albemarle and Chesapeake Canal near Princess Anne in Virginia, and at Coinjock, Bell Island, Poplar Branch, and Point Harbor in North Carolina. Flow velocity also was measured at the West Neck Creek and Coinjock sites. The maximum water-level range during the study period was observed near the lower midpoint of Currituck Sound at Poplar Branch. Generally, water levels at all sites were highest during March and April, and lowest during November and December. Winds from the south typically produced higher water levels in Currituck Sound, whereas winds from the north typically produced lower water levels. Although wind over Currituck Sound is associated with fluctuations in water level within the sound, other mechanisms, such as the effects of wind on Albemarle Sound and on other water bodies south of Currituck Sound, likely affect low-frequency water-level variations in Currituck Sound. Flow in West Neck Creek ranged from 313 cubic feet per second to the south to -227 cubic feet per second to the north (negative indicates flow to the north). Flow at the Coinjock site ranged from 15,300 cubic feet per second to the south to -11,700 cubic feet per second to the north. Flow was to the south 68 percent of the time at the West Neck Creek site and 44 percent of the time at the Coinjock site. Daily flow volumes were calculated as the sum of the instantaneous flow volumes. The West Neck Creek site had a cumulative flow volume to the south of 7.69 x 108 cubic feet for the period March 1, 1998, to February 28, 1999; the Coinjock site had a cumulative flow volume to the north of -1.33 x 1010 cubic feet for the same study period. Wind direction and speed influence flow at the West Neck Creek and Coinjock sites, whereas precipitation alone has little effect on flow at these sites. Flow at the West Neck Creek site is semidiurnal but is affected by wind direction and speed. Flow to the south (positive flow) was associated with wind speeds averaging more than 15 miles per hour from the northwest; flow to the north (negative flow) was associated with wind speeds averaging more than 15 miles per hour from the south and southwest. Flow at the Coinjock site reacted in a more unpredictable manner and was not affected by winds or tides in the same manner as West Neck Creek, with few tidal characteristics evident in the record. Throughout the study period, maximum salinity exceeded 3.5 parts per thousand at all sites; however, mean and median salinities were below 3.5 parts per thousand at all sites except the Point Harbor site (3.6 and 4.2 parts per thousand, respectively) at the southern end of the sound. Salinities were less than or equal to 3.5 parts per thousand nearly 100 percent of the time at the Bell Island and Poplar Branch sites in Currituck Sound and about 86 percent of the time at the Albemarle and Chesapeake Canal site north of the sound. Salinity at the West Neck Creek and Coinjock sites was less than or equal to 3.5 parts per thousand about 82 percent of the time. During this study, prevailing winds from the north were associated with flow to the south and tended to increase salinity at the West Neck Creek and the Albemarle and Chesapeake Canal sites. Conversely, these same winds tended to decrease salinity at the other sites. Prevailing winds from the south and southwest were associated with flow to the north and tended to increase salinity at the Poplar Branch and Point Harbor sites in Currituck Sound and at the Coinjock site, but these same winds tended to decrease salinity at the West Neck Creek and the Albemarle and Chesapeake Canal sites. The greatest variations in salinity were observed at the northernmost site, West Neck Creek, and thesouthernmost site, Point Harbor. The least variation in salinity was observed at the upper midpoint of the sound at the Bell Island site. Daily salt loads were computed for 364 days at the West Neck Creek site and 348 days at the Coinjock site from March 1, 1998, to February 28, 1999. The cumulative salt load at West Neck Creek was 28,170 tons to the south, and the cumulative salt load at the Coinjock site was -872,750 tons to the north. The cumulative salt load passing the West Neck Creek site during the study period would be 0.01 part per thousand if uniformly distributed throughout the sound (approximately 489,600 acre-feet in North Carolina). If the cumulative salt load passing the Coinjock site were uniformly distributed throughout the sound, the salinity in the sound would be 0.32 part per thousand. The net transport at the West Neck Creek and Coinjock sites indicates inflow of salt into the sound. A constant inflow of freshwater from tributaries and ground-water sources also occurs; however, the net flow volumes from these freshwater sources are not documented, and the significance of these freshwater inflows toward diluting the net import of salt into the sound is beyond the scope of this study.

North Carolina, Virginia↗
USGS2002

Simulation of hydrodynamics, temperature, and dissolved oxygen in Beaver Lake, Arkansas, 1994-1995

The tailwaters of Beaver Lake and other White River reservoirs support a cold-water trout fishery of significant economic yield in northwestern Arkansas. The Arkansas Game and Fish Commission has requested an increase in existing minimum flows through the Beaver Lake dam to increase the amount of fishable waters downstream. Information is needed to assess the impact of additional minimum flows on temperature and dissolved-oxygen qualities of reservoir water above the dam and the release water. A two-dimensional, laterally averaged hydrodynamic, thermal and dissolved-oxygen model was developed and calibrated for Beaver Lake, Arkansas. The model simulates surface-water elevation, currents, heat transport and dissolved-oxygen dynamics. The model was developed to assess the impacts of proposed increases in minimum flows from 1.76 cubic meters per second (the existing minimum flow) to 3.85 cubic meters per second (the additional minimum flow). Simulations included assessing (1) the impact of additional minimum flows on tailwater temperature and dissolved-oxygen quality and (2) increasing initial water-surface elevation 0.5 meter and assessing the impact of additional minimum flow on tailwater temperatures and dissolved-oxygen concentrations. The additional minimum flow simulation (without increasing initial pool elevation) appeared to increase the water temperature (<0.9 degrees Celsius) and decrease dissolved oxygen concentration (<2.2 milligrams per liter) in the outflow discharge. Conversely, the additional minimum flow plus initial increase in pool elevation (0.5 meter) simulation appeared to decrease outflow water temperature (0.5 degrees Celsius) and increase dissolved oxygen concentration (<1.2 milligrams per liter) through time. However, results from both minimum flow scenarios for both water temperature and dissolved oxygen concentration were within the boundaries or similar to the error between measured and simulated water column profile values.

Water-Resources Investigations Report↗
USGS2002

Simulation of hydrodynamics, temperature, and dissolved oxygen in Norfork Lake, Arkansas, 1994-1995

Outflow from Norfork Lake and other White River reservoirs support a cold-water trout fishery of significant economic yield in north-central Arkansas and south-central Missouri. The Arkansas Game and Fish Commission has requested an increase in existing minimum flows through the Norfork Lake dam to increase the amount of fishable waters downstream. Information is needed to assess the impact of increased minimum flows on temperature and dissolved-oxygen concentrations of reservoir water and the outflow. A two-dimensional, laterally averaged, hydrodynamic, temperature, and dissolved-oxygen model was developed and calibrated for Norfork Lake, located on the Arkansas-Missouri State line. The model simulates water-surface elevation, heat transport, and dissolved-oxygen dynamics. The model was developed to assess the impacts of proposed increases in minimum flow from 1.6 cubic meter per second (the existing minimum flow) to 8.5 cubic meters per second (the increased minimum flow). Simulations included assessing the impact of (1) increased minimum flows and (2) increased minimum flows with increased water-surface elevation of 1.1 meter in Norfork Lake on outflow temperatures and dissolved-oxygen concentrations. The increased minimum flow simulation (without increasing initial water-surface elevation) appeared to increase the water temperature and decrease dissolved-oxygen concentration in the outflow. Conversely, the increased minimum flow and initial increase in water-surface elevation (1.1 meter) simulation appeared to decrease outflow water temperature and increase dissolved-oxygen concentration through time. However, results from both scenarios for water temperature and dissolved-oxygen concentration were within the boundaries or similar to the error between measured and simulated water column profile values.

Arkansas↗
USGS2003

Methodology for estimating times of remediation associated with monitored natural attenuation

Natural attenuation processes combine to disperse, immobilize, and biologically transform anthropogenic contaminants, such as petroleum hydrocarbons and chlorinated ethenes, in ground-water systems. The time required for these processes to lower contaminant concentrations to levels protective of human health and the environment, however, varies widely between different hydrologic systems, different chemical contaminants, and varying amounts of contaminants. This report outlines a method for estimating timeframes required for natural attenuation processes, such as dispersion, sorption, and biodegradation, to lower contaminant concentrations and mass to predetermined regulatory goals in groundwater systems. The time-of-remediation (TOR) problem described in this report is formulated as three interactive components: (1) estimating the length of a contaminant plume once it has achieved a steady-state configuration from a source area of constant contaminant concentration, (2) estimating the time required for a plume to shrink to a smaller, regulatoryacceptable configuration when source-area contaminant concentrations are lowered by engineered methods, and (3) estimating the time needed for nonaqueous phase liquid (NAPL) contaminants to dissolve, disperse, and biodegrade below predetermined levels in contaminant source areas. This conceptualization was used to develop Natural Attenuation Software (NAS), an interactive computer aquifers. NAS was designed as a screening tool and requires the input of detailed site information about hydrogeology, redox conditions, and the distribution of contaminants. Because NAS is based on numerous simplifications of hydrologic, microbial, and geochemical processes, the program may introduce unacceptable errors for highly heterogeneous hydrologic systems. In such cases, application of the TOR framework outlined in this report may require more detailed, site-specific digital modeling. The NAS software may be downloaded from the Web site http://www.cee.vt.edu/NAS/ Application of NAS illustrates several general characteristics shared by all TOR problems. First, the distance of stabilization of a contaminant plume is strongly dependent on the natural attenuation capacity of particular ground-water systems. The time that it takes a plume to reach a steady-state configuration, however, is independent of natural attenuation capacity. Rather, the time of stabilization is most strongly affected by the sorptive capacity of the aquifer, which is dependent on the organic matter content of the aquifer sediments, as well as the sorptive properties of individual contaminants. As a general rule, a high sorptive capacity retards a plume.s growth or shrinkage, and increases the time of stabilization. Finally, the time of NAPL dissolution depends largely on NAPL mass, composition, geometry, and hydrologic factors, such as ground-water flow rates. An example TOR analysis for petroleum hydrocarbon NAPL was performed for the Laurel Bay site in South Carolina. About 500 to 1,000 pounds of gasoline leaked into the aquifer at this site in 1991, and the NAS simulations suggested that TOR would be on the order of 10 years for soluble and poorly sorbed compounds, such as benzene and methyl tertiary-butyl ether (MTBE). Conversely, TOR would be on the order of 40 years for less soluble, more strongly sorbed compounds, such as toluene, ethylbenzene, and xylenes (TEX). These TOR estimates are roughly consistent with contaminant concentrations observed over 10 years of monitoring at this site where benzene and MTBE concentrations were observed to decrease rapidly and are approaching regulatory maximum concentration limits, whereas toluene, ethylbenzene, and xylene concentrations decreased at a slower rate and have remained relatively high. An example TOR analysis for petroleum hydrocarbon NAPL was performed for the Laurel Bay site in South Carolina.

South Carolina↗
USGS2003

Simulation of hydrodynamics, temperature, and dissolved oxygen in Bull Shoals Lake, Arkansas, 1994-1995

Outflow from Bull Shoals Lake and other White River reservoirs supports a cold-water trout fishery of substantial economic yield in north-central Arkansas and south-central Missouri. The Arkansas Game and Fish Commission has requested an increase in existing minimum flows through the Bull Shoals Lake dam to increase the amount of fishable waters downstream. Information is needed to assess the impact of increased minimum flows on temperature and dissolved-oxygen concentrations of reservoir water and the outflow.A two-dimensional, laterally averaged, hydrodynamic, temperature, and dissolved-oxygen model was developed and calibrated for Bull Shoals Lake, located on the Arkansas-Missouri State line. The model simulates water-surface elevation, heat transport, and dissolved- oxygen dynamics. The model was developed to assess the impacts of proposed increases in minimum flow from 4.6 cubic meters per second (the existing minimum flow) to 22.6 cubic meters per second (the increased minimum flow). Simulations included assessing the impact of (1) increased minimum flows and (2) increased minimum flows with increased initial water-surface elevation of 1.5 meters in Bull Shoals Lake on outflow temperatures and dissolved-oxygen concentrations.The increased minimum flow simulation (without increasing initial water-surface elevation) increased the water temperature and dissolved-oxygen concentration in the outflow. Conversely, the increased minimum flow and increased initial water-surface elevation (1.5 meters) simulation decreased outflow water temperature and dissolved-oxygen concentration through time. However, results from both scenarios for water temperature and dissolved-oxygen concentration were within the boundaries of the error between measured and simulated water column profile values.

Water-Resources Investigations Report↗
USGS2004

Loads and yields of selected constituents in streams and rivers of Monroe County, New York, 1984-2001

Hydrologic data collected in Monroe County since the 1980s and earlier, including long-term records of streamflow and chemical loads, provide a basis for assessment of water-management practices. All monitored streams except Northrup Creek showed a slight (nonsignificant) overall decrease in annual streamflow over their period of record; Northrup Creek showed a slight increase. The highest yields of all constituents except chloride and sulfate were at Northrup Creek; these values exceeded those of the seven Irondequoit Creek basin sites and the Genesee River site. The highest yields of dissolved chloride were at the most highly urbanized site (Allen Creek), whereas the highest yields of dissolved sulfate were at the most upstream Irondequoit Creek sites -- Railroad Mills (active) and Pittsford (inactive). Yields of all constituents in the Genesee River at the Charlotte Pump Station were within the range of those at the Irondequoit Creek basin sites. The four active Irondequoit Creek basin sites showed significant downward trends in flow-adjusted loads of ammonia + organic nitrogen, possibly from the conversion of agricultural land to suburban land. Two active sites (Allen Creek and Blossom Road) and one inactive site (Thomas Creek) showed downward trends in loads of ammonia. All active sites showed significant upward trends in dissolved chloride loads. Northrup Creek showed a significant downward trend in total phosphorus load since the improvement in phosphorus removal at the Spencerport wastewater-treatment plant, and upward trends in dissolved chloride and sulfate loads. The Genesee River at the Charlotte Pump Station showed significant downward trends in loads of ammonia + organic nitrogen and chloride, and an upward trend in loads of orthophosphate. The improved treatment or diversion of sewage-treatment-plant-effluent has produced decreased yields of some constituents throughout the county, particularly in the Irondequoit Creek basin, where the loads of nutrients delivered to Irondequoit Bay have been decreased.

New York↗
USGS2004

Water quality in Big Cypress National Preserve and Everglades National Park — Trends and spatial characteristics of selected constituents

Seasonal changes in water levels and flows in Big Cypress National Preserve (BICY) and Everglades National Park (EVER) affect water quality. As water levels and flows decline during the dry season, physical, geochemical and biological processes increase the breakdown of organic materials and the build-up of organic waste, nutrients, and other constituents in the remaining surface water. For example, concentrations of total phosphorus in the marsh are less than 0.01 milligram per liter (mg/L) during much of the year. Concentrations can rise briefly above this value during the dry season and occasionally exceed 0.1 mg/L under drought conditions. Long-term changes in water levels, flows, water management, and upstream land use also affect water quality in BICY and EVER, based on analysis of available data (1959-2000). During the 1980's and early 1990's, specific conductance and concentrations of chloride increased in the Taylor Slough and Shark River Slough. Chloride concentrations more than doubled from 1960 to 1990, primarily due to greater canal transport of high dissolved solids into the sloughs. Some apparent long-term trends in sulfate and total phosphorus were likely attributable, at least in part, to high percentages of less-than and zero values and to changes in reporting levels over the period of record. High values in nutrient concentrations were evident during dry periods of the 1980's and were attributable either to increased canal inflows of nutrient-rich water, increased nutrient releases from breakdown of organic bottom sediment, or increased build-up of nutrient waste from concentrations of aquatic biota and wildlife in remaining ponds. Long-term changes in water quality over the period of record are less pronounced in the western Everglades and the Big Cypress Swamp; however, short-term seasonal and drought-related changes are evident. Water quality varies spatially across the region because of natural variations in geology, hydrology, and vegetation and because of differences in water management and land use. Nutrient concentrations are relatively low in BICY and EVER compared with concentrations in parts of the northern Everglades that are near agricultural and urban lands. Concentrations of total phosphorus generally are higher in BICY (median values, 1991-2000, were mostly greater than 0.015 mg/L) than in EVER (median values, 1991-2000, less than 0.01 mg/L), probably because of higher phosphorus in natural sources such as shallow soils, rocks, and ground water in the Big Cypress region than in the Everglades region. Conversely, concentrations of chloride and sulfate are higher in EVER (median values in Shark River Slough, 1991-2000, mostly greater than 2 mg/L sulfate and 50 mg/L chloride) than in BICY (median values, 1991-2000, less than 1 mg/L sulfate and at most sites less than 20 mg/L chloride), probably because of the canal transport system, which conveys more water from an agricultural source into EVER than into BICY. Trace elements and contaminants such as pesticides and other toxic organic compounds are in relatively low concentrations in BICY and EVER compared with concentrations in parts of the northern Everglades near agricultural and urban sources. Concentrations rarely exceeded aquatic life criteria in BICY and EVER. Atrazine was the only pesticide found in water that exceeded the criteria (in 2 out of 304 samples). The pesticides heptachlor expoxide, lindane, and p,p?-DDE exceeded criteria in canal bed sediments in 1, 2, and 16 percent of the samples, respectively.

Florida↗
USGS2004

Hydrogeologic characteristics of four public drinking-water supply springs in northern Arkansas

In October 2000, a study was undertaken by the U.S. Geological Survey (USGS) in cooperation with the Arkansas Department of Health to determine the hydrogeologic characteristics, including the extent of the recharge areas, for Hughes Spring, Stark Spring, Evening Shade Spring, and Roaring Spring, which are used for public-water supply in northern Arkansas. Information pertaining to each spring can be used to enable development of effective management plans to protect these water resources and public health. An integrated approach to determine the ground-water characteristics and the extent of the local recharge areas of the four springs incorporated tools and methods of hydrology, structural geology, geomorphology, geophysics, and geochemistry. Analyses of discharge, temperature, and water quality were completed to describe ground-water flow characteristics, source-water characteristics, and connectivity of the ground-water system with surface runoff. Water-level contour maps were constructed to determine ground-water flow directions and ground-water tracer tests were conducted to determine the extent of the recharge areas and ground-water flow velocities. Hughes Spring supplies water for the city of Marshall, Arkansas, and the surrounding area. The mean annual discharge for Hughes Spring was 2.9 and 5.2 cubic feet per second for water years 2001 and 2002, respectively. Recharge to the spring occurs mainly from the Boone Formation (Springfield Plateau aquifer). Ground-water tracer tests indicate the recharge area for Hughes Spring generally coincides with the surface drainage area (15.8 square miles) and that Hughes Spring is connected directly to the surface flow in Brush Creek. The geochemistry of Hughes Spring demonstrated variations with flow conditions and the influence of surface-runoff in the recharge area. Calcite saturation indices, total dissolved solids concentrations, and hardness demonstrate noticeable differences with flow conditions reflecting the reduced residence time and interaction of water with the source rock within the ground-water system at higher discharges for Hughes Spring. Concentrations of fecal indicator bacteria also demonstrated a substantial increase during high-flow conditions, suggesting that a non-point source of bacteria possibly from livestock may enter the system. Conversely, nutrient concentrations did not vary with flow and were similar to concentrations reported for undeveloped sites in the Springfield Plateau and Ozark aquifers in northern Arkansas and southern Missouri. Deuterium and oxygen-18 data show that the Hughes Spring discharge is representative of direct precipitation and not influenced by water enriched in oxygen-18 through evaporation. Discharge data show that Hughes Spring is dominated by conduit type ground-water flow, but a considerable component of diffuse flow also exists in the ground-water system. Carbon-13 data indicate a substantial component of the recharge water interacts with the surface material (soil and regolith) in the recharge area before entering the ground-water system for Hughes Spring. Tritium data for Hughes Spring indicate that the discharge water is a mixture of recent recharge and sub-modern water (recharged prior to 1952). Stark Spring supplies water for the city of Cushman, Arkansas, and the surrounding area. 2 Hydrogeologic Characteristics of Four Public Drinking-Water Supply Springs in Northern Arkansas The mean annual discharge for Stark Spring was 0.5 and 1.5 cubic feet per second for water years 2001 and 2002, respectively. The discharge and water-quality data show the ground-water system for Stark Spring is dominated by rapid recharge from surface runoff and mainly consists of a conduit- type flow system with little diffuse-type flow. Analyses of discharge data show that the estimated recharge area (0.79 square mile) is larger than the surface drainage area (0.34 square mile). Ground-water tracer tests and the outcrop of the

Water-Resources Investigations Report↗
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↗
USGS1980

Waste-assimilation capacity of the Arkansas River in Pueblo County, Colorado, as it relates to water-quality guidelines and stream classification

The waste-assimilation capacity of a 42-mile reach of the Arkansas River in Pueblo County, Colo., was evaluated using a one-dimensional steady-state water-quality model. The model was calibrated and verified using hydraulic and water-quality data collected in 1976 and 1979. The water-quality con-stituents modeled were 5-day carbonaceous biochemical oxygen demand, total organic nitrogen, total ammonia, total nitrite, total nitrate, and dissolved oxygen. Model calibration was acceptable for all constituents except total organic nitrogen, and verification was acceptable for all constituents except total organic nitrogen and total nitrite. A relationship between nonionized and total ammonia was defined to provide simulation capability for nonionized ammonia. The model was used to simulate the water-quality effects of 63 combinations of wastewater treatment. The water-quality effects were evaluated with respect to water-quality guidelines that may be applied based on possible stream-use classifications. Model simulations were based on a 7-day low flow with a 10-year recurrence interval that occurs between August 15 and October 15 and on a winter low-flow period that occurs as a result of upstream storage of water. The mixing zone downstream from the Pueblo Wastewater Treatment Plant outfall was evaluated to determine where the water-quality guidelines should apply for the model simulations. Complete lateral mixing of the effluent from the Pueblo Wastewater Treatment Plant occurred 2.7 river miles downstream from the outfall. Model simulations indicated a water-quality guideline of 0.06 milligram per liter nonionized ammonia nitrogen would be exceeded at the end of the mixing zone for Q7,10 conditions with secondary treatment at the Pueblo Wastewater Treatment Plant and a projected effluent discharge for the year 2000, and that a water-quality guideline of 0.5 milligram per liter total nitrite nitrogen would be exceeded for winter conditions and the same waste-water-treatment possibility. Wastewater-treatment possibilities with a pro-jected discharge for the year 2000 which would result in both water-quality guidelines being met include land application of treated effluent and advanced secondary treatment at the Pueblo Wastewater Treatment Plant with conversion of ammonia to nitrate to result in an effluent total ammonia nitrogen concentration of 5.4 to 10.6 milligrams per liter, depending on the quality of effluent from the downstream discharge from the CF&I Steel Corp. Model simulations also included an evaluation of flow augmentation necessary to meet a water-quality guideline of 0.06 milligram per liter non-ionized ammonia nitrogen. The evaluation was made for the n,7,10 period, secondary treatment at the Pueblo Wastewater Treatment Plant with a projected discharge for the year 2000, and effluent water quality at a downstream discharge which could contain twice the estimated ammonia concentration allowable for best available technology treatment for the iron and steel industry. The flow augmentation necessary to meet the water-quality guideline, based on the model simulations, is approximately 140 cubic feet per second.

Colorado↗
USGS1985

Cost-effectiveness of the stream-gaging program in North Carolina

This report documents the results of a study of the cost-effectiveness of the stream-gaging program in North Carolina. Data uses and funding sources are identified for the 146 gaging stations currently operated in North Carolina with a budget of $777,600 (1984). As a result of the study, eleven stations are nominated for discontinuance and five for conversion from recording to partial-record status. Large parts of North Carolina 's Coastal Plain are identified as having sparse streamflow data. This sparsity should be remedied as funds become available. Efforts should also be directed toward defining the efforts of drainage improvements on local hydrology and streamflow characteristics. The average standard error of streamflow records in North Carolina is 18.6 percent. This level of accuracy could be improved without increasing cost by increasing the frequency of field visits and streamflow measurements at stations with high standard errors and reducing the frequency at stations with low standard errors. A minimum budget of $762,000 is required to operate the 146-gage program. A budget less than this does not permit proper service and maintenance of the gages and recorders. At the minimum budget, and with the optimum allocation of field visits, the average standard error is 17.6 percent.

North Carolina↗
USGS1985

Cost effectiveness of the stream-gaging program in Pennsylvania

This report documents a cost-effectiveness study of the stream-gaging program in Pennsylvania. Data uses and funding were identified for 223 continuous-record stream gages operated in 1983; four are planned for discontinuance at the close of water-year 1985; two are suggested for conversion, at the beginning of the 1985 water year, for the collection of only continuous stage records. Two of 11 special-purpose short-term gages are recommended for continuation when the supporting project ends; eight of these gages are to be discontinued and the other will be converted to a partial-record type. Current operation costs for the 212 stations recommended for continued operation is $1,199,000 per year in 1983. The average standard error of estimation for instantaneous streamflow is 15.2%. An overall average standard error of 9.8% could be attained on a budget of $1,271,000, which is 6% greater than the 1983 budget, by adopted cost-effective stream-gaging operations. (USGS)

Water-Resources Investigations Report↗
USGS1989

A computer program for converting rectangular coordinates to latitude-longitude coordinates

A computer program was developed for converting the coordinates of any rectangular grid on a map to coordinates on a grid that is parallel to lines of equal latitude and longitude. Using this program in conjunction with groundwater flow models, the user can extract data and results from models with varying grid orientations and place these data into grid structure that is oriented parallel to lines of equal latitude and longitude. All cells in the rectangular grid must have equal dimensions, and all cells in the latitude-longitude grid measure one minute by one minute. This program is applicable if the map used shows lines of equal latitude as arcs and lines of equal longitude as straight lines and assumes that the Earth 's surface can be approximated as a sphere. The program user enters the row number , column number, and latitude and longitude of the midpoint of the cell for three test cells on the rectangular grid. The latitude and longitude of boundaries of the rectangular grid also are entered. By solving sets of simultaneous linear equations, the program calculates coefficients that are used for making the conversion. As an option in the program, the user may build a groundwater model file based on a grid that is parallel to lines of equal latitude and longitude. The program reads a data file based on the rectangular coordinates and automatically forms the new data file. (USGS)

Water-Resources Investigations Report↗
USGS1990

Water quality of alluvial aquifers, Carroll and Guthrie counties, Iowa, with emphasis on the occurrence of nitrate and pesticides, 1986-87

Samples collected from wells in Carroll and Guthrie Counties, Iowa, were analyzed to describe the chemical quality of the ground water in shallow aquifers. The study began in June 1986 with the selection of 20 shallow wells in Carroll County and 22 shallow wells in Guthrie County. These wells were sampled in the summer and fall of 1986 and 1987. Samples from the wells were analyzed for major ions, nutrients, trace elements, radiochemicals, nitrate, and pesticides. Median and mean nitrate concentrations were 95 and 11 milligrams per liter. About 60 percent of the samples had nitrate concentrations greater than 5.0 milligrams per liter. Detectable concentrations of a least one pesticide were in 27 percent of the samples. Atrazine, the most prevalent pesticide, was detected in 25 percent of the samples; alachlor was detected in 6 percent; and cyanazine was detected in 5 percent. Dicamba, metolachlor, trifluralin, and2,4-D were detected in 2 percent or less of the samples. In the summer and fall 1986,43 and 45 percent of the water samples had nitrate concentrations larger than 10 milligrams per liter, the maximum contaminant level for public drinking water specified by the State of Iowa; in the summer and fall 1987,41 and 55 percent of the samples had nitrate concentrations larger than the maximum contaminant level. In the summer and fall 1986,23 and 18 percent of the samples contained detectable concentrations of at least one pesticide; in the summer and fall 1987,21 and 47 percent of the samples contained detectable concentrations of at least one pesticide. Detection frequencies ofatrazine, alachlor, and cyanazine increased for samples collected in October 1987. Pesticides were more frequently detected along Brushy Creek, and the East Nishnabotna, Middle, North Raccoon, and South Raccoon Rivers. However, pesticides also were detected along the Middle Raccoon and West Nishnabotna Rivers. Detection frequencies were greatest (50 percent) for the East Nishnabotna River and Middle River alluvial settings. Increased nitrate concentrations generally were observed in the shallower wells and were larger than those previously reported for shallow municipal wells. Pesticide detection relative to well depth was inconsistent with the trend observed for nitrate. Pesticide detection frequencies were greater for wells that were 40 to 80 feet deep (about 40 percent) than for wells less that 40 feet deep (about 20 percent). Of the water samples with nitrate concentrations greater than or equal to 5.0 milligrams per liter, 33 percent had detectable pesticide concentrations. Conversely, for those samples with detectable pesticide concentrations, 76 percent had nitrate concentrations larger than or equal to 5.0 milligrams per liter and 67 percent were larger than or equal to 10 milligrams per liter. The median concentration of nitrate for samples containing at least one detectable pesticide was 15 milligrams per liter and was greater than the overall median nitrate concentration of 95 milligrams per liter. The median for samples that did not contain a detectable pesticide was 73 milligrams per liter.

Iowa↗
USGS1990

Sources and distribution of nitrate in ground water at a farmed field irrigated with sewage treatment-plant effluent, Tallahassee, Florida

The city of Tallahassee, Florida began applying sewage treatment-plant effluent to a sprayfield southeast of the city in 1980. Fertilizers containing inorganic nitrogen were also applied in conjunction with the operation of a commercial farm at this site. Analysis of groundwater in the surficial aquifer and the Upper Floridan aquifer have indicated that nitrate concentrations in some wells exceed the prescribed drinking water maximum contaminant level of 10 mg/L (nitrate as nitrogen). Nitrate concentrations greater than the maximum contaminant level were not detected in samples from monitoring wells outside the sprayfield boundary. Analyses of water from the unsaturated zone indicated that conversion of organic nitrogen and ammonia to nitrate was complete before the nitrogen- enriched water reached the water table. Groundwater samples from wells in the surficial and Upper Floridan aquifers less than 100 ft deep located inside sprayed areas had mean concentrations of nitrate much higher than samples from similar wells located outside sprayed areas at the southeast sprayfield. These shallow wells inside the sprayed areas were the only wells in which the maximum contaminant level for nitrate was exceeded. Analyses of the nitrogen isotope ratios in groundwater were used to determine whether the major source of nitrogen was treated sewage or fertilizers. The nitrogen isotope ratios in contaminated groundwater at the southeast sprayfield were compared to those at another sprayfield southwest of the city, where treated sewage was the sole source of nitrogen. Statistical analyses indicated a significant difference in the nitrogen isotope ratios at the two sites, indicating that both nitrogen sources are significant at the southeast sprayfield. (USGS)

Water-Resources Investigations Report↗