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USGS2012

Assessment of the Coal-Bed Gas Total Petroleum System in the Cook Inlet-Susitna region, south-central Alaska

The Cook Inlet-Susitna region of south-central Alaska contains large quantities of gas-bearing coal of Tertiary age. The U.S. Geological Survey in 2011 completed an assessment of undiscovered, technically recoverable coal-bed gas resources underlying the Cook Inlet-Susitna region based on the total petroleum system (TPS) concept. The Cook Inlet Coal-Bed Gas TPS covers about 9,600,000 acres and comprises the Cook Inlet basin, Matanuska Valley, and Susitna lowland. The TPS contains one assessment unit (AU) that was evaluated for coal-bed gas resources between 1,000 and 6,000 feet in depth over an area of about 8,500,000 acres. Coal beds, which serve as both the source and reservoir for natural gas in the AU, were deposited during Paleocene-Pliocene time in mires associated with a large trunk-tributary fluvial system. Thickness of individual coal beds ranges from a few inches to more than 50 feet, with cumulative coal thickness of more than 800 feet in the western part of the basin. Coal rank ranges from lignite to subbituminous, with vitrinite reflectance values less than 0.6 percent throughout much of the AU. The AU is considered hypothetical because only a few wells in the Matanuska Valley have tested the coal-bed reservoirs, so the use of analog coal-bed gas production data was necessary for this assessment. In order to estimate reserves that might be added in the next 30 years, coal beds of the Upper Fort Union Formation in the Powder River Basin of Wyoming and Montana were selected as the production analog for Tertiary coal beds in the Cook Inlet-Susitna region. Upper Fort Union coal beds have similar rank (lignite to subbituminous), range of thickness, and coal-quality characteristics as coal beds of the Tertiary Kenai Group. By use of this analog, the mean total estimate of undiscovered coal-bed gas in the Tertiary Coal-Bed Gas AU is 4.674 trillion cubic feet (TCF) of gas.

Alaska↗
USGS2005

Occurrence of fecal-indicator bacteria and protocols for identification of fecal-contamination sources in selected reaches of the West Branch Brandywine Creek, Chester County, Pennsylvania

The presence of fecal-indicator bacteria indicates the potential presence of pathogens originating from the fecal matter of warm-blooded animals. These pathogens are responsible for numerous human diseases ranging from common diarrhea to meningitis and polio. The detection of fecal-indicator bacteria and interpretation of the resultant data are, therefore, of great importance to water-resource managers. Current (2005) techniques used to assess fecal contamination within the fluvial environment primarily assess samples collected from the water column, either as grab samples or as depth- and (or) width-integrated samples. However, current research indicates approximately 99 percent of all bacteria within nature exist as attached, or sessile, bacteria. Because of this condition, most current techniques for the detection of fecal contamination, which utilize bacteria, assess only about 1 percent of the total bacteria within the fluvial system and are, therefore, problematic. Evaluation of the environmental factors affecting the occurrence and distribution of bacteria within the fluvial system, as well as the evaluation and modification of alternative approaches that effectively quantify the larger population of sessile bacteria within fluvial sediments, will present water-resource managers with more effective tools to assess, prevent, and (or) eliminate sources of fecal contamination within pristine and impaired watersheds. Two stream reaches on the West Branch Brandywine Creek in the Coatesville, Pa., region were studied between September 2002 and August 2003. The effects of sediment particle size, climatic conditions, aquatic growth, environmental chemistry, impervious surfaces, sediment and soil filtration, and dams on observed bacteria concentrations were evaluated. Alternative approaches were assessed to better detect geographic sources of fecal contamination including the use of turbidity as a surrogate for bacteria, the modification and implementation of sandbag bacteria samplers, and the use of optical brighteners. For the purposes of this report, sources of bacteria were defined as geographic locations where elevated concentrations of bacteria are observed within, or expected to enter, the main branch of the West Branch Brandywine Creek. Biologic sources (for example, waterfowl) were noted where applicable; however, no specific study of biologic sources (such as bacterial source tracking) was conducted. Data indicated that specific bacterial populations within fluvial sediments could be related to specific particle-size ranges. This relation is likely the result of the reduced porosity and permeability associated with finer sediments and the ability of specific bacteria to tolerate particular environments. Escherichia coli (E. coli) showed a higher median concentration (2,160 colonies per gram of saturated sediment) in the 0.125 to 0.5-millimeter size range of natural sediments than in other ranges, and enterococcus bacteria showed a higher median concentration (61,830 colonies per gram of saturated sediment) in the 0.062 to 0.25-millimeter size range of natural sediments than in other ranges. There were insufficient data to assess the particle-size relation to fecal coliform bacteria and (or) fecal streptococcus bacteria. Climatic conditions were shown to affect bacteria concentrations in both the water column and fluvial sediments. Drought conditions in 2002 resulted in lower overall bacteria concentrations than the more typically wet year of 2003. E. coli concentrations in fluvial sediment along the Coatesville study reach in 2002 had a median concentration of 92 colonies per gram of saturated sediment; in 2003, the median concentration had risen to 4,752 colonies per gram of saturated sediment. Symbiotic relations between bacteria and aquatic growth were likely responsible for increased bacteria concentrations observed within an impoundment area on the Coatesville study reach. This reach showed evidence of elevated aquatic growth and sharp increases in E. coli concentrations from upstream to downstream through the impoundment area in both 2002 and 2003. In 2003, E. coli concentrations within the waters column increased from 940 colonies per 100 milliliters upstream to 6,000 colonies per 100 milliliters at the dam crest. Given that these bacteria likely resulted from natural bacterial regrowth, the use of E. coli as an indicator of fecal contamination was severely impaired. Variable environmental conditions along the West Branch Brandywine Creek made the common field-chemical parameters of specific conductance, temperature, pH, and dissolved oxygen ineffective and (or) impossible to use for the determination of inputs of fecal contamination. Extreme variations in chemical gradients commonly were related to the urban/industrial signature of the watershed. For example, during base-flow sampling in 2002, specific-conductance values exceeding 1,000 microsiemens per centimeter observed in effluent from a local steel mill. This effluent raised the specific conductance within the West Branch Brandywine from just above 200 microsiemens per centimeter upstream from the outfall to just below 500 microsiemens per centimeter downstream from the outfall. These chemical gradients also, likely, had an effect on the initial colonization of bacteria, the formation of biofilms, and the persistence of certain types of bacteria along the study reach. Data collected in 2003 indicated that nutrients increased during both base-flow and stormflow conditions along the Coatesville study reach. For example, during base-flow sampling in 2003, 20 pounds of phosphorus was shown to enter the West Branch Brandywine Creek along the Coatesville study reach. The largest contributors to this base-flow nutrient load were likely two wastewater-treatment facilities adjacent to the study reach. During stormflow sampling in 2003, 480 pounds of phosphorus was shown to enter the West Branch Brandywine Creek along the Coatesville study reach. Data, along with other research, indicated the largest contributor to this stormflow nutrient load was likely remobilized sediment originating from a large dam impoundment. These elevated nutrient concentrations were considered sufficient to promote accelerated aquatic growth along the reach. Data collected in 2003 showed that wastewater constituents entered the West Branch Brandywine Creek largely from urban storm-sewer systems. Samples from the primary storm sewer for the city of Coatesville had detections for 20 of 69 wastewater constituents. These constituents included both strong and weak indicators of fecal contamination and generally indicated the storm-sewer system along the Coatesville study reach was a likely source of fecal-indicator bacteria and fecal contamination under base-flow conditions. By comparison, 5 constituents were detected in samples from the upstream end of the reach, and 10 constituents were detected in samples from the downstream end of the reach. During stormflow, numbers of detections were similar along the entire length of the study reach-five in samples from the upstream end, eight in samples from the center of the reach, and seven in samples from the downstream end of the reach. These data indicate that point sources (such as culverts and pipes, septic systems, and wastewater-treatment facilities) are not likely the origin of bacteria contamination during stormflow. The bacteria concentrations observed during stormflow events probably result from remobilized sessile bacteria stored within fluvial sediments. In this case, these bacteria should not be considered indicators of current fecal contamination. Impervious surfaces were found to increase bacteria concentrations along the West Branch Brandywine Creek because contaminated runoff from impervious areas generally flows into, and is concentrated within, the confines of the local storm-sewer system. During 2002, storm-sewer outfalls draining impervious areas were associated with all major locations of elevated bacterial concentrations (greater than 1,200 colonies per gram of saturated sediment) in fluvial sediments. During 2003, wetter conditions and overall bacteria concentrations higher than in 2002 resulted in point sources of bacterial contamination becoming less pronounced; however, the storm-sewer system, draining adjacent impervious areas, was still observed to be the primary source of bacteria along the reach. Where stormwater and (or) other runoff from these areas was allowed to infiltrate and (or) flow through wetland and riparian buffers, bacteria concentrations were not observed to be elevated above background levels commonly observed throughout similar areas of the same reach. Two run-of-the-river dams along the Coatesville study reach were evaluated for their effects on observed bacterial concentrations. These dams were shown to have greater or lesser effects on bacterial concentrations depending on the size of the structure and the capacity of the structure to impede flows. The smaller upstream dam had an approximate height of 3 feet and showed little observed effect on measured turbidity values; these data indicated that the dam did not effectively impede the flow of water or sediment within the West Branch Brandywine Creek. Consequently, this small dam did not show any observed effect on bacterial concentrations either upstream or downstream of the structure. The larger dam, near the middle of the reach, had an approximate height of 20 feet and showed greater effects on both turbidity and bacteria concentrations. The capacity of the larger dam to impede flows, combined with nutrients entering the reach, resulted in increased biologic activity throughout the impoundment area. Within this larger impoundment, enterococcus bacteria populations were observed to decrease sharply and E. coli bacteria populations were observed to increase sharply as flow approached the dam crest. All bacteria levels were then observed to drop to background levels, in both the water column and fluvial sediment, immediately downstream from the dam crest. Additional study is required to determine the cause for this rapid die off. Turbidity was assessed as a potential surrogate for E. coli bacteria. Regression analysis indicated higher turbidity levels usually can indicate higher concentrations of bacteria (R2 = 0.67), but the relation was too sporadic on the West Branch Brandywine Creek to use turbidity as a surrogate for estimated bacteria concentrations. Evaluation of data from individual base-flow and stormflow events resulted in variable and generally poor statistical relations between E. coli bacteria and turbidity (R2 values ranged from 0.02 to 0.94). Sandbag samplers were used in 2003 to determine their suitability for the assessment of fecal contamination. Sandbag samplers rely on the ability of bacteria to attach to surfaces and use the larger sessile bacteria populations instead of the more commonly used planktonic bacteria populations. E. coli bacteria concentrations observed in the sandbag samplers, after 1 week in place, were similar to those found within natural sediments collected concurrently. Enterococcus bacteria concentrations within the same sandbag samplers were not similar, and were generally lower, than those observed within the natural sediments. This discrepancy was likely because sand within the samplers was sieved to a size that was likely too coarse for enterococcus bacteria to persist. Optical-brightener samplers were installed along with each sandbag sampler. Optical brighteners are additives used in common household detergents; therefore, detection of optical brighteners, along with elevated fecal-indicator bacteria concentrations, strongly indicates a link to humans. Positive results for optical brighteners were detected only at the outfalls of two sewage-treatment facilities; because of treatment of the effluent from these facilities, these samples did not have elevated bacteria concentrations. The lack of additional positive results was largely because this method is not sensitive to low concentrations of optical brighteners.

Pennsylvania↗
USGS2018

Preliminary groundwater salinity mapping near selected oil fields using historical water-sample data, central and southern California

The distribution of groundwater salinity was mapped for 31 oil fields and adjacent aquifers and summarized by 8 subregions across major oil-producing areas of central and southern California. The objectives of this study were to describe the distribution of groundwater near oil fields having total dissolved solids less than 10,000 milligrams per liter (mg/L) based on available data and to document where data gaps exist. Salinity was represented by the measured or calculated concentration of total dissolved solids (TDS) in samples of produced water obtained from petroleum wells and groundwater obtained from water wells. The water chemistry data were used to estimate the minimum depths of TDS greater than 3,000 mg/L and greater than 10,000 mg/L in areas near selected oil fields using historical water-chemistry data coupled with available well-location and construction information. The 10,000 mg/L threshold, representing the highest level of TDS concentration of water that could be considered as a potential source of drinking water, was present in all but 4 (Jasmin, Kern Bluff, Kern Front, and Mount Poso) of the 31 individual oil fields. Among petroleum wells, the median TDS concentration of produced water ranged from 500 mg/L for the Jasmin field to 32,636 mg/L for the Elk Hills field. Among water wells, median TDS concentrations, either reported or calculated from specific conductance, ranged from 151 mg/L for wells within 2 miles of the Ten Section field to 9,750 mg/L for wells within 2 miles of the combined North and South Belridge fields. In general, TDS across the eight geographic subregions increased with depth, but the relation of TDS with depth varied regionally. The most pronounced increases in TDS with depth were across the West Kern Valley Floor and West Kern Valley Margin subregions on the west side of the San Joaquin Valley, and in the vicinity of the Wilmington field in the Los Angeles Basin subregion; in these areas, relatively high TDS concentrations greater than 10,000 mg/L were present within the upper few hundred to several thousand feet of land surface. Total dissolved solids concentrations increased more gradually with depth in the Middle Kern Valley Floor subregion, in the South Kern Valley Margin subregion, in the vicinity of the Montebello and Santa Fe Springs fields in the Los Angeles Basin subregion, and in the Central Coast Basin subregion. The Kern Sierran Foothills and East Kern Valley Floor subregions, on the east side of the San Joaquin Valley, had the most gradual increases in TDS with depth. Fields in the East Kern Valley Floor subregion generally had groundwater and produced water with TDS less than 10,000 mg/L that extended to a large depth compared to most other subregions. Overall, the west side of the San Joaquin Valley in Kern County and the Wilmington field in Los Angeles County generally have the highest TDS values and the shallowest depths to high TDS. High TDS at relatively shallow depths on the west side of the San Joaquin Valley may be because of a combination of natural conditions and anthropogenic factors. In the vicinity of the Wilmington field in the Los Angeles Basin subregion, high TDS at relatively shallow depths is attributable at least in part to seawater intrusion. Fields on the east side of the San Joaquin Valley in Kern County have the lowest TDS and greatest depths to TDS greater than 10,000 mg/L because of their geologic setting adjacent to Sierra Nevada recharge areas. Reconnaissance salinity mapping was limited by several factors. The primary limitation was the lack of well-construction data for a significant number of water wells. Bottom perforation, well depth, or hole depth were not available for 35 percent of wells used for salinity mapping. A second limitation was variability in data quality. Total dissolved solids and specific conductance data were compiled from different data sources with varying degrees of documentation that ranged from comprehensive to very little or none. As a result, it was not always possible to assess the quality of the provided data with respect to either conditions at each well during sampling or the methodology used for sample collection and analysis. A third limitation was the lack of wells, either petroleum or water, and associated TDS data over large vertical intervals for some fields. As a result, the distribution of salinity and the depths at which TDS concentration exceeds the 3,000 and 10,000 mg/L thresholds could not always be precisely determined. This analysis highlights key gaps that need to be filled with additional analysis of other sources of information, such as borehole geophysical logs and new water sample or geophysical data collection.

California↗
USGS2025

Fisheries research and monitoring activities of the Lake Erie Biological Station, 2024

A comprehensive understanding of fish populations and their interactions is the cornerstone of modern fishery management and the basis for Lake Erie’s Fish Community Objectives (FCOs) developed in 2020 (Francis et al. 2020). The 2024 U.S. Geological Survey (USGS) Lake Erie Biological Station Annual Report is responsive to these FCOs and the USGS obligations via a Memorandum of Understanding (MOU 2017) with the Great Lakes Fishery Commission (GLFC) Council of Lake Committees (CLC) to provide scientific information in support of fishery management. Goals for the USGS Great Lakes Deepwater Fish Assessment and Ecological Studies were to monitor long-term changes in the fish community and track population dynamics of key fishes of interest to management agencies. Specific to Lake Erie, expectations were sustained investigations of native percids, prey fish populations, and Lake Trout. All work was conducted as part of the Deepwater Science Program under the authority of the Great Lakes Fishery Research Authorization Act of 2019 (16 USC §941h). The USGS 2024 Deepwater Science Program fieldwork began in Lake Erie in March and concluded in December, using trawl, gill net, hydroacoustic, lower trophic sampling devices, and telemetry methods. This work resulted in 44 bottom trawls covering 41 ha of lake bottom and catching 48,936 fish totaling 995 kg in the West Basin of Lake Erie, with detailed results described below. Overnight gill net sets (n=25) for coldwater species were performed in the East Basin of Lake Erie. A total of 8 km of gillnet was deployed during these surveys, which caught 106 fish, 92 of which were native coldwater species: Lake Trout, Burbot, and Lake Whitefish. Results from coldwater species assessments will be reported in the Coldwater Task Group report to the GLFC and the CLC (CTG 2025). These reports are used to inform Lake Trout stocking decisions and direct lamprey control measures (16 USC §939a). USGS hydroacoustic sampling included twenty-six 5-km transects (130 km total) in the Central Basin as part of a collaborative lake-wide survey with details and results reported by the Forage Task Group (FTG 2025). Lower trophic sampling provided data from zooplankton samples (n=12) and water quality profiles (n=12) to populate a database maintained by the Michigan Department of Natural Resources (MDNR), Ontario Ministry of Natural Resources (OMNR), Ohio Department of Natural Resources (ODNR), Pennsylvania Fish and Boat Commission (PFBC), and New York State Department of Environmental Conservation (NYSDEC). USGS also assisted CLC member agencies with deployment and maintenance of Great Lakes Acoustic Telemetry Observation System (GLATOS) infrastructure throughout all three Lake Erie basins and tributaries, supporting multiple coordinated telemetry investigations. This report presents biomass-based summaries of fish communities in western Lake Erie derived from USGS bottom trawl surveys conducted from 2013 to 2024 during June and September. The survey design compliments the August ODNR- OMNRF effort by reinforcing stock assessments with more robust data. Analyses herein evaluated trends in total biomass, abundance of dominant predator and forage species, non-native species composition, biodiversity, and community structure. Data from this effort are accessible for download (Keretz et al. 2025)

Lake Erie↗
USGS2013

Emergent sandbar dynamics in the lower Platte River in eastern Nebraska: methods and results of pilot study, 2011

The lower Platte River corridor provides important habitats for two State- and federally listed bird species: the interior least tern (terns; Sternula antillarum athallassos) and the piping plover (plovers; Charadrius melodus). However, many of the natural morphological and hydrological characteristics of the Platte River have been altered substantially by water development, channelization, hydropower operations, and invasive vegetation encroachment, which have decreased the abundance of high-quality nesting and foraging habitat for terns and plovers. The lower Platte River (LPR), defined as 103 miles (mi) of the Platte River between its confluence with the Loup River and its confluence with the Missouri River, has narrowed since the late-19th and early-20th centuries, yet it partially retains many geomorphologic and hydrologic characteristics important to terns and plovers. These birds nest on the sandbars in the river and along shorelines at sand- and gravel-pit lakes in the adjacent valley. The need to balance continued economic, infrastructure, and resource development with the conservation of important physical and aquatic habitat resources requires increased understanding of the physical and biological dynamics of the lower Platte River. Spatially and temporally rich datasets for emergent sandbar habitats are necessary to quantify emergent sandbar dynamics relative to hypothesized controls and stressors. In cooperation with the Lower Platte South Natural Resources District, the U.S. Geological Survey initiated a pilot study of emergent sandbar dynamics along a 22-mi segment of the LPR downstream from its confluence with Salt Creek, near Ashland, Nebraska. The purposes of the study were to: (1) develop methods to rapidly assess sandbar geometries and locations in a wide, sand-bed river, and (2) apply and validate the method to assess emergent sandbar dynamics over three seasons in 2011. An examination of the height of sandbars relative to the local stage of the formative discharge event, and how subsequent river discharges, of both high and low magnitude, alter sandbar geometries and abundance within the LPR was of particular interest. A “rapid-assessment” method was developed with the goal of characterizing the spatial distribution and habitat-relevant geometries of the complete population of sandbars along the study segment. Three primary measures were used to assess emergent sandbar dynamics in the study segment: sandbar area, sandbar height, and sandbar location. Data to derive these measures were collected during three, week-long survey periods in 2011, herein named “spring survey period,” “summer survey period,” and “fall survey period.” Emergent sandbars were grouped into one of three generalized types: (1) bank-attached, (2) island-attached, and (3) mid-channel.

Nebraska↗
USGS2015

Potentiometric surface of the Catahoula aquifer in central Louisiana, 2013

The Catahoula aquifer is an important source of fresh groundwater in central Louisiana. In 2010, about 3.96 million gallons per day (Mgal/d) were withdrawn from the Catahoula aquifer in Louisiana. In 2012, the U.S. Geological Survey in cooperation with the Louisiana Department of Natural Resources began a study to document current water levels in selected aquifers in Louisiana. This report presents water-level data and a map that illustrates the potentiometric surface of the Catahoula aquifer in 2013. The Catahoula aquifer crops out in a narrow band across north-central Louisiana. This band is broken by alluvial deposits in the valleys of the Red, Little, and Ouachita Rivers that have incised into the aquifer. Saltwater ridges under the Red, Little, and Tensas River Valleys divide the freshwater extents of the Catahoula aquifer and limit the flow of freshwater between these areas. The Catahoula aquifer generally ranges in thickness from about 50 feet (ft) in the outcrop area to about 450 ft in southern Vernon Parish. Sand beds in the aquifer are generally discontinuous, lenticular, and interbedded with silts and clays. The potentiometric surface of the Catahoula aquifer was constructed by using the altitude of water levels measured at 29 wells during the period May through September 2013. The altitude of water levels ranged from 0.02 ft above the National Geodetic Vertical Datum of 1929 (NGVD 29) in well Co-51 to 238 ft above NGVD 29 in well Na-317. Groundwater movement in the Catahoula aquifer is generally to the southeast and towards discharge areas beneath the Sabine, Red, Little, and Tensas River Valleys.

Louisiana↗
USGS2006

Annual ground-water discharge by evapotranspiration from areas of spring-fed riparian vegetation along the eastern margin of Death Valley, 2000-02

Flow from major springs and seeps along the eastern margin of Death Valley serves as the primary local water supply and sustains much of the unique habitat in Death Valley National Park. Together, these major spring complexes constitute the terminus of the Death Valley Regional Ground-Water Flow System--one of the larger flow systems in the Southwestern United States. The Grapevine Springs complex is the least exploited for water supply and consequently contains the largest area of undisturbed riparian habitat in the park. Because few estimates exist that quantify ground-water discharge from these spring complexes, a study was initiated to better estimate the amount of ground water being discharged annually from these sensitive, spring-fed riparian areas. Results of this study can be used to establish a basis for estimating water rights and as a baseline from which to assess any future changes in ground-water discharge in the park. Evapotranspiration (ET) is estimated volumetrically as the product of ET-unit (general vegetation type) acreage and a representative ET rate. ET-unit acreage is determined from high-resolution multi-spectral imagery; and a representative ET rate is computed from data collected in the Grapevine Springs area using the Bowen-ratio solution to the energy budget, or from rates given in other ET studies in the Death Valley area. The ground-water component of ET is computed by removing the local precipitation component from the ET rate. Two different procedures, a modified soil-adjusted vegetation index using the percent reflectance of the red and near-infrared wavelengths and land-cover classification using multi-spectral imagery were used to delineate the ET units within each major spring-discharge area. On the basis of the more accurate procedure that uses the vegetation index, ET-unit acreage for the Grapevine Springs discharge area totaled about 192 acres--of which 80 acres were moderate-density vegetation and 112 acres were high-density vegetation. ET-unit acreage for two other discharge areas delineated in the Grapevine Springs area (Surprise Springs and Staininger Spring) totaled about 6 and 43 acres, respectively; and for the discharge areas delineated in the Furnace Creek area (Nevares Springs, Cow Creek-Salt Springs, Texas Spring, and Travertine Springs) totaled about 29, 13, 11, and 21 acres, respectively. In discharge areas other than Grapevine Springs, watering and spring diversions have altered the natural distribution of the vegetation. More...

Scientific Investigations Report↗
USGS2008

Investigation of Contaminated Ground Water at Solid Waste Management Unit 12, Naval Weapons Station Charleston, North Charleston, South Carolina, 2006-2007

The U.S. Geological Survey investigated natural and engineered remediation of chlorinated volatile organic compound (VOC) ground-water contamination at Solid Waste Management Unit 12 at the Naval Weapons Station Charleston, North Charleston, South Carolina, beginning in 2000. The primary contaminants of interest in the study are tetrachloroethene, 1,1,1-trichloroethane, trichloroethene, cis-1,2-dichloroethene, vinyl chloride, 1,1-dichloroethane, and 1,1-dichloroethene. The permeable reactive barrier (PRB) along the main axis of the contaminant plume appears to be actively removing contamination. In contrast to the central area of the PRB, the data from the southern end of the PRB indicate that contaminants are moving around the PRB. Concentrations in wells 12MW-10S and 12MW-03S, upgradient from the PRB, showed a general decrease in VOC concentrations. VOC concentrations in some wells in the forest showed a sharp increase, followed by a decrease. In 2007, the VOC concentrations began to increase in well 12MW-12S, downgradient from the PRB and thought to be unaffected by the PRB. The VOC-concentration changes in the forest, such as at well 12MW-12S, may represent lateral shifting of the plume in response to changes in ground-water-flow direction or may represent movement of a contamination pulse through the forest.

South Carolina↗
USGS2022

Suspended-sediment transport and water management, Jemez Canyon Dam, New Mexico, 1948–2018

Construction and operation of dams provide sources of clean drinking water, support large-scale irrigation, generate hydroelectricity, control floods, and improve river navigation. Yet these benefits are not without cost. Dams affect the natural flow regime, downstream sediment fluxes, and riverine and riparian ecosystems. The Jemez Canyon Dam in New Mexico was constructed in 1953 by the U.S. Army Corps of Engineers with authorizations for flood control and sediment retention. Water managers of the dam use various operational techniques to restore peak streamflow, improve sediment management, and restore altered ecosystem processes, while maintaining the authorized purposes of the dam. This study focuses on four distinct reservoir management operation periods implemented at the Jemez Canyon Dam: (1) predam (pre-1953), (2) a seasonal 24-hour hold pool (1953–79), (3) a permanent pool (1979–2001), and (4) dry reservoir (2001–18). Results of this study indicate successful flood control and reduction in peak instantaneous streamflow events following construction of the dam, specifically documented in 1958 and 2013. During the second water management operation period, moderate sediment retention (also defined as trap efficiency, which is the percentage of incoming sediments trapped within a reservoir during a given time) occurred (between 41.0 and 67.0 percent of sediments were retained). During the third period (1979–2001), between 61.2 and 99.8 percent of sediments were retained. During the fourth period (2001–18), at least 1,909 acre-feet of accumulated sediment were remobilized. The estimated dam trap efficiency during the fourth water management operation period was −37.2 percent, indicating that more sediments were being removed from the Jemez Canyon Reservoir than were being deposited. These remobilized sediments supplemented the natural sediment delivery in the Jemez River to the middle Rio Grande. The current (2022) dry reservoir operation allows sediment delivery during periods when flooding is not a concern while still providing flood control when needed. Suspended-sediment particle size data indicate potential coarsening of suspended sediments during the fourth water management operation period, likely resulting from erosion of coarse bed sediments deposited in the reservoir. Suspended-sediment particle size data during the first and fourth water management operation periods indicate that finer sediment mobilized during monsoon season than during snowmelt. Also, suspended-sediment concentrations during the predam and post-hold pool periods indicate concentrations were higher during monsoon season than during snowmelt. Seasonal variations in suspended-sediment concentration and particle size may help dam managers make operational decisions by increasing the understanding of particle size, concentration, and variation of suspended sediment during a given year. The seasonality of suspended-sediment transport can also vary, depending not only on concentration and particle size, but on precipitation. The maximum annual suspended-sediment loads occurred during all three seasonal categories analyzed in this study: snowmelt, monsoon, and the remainder of the year. This indicates that, in addition to sediment particle size and concentration, understanding the variability of transport mechanisms of suspended-sediment load can also guide optimal water management operations at a dam.

New Mexico↗
USGS2018

Seeking excellence: An evaluation of 235 international laboratories conducting water isotope analyses by isotope-ratio and laser-absorption spectrometry

Rationale Water stable isotope ratios ( δ 2 H and δ 18 O values) are widely used tracers in environmental studies; hence, accurate and precise assays are required for providing sound scientific information. We tested the analytical performance of 235 international laboratories conducting water isotope analyses using dual-inlet and continuous-flow isotope ratio mass spectrometers and laser spectrometers through a water isotope inter-comparison test. Methods Eight test water samples were distributed by the IAEA to international stable isotope laboratories. These consisted of a core set of five samples spanning the common δ -range of natural waters, and three optional samples (highly depleted, enriched, and saline). The fifth core sample contained unrevealed trace methanol to assess analyst vigilance to the impact of organic contamination on water isotopic measurements made by all instrument technologies. Results For the core and optional samples ~73 % of laboratories gave acceptable results within 0.2 ‰ and 1.5 ‰ of the reference values for δ 18 O and δ 2 H, respectively; ~27 % produced unacceptable results. Top performance for δ 18 O values was dominated by dual-inlet IRMS laboratories; top performance for δ 2 H values was led by laser spectrometer laboratories. Continuous-flow instruments yielded comparatively intermediate results. Trace methanol contamination of water resulted in extreme outlier δ -values for laser instruments, but also affected reactor-based continuous-flow IRMS systems; however, dual-inlet IRMS δ -values were unaffected. Conclusions Analysis of the laboratory results and their metadata suggested inaccurate or imprecise performance stemmed mainly from skill- and knowledge-based errors including: calculation mistakes, inappropriate or compromised laboratory calibration standards, poorly performing instrumentation, lack of vigilance to contamination, or inattention to unreasonable isotopic outcomes. To counteract common errors, we recommend that laboratories include 1–2 'known' control standards in all autoruns; laser laboratories should screen each autorun for spectral contamination; and all laboratories should evaluate whether derived d- excess values are realistic when both isotope ratios are measured. Combined, these data evaluation strategies should immediately inform the laboratory about fundamental mistakes or compromised samples.

Rapid Communications in Mass Spectrometry↗
USGS2025

Estimation of baseflow and flooding characteristics for East Canyon Creek, Summit and Morgan Counties, Utah

An improved understanding of hydrologic responses to changing climatic conditions is needed to better inform water management practices. East Canyon Creek, a perennial, snowmelt-dominated stream in the Wasatch Mountains of northern Utah, is subjected to increasing development and demands on water in the Snyderville Basin and adjacent areas. In this study, streamflow and specific conductance measured at three U.S. Geological Survey streamgages on East Canyon Creek were used to estimate daily baseflow for water years 2011–22. Trends in these estimates and correlations with climate data from two Natural Resource Conservation Service snow telemetry (SNOTEL) stations within the Snyderville Basin above East Canyon Reservoir, were quantified and reported. Peak annual streamflow also was assessed for flood potential on the study reach of East Canyon Creek. The hydrograph separations showed consistent baseflow indices among all sites, with a larger baseflow component during the fall–spring period (September–April; baseflow indices approximately equal to [≈] 0.751–0.835) and smaller component during the summer period (May–August; baseflow indices ≈ 0.428–0.532). In-stream specific conductance during spring (February–April) was influenced by road salt application, limiting the utility of the hydrograph separation approach. Annual streamflow and climate data were evaluated for trends using the nonparametric Mann–Kendall test, with inconclusive results. Related tests for trends, the Seasonal and Regional Kendall tests, were used to evaluate data at monthly timesteps and indicated a decreasing trend in total streamflow and baseflow at all streamgages. The rank-based Kendall’s tau test for correlation was used to measure the ordinal association with climatic data at co-located SNOTEL stations. Total streamflow and baseflow were strongly correlated with precipitation and snow-water equivalent. By incorporating a predictive regression model, the nonparametric Theil–Sen line, these correlations could support the development of streamflow forecast models using climate data from SNOTEL stations. Such models would provide water managers with tools to help make proactive decisions, such as reservoir or water reclamation releases and curtailment of withdrawals, in response to regional drought or varying snowpack and spring runoff in a given year.

Utah↗
USGS2007

Hydrogeologic Appraisal of the Valley-Fill Aquifer in the Port Jervis Trough, Sullivan and Ulster Counties, New York

The nature and extent of valley-fill aquifers in the Port Jervis Trough was evaluated for a 16 mile section of this valley from the Orange-Sullivan County line near Westbrookville to the village of Napanoch in Ulster County as part of the U.S. Geological Survey's Detailed Aquifer Mapping Program in New York State. The principal aquifer in the Port Jervis Trough is a 50 feet thick outwash aquifer that extends from the Phillipsport Moraine near Summitville, southward through the study area to Port Jervis, N.Y. Previous studies had estimated as much as 500 feet of saturated drift in parts of the Trough, but new well data show that much of the valley fill consists of fine-grained lacustrine sediments. Drillers' logs show that the outwash aquifer south of Summitville is underlain by as much as 275 feet of lacustrine silt and clay. North of the Phillipsport Moraine, three large glaciolacustrine deltas that were built into Glacial Lake Wawarsing provide some local and discontinuous confined aquifers through their coarser bottomset beds. Elsewhere in the Trough, collapsed and buried portions of kame deltas and terraces provide local confined aquifers. The outwash aquifer appears to be very transmissive, as evidenced by the high specific capacity of 130 gallons per minute per foot [(gal/min)/ft] of a commercial test well screened in the aquifer.

Scientific Investigations Map↗
USGS2006

Hydrology and water quality in the Green River and surrounding agricultural areas near Green River in Emery and Grand Counties, Utah, 2004-05

Water from the Colorado River and its tributaries is used for municipal and industrial purposes by about 27 million people and irrigates nearly 4 million acres of land in the Western United States. Water users in the Upper Colorado River Basin consume water from the Colorado River and its tributaries, reducing the amount of water in the river. In addition, application of water to agricultural land within the basin in excess of crop needs can increase the transport of dissolved solids to the river. As a result, dissolved-solids concentrations in the Colorado River have increased, affecting downstream water users. During 2004-05, the U.S. Geological Survey, in cooperation with the Natural Resources Conservation Service, investigated the occurrence and distribution of dissolved solids in water from the agricultural areas near Green River, Utah, and in the adjacent reach of the Green River, a principle tributary of the Colorado River. The flow-weighted concentration of dissolved solids diverted from the Green River for irrigation during 2004 and 2005 was 357 milligrams per liter and the mean concentration of water collected from seeps and drains where water was returning to the river during low-flow conditions was 4,170 milligrams per liter. The dissolved-solids concentration in water from the shallow part of the ground-water system ranged from 687 to 55,900 milligrams per liter. Measurable amounts of dissolved solids discharging to the Green River are present almost exclusively along the river banks or near the mouths of dry washes that bisect the agricultural areas. The median dissolved-solids load in discharge from the 17 drains and seeps visited during the study was 0.35 ton per day. Seasonal estimates of the dissolved-solids load discharging from the study area ranged from 2,800 tons in the winter to 6,400 tons in the spring. The estimate of dissolved solids discharging from the study area annually is 15,700 tons. Water samples collected from selected sites within the Green River agricultural areas were analyzed for naturally occurring isotopes of strontium and boron, which can be useful for differentiating dissolved-solids sources. Substantial variations in the delta strontium-87 and delta boron-11 values among the sites were measured. Canal and river samples had relatively low concentrations of strontium and the most positive (heavier) isotopic ratios, while drains and seeps had a wide range of strontium concentrations and isotopic ratios that generally were less positive (lighter). Further study of the variation in strontium and boron concentrations and isotope ratios may provide a means to distinguish end members and discern processes affecting dissolved solids within the Green River study area; however, the results from isotope data collected during this study are inconclusive. Flow and seepage losses were estimated for the three main canals in the study area for May 2 to October 4 in any given year. This period coincides with the frost-free period in the Green River area. Estimated diversion from the Green River into the Thayn, East Side, and Green River Canals is 6,600, 6,070, and 19,900 acre-feet, respectively. The estimated seepage loss to ground water from the Thayn, East Side, and Green River Canals during the same period is 1,550, 1,460, and 4,710 acre-feet, respectively.

Utah↗
USGS2024

Distribution of ancient carbon in groundwater and soil gas from degradation of petroleum near the Red Hill Bulk Fuel Storage Facility, O‘ahu, Hawai‘i

The groundwater below the Red Hill Bulk Fuel Storage Facility (the facility) in Oʻahu, Hawaiʻi, contains fuel compounds from past spills. This study used carbon-14 analyses to distinguish fuel-derived carbon from background carbon, along with other biodegradation indicators, to address two goals: (1) determine the extent and migration direction of groundwater affected by residual fuel below the facility and (2) determine if residual fuel locations in the subsurface could be identified by analyzing soil gas at the surface above the facility. Groundwater from 19 wells was sampled between September 2022 and April 2023. Nonvolatile dissolved organic carbon (NVDOC) from a well presumed to be unaffected by past spills contained 38 percent ancient carbon indicating a natural source of ancient carbon in the subsurface. The NVDOC concentrations and ancient carbon percentages indicate fuel biodegradation products are likely present on the north and south of Red Hill with the greatest effects at well RHMW02 near the 2014 spill site. The NVDOC concentrations are almost three times higher than diesel range organic (DRO) concentrations in groundwater from the same sites. Major ion data indicate that iron reduction is an important biodegradation process. Soil probe samples and soil carbon traps were used to determine the carbon-14 content of soil carbon dioxide. Ancient carbon from fuel biodegradation was not detected at any soil probe or carbon trap site in contrast to a 2017 study which reported ancient carbon detections. A reanalysis of the 2017 results using a range of local values for background carbon-14 indicates that ancient carbon from fuel biodegradation was probably only detected in lower tunnel exhaust system samples and not in any soil carbon trap samples. Measurements of carbon dioxide efflux with a dynamic closed chamber were highly variable. The soil gas results indicate that soil gas measurements at land surface were not useful for detecting residual fuel at the facility.

Hawaii↗
USGS2010

Logs and Geologic Data from a Paleoseismic Investigation of the Susitna Glacier fault, Central Alaska Range, Alaska

This report contains field and laboratory data from a paleoseismic study of the Susitna Glacier fault, Alaska. The initial M 7.2 subevent of the November 3, 2002, M 7.9 Denali fault earthquake sequence produced a 48-km-long set of complex fault scarps, folds, and aligned landslides on the previously unknown, north-dipping Susitna Glacier thrust fault along the southern margin of the Alaska Range in central Alaska. Most of the 2002 folds and fault scarps are 1-3 m high, implying dip-slip thrust offsets (assuming a near-surface fault dip of approximately 20 degrees)of 3-5 m. Locally, some of the 2002 ruptures were superimposed on preexisting scarps that have as much as 5-10 m of vertical separation and are evidence of previous surface-rupturing earthquakes on the Susitna Glacier fault. In 2003-2005, we focused follow-up studies on several of the large scarps at the 'Wet fan' site in the central part of the 2002 rupture to determine the pre-2002 history of large surface-rupturing earthquakes on the fault. We chose this site for several reasons: (1) the presence of pre-2002 thrust- and normal-fault scarps on a gently sloping, post-glacial alluvial fan; (2) nearby natural exposures of underlying fan sediments revealed fine-grained fluvial silts with peat layers and volcanic ash beds useful for chronological control; and (3) a lack of permafrost to a depth of more than 1 m. Our studies included detailed mapping, fault-scarp profiling, and logging of three hand-excavated trenches. We were forced to restrict our excavations to 1- to 2-m-high splay faults and folds because the primary 2002 ruptures mostly were superimposed on such large scarps that it was impossible to hand dig through the hanging wall to expose the fault plane. Additional complications are the pervasive effects of cryogenic processes (mainly solifluction) that can mask or mimic tectonic deformation. The purpose of this report is to present photomosaics, trench logs, scarp profiles, and fault slip, radiocarbon, tephrochronologic, and unit description data obtained during this investigation. We do not attempt to use the data presented herein to construct a paleoseismic history of the Susitna Glacier fault; that history will be the subject of a future report. When completed, our results will be used to compare the Susitna Glacier fault paleoseismic record with results of similar studies on the nearby Denali fault to determine if the simultaneous rupture of these two faults during the 2002 Denali fault earthquake sequence is typical or atypical of their long-term interaction.

Scientific Investigations Map↗
USGS2013

Brookian sequence well log correlation sections and occurrence of gas hydrates, north-central North Slope, Alaska

Gas hydrates are naturally occurring crystalline, ice-like substances that consist of natural gas molecules trapped in a solid-water lattice. Because of the compact nature of their structure, hydrates can effectively store large volumes of gas and, consequently, have been identified as a potential unconventional energy source. First recognized to exist geologically in the 1960s, significant accumulations of gas hydrate have been found throughout the world. Gas hydrate occurrence is limited to environments such as permafrost regions and subsea sediments because of the pressure and temperature conditions required for their formation and stability. Permafrost-associated gas hydrate accumulations have been discovered in many regions of the Arctic, including Russia, Canada, and the North Slope of Alaska. Gas hydrate research has a long history in northern Alaska. This research includes the drilling, coring, and well log evaluation of two gas hydrate stratigraphic test wells and two resource assessments of gas hydrates on the Alaska North Slope. Building upon these previous investigations, this report provides a summary of the pertinent well log, gas hydrate, and stratigraphic data for key wells related to gas hydrate occurrence in the north-central North Slope. The data are presented in nine well log correlation sections with 122 selected wells to provide a regional context for gas hydrate accumulations and the relation of the accumulations to key stratigraphic horizons and to the base of the ice-bearing permafrost. Also included is a well log database that lists the location, available well logs, depths, and other pertinent information for each of the wells on the correlation section.

Alaska↗
USGS2007

Applying radar technology to migratory bird conservation and management: Strengthening and expanding a collaborative

Executive Summary Understanding the factors affecting migratory bird and bat populations during all three phases of their life cycle—breeding, nonbreeding, and migration—is critical to species conservation planning. This includes the need for information about these species’ responses to natural challenges, as well as information about the effects of human activities and structures. Habitats and other resources critical to migrants during passage and stopover are being destroyed, degraded, and threatened by human activities. Birds and bats are also uniquely susceptible to human use of the airspace. Wind turbines, communication and power transmission towers, and other tall structures, known to cause bird and bat mortality, are being erected or proposed in increasing numbers across the country. In addition, the potential for bird/aircraft collisions poses human safety threats. Management and regulatory agencies, conservation organizations, and industry currently lack the information they need to meet their missions and statutory responsibilities. The biological data available from various radar technologies offer a unique opportunity to learn more about the spatiotemporal distribution patterns, flight characteristics, and habitat use of “aero-fauna.” Recognizing the opportunities presented by radar technologies, the U.S. Geological Survey (USGS), the U.S. Fish and Wildlife Service (USFWS), and university partners collaborated first on individual projects and then in a broader, informal “collaborative” to coordinate their radar-related research and work together to develop the suite of products needed for conservation of birds and bats. Having produced two summary documents (Sojda and others, 2005; Ruth and others, 2005), the next objective was to convene a workshop for researchers, management and regulatory agencies, and other interested parties. The focus of this initial workshop was on strengthening the existing USGS-USFWS-university partnership and expanding the “collaborative” to include new Federal agency partners. The subject matter was centered on discussing available technologies, appropriate applications, management-related needs, and ways to strengthen collaborative research and conservation efforts. The workshop opened with presentations about the history of the “radar collaborative,” a description of the workshop objectives and focuses, and a summary of resource management and regulatory needs. Scientific presentations describing current research projects or subjects followed, given by USGS scientists, as well as scientists from other Federal agencies, academia, conservation and ornithological organizations, and a private contracting firm. Presenters addressed a wide variety of management issues including siting of wind-power facilities, bird/aircraft collisions, effects of hurricanes Katrina and Rita on bird migration, bird use of Conservation Reserve Program land, defining bird migration patterns at a broad regional scale, and associating migrant birds with their stopover habitats. Presentations described a variety of radar technologies including NEXRAD weather surveillance radar, modified mobile marine radar, military tracking radar, pencil beam radar, and dual polarization radar, as well as complementary techniques and analysis methods such as acoustic monitoring, thermal imaging, artificial intelligence, and individual-based modeling. Key issues, themes, and questions identified during the open discussions that followed fell into five main categories: (1) agency needs and challenges; (2) radar technology and applications—technical questions and issues; (3) tools and resources for managers and researchers; (4) standardization of protocols; and (5) collaborative opportunities. Participants identified the following management, regulatory, or business issues facing them which may be addressed with radar technologies: tall structures; wind turbines; identification and protection of key habitats; assessment of management activities; and bird/aircraft strikes. Participants frequently expressed the need for specific information about which radar technologies are best used for answering particular questions. User groups emphasized the importance of clear, defensible scientific information on which they can base their activities. In turn, researchers emphasized their need for clearly defined, specific questions from managers so that they can design and conduct the required research. Discussions about technical issues requiring further research and collaboration included target identity, ground-truthing, linking migrants to habitat, and standardized protocols for applied research. Workshop participants identified and endorsed a series of seven action items that would promote collaboration and begin to address key issues identified at the workshop: Action Item #1 : Establish a working subgroup to address large-scale surveillance radar standardization issues. Action Item #2 : Establish a working subgroup to address small-scale radar standardization issues. Action Item #3 : Bring management and regulatory agencies together to identify the three most important information needs for each key management issue relating to radar technologies. Action Item #4 : Develop Fact Sheet(s) to provide information about radar technology applications to migratory bird and bat conservation issues. Action Item #5 : Create a “radar collaborative” Website to provide information about radar biology applications, contacts, publications, and so forth. Action Item #6 : Formalize and expand the USGS-USFWS “radar collaborative.” Action Item #7 : Advance basic research, such as target identity and validation, which will support and improve our abilities to apply radar technologies to conservation objectives. There was considerable interest in expanding the “radar collaborative” to include those agencies, organizations, and industries represented at the workshop. It was felt that the publication of the workshop proceedings, implementation of action items, and additional future meetings or workshops will be crucial in strengthening the “radar collaborative” effort and promoting the use of these valuable technologies for conserving migratory species.

Open-File Report↗
USGS2015

Relations between well-field pumping and induced canal leakage in east-central Miami-Dade County, Florida, 2010-2011

An extensive canal and water management system exists in south Florida to prevent flooding, replenish groundwater, and impede saltwater intrusion. The unconfined Biscayne aquifer, which underlies southeast Florida and provides water for millions of residents, interacts with the canal system. The Biscayne aquifer is composed of a highly transmissive karst limestone; therefore, canal stage and flow may be affected by production well pumping, especially in locations where production wells and canals are in proximity. The U.S. Geological Survey developed a local-scale, transient, numerical groundwater flow model of a well field in Miami-Dade County to (1) quantify relations between well-field pumping and C-2 Canal (herein referred to as the Snapper Creek Canal) leakage, (2) determine primary controls on canal leakage variability, and (3) summarize results that could simplify characterization of canal/well-field interactions in other locations. In addition to the groundwater model development, stable isotope data from water-quality samples were used to characterize the relations between production well pumping and canal leakage. The results from the groundwater model and the isotope data were used to refine the conceptual flow model of the study area. The groundwater flow model MODFLOW-NWT was used for simulating groundwater flow and quantifying interactions between pumping from the well field and Snapper Creek Canal leakage. Input data for the groundwater model included precipitation, evapotranspiration, pumping, canal stage, and regional groundwater elevation. The inverse modeling tool UCODE and groundwater data from June 2010 to July 2011 were used to calibrate the model. Parameter sensitivity analyses were performed with UCODE. Model sensitivities to geologic heterogeneity, non-laminar flow, and changes in the regional flow boundary were evaluated. The groundwater model generally fits the calibration criteria well within estimated error ranges for groundwater elevations and canal leakage values. The mean average error for heads simulated with the model was 0.19 meter, and head residuals were generally randomly distributed. The model simulated groundwater flow under ambient conditions without production well pumping to establish background leakage. Groundwater flow also was simulated with production well pumping to estimate induced leakage from the Snapper Creek Canal that occurs in response to pumping. Canal leakage was quantified as a percentage of total canal leakage. The percentage of leakage during pumping increased non-linearly with pumping rate, indicating a decreasing sensitivity of canal leakage to pumping at relatively large pumping magnitudes. The results for Snapper Creek Canal may serve as an upper limit for well-field interaction with surface-water features in Miami-Dade County, given the proximity (about 50 meters) of the pumping wells in this study to the Snapper Creek Canal. The isotopic compositions of hydrogen (H) and oxygen (O) in groundwater samples were used to distinguish sources for groundwater within the study area and to assess the extent of natural mixing and pumping-induced mixing with water in the Snapper Creek Canal. Water-level data and water-quality samples were collected from monitoring well clusters, production wells, and the Snapper Creek Canal during discrete sampling events under ambient and pumping conditions. Trends in the isotope data generally follow the regional west-to-east hydraulic gradient across the study area. Data collected within the monitoring-well clusters in closest proximity to the canal indicate that groundwater/surface-water interactions are greatest within the shallow flow zone of the aquifer, especially during pumping conditions. The isotopic composition of samples collected within the study area indicates that the shallow, highly transmissive preferential flow zone receives substantial recharge from the canal. The isotope data from the production wells which are open to the deeper flow zone within the aquifer, indicate only traces of mixing with a 2 H- and 18 O-enriched source, suggesting little canal admixture with waters of the deeper flow zone. Results from the groundwater model and the stable isotope data analysis indicate the importance of considering geologic heterogeneity when investigating the relations between pumping and canal leakage, not only at this site, but also at other sites with similar heterogeneous geology. The model results were consistently sensitive to the hydrogeologic framework and changes in hydraulic conductivities. The model and the isotope data indicate that the majority of the groundwater/surface-water interactions occurred within the shallow flow zone. A relatively lower-permeability geologic layer occurring between the shallowest and deep preferential flow zones lessens the interactions between the production wells and the canal.

Florida↗