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USGS1994

Bathymetric map of Coeur D'Alene Lake, Idaho

The U.S. Geological Survey investigated nutrient and trace-element enrichment in Coeur d'Alene Lake, northern Idaho, during 1991-92. The objectives of the investigation were to characterize limnology, quantify hydrologic and nutrient budgets, and develop a nutrient-load/lake-response model. The model required bathymetric data to compute mass balances of water and nutrients within many depth layers in the lake. A review of historical bathymetric data for the lake (Funk and others, 1973; U.S. Environmental Protection Agency, 1977; Milligan and others, 1983) revealed a need for contoured bathymetric data. Therefore, to augment past studies, the U.S. Geological Survey collected extensive bathymetric data and developed a bathymetric map of Coeur d'Alene Lake.

Idaho↗

USGS1958

Ground-water resources of the Hueco Bolson northeast of El Paso, Texas

The Hueco Bolson is in the extreme western part of Texas and south- central New Mexico, covering parts of El Paso County, Tex., and Dona Ana and Otero Counties, N. Mex. Wells tapping the bolson deposits furnish the major part of the water supply for the city of El Paso, Ciudad Juarez, Fort Bliss, Biggs Air Force Base, and private industries. in the area. The progressively increasing demand for water made it obvious that a comprehensive investigation of the quantity and quality of water in storage in the entire Hueco Bolson would be essential for the proper planning of future water supplies. A test-drilling program was started in 1953, jointly sponsored by the city of El Paso, the United States Army, the United States Air Force, and the Texas Board of Water Engineers. The drilling was supervised by the United States Geological Survey.

New Mexico, Texas↗

USGS1996

Colloidal-facilitated transport of inorganic contaminants in ground water: part 1, sampling considerations

Investigations at Pinal Creek, Arizona, evaluated routine sampling procedures for determination of aqueous inorganic geochemistry and assessment of contaminant transport by colloidal mobility. Sampling variables included pump type and flow rate, collection under air or nitrogen, and filter pore diameter. During well purging and sample collection, suspended particle size and number as well as dissolved oxygen, temperature, specific conductance, pH, and redox potential were monitored. Laboratory analyses of both unfiltered samples and the filtrates were performed by inductively coupled argon plasma, atomic absorption with graphite furnace, and ion chromatography. Scanning electron microscopy with Energy Dispersive X-ray was also used for analysis of filter particulates. Suspended particle counts consistently required approximately twice as long as the other field-monitored indicators to stabilize. High-flow-rate pumps entrained normally nonmobile particles. Difference in elemental concentrations using different filter-pore sizes were generally not large with only two wells having differences greater than 10 percent in most wells. Similar differences (>10%) were observed for some wells when samples were collected under nitrogen rather than in air. Fe 2+ /Fe 3+ ratios for air-collected samples were smaller than for samples collected under a nitrogen atmosphere, reflecting sampling-induced oxidation.

Arizona↗

USGS1978

A progress report on estuary modeling by the finite-element method

Various schemes are investigated for finite-element modeling of two-dimensional surface-water flows. The first schemes investigated combine finite-element spatial discretization with split-step time stepping schemes that have been found useful in finite-difference computations. Because of the large number of numerical integrations performed in space and the large sparse matrices solved, these finite-element schemes were found to be economically uncompetitive with finite-difference schemes. A very promising leapfrog scheme is proposed which, when combined with a novel very fast spatial integration procedure, eliminates the need to solve any matrices at all. Additional problems attacked included proper propagation of waves and proper specification of the normal-flow boundary condition. This report indicates work in progress and does not come to a definitive conclusion as to the best approach for finite-element modeling of surface-water problems. The results presented herein represent findings obtained between September 1973 and July 1976.

Open-File Report↗

USGS2001

Soil analyses for 1,3-dichloropropene (1,3-DCP), sodium n-methyldithiocarbamate (metam-sodium), and their degradation products near Fort Hall Idaho, September 1999 through March 2000

Between September 1999 and March 2000, soil samples from the Fort Hall, Idaho, area were analyzed for two soil fumigants, 1,3-dichloropropene (1,3-DCP) and sodium n-methyldithiocarbamate (metam-sodium), and their degradation products. Ground water is the only source of drinking water at Fort Hall, and the purpose of the investigation was to determine potential risk of ground-water contamination from persistence and movement of these pesticides in cropland soils. 1,3-DCP, metam-sodium, or their degradation products were detected in 42 of 104 soil samples. The samples were collected from 1-, 2-, and 3-foot depths in multiple backhoe trenches during four sampling events—before pesticide application in September; after application in October; before soil freeze in December; and after soil thaw in March. In most cases, concentrations of the pesticide compounds were at or near their laboratory minimum reporting limits. U.S. Environmental Protection Agency Method 5035 was used as the guideline for soil sample preparation and analyses, and either sodium bisulfate (NaHSO4), an acidic preservative, or pesticide-free water was added to samples prior to analyses. Addition of NaHSO4 to the samples resulted in a greater number of compound detections, but pesticide-free water was added to most samples to avoid the strong reactions of soil carbonate minerals with the NaHSO4. As a result, nondetection of compounds in samples containing pesticide-free water did not necessarily indicate that the compounds were absent. Detections of these compounds were inconsistent among trenches with similar soil characteristics and histories of soil fumigant use. Compounds were detected at different depths and different trench locations during each sampling event. Overall results of this study showed that the original compounds or their degradation products can persist in soil 6 months or more after their application and are present to at least 3 feet below land surface in some areas. A few of the soil analyses results were unexpected. Degradation products of metam-sodium were detected in samples from croplands with a history of 1,3-DCP applications only, and were not detected in samples from croplands with a history of metam-sodium applications. Although 1,2-dibromoethane (EDB) has not been used in the area for many years, EDB was detected in a few soil samples. The presence of EDB in soil could be caused by irrigation of croplands with EDBcontaminated ground water. Analyses of these soil samples resulted in many unanswered questions, and further studies are needed. One potential study to determine vertical extent of pesticide compound migration in sediments, for example, would include analysis of one or more columns of soil and sediments (land surface to ground water, about 35 to 50 feet below land surface) in areas with known soil contamination. Another study would expand the scope of soil contamination to include broader types of cropland conditions and compound analyses.

Idaho↗

USGS1995

Hydrogeology and ground-water flow at the Muddy Brook riparian zone, north-central Connecticut

The hydrogeology and ground-water flow of Muddy Brook were investigated as part of a study to determine the effects of restoring agricultural riparian land to forest on water quality. Test-hole drilling, well installation, and slug-test analyses indicate that the part of Muddy Brook studied is underlain by thin stratified-drift deposits. These deposits are mostly less than 10 feet thick and have estimated horizontal hydraulic conductivities of 4 to 30 feet per day. Till deposits from 1 to 14 feet thick underlie the stratified-drift deposits and have estimated horizontal hydraulic conductivities of 0.1 and 4.3 feet per day. The water table in stratified drift is less than 10 feet below land surface during most of the year, and the horizontal hydraulic gradient varies seasonally and areally from 0.015 to 0.07 feet per foot. The horizontal hydraulic gradient in the till deposits is as great as 0.1 feet per foot. Vertical hydraulic gradients of as large as 0.4 feet per foot are present between the till and stratified drift and are predominantly upward from the till into the stratified drift but can reverse direction in response to recharge. Ground-water discharge to Muddy Brook comes mostly from the saturated stratified-drift deposits, and during April through September 1992, flowed at a rate of 0.015 to 0.027 cubic feet per second. Average ground-water velocity is about 1 feet per day in the stratified drift and about 0.2 foot per day through the till deposits. Discharge of ground water from the till can contribute as much as 0.006 cubic feet per second of water to the stratified drift.

Water-Resources Investigations Report↗

USGS1999

Simulated effects of projected ground-water withdrawals in the Floridan aquifer system, greater Orlando metropolitan area, east-central Florida

Ground-water levels in the Floridan aquifer system within the greater Orlando metropolitan area are expected to decline because of a projected increase in the average pumpage rate from 410 million gallons per day in 1995 to 576 million gallons per day in 2020. The potential decline in ground-water levels and spring discharge within the area was investigated with a calibrated, steady-state, ground-water flow model. A wetter-than-average condition scenario and a drought-condition scenario were simulated to bracket the range of water-levels and springflow that may occur in 2020 under average rainfall conditions. Pumpage used to represent the drought-condition scenario totaled 865 million gallons per day, about 50 percent greater than the projected average pumpage rate in 2020. Relative to average 1995 steady-state conditions, drawdowns simulated in the Upper Floridan aquifer exceeded 10 and 25 feet for wet and dry conditions, respectively, in parts of central and southwest Orange County and in north Osceola County. In Seminole County, drawdowns of up to 20 feet were simulated for dry conditions, compared with 5 to 10 feet simulated for wet conditions. Computed springflow was reduced by 10 percent for wet conditions and by 38 percent for dry conditions, with the largest reductions (28 and 76 percent) occurring at the Sanlando Springs group. In the Lower Floridan aquifer, drawdowns simulated in southwest Orange County exceeded 20 and 40 feet for wet and dry conditions, respectively.

Water-Resources Investigations Report↗

USGS2008

Precipitation, Ground-water Hydrology, and Recharge Along the Eastern Slopes of the Sandia Mountains, Bernalillo County, New Mexico

The spatial and temporal distribution of recharge to carbonate and clastic aquifers along the eastern slopes of the Sandia Mountains was investigated by using precipitation, water-level, dissolved chloride, and specific-conductance data. The U.S. Geological Survey (USGS), in cooperation with the Bernalillo County Public Works Division, conducted a study to assess ground-water conditions and provide technical data that could be used as a basis for management and future planning of eastern Bernalillo County water resources. The intent of the investigation was to improve the current understanding of subsurface mechanisms controlling recharge dynamics in a geologically complex aquifer system. In the Sandia Mountains, precipitation events are generally limited to snowfalls in winter months and monsoon rainfall in late summer. Monthly meteorological data from weather stations in the study area indicate that monsoon rainfall during July and August constitutes close to one-third of annual precipitation totals. Following precipitation and snowmelt events, daily ground-water level data show low-amplitude, long-duration peaks in hydrographs of wells north and west of the Tijeras Fault. Hydrographs of monthly and biannual water-level data from across the study area show seasonal variation and water-level fluctuations in excess of 30 ft during a period of below-average precipitation. Water level observations in 67 percent of wells showing drought-induced water-level declines rebounded to at or near predrought conditions within 6 months of return to normal climate conditions. Cross-correlation of annual hydrologic data shows aquifer response to periods of monsoon recharge to persist from 1 to 6 months following events. The lag time between precipitation input and response of water levels or solute concentrations was largest near the Tijeras and Gutierrez Faults. These results indicate regional faults hydrologically isolate the Tijeras Graben from groundwater recharge originating at high elevations along the eastern slopes of the Sandia Mountains. Recharge rates calculated by using the chloride-mass-balance method for five springs located at the base of the Sandia Mountains ranged from 1 to 23 percent of annual precipitation.

Scientific Investigations Report↗

USGS2000

Assessment of volatile organic compounds in surface water at West Branch Canal Creek, Aberdeen Proving Ground, Maryland, 1999

The U.S. Geological Survey (USGS) collected 13 surface-water samples and 3 replicates from 5 sites in the West Branch Canal Creek area at Aberdeen Proving Ground from February through August 1999, as a part of an investigation of ground-water contamination and natural attenuation processes. The samples were analyzed for volatile organic compounds, including trichloroethylene, 1,1,2,2-tetrachloroethane, carbon tetrachloride, and chloroform, which are the four major contaminants that were detected in ground water in the Canal Creek area in earlier USGS studies. Field blanks were collected during the sampling period to assess sample bias. Field replicates were used to assess sample variability, which was expressed as relative percent difference. The mean variability of the surface-water replicate analyses was larger (35.4 percent) than the mean variability of ground-water replicate analyses (14.6 percent) determined for West Branch Canal Creek from 1995 through 1996. The higher variability in surface-water analyses is probably due to heterogeneities in the composition of the surface water rather than differences in sampling or analytical procedures. The most frequently detected volatile organic compound was 1,1,2,2- tetrachloroethane, which was detected in every sample and in two of the replicates. The surface-water contamination is likely the result of cross-media transfer of contaminants from the ground water and sediments along the West Branch Canal Creek. The full extent of surface-water contamination in West Branch Canal Creek and the locations of probable contaminant sources cannot be determined from this limited set of data. Tidal mixing, creek flow patterns, and potential effects of a drought that occurred during the sampling period also complicate the evaluation of surface-water contamination.

Open-File Report↗

USGS1981

Water resources data for Tennessee, water year 1981

Water resources data for the 1981 water year for Tennessee consist of records of stage, discharge, and water quality of streams and springs; stage, contents, and water quality of lakes and reservoirs; and water levels and water quality of wells. This report contains discharge records for 114 gaging stations; stage only records for one lake gaging station; elevation and contents for 27 lakes and reservoirs; water quality for 73 stations and 45 wells; and water levels for 30 observation wells. Also included are 127 crest-stage partial-record stations, 77 low-flow partial-record stations, and 81 coal-hydrology partial-record stations. Additional water data were collected at various stream and spring sites not involved in the systematic data collection program and are published as miscellaneous measurements and analyses, or as seepage investigations of discharge and water quality. These data represent that part of the National Water Data System operated by the U.S. Geological Survey and cooperating State and Federal agencies in Tennessee.

Tennessee↗

USGS1999

Surface-geophysical investigation of the University of Connecticut landfill, Storrs, Connecticut

A surface-geophysical investigation of the former landfill area at the University of Connecticut in Storrs, Conn. was conducted as part of a preliminary hydrogeologic assessment of the contamination of soil, surface water, and ground water at the site. Geophysical data were used to help determine the dominant direction of fracture strike; subsurface structure of the landfill; locations of possible leachate plumes, fracture zones or conductive lithologic layers; and the location and number of chemical waste-disposal pits. Azimuthal square-array direct-current (dc) resistivity, two-dimensional (2D) dc-resistivity, inductive terrain conductivity, and ground-penetrating radar (GPR) were the methods used to characterize the landfill area.The dominant strike direction of bedrock fractures interpreted from azimuthal square-array resistivity data is north, ranging from 285 to 30 degrees east of True North. These results complement local geologic maps that identify bedrock foliation and fractures that strike approximately north-south and dip 30 to 40 degrees west.The subsurface structure of the landfill was imaged with 2D dc-resistivity profiling data, which were used to interpret a landfill thickness of 10 to 15 meters. Orientation of the landfill trash disposal trenches were detected by azimuthal square-array resistivity soundings; the dimension and the orientation of the trenches were verified by aerial photographs.Inductive terrain conductivity and 2D dc-resistivity profiling detected conductive anomalies that were interpreted as possible leachate plumes near two surface-water discharge areas. The conductive anomaly to the north of the landfill is interpreted to be a shallow leachate plume and dissipates to almost background levels 45 meters north of the landfill. The anomaly to the southwest is interpreted to extend vertically through the overburden and into the shallow bedrock and laterally along the intermittent drainage to Eagleville Brook, terminating 140 meters south of the landfill. Inductive terrain conductivity and 2D dc-resistivity profiling also detected two dipping, sheet-like conductive features that extend vertically into the bedrock. These features were interpreted either as fracture zones filled with conductive fluids or conductive lithologic layers between more resistive layers. One dipping conductive feature was detected south of the landfill, and the other feature was detected to the west of the former chemical waste-disposal pits. Both anomalies strike approximately north-south and dip about 30 degrees to the west.GPR was used unsuccessfully to locate the former chemical waste-disposal pits. Although the entire overburden and the upper few meters of bedrock were imaged, no anomalous features were detected with GPR that could be correlated with the pits. It is possible that the area surveyed by GPR was entirely backfilled after the soil was removed from the site and that the outline of the former chemical waste-disposal pits no longer exists.

Connecticut↗

USGS1955

Ground water in the Yelm area, Thurston and Pierce counties, Washington

This report presents the results of an investigation of the ground-water resources of the Yelm area, Pierce and Thurston Counties, Wash. It was made at the request of the Division of Water Resources, Washington State Department of Conservation and Development, for the purpose of determining the availability of ground water for irrigation to replace surface water that is no longer available as a result of the abandonment of the Yelm Irrigation Ditch.

Washington↗

USGS2009

Water uptake and nutrient concentrations under a floodplain oak savanna during a non-flood period, lower Cedar River, Iowa

Floodplains during non-flood periods are less well documented than when flooding occurs, but non-flood periods offer opportunities to investigate vegetation controls on water and nutrient cycling. In this study, we characterized water uptake and nutrient concentration patterns from 2005 to 2007 under an oak savanna located on the floodplain of the Cedar River in Muscatine County, Iowa. The water table ranged from 0.5 to 2.5 m below ground surface and fluctuated in response to stream stage, plant water demand and rainfall inputs. Applying the White method to diurnal water table fluctuations, daily ET from groundwater averaged more than 3.5 mm/day in June and July and approximately 2 mm/day in May and August. Total annual ET averaged 404 mm for a growing season from mid-May to mid-October. Savanna groundwater concentrations of nitrate-N, ammonium-N, and phosphate-P were very low (mean <0.18, <0.14, <0.08 mg/l, respectively), whereas DOC concentrations were high (7.1 mg/l). Low concentrations of N and P were in contrast to high nutrient concentrations in the nearby Cedar River, where N and P averaged 7.5 mg/ l and 0.13, respectively. In regions dominated by intensive agriculture, study results document valuable ecosystem services for native floodplain ecosystems in reducing watershed-scale nutrient losses and providing an oasis for biological complexity. Improved understanding of the environmental conditions of regionally significant habitats, including major controls on water table elevations and water quality, offers promise for better management aimed at preserving the ecology of these important habitats. Copyright ?? 2009 John Wiley & Sons, Ltd.

Hydrological Processes↗

USGS2013

Impacts of migratory Sandhill Cranes (Grus canadensis) on microbial water quality in the central Platte River, Nebraska, USA

Wild birds have been shown to be significant sources of numerous types of pathogens that are relevant to humans and agriculture. The presence of large numbers of migratory birds in such a sensitive and important ecosystem as the Platte River in central Nebraska, USA, could potentially serve a significant source of bird-derived pathogens in the water/sediment and riverine environment. In 2009 and 2010, a study was completed to investigate the potential water-quality impacts of Sandhill Cranes and Snow Geese on the microbial water quality of the central Platte River during their spring migration period. Fecal material, river-bottom sediment, and water samples were collected from January through May of each year during the spring migration season of Sandhill Cranes in the Central Flyway of North America. Results indicate that several types of fecal indicator bacteria and from a range of viral, protozoan, and bacterial pathogens, Campylobacter jejuni were present in Sandhill Crane excreta, and at significantly higher frequency and densities in water and sediments when the Sandhill Cranes were present, particularly during evening roosts within the Platte River environment. Therefore, further investigation of the health significance of avian pathogens is warranted for the Platte River in Central Nebraska during migration of Sandhill Cranes and other waterfowl.

Nebraska↗

USGS2006

Sources of water to wells in updip areas of the Wenonah-Mount Laurel aquifer, Gloucester and Camden Counties, New Jersey

Since 1996, when the New Jersey Department of Environmental Protection (NJDEP) restricted ground-water withdrawals from the Potomac-Raritan-Magothy aquifer system in the southern New Jersey Coastal Plain as a result of excessive drawdown, Coastal Plain communities have been interested in developing alternate sources of water supply for their residents. The use of ground water from areas near the updip parts of the overlying confined aquifers where withdrawals are not restricted is being considered to meet the demand for drinking water. Concerns have arisen, however, regarding the potential effects of increased withdrawals from these areas on ground-water flow to streams and wetlands as well as to the deeper, confined parts of the aquifers. Therefore, the U.S. Geological Survey, in cooperation with the NJDEP, conducted a study to investigate the sources of water to currently inactive wells in the updip part of the Wenonah-Mount Laurel aquifer in Gloucester and Camden Counties, New Jersey. Of particular interest is whether the primary source of the increased withdrawals is likely to be the aquifer outcrop or the downdip, confined part of the aquifer. The outcrop of the Wenonah-Mount Laurel aquifer covers nearly 8 mi2 (square miles), or about 46 percent of Deptford Township's 17.56-mi2 area. The Deptford Township Municipal Utilities Authority owns six currently (2005) inactive wells in the Wenonah-Mount Laurel aquifer at the southeastern boundary of Deptford Township, 1.25 mi (miles) from the outcrop. For the purposes of this study, an existing ground-water-flow model of the New Jersey Coastal Plain aquifers was used to simulate ground-water-flow conditions in Gloucester and Camden Counties in 1998. Two alternative withdrawal scenarios were superimposed on the results of the 1998 simulation. In the first (the 'full-allocation' scenario), full-allocation withdrawal rates established by the NJDEP were applied to 45 existing wells in the Deptford Township area. In the second (the 'additional-withdrawal' scenario), the full-allocation scenario was modified by adding an additional withdrawal of 1.62 million gallons per day from the six inactive Deptford Township withdrawal wells. Simulated drawdown for the full-allocation scenario is zero to near zero in Deptford Township. Changes are greatest downdip from Deptford Township, where a broad area of 5- to 10-ft (feet) drawdowns is simulated; maximum drawdown at the center of the cone of depression is 20 ft. Water levels declined as much as 10 ft around individual wells whose current withdrawals are only a small percentage of their allotted allocation. Simulated drawdown for the additional-withdrawal scenario exceeds 40 ft and is centered around the six inactive Deptford Township withdrawal wells. The area in which the simulated drawdown is 5 ft extends approximately 3.75 mi downdip from the wells and 2 mi updip, into the outcrop. Water budgets based on the simulation results for the full-allocation and additional-withdrawal scenarios were calculated and compared, with particular focus on a 75-mi2 area in and around Deptford Township that includes the outcrop of the Wenonah-Mount Laurel aquifer and part of the area downdip from the outcrop (budget zone 2). The comparison of the two water budgets for zone 2 shows that 46 percent of the withdrawals from the six inactive Deptford Township wells would result from reduced stream base flow in the outcrop of the Wenonah-Mount Laurel aquifer and 35 percent would result from increased downward flow from the overlying Vincentown aquifer. Four percent would result from increased flow from the downdip areas of the Wenonah-Mount Laurel aquifer, 5 percent would result from decreased flow to the downdip areas of the Wenonah-Mount Laurel aquifer, and 5 percent would result from decreased flow to the underlying Englishtown aquifer system. The remaining 4 percent was attributed to decreased upward flow to the overlying Vincentown aquifer.

Scientific Investigations Report↗

USGS2013

An evaluation of seepage gains and losses in Indian Creek Reservoir, Ada County, Idaho, April 2010–November 2011

The U.S. Geological Survey, in cooperation with the Idaho Department of Water Resources, conducted an investigation on Indian Creek Reservoir, a small impoundment in east Ada County, Idaho, to quantify groundwater seepage into and out of the reservoir. Data from the study will assist the Idaho Water Resources Department’s Comprehensive Aquifer Management Planning effort to estimate available water resources in Ada County. Three independent methods were utilized to estimate groundwater seepage: (1) the water-budget method; (2) the seepage-meter method; and (3) the segmented Darcy method. Reservoir seepage was quantified during the periods of April through August 2010 and February through November 2011. With the water-budget method, all measureable sources of inflow to and outflow from the reservoir were quantified, with the exception of groundwater; the water-budget equation was solved for groundwater inflow to or outflow from the reservoir. The seepage-meter method relies on the placement of seepage meters into the bottom sediments of the reservoir for the direct measurement of water flux across the sediment-water interface. The segmented-Darcy method utilizes a combination of water-level measurements in the reservoir and in adjacent near-shore wells to calculate water-table gradients between the wells and the reservoir within defined segments of the reservoir shoreline. The Darcy equation was used to calculate groundwater inflow to and outflow from the reservoir. Water-budget results provided continuous, daily estimates of seepage over the full period of data collection, while the seepage-meter and segmented Darcy methods provided instantaneous estimates of seepage. As a result of these and other difference in methodologies, comparisons of seepage estimates provided by the three methods are considered semi-quantitative. The results of the water-budget derived estimates of seepage indicate seepage to be seasonally variable in terms of the direction and magnitude of flow. The reservoir tended to gain water from seepage of groundwater in the early spring months (March–May), while seepage losses to groundwater from the reservoir occurred in the drier months (June–October). Net monthly seepage rates, as computed by the water-budget method, varied greatly. Reservoir gains from seepage ranged from 0.2 to 59.4 acre-feet per month, while reservoir losses to seepage ranged from 1.6 and 26.8 acre-feet per month. An analysis of seepage meter estimates and segmented-Darcy estimates qualitatively supports the seasonal patterns in seepage provided by the water-budget calculations, except that they tended to be much smaller in magnitude. This suggests that actual seepage might be smaller than those estimates made by the water-budget method. Although the results of all three methods indicate that there is some water loss from the reservoir to groundwater, the seepage losses may be due to rewetting of unsaturated near-shore soils, possible replenishment of a perched aquifer, or both, rather than through percolation to the local aquifer that lies 130 feet below the reservoir. A lithologic log from an adjacent well indicates the existence of a clay lithology that is well correlated to the original reservoir’s base elevation. If the clay lithologic unit extends beneath the reservoir basin underlying the fine-grain reservoir bed sediments, the clay layer should act as an effective barrier to reservoir seepage to the local aquifer, which would explain the low seepage loss estimates calculated in this study.

Idaho↗

USGS2003

Partitioning of water flux in a Sierra Nevada ponderosa pine plantation

The weather patterns of the west side of the Sierra Nevada Mountains (cold, wet winters and hot, dry summers) strongly influence how water is partitioned between transpiration and evaporation and result in a specific strategy of water use by ponderosa pine trees (Pinus ponderosa) in this region. To investigate how year-round water fluxes were partitioned in a young ponderosa pine ecosystem in the Sierra Nevada Mountains, water fluxes were continually measured from June 2000 to May 2001 using a combination of sap flow and eddy covariance techniques (above- and below-canopy). Water fluxes were modeled at our study site using a biophysical model, FORFLUX. During summer and fall water fluxes were equally partitioned between transpiration and soil evaporation while transpiration dominated the water fluxes in winter and spring. The trees had high rates of canopy conductance and transpiration in the early morning and mid-late afternoon and a mid-day depression during the dry season. We used a diurnal centroid analysis to show that the timing of high canopy conductance and transpiration relative to high vapor pressure deficit (D) shifted with soil moisture: during periods of low soil moisture canopy conductance and transpiration peaked early in the day when D was low. Conversely, during periods of high soil moisture canopy conductance and transpiration peaked at the same time or later in the day than D. Our observations suggest a general strategy by the pine trees in which they maximize stomatal conductance, and therefore carbon fixation, throughout the day on warm sunny days with high soil moisture (i.e. warm periods in winter and late spring) and maximize stomatal conductance and carbon fixation in the morning through the dry periods. FORFLUX model estimates of evaporation and transpiration were close to measured/calculated values during the dry period, including the drought, but underestimated transpiration and overestimated evaporation during the wet period. ?? 2003 Elsevier Science B.V. All rights reserved.

Agricultural and Forest Meteorology↗

USGS2005

Implications of ground water chemistry and flow patterns for earthquake studies

Ground water can facilitate earthquake development and respond physically and chemically to tectonism. Thus, an understanding of ground water circulation in seismically active regions is important for earthquake prediction. To investigate the roles of ground water in the development and prediction of earthquakes, geological and hydrogeological monitoring was conducted in a seismogenic area in the Yanhuai Basin, China. This study used isotopic and hydrogeochemical methods to characterize ground water samples from six hot springs and two cold springs. The hydrochemical data and associated geological and geophysical data were used to identify possible relations between ground water circulation and seismically active structural features. The data for ??18O, ??D, tritium, and 14C indicate ground water from hot springs is of meteoric origin with subsurface residence times of 50 to 30,320 years. The reservoir temperature and circulation depths of the hot ground water are 57??C to 160??C and 1600 to 5000 m, respectively, as estimated by quartz and chalcedony geothermometers and the geothermal gradient. Various possible origins of noble gases dissolved in the ground water also were evaluated, indicating mantle and deep crust sources consistent with tectonically active segments. A hard intercalated stratum, where small to moderate earthquakes frequently originate, is present between a deep (10 to 20 km), high-electrical conductivity layer and the zone of active ground water circulation. The ground water anomalies are closely related to the structural peculiarity of each monitoring point. These results could have implications for ground water and seismic studies in other seismogenic areas. Copyright ?? 2005 National Ground Water Association.

Yanhuai Basin↗