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USGS1995

Hydrogeology and water quality at the management systems evaluation area near Piketon, Ohio

This report presents the results of a study by the U.S. Geological Survey, The Ohio State University, and the U.S. Department of Agriculture to describe the hydrology, water quality, and geochemical factors controlling water quality at the Ohio Management Systems Evaluation Area (MSEA). The Ohio MSEA is located on a 650-acre farm in the Scioto River Valley in Pike County, south-central Ohio. The farm is underlain by an incised bedrock valley filled with about 70 feet of sand and gravel outwash deposits that are covered by a veneer of silty clay alluvium and silty loam and sandy loam soils. Outwash sediment are composed predominantly of dolomite, quartz, and calcite, and have a median organic carbon concentration of 0.39 weight percent. Horizontal hydraulic conductivity of the sediment based on results of multiple-well aquifer tests ranges from 400 to 560 feet per day. Ground-water flow is from east to west-southwest at an average velocity of 1.5 to 2.5 feet per day. Ground water and surface water at the site are highly interconnected. Big Beaver Creek recharges the outwash aquifer along the eastern edge of the study area, and ground water discharges to the Scioto River at the western edge of the study area. High-stage events on the Scioto River cause frequent flow reversals in the aquifer that allow streamwater to travel a maximum observed distance of 190 feet inland. A zone of oxidizing waters (characterized by high dissolved oxygen concentration and Eh) is found in shallow ground water for several hundred feet adjacent to Big Beaver Creek and the Scioto River. This zone of oxidizing ground water is caused by the periodic inflow of surface waters to the aquifer. A ground-water budget for the study area indicates that the aquifer received 17.7 inches of recharge during water year 1992; of this amount, 72 percent originated as infiltrating precipitation, 28 percent as infiltration of surface water from Big Beaver Creek, and 0.2 percent as leakage from bedrock. Areal variation in water quality is caused by areal differences in the relative importance of these three recharge sources. The effects of bedrock leakage are evident only in the northeast corner of the study area. Here, deep outwash waters are transitional in composition between the calcium magnesium bicarbonate waters found elsewhere in the outwash aquifer and the calcium sodium chloride waters of the bedrock aquifer. Mixing calculations indicate that these deep outwash waters are composed of as much as 26 percent bedrock water. In the southern part of the MSEA, ground water is diluted by surface water from Big Beaver Creek as it recharges the aquifer through a sand and gravel streambed. At the northeast corner of the MSEA, however, Big Beaver Creek flows across a shale streambed through which no infiltration occurs. Redox reactions in the outwash aquifer control variations in aquifer chemistry with depth. From the water table to about 40 feet below land surface, oxidizing conditions are characterized by the presence of dissolved oxygen and nitrates in ground water, Eh greater than 200 millivolts, ferrihydrite coatings on sediment grains, and the absence of dissolved iron and manganese. From about 40 feet below land surface to the base of the aquifer, reducing conditions are characterized by dissolved oxygen concentrations less than 2 mg/L, Eh less than 200 millivolts, and the presence of dissolved iron and manganese. Denitrification in the reducing zone naturally remediates anthropogenic nitrate contamination of the aquifer while oxidizing pyrite in the aquifer sediment.

Ohio↗

USGS1987

Source of salts in the Waianae part of the Pearl Harbor aquifer near Barbers Point water tunnel, Oahu, Hawaii

The salinity of the water supply of Barbers Point Naval Air Station has increased markedly since 1983. The Naval Air Station obtains its water, about 3 million gal/day, from Barbers Point shaft, a water shaft that taps the Waianae part of the Pearl Harbor aquifer underlying the dry, southeastern flank of the Waianae mountains on the island on Oahu, Hawaii. From 1983 to 1985 the chloride concentration of the water, increased from 220 to 250 mg/L and has remained near that level through 1986. The EPA has established 250 mg/L as the maximum recommended chloride concentration in drinking water because above that level many people can taste the salt. The high chloride concentration in shallow groundwater at all wells in the area indicates that most of the salts in the freshwater lens are contributed by rainfall, sea spray, and irrigation return water. At Barbers Point shaft, pumping may draw a small amount of saltwater from the transition zone and increase the chloride concentration in the pumped water by about 20 mg/L. Salinity of the lens decreases progressively inland in response to recharge from relatively fresher water and in response to an increasing lens thickness with increasing distance from the shoreline. The increase, in 1983, in the chloride concentration of water at the shaft was most probably the result of saltier recharge water reaching the water table, and not the result of increased mixing of underlying saltwater with the freshwater. The chloride concentration of the recharge water has probably increased because, in 1980, the drip method of irrigation began to replace the furrow method on sugarcane fields near the shaft. A mixing-cell model was used to estimate the effect of drip irrigation on the chloride concentration of the groundwater in the vicinity of Barbers Point shaft. The model predicted an increase in chloride concentration of about 50 mg/L. The observed increase was about 30 mg/L and the chloride concentration is presently stable at 245 to 250 mg/L; hence, the chloride concentration is not expected to increase significantly more. (Lantz-PTT)

Water-Resources Investigations Report↗

USGS2004

Predicting water quality by relating secchi-disk transparency and chlorophyll a measurements to satellite imagery for Michigan inland lakes, August 2002

Inland lakes are an important economic and environmental resource for Michigan. The U.S. Geological Survey and the Michigan Department of Environmental Quality have been cooperatively monitoring the quality of selected lakes in Michigan through the Lake Water Quality Assessment program. Through this program, approximately 730 of Michigan's 11,000 inland lakes will be monitored once during this 15-year study. Targeted lakes will be sampled during spring turnover and again in late summer to characterize water quality. Because more extensive and more frequent sampling is not economically feasible in the Lake Water Quality Assessment program, the U.S. Geological Survey and Michigan Department of Environmental Quality investigate the use of satellite imagery as a means of estimating water quality in unsampled lakes. Satellite imagery has been successfully used in Minnesota, Wisconsin, and elsewhere to compute the trophic state of inland lakes from predicted secchi-disk measurements. Previous attempts of this kind in Michigan resulted in a poorer fit between observed and predicted data than was found for Minnesota or Wisconsin. This study tested whether estimates could be improved by using atmospherically corrected satellite imagery, whether a more appropriate regression model could be obtained for Michigan, and whether chlorophyll a concentrations could be reliably predicted from satellite imagery in order to compute trophic state of inland lakes. Although the atmospheric-correction did not significantly improve estimates of lake-water quality, a new regression equation was identified that consistently yielded better results than an equation obtained from the literature. A stepwise regression was used to determine an equation that accurately predicts chlorophyll a concentrations in northern Lower Michigan.

Michigan↗

USGS2004

Ground-water quality of coastal aquifer systems in the West Coast Basin, Los Angeles County, California, 1999-2002

The extensive use of ground water throughout the Central and West Coast Basins of Los Angeles County during the first half of the 20th century resulted in declining water levels, widespread seawater intrusion, and deterioration of water quality along most reaches of the coast. In order to control seawater intrusion in the West Coast Basin, freshwater is injected into a series of wells at two seawater barrier projects. In order to better understand the processes of seawater intrusion and the efficiency of current barrier operation, data were collected from multiple-well monitoring sites installed by the U.S. Geological Survey, from local observation wells, and from production wells. The occurrence and areal extent of native, saline, and recently injected ground water near the coast were defined through the collection and analysis of inorganic and isotopic water-quality data and geophysical logs. Most water in the West Coast Basin with a dissolved-solids concentration less than 500 milligrams per liter generally has a sodium-bicarbonate to sodium/calcium-bicarbonate character. Water with a dissolved-solids concentration greater than 1,000 milligrams per liter also contains variable amounts of calcium and sodium, but chloride is predominant. Most of these high-dissolved-solids wells are perforated in the Upper aquifer systems; several have dissolved-chloride values near that of seawater. Elevated chloride concentrations were measured at many wells in both the Upper and Lower aquifer systems inland from the barrier projects. Although water levels have increased in many wells over the last 30 years, some of the wells do not show a corresponding decrease in dissolved chloride. A detailed assessment of saline ground water was provided by examining the ratios of chloride to bromide, iodide, and boron. Seawater-freshwater mixing lines were constructed using all three ratios. These ion ratios also identify water affected by mixing with injected imported water and oil-field brine water. Isotopic data -oxygen-18, deuterium, strontium-87, boron-11, tritium, and carbon-14-also were collected. The stable isotopes oxygen-18 and deuterium were used to distinguish between isotopically heavier water that originated in the Los Angeles Forebay, isotopically lighter water that originated in the Montebello Forebay, local recharge, and water containing a mixture of seawater and imported water. Tritium data were used to identify recent water (less than 50 years old) present in the Upper and Lower aquifer systems inland from the seawater barrier projects, and present locally near the Dominguez Gap. Carbon-14 data indicate that water with uncorrected ages ranging from about 4,000 years to more than 20,000 years before present occurs in the Lower aquifer systems and in the Pico unit. Borehole electromagnetic conductivity logs, combined with gamma-ray logs, were used to identify potential saline zones throughout the entire well depth; this provides an indicator of intrusion in zones that are not being monitored by a piezometer. Temperature logging was used to track the thermal effects of the cooler water used for injection. Specific-conductance logs provided a screening-level indicator of poor-quality water in monitoring wells.

Scientific Investigations Report↗

USGS1997

Effects of salinity on baldcypress seedlings: Physiological responses and their relation to salinity tolerance

Growth and physiological responses of 15 open-pollinated families of baldcypress ( Taxodium distichum var. distichum ) subjected to flooding with saline water were evaluated in this study. Ten of the families were from coastal sites in Louisiana and Alabama, USA that have elevated levels of soil-water salinity. The other five families were from inland, freshwater sites in Louisiana. Seedlings from all families tolerated flooding with water of low (2 g 1 −1 ) salinity. Differences in biomass among families became most apparent at the highest salinity levels (6 and 8 g 1 −1 ). Overall, increasing salinity reduced leaf biomass more than root biomass, which in turn was reduced more than stem biomass. A subset of seedlings from the main greenhouse experiment was periodically placed indoors under artificial light, and measurements were made of gas exchange and leaf water potential. Also, tissue concentrations of Cl − , Na + , K + , and Ca 2+ were determined at the end of the greenhouse experiment. Significant intraspecific variation was found for nearly all the physiological parameters evaluated, but only leaf concentrations of Na + and Cl − were correlated with an index of family-level differences in salt tolerance.

Alabama, Louisiana↗

USGS1995

Discharge ratings for tainter gates and roller gates at Lock and Dam No. 7 on the Mississippi River, La Crescent, Minnesota

The water-surface elevations on the Inland Waterway Navigation System of the upper Mississippi River are controlled during normal operating conditions by various flow controls at 29 locks and dams. The headwater (navigation pool) and tailwater elevations at Lock and Dam No. 7 are controlled by the regulation of 11 tainter gates and 5 roller gates. Discharge ratings for these tainter and roller gates were developed for use in computing discharge through Dam No. 7 and to aid in regulating the navigation pool within its normal operating limits of 639.00 ± 0.20 feet (NGVD 1912). Hydraulic-control variables and discharges were measured at the tainter and roller gates and analyzed for this report. Fifty-two current-meter measurements of discharges that ranged from discharges too low to measure to 12,600 cubic feet per second were made in the forebays of the tainter and roller gates. The measured discharges were used to define flow regimes as a function of static-headwater depth (hi), static-tailwater depth (03), and vertical height of tainter or roller gate opening (hg). Submerged-orifice flow is the predominant flow regime at Lock and Dam No. 7. Twenty-four discharge measurements were used to develop submerged-orifice discharge coefficient relations for the 11 tainter gates. Twenty discharge measurements were used to develop a submerged-orifice discharge coefficient relation for the five roller gates. Coefficients of discharge (Cgs) ranged fron 0.126 (hg = 1 foot) to 1.089 (hg = 10 feet) for tainter gates and from 0.050 (hg = 1 foot) to 0.302 (hg = 14 feet) for roller gates. Disch^ge was measured at three different tainter gates with the gates closed (hg = 0) to evaluate tH tainter-gate leakage-discharge relations. No measurable leakage was observed. The resulting equations can be used to compute discharge at Lock and Dam No. 7 for the tainter and re Her gates under normal flow conditions. Discharge rating tables for the tainter and roller gates are given with a headwater elevation of 639.00 feet normal pool elevation for selected tailwate" elevations and gate openings.

Minnesota↗

USGS1993

Worldwide distribution of subaquatic gas hydrates

Sediments containing natural gas hydrates occur worldwide on continental and insular slopes and rises of active and passive margins, on continental shelves of polar regions, and in deep-water (> 300 m) environments of inland lakes and seas. The potential amount of methane in natural gas hydrates is enormous, with current estimates at about 1019 g of methane carbon. Subaquatic gas hydrates have been recovered in 14 different areas of the world, and geophysical and geochemical evidence for them has been found in 33 other areas. The worldwide distribution of natural gas hydrates is updated here; their global importance to the chemical and physical properties of near-surface subaquatic sediments is affirmed. ?? 1993 Springer-Verlag.

Geo-Marine Letters↗

USGS2017

Assessing the global distribution of river fisheries harvest: A systematic map protocol

Background Although surface freshwater comprises < 0.01% of the total water volume of earth, freshwater inland capture fisheries and aquaculture represent 40% of the global reported finfish harvest. While the social, economic, and ecological importance of inland fish and fisheries is difficult to overstate, they are often undervalued and underappreciated. Accurate information about these highly dispersed fisheries is inherently difficult to acquire, often unreported, and not collected in a standardized format globally. A standardized river fishery database is needed for managing aquatic systems as well as for defining relevant development policies. Here, we describe our methodology to search, identify, and describe available river fisheries information to create a harmonized global database of river fisheries harvest. This database will provide the first global database of spatially and temporally explicit river fisheries data. The database can be used to identify locations, hotspots of data collection, and gaps in existing knowledge and will be especially important to inform studies and management at larger spatial scales (i.e., watershed, regional, or global scales). This database will also be critical for developing fish biomass models for rivers, which can provide managers with information critical for decision-making, such as improved valuation methods for river fish and fisheries. Methods This systematic map protocol describes the methodology to search, identify, and describe available information on river fish and fisheries across the globe. We define river fisheries as “both capture and aquaculture of river finfish species for food, income, or recreation”. River fish species are those finfish that live part, or all of their lives in rivers. The searches will be conducted for the period from 1950 to present using bibliographic databases and grey literature sources. To identify relevant evidence, pre-defined inclusion and exclusion criteria will be used to screen articles at title, abstract, and full text. A searchable database containing extracted meta-data from relevant included studies will be developed and presented as a geodatabase. The final systematic map will consist of a descriptive narrative report of the distribution and content of river fish literature including a geodatabase of available information.

Environmental Evidence↗

USGS2019

Identifying and characterizing extrapolation in multivariate response data

Faced with limitations in data availability, funding, and time constraints, ecologists are often tasked with making predictions beyond the range of their data. In ecological studies, it is not always obvious when and where extrapolation occurs because of the multivariate nature of the data. Previous work on identifying extrapolation has focused on univariate response data, but these methods are not directly applicable to multivariate response data, which are common in ecological investigations. In this paper, we extend previous work that identified extrapolation by applying the predictive variance from the univariate setting to the multivariate case. We propose using the trace or determinant of the predictive variance matrix to obtain a scalar value measure that, when paired with a selected cutoff value, allows for delineation between prediction and extrapolation. We illustrate our approach through an analysis of jointly modeled lake nutrients and indicators of algal biomass and water clarity in over 7000 inland lakes from across the Northeast and Mid-west US. In addition, we outline novel exploratory approaches for identifying regions of covariate space where extrapolation is more likely to occur using classification and regression trees. The use of our Multivariate Predictive Variance (MVPV) measures and multiple cutoff values when exploring the validity of predictions made from multivariate statistical models can help guide ecological inferences.

PLoS ONE↗

USGS2007

Mapping and vessel-based capabilities

U.S. Geological Survey (USGS) scientists from the Florida Integrated Science Center (FISC) conduct scientific investigations of submerged coastal and marine resources using new and existing technologies. Each contributing technique, method, or product adds to our understanding of coastal and marine resources and provides information for resource-management decisionmaking. In support of this mission, the USGS St. Petersburg office maintains a fleet of research vessels used for inland, coastal, and open-water marine surveys and investigations. Each vessel has advantages and limitations related to water depth, carrying capacity, speed, operation in open water, and other functions. These research platforms are staffed by experienced technical and scientific professionals with expertise in marine navigation, geology, geophysics, engineering, biology, and oceanography.

Fact Sheet↗

USGS2013

Integrated synoptic surveys using an autonomous underwater vehicle and manned boats

Traditional surface-water surveys are being combined with autonomous technology to produce integrated surveys of bathymetry, water quality, and velocity in inland lakes and reservoirs. This new technology provides valuable, high-resolution, integrated data that allow a systems-based approach to understanding common environmental problems. This fact sheet presents several example applications of integrated surveys within inland lakes and coastal Lake Michigan and Lake Erie.

Lake Erie, Lake Michigan↗

USGS2004

Estimating monthly, annual, and low 7-day, 10-year streamflows for ungaged rivers in Maine

Regression equations to estimate monthly, annual, and low 7-day, 10-year (7Q10) streamflows were derived for rivers in Maine. The derived regression equations for estimating mean monthly, mean annual, median monthly, median annual, and low 7Q10 streamflows for ungaged rivers in Maine presented in this report supersede those derived in previous studies. Twenty-six U.S. Geological Survey streamflow-gaging stations on unregulated, rural rivers in Maine with 10 years or more of recorded streamflow were used to develop the regression equations. Ordinary least squares (OLS) regression techniques were used to select the explanatory variables (basin and climatic characteristics) that would appear in the final regression equations. OLS regression of all possible subsets was done with 62 explanatory variables for each of 27 response variables. Five explanatory variables were chosen for the final regression equations: drainage basin area, areal fraction of the drainage basin underlain by sand and gravel aquifers, distance from the coast to the drainage basin centroid, mean drainage basin annual precipitation, and mean drainage basin winter precipitation (the sum of mean monthly precipitation for December, January, and February). Generalized least-squares regression techniques were used to derive the final coefficients and measures of uncertainty for the regression equations. The forms of many of the derived regression equations indicate some physical, mechanistic processes. Drainage basin area is the most statistically important explanatory variable and appears in all derived regression equations. Monthly streamflows are related inversely to the distance from the coast to the drainage basin centroid during December, January, February, and March; that is, the closer a river basin is to the coast, the higher monthly streamflows are per unit drainage basin area during the winter. The relation reverses in May when higher streamflows are attributed to basins farther from the coast. These relations are consistent with colder, inland drainage basins storing more water in snowpack during the winter and releasing it in the spring. The monthly streamflows (and low 7Q10) during July, August, September, and October are related positively to areal fraction of the drainage basin underlain by sand and gravel aquifers. In general, sand and gravel aquifers underlying Maine river basins have excellent water-yielding characteristics and can provide water to streams during low-flow conditions in the summer and early fall.

Maine↗

USGS1996

Hydrologic feasibility of water-supply-development alternatives in Cape May County, New Jersey

Increasing public-supply withdrawals in Cape May County, New Jersey associated with increasing residential and seasonal tourist populations have led to regionally lowered ground-water levels, a reversal of ground-water flow directions toward onshore, and landward encroachment of saltwater in the shallow aquifer system. The three aquifers composing the shallow system are, in order of increasing depth, the unconfined Holly Beach water-bearing zone and the confined estuarine sand and Cohansey aquifers. The changes to the ground-water system have been greatest in the confined aquifers near the three major well fields on the Cape May peninsula. Formerly productive water-supply wells have been abandoned because of saltwater contamination. Concern about anthropogenic contamination has prevented shifting of withdrawals to the unconfined aquifer. Surface- water sources have also been little used. Further development on the peninsula involving increased water demand will exacerbate the current saltwater-encroachment problems. The purpose of this study was to test the feasibility of possible water-supply-development alternatives by use of predictive ground-water flow simulations. The alternatives involve (1) injection of tertiary- treated wastewater to replenish aquifer storage and create a hydraulic barrier to saltwater encroachment, (2) withdrawal of brackish water in order to create a hydraulic barrier, (3) conjunctive use of ground water and surface water, enabling the reduction of ground-water withdrawals, and (4) redistribution of withdrawals inland to the unconfined aquifer. Results of these simulations can potentially be used in the design of a water-supply-development strategy that preserves supply and a monitoring program that ensures early warning of saltwater encroachment, thereby allowing sufficient time for development of an alternative supply. The water-supply- development alternatives were evaluated by comparison of results of predictive simulations made with a previously calibrated ground-water flow model of the shallow aquifer system. The quasi-three-dimensional sharp-interface model was calibrated to 1988 annual average hydrologic conditions. The planning period for the predictive simulations is 1989-2049. For the planning period, total public-supply withdrawals were increased 100 percent over average 1983-88 withdrawals. Results of a baseline simulation involving only the increased withdrawals were compared to each of the simulated alternatives, which also include the withdrawals. Hydraulic heads, saltwater- freshwater interface movement, and ground-water flows were compared. Simulation results indicate that the barrier-injection or barrier-withdrawal scheme could be useful in managing the water supply for a specific location. The conjunctive- use scheme would provide a marginal regional hydrologic benefit. Redistribution of withdrawals appears to be the only regional alternative that would result in recovery of ground-water levels and would substantially slow saltwater encroachment; however, anthropogenic land-surface contamination of the unconfined aquifer would have to be considered if the redistribution alternative is acted upon.

Water-Resources Investigations Report↗

USGS1987

Changes in water quality of Michigan streams near urban areas, 1973-84

Monthly water-quality monitoring of streams was begun by Michigan Department of Natural Resources in 1973 to (1) determine temporal and spatial variability, (2) detect long-term trends, and (3) describe changes in water quality near urban areas. This report provides a statistical analysis and summary of data collected from 1973 through 1984. Concentrations and discharges of nine commonly measured water-quality constituents and specific conductance are examined. Twenty-three sites on inland streams (streams draining basins wholly within Michigan) and 20 sites on Detroit River are discussed. The changes in water quality in 9 rivers near 12 urban areas in Michigan's southern Lower Peninsula and the relation between streamflow and selected waterquality characteristics, including phosphorus, chloride, sulfate, nitrogen, specific conductance, and solid residues are described. Results show that the median dissolved-solids concentration in Clinton River downstream from Pontiac exceed Michigan's 1986 stream water-quality standard. Among inland streams, constituent concentrations and discharges generally were greatest in Saginaw River and least in Grand River upstream from Jackson. Upstream from Detroit, constituent concentrations in Detroit River did not differ appreciably across the Windmill Point Transect; downstream from Detroit, at the Fermi Transect across Detroit River, most constituent concentrations were higher near the American and Canadian shorelines. Among urban areas, greatest changes in constituent concentrations occurred in the Grand River near Jackson, in the Clinton River near Pontiac, and in the Tittabawassee River near Midland; the least changes in constituent concentrations occurred in the Saginaw River near Saginaw, in Detroit River near Detroit and the Kalamazoo River near Battle Creek. Greatest changes in constituent discharges occurred in the Detroit River near the Detroit area; the least occurred in the Chippewa River near Mount Pleasant. Of the 230 regressions between streamflow and constituent concentrations in inland streams, about 73 percent were significant at the 5-percent level. The degree of the correlation and nature of the relation varied among sites and constituents. Generally, higher streamflows were associated with lower concentrations. Changes in streamflow and changes in constituent concentrations near urban areas were correlated in 57 percent of the 120 analyses. Generally, higher changes in streamflow were associated with lower changes in concentrations.

Michigan↗

USGS1997

Secondary precious metal enrichment by steam-heated fluids in the Crofoot-Lewis hot spring gold-silver deposit and relation to paleoclimate

The Crofoot-Lewis deposit is an adularia-sericite-type (low-sulfidation) epithermal Au-Ag deposit, whose well-preserved paleosurface includes abundant opaline sinters, widespread and intense silicification, bedded hydrothermal eruption breccias, and a large zone of acid sulfate alteration. Radiogenic isotope ages indicate that the system was relatively long-lived, with hydrothermal activity starting around 4 Ma and extending, at least intermittently, for the next 3 m.y.Field evidence indicates that the surficial zone of acid sulfate alteration formed in a steam-heated environment within an active geothermal system. A drop in the water table enabled descending acid sulfate waters to leach Au and Ag from zones of low-grade disseminated mineralization, resulting in the redistribution and concentration of Au and Ag into ore-grade concentrations. These zones of secondary Au-Ag enrichment are associated with opal + alunite + kaolinite + montmorillonite + or - hematite and were deposited in open space fractures at, and within a few tens of meters below, the paleowater table.The stable isotope systematics of alunite and kaolinite in the steam-heated environment are relatively complex, due to variations in the residence time of aqueous SO 4 that formed from the oxidation of H 2 S prior to precipitation of alunite, and the susceptibility of fine-grained kaolinites to hydrogen isotope exchange with later waters. Most of the alunites are enriched in 34 S relative to early sulfide minerals, reflecting partial S isotope exchange between aqueous SO 4 and H 2 S. About half of the alunites give reasonable calculated delta 18 O (sub SO 4 -OH) temperatures for a steam-heated environment indicating O isotope equilibrium between aqueous SO 4 and water. The delta D (sub H 2 O) values of the hydrothermal fluids varied by almost 60 per rail over the life of the meteoric water-dominated system, suggesting significant climate changes.Mineralization is believed to have resulted from large-scale convection of meteoric water controlled largely by basin and range fractures and a high geothermal gradient with H 2 S for Au complexing derived from organic matter in basin sediments. A wet climate resulted in the formation of a large inland lake which provided abundant recharge water for the hydrothermal system. A fluctuating water table controlled by changing climatic conditions enabled steam-heated acid sulfate fluids to overprint lower grade mineralization resulting in ore-grade precious metal enrichment.

Economic Geology↗

USGS2014

Analysis of projected water availability with current basin management plan, Pajaro Valley, California

The projection and analysis of the Pajaro Valley Hydrologic Model (PVHM) 34 years into the future using MODFLOW with the Farm Process (MF-FMP) facilitates assessment of potential future water availability. The projection is facilitated by the integrated hydrologic model, MF-FMP that fully couples the simulation of the use and movement of water from precipitation, streamflow, runoff, groundwater flow, and consumption by natural and agricultural vegetation throughout the hydrologic system at all times. MF-FMP allows for more complete analysis of conjunctive-use water-resource systems than previously possible with MODFLOW by combining relevant aspects of the landscape with the groundwater and surface-water components. This analysis is accomplished using distributed cell-by-cell supply-constrained and demand-driven components across the landscape within “water-balance subregions” (WBS) comprised of one or more model cells that can represent a single farm, a group of farms, watersheds, or other hydrologic or geopolitical entities. Analysis of conjunctive use would be difficult without embedding the fully coupled supply-and-demand into a fully coupled simulation, and are difficult to estimate a priori. The analysis of projected supply and demand for the Pajaro Valley indicate that the current water supply facilities constructed to provide alternative local sources of supplemental water to replace coastal groundwater pumpage, but may not completely eliminate additional overdraft. The simulation of the coastal distribution system (CDS) replicates: 20 miles of conveyance pipeline, managed aquifer recharge and recovery (MARR) system that captures local runoff, and recycled-water treatment facility (RWF) from urban wastewater, along with the use of other blend water supplies, provide partial relief and substitution for coastal pumpage (aka in-lieu recharge). The effects of these Basin Management Plan (BMP) projects were analyzed subject to historical climate variations and assumptions of 2009 urban water demand and land use. Water supplied directly from precipitation, and indirectly from reuse, captured local runoff, and groundwater is necessary but inadequate to satisfy agricultural demand without coastal and regional storage depletion that facilitates seawater intrusion. These facilities reduce potential seawater intrusion by about 45% with groundwater levels in the four regions served by the CDS projected to recover to levels a few feet above sea level. The projected recoveries are not high enough to prevent additional seawater intrusion during dry-year periods or in the deeper aquifers where pumpage is greater. While these facilities could reduce coastal pumpage by about 55% of the historical 2000–2009 pumpage for these regions, and some of the water is delivered in excess of demand, other coastal regions continue to create demands on coastal pumpage that will need to be replaced to reduce seawater intrusion. In addition, inland urban and agricultural demands continue to sustain water levels below sea level causing regional landward gradients that also drive seawater intrusion. Seawater intrusion is reduced by about 45% but it supplies about 55% of the recovery of groundwater levels in the coastal regions served by the CDS. If economically feasible, water from summer agricultural runoff and tile-drain returnflows could be another potential local source of water that, if captured and reused, could offset the imbalance between supply and demand as well as reducing discharge of agricultural runoff into the National Marine Sanctuary of Monterey Bay. A BMP update (2012) identifies projects and programs that will fund a conservation program and will provide additional, alternative water sources to reduce or replace coastal and inland pumpage, and to replenish the aquifers with managed aquifer recharge in an inland portion of the Pajaro Valley.

California↗

USGS2008

Complex seasonal patterns of primary producers at the land-sea interface

Seasonal fluctuations of plant biomass and photosynthesis are key features of the Earth system because they drive variability of atmospheric CO 2 , water and nutrient cycling, and food supply to consumers. There is no inventory of phytoplankton seasonal cycles in nearshore coastal ecosystems where forcings from ocean, land and atmosphere intersect. We compiled time series of phytoplankton biomass (chlorophyll a ) from 114 estuaries, lagoons, inland seas, bays and shallow coastal waters around the world, and searched for seasonal patterns as common timing and amplitude of monthly variability. The data revealed a broad continuum of seasonal patterns, with large variability across and within ecosystems. This contrasts with annual cycles of terrestrial and oceanic primary producers for which seasonal fluctuations are recurrent and synchronous over large geographic regions. This finding bears on two fundamental ecological questions: (1) how do estuarine and coastal consumers adapt to an irregular and unpredictable food supply, and (2) how can we extract signals of climate change from phytoplankton observations in coastal ecosystems where local‐scale processes can mask responses to changing climate?

Ecology Letters↗

USGS1996

Hydrogeology and water quality of the shallow aquifer system at the Mainside, Naval Surface Warfare Center, Dahlgren Site, Dahlgren, Virginia

Lithologic and geophysical logs of boreholes at 29 sites show that the hydrogeologic framework of the Mainside of the Naval Surface Warfare Center, Dahlgren Site at Dahlgren, Virginia, consists of un-consolidated sedimentary deposits of gravel, sand, silt, and clay. The upper 220 feet of these sediments are divided into five hydrogeologic units, including the (1) Columbia (water-table) aquifer, (2) upper confining unit, (3) upper confined aquifer, (4) Nanjemoy-Marlboro confining unit, and (5) Aquia aquifer. The Columbia aquifer in the study area is a local system that is not affected by regional pumping. Ground-water recharge occurs at topographic highs in the northern part of the Mainside, and ground-water discharge occurs at topographic lows associated with adjacent surface-water bodies. Regionally, the direction of ground-water flow in the upper confined and Aquia aquifers is toward the southwest and southeast, respectively. A downward hydraulic gradient exists between the aquifers in the shallow system, and stresses on the Aquia aquifer are indicated by heads that range between 2 and 12 feet below sea level. The ratio of median horizontal hydraulic conductivity of the Columbia aquifer to median vertical hydraulic con-ductivity of the upper confining unit, however, is approximately 2,600:1; therefore, under natural- flow conditions, most water in the Columbia aquifer probably discharges to adjacent surface- water bodies. The composition and distribution of major ions vary in the Columbia aquifer. In general, water samples from wells located along the inland perimeter roads of the study area have chloride or a combination of chloride and sulfate as the dominant anions, and water samples from wells located in the interior of the study area have bicarbonate or a combination of bicarbonate and sulfate as the dominant anions. Sodium and calcium were the dominant cations in most samples. Dissolved solids and four inorganic constituents are present in water from the Columbia aquifer at concentrations that exceed the secondary maximum contaminant levels (SMCL's) for drinking water established by the U.S. Environmental Protection Agency. Concentration of dissolved solids exceed the SMCL of 500 milligrams per liter in 3 of 29 samples from the Columbia aquifer. An elevated concentration of sodium is present in one water sample, and elevated concentrations of chloride are present in two water samples. Concentrations of dissolved iron and manga-nese exceed the SMCL in 10 and 17 of 29 water samples, respectively, and are the most extensive water-quality problem with regard to inorganic constituents in the Columbia aquifer.

Water-Resources Investigations Report↗