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At least 505 records · Page 28Linked to original sources
USGS2004

Effect of water-column pH on sediment-phosphorus release rates in Upper Klamath Lake, Oregon, 2001

Sediment-phosphorus release rates as a function of pH were determined in laboratory experiments for sediment and water samples collected from Shoalwater Bay in Upper Klamath Lake, Oregon, in 2001. Aerial release rates for a stable sediment/water interface that is representative of the sediment surface area to water column volume ratio (1:3) observed in the lake and volumetric release rates for resuspended sediment events were determined at three different pH values (8.1, 9.2, 10.2). Ambient water column pH (8.1) was maintained by sparging study columns with atmospheric air. Elevation of the water column pH to 9.2 was achieved through the removal of dissolved carbon dioxide by sparging with carbon dioxide-reduced air, partially simulating water chemistry changes that occur during algal photosynthesis. Further elevation of the pH to 10.2 was achieved by the addition of sodium hydroxide, which doubled average alkalinities in the study columns from about 1 to 2 milliequivalents per liter. Upper Klamath Lake sediments collected from the lake bottom and then placed in contact with lake water, either at a stable sediment/water interface or by resuspension, exhibited an initial capacity to take up soluble reactive phosphorus (SRP) from the water column rather than release phosphorus to the water column. At a higher pH this initial uptake of phosphorus is slowed, but not stopped. This initial phase was followed by a reversal in which the sediments began to release SRP back into the water column. The release rate of phosphorus 30 to 40 days after suspension of sediments in the columns was 0.5 mg/L/day (micrograms per liter per day) at pH 8, and 0.9 mg/L/day at pH 10, indicating that the higher pH increased the rate of phosphorus release by a factor of about two. The highest determined rate of release was approximately 10% (percent) of the rate required to explain the annual internal loading to Upper Klamath Lake from the sediments as calculated from a lake-wide mass balance and observed in total phosphorus data collected at individual locations.

Water-Resources Investigations Report↗
USGS2002

Numerical simulation of ground-water withdrawals in the southern Lihue Basin, Kauai, Hawaii

Numerical simulations indicate that ground-water withdrawals from the Hanamaulu and Puhi areas of the southern Lihue Basin will result in a decline in water levels and reductions in base flows of streams near proposed new water-supply wells. Most of the changes will be attained within 10 to 20 years of the start of pumping. Except for areas such as Puhi and Kilohana, the freshwater lens in most inland areas of the southern Lihue Basin is thick and model simulations indicate that changes in water level and the position of the freshwater- saltwater interface in response to pumping will be small relative to the present thickness of the freshwater lens. Effects of the proposed withdrawals on streamflow depend on withdrawal rate and proximity of the wells to streams. Placing pumped wells away from streams with low base flow and toward streams with high base flow can reduce the relative effect on individual streams. Simulation of the 0.42-million-gallon-per-day increase in withdrawal projected for 2000 indicates that the resulting changes in water levels and interface position, relative to conditions prior to the withdrawal increase, will be small, and that stream base flow will be reduced by less than 10 percent. Simulation of the 0.83-million-gallon-per-day withdrawal projected for 2010 indicates further thinning of the freshwater lens in the Puhi area, where the lens already may be thin, as well as base-flow reduction in Nawiliwili Stream. Simulation of an alternative distribution of the 0.83-million-gallon-per-day withdrawal indicates that the effects can be reduced by shifting most of the new withdrawal to the Hanamaulu area where the freshwater lens is thicker and stream base flows are greater. Simulation of the 1.16-million-gallon-per-day increase in withdrawal projected for 2020 indicates that if withdrawal is distributed only among Hana-maulu wells 1, 3, and 4, and Puhi well 5A, further thinning of the already-thin freshwater lens in the Puhi area would occur. Such a distribution would also exceed the maximum draft recommended by the water-systems standards used in Hawaii. Another simulation in which part of the 1.16 million gallons per day was distributed among three additional hypothetical wells in the Hanamaulu area showed that the pumping effects could be shifted from the Puhi area to the Hanamaulu area, where the freshwater lens is thicker, but that base flow in Hanamaulu Stream may decrease by as much as 16 percent.

Hawaii↗
USGS1981

Relation between freshwater flow and salinity distributions in the Alafia River, Bullfrog Creek, and Hillsborough Bay, Florida

Data on streamflow, tide stage, specific conductance, and chloride concentration were collected in the Alafia River and Bullfrog Creek to describe the salinity and physical characteristics of the saltwater wedge. The location of the saltwater-freshwater interface for both streams was described by multiple regression equations involving streamflow and tide stage. Low-flow frequency data were used with regression relationships to show the effect of withdrawals of freshwater from the Alafia River on the location of the saltwater interface. Examples are presented without storage and with storage and minimum streamflow requirements. In every case, the effect of reductions in streamflow was upstream encroachment of saltwater. Salinity in Hillsborough Bay in the vicinity of the Alafia River and Bullfrog Creek was evaluated using a salt-transport model for various freshwater inflow conditions. Model results indicate that freshwater inflow from these streams has the greatest effect on the salinity of areas closest to the mouth during periods of above average inflow. (USGS)

Water-Resources Investigations Report↗
USGS1983

Evaluation of ground-water quality data from Kentucky

The report reviews and summarizes 10,578 chemical analyses, from 2,362 wells and springs in Kentucky. These water-quality data were collected prior to September 30, 1981, and are available in computer files of the U.S. Geological Survey. The principal water-bearing rocks in Kentucky were combined into 10 major groups to aid in data summary preparation and general description of the ground-water quality of the State. Ground water in Kentucky is generally fresh near the outcrop of the rocks comprising the aquifer. Slightly saline to briny water occurs at variable depths beneath the freshwater. Preparation of quadrilinear diagrams revealed three principal geochemical processes in the aquifers of Kentucky: (1) mixing of freshwater and saline water in an interface zone; (2) dedolomitization of the Devonian and Silurian and Lower Mississippian carbonate rocks; (3) sodium for calcium exchange in the freshwater sections of many of the sandstone-shale aquifers. A number of errors and deficiencies were found in the data base. The principal deficiencies were: (1) very few complete analyses which included important field measurements; (2) inadequate definition of the chemistry of the freshwater-saline water interface zone throughout much of the State; (3) no analyses of stable isotopes and dissolved gases; (4) fewer than 10 analyses of most trace metals, radionuclides, and man-made organic chemicals; and (5) no data on bacteria in ground water from any aquifer in the State. (USGS)

Kentucky↗
USGS1986

Geohydrology and ground-water quality on Shelter Island, Suffolk County, New York, 1983-84

Shelter Island, with an area of about 11 sq mi, lies between the north and south forks of eastern Long Island in Suffolk County. The thin upper glacial (water table) aquifer contains the lens-shaped freshwater body that is the sole source of freshwater for the Town 's population of about 2,200 year-round and 10,000 summer residents. Chloride concentrations in groundwater above the freshwater/saltwater interface, defined as 40 mg/L Cl-, are relatively constant with depth. Below the interface, however, chloride concentrations increase rapidly--as much as an order of magnitude within 10 ft--until they reach 19 ,000 mg/L, the chloride concentration of seawater. Chloride concentrations in shallow groundwater from wells screened in or near the zone of diffusion may range over two orders of magnitude in response to variations in recharge and groundwater withdrawal. After the summer season of relatively low recharge and peak water demand, the thickness of the freshwater lens is < 20 ft in many nearshore areas. A map showing the configuration of the water table in December 1983 indicates freshwater mounds in the center of the island, in the Mashomack Preserve, on the Dering Harbor-Hay Beach peninsula, and in the area between Shelter Island Heights and West Neck Bay. Areas in which the supply of fresh groundwater is severely limited include all coastal areas, the southernmost part of the West Neck peninsula, and Little Ram Island. Water levels in most locations are < 6 ft above sea level. During 1974-83, seasonal water table fluctuations were greater than variations that occurred from year to year. Groundwater quality on Shelter Island is generally good and usually meets Federal and State drinking water standards. However, many wells contain water that has excessive concentrations of dissolved iron and manganese (up to 5.0 mg/L and 3.0 mg/L, respectively), and elevated chloride and dissolved solids concentrations (up to 310 mg/L and 585 mg/L, respectively) have been found in some nearshore wells. Increased withdrawal of fresh groundwater in nearshore areas will cause further landward movement of saline groundwater; in other areas, excessive pumping may cause upconing. A system of widely spaced pumping wells that avoid nearshore areas would minimize these effects. (Lantz-PTT)

Water-Resources Investigations Report↗
USGS1990

Water-resources potential of the freshwater lens at Key West, Florida

The island of Key West lies at the end of the Florida Keys, about 150 miles southwest of Miami. The public-water supply for the island is provided by the Florida Keys Aqueduct Authority Well Field near Miami. However, there are many privately owned wells on the island that tap the local fresh ground-water lens for potable and nonpotable water supply. The number of people who use water from the wells for drinking purposes is unknown. From 1985 to 1988, the U.S. Geological Survey, in cooperation with the South Florida Water Management District, conducted an investigation to characterize the Key West freshwater lens. Observation wells were drilled to determine the extent of the lens and to characterize the water quality. Previous well logs and well-core data collected during the investigation showed the aquifer to be a highly permeable, porous, solution-riddled, oolitic limestone that allows rainfall recharge to quickly seep into the ocean and saltwater to easily intrude the aquifer. The small freshwater lens (250 milligrams per liter of chloride concentration, or less) averages 5 feet in thickness below the center of the western half (Old Town) of the island. The lens contains about 20 million gallons of fresh-water during the dry season and about 30 million gallons during the wet season. Underlying the freshwater lens is a transition zone of freshwater-saltwater mix that extends to the saltwater interface (19,000 milligrams per liter of chloride concentration), which is about 40-feet deep at the center of the lens. The water table fluctuates and the configuration of the lens constantly changes, largely as a result of tidal effects. Other events, such as rainfall, pumping, and evapotranspiration, are masked by the tidal effects. The freshwater lens is a calcium bicarbonate water that grades to a sodium chloride type near the saltwater interface. Elevated concentrations of nitrate nitrogen were found in water samples from wells in the Old Town district. However, concentrations generally were not above the maximum contaminant level of 10 milligrams per liter for drinking water established by the Florida Department of Environmental Regulation. Water samples near an old land-fill in the eastern half of the island had concentrations of iron (600-1,900 micrograms per liter) and lead (40-800 micrograms per liter) that extended maximum contaminant levels of 300 and 50 micrograms per liter. These trace-element concentrations generally decreased with distance from the landfill. Although the freshwater lens is a potential source of water for additional nonpotable water needs in Key West, any large-scale pumping could quickly exhaust the freshwater lens, and saline water could be rapidly drawn though the porous limestone aquifer. Water-quality data indicate that the lens is an unlikely source of potable water.

Florida↗
USGS1994

Ground-water resources of southern Tangipahoa Parish and adjacent areas, Louisiana

Groundwater resources in southern Tangipahoa Parish and adjacent areas were studied to determine their potential for development as an alternative to the Mississippi River as a water-supply source for Jefferson Parish. Eight major aquifers consisting of thick sand units that underlie the study area are, in descending order: (1) shallow, (2) upper Ponchatoula, (3) lower Ponchatoula, (4) Abita, (5) Covington, (6) Tchefuncta, (7) Hammond, and (8) Amite. A fault zone, referred to as the Baton Rouge fault, crosses southern Tangipahoa Parish. Analyses of geophysical logs indicated that the deep aquifers south of the fault zone had been displaced from 350 to 400 feet, and that the deeper aquifers were not in hydraulic connection with the flow system north of the fault. The groundwater resources of southeastern Louisiana are immense and the quality of groundwater in Tangipahoa Parish is suitable for most uses. The quality of water in these aquifers generally meets the U.S. Environmental Protection Agency's standards for public supply. The hydrologic system underlying Tangipahoa Parish and adjacent areas in 1990 supplied about 19 Mgal/d of water that was suitable for public supply. However, substantial increases in pumping from the aquifer system would result in renewed water-level declines throughout the hydrologic system until a new equilibrium is established. A test we11 in southern Tangipahoa Parish, penetrated all eight aquifers. Total thickness of freshwater sand beds penetrated by the 3003-ft test hole was more than 1900 ft. Resistivity values from an electric log of the test typically averaged 200 ohm-meters, which indicates that the water has low dissolved-solids and chloride concentrations. An analysis of the Abita aquifer at Ruddock in St. John the Baptist Parish, for two of three hypothetical well fields, indicated that for a hypothetical we11 field with a pumping rate of 112 Mgal/d, the freshwater/saltwater interface could arrive at the outer perimeter we11 in 10 to 14 years. The 1990 location of the interface in the Abita aquifer is 1.9 mi from the southernmost part of the potential location of the 112 Mgal/d well field.

Water-Resources Investigations Report↗
USGS1994

Hydrogeology and the distribution and origin of salinity in the Floridan aquifer system, southeastern Florida

The Floridan aquifer system in southeastern Florida consists of the Upper Floridan aquifer, the middle confining unit, and the Lower Floridan aquifer. An upper zone of brackish water and a lower zone of water with a salinity similar to that of seawater are present in the Floridan aquifer system. The brackish-water zone is defined as that in which water has a dissolved-solids concentration of less than 10,000 milligrams per liter (chloride concentration less than about 5,240 milligrams per liter), and water in the the saline-water zone has a dissolved solids concentration of about 35,000 milligrams per liter (about 18,900 milligrams per liter chloride concentration). The brackish-water and saline-water zones are separated by a transitional zone, typically 100 feet thick, in which salinity increases abruptly with depth. The base of the brackish-water zone lies within the Upper Floridan aquifer along the coast but extends into the middle confining unit inland. The brackish- water zone is as much as 1,200 feet thick inland, whereas the Upper Floridart aquifer is typically 500 to 600 feet thick. Changes in lithology or permeability do not usually control the position of the boundary between the brackish-water and saline-water zones. Calculations of the depth of a brackish-water and saline-water interface using the Ghyben-Herzberg relation show good agreement between calculated and actual positions of the interface, indicating equilibrium between the zones. Several areas of high salinity with chloride concentrations greater than 3,000 milligrams per liter are present in the upper interval of the brackish-water zone near the coast, and in one of these areas in northeastern Broward County, salinity decreases with depth from the upper to lower interval. The high salinities could be a result of seawater preferentially encroaching into zones of higher permeability in the Upper Flofidan aquifer during Pleistocene high stands of sea level and incomplete flushing of the seawater by the present-day flow system.

Florida↗
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↗
USGS1996

Time-dependent Data System (TDDS); an interactive program to assemble, manage, and appraise input data and numerical output of flow/transport simulation models

A system of functional utilities and computer routines, collectively identified as the Time-Dependent Data System CI DDS), has been developed and documented by the U.S. Geological Survey. The TDDS is designed for processing time sequences of discrete, fixed-interval, time-varying geophysical data--in particular, hydrologic data. Such data include various, dependent variables and related parameters typically needed as input for execution of one-, two-, and three-dimensional hydrodynamic/transport and associated water-quality simulation models. Such data can also include time sequences of results generated by numerical simulation models. Specifically, TDDS provides the functional capabilities to process, store, retrieve, and compile data in a Time-Dependent Data Base (TDDB) in response to interactive user commands or pre-programmed directives. Thus, the TDDS, in conjunction with a companion TDDB, provides a ready means for processing, preparation, and assembly of time sequences of data for input to models; collection, categorization, and storage of simulation results from models; and intercomparison of field data and simulation results. The TDDS can be used to edit and verify prototype, time-dependent data to affirm that selected sequences of data are accurate, contiguous, and appropriate for numerical simulation modeling. It can be used to prepare time-varying data in a variety of formats, such as tabular lists, sequential files, arrays, graphical displays, as well as line-printer plots of single or multiparameter data sets. The TDDB is organized and maintained as a direct-access data base by the TDDS, thus providing simple, yet efficient, data management and access. A single, easily used, program interface that provides all access to and from a particular TDDB is available for use directly within models, other user-provided programs, and other data systems. This interface, together with each major functional utility of the TDDS, is described and documented in this report.

Water-Resources Investigations Report↗
USGS2000

Hydrogeology and the distribution of salinity in the Floridan Aquifer system, southwestern Florida

A study was conducted to establish a detailed hydrogeologic framework in the complex Floridan aquifer system of southwestern Florida, and to evaluate and relate the distribution of salinity found in this system. The Floridan aquifer system consists of the Upper Floridan aquifer, middle confining unit, and Lower Floridan aquifer. The Upper Floridan aquifer extends into a basal unit of the Hawthorn Group; however, a regional unconformity present at the base of this unit generally marks the top of the Floridan aquifer system, as it does in the rest of southern Florida. The basal Hawthorn unit, which is defined at its top by a correlative marker unit, ranges in thickness from 120 to 460 feet. Paleotopography present prior to deposition of the basal Hawthorn unit, which resulted at least in part from erosion, is believed to have caused some of this variation in thickness. However, in some areas where the basal Hawthorn unit is thick, particularly in Lee County, depositional buildup created paleotopographic highs at the top of the unit. In these areas, permeable limestone zones are present in the unit, giving the unit a high transmissivity. In most of the study area, the Floridan aquifer system can be divided into a brackish-water zone, a salinity transition zone, and a saline-water zone. The brackish-water zone contains water with a dissolved-solids concentration of less than 10,000 milligrams per liter. The saline-water zone has a dissolved-solids concentration of at least 35,000 milligrams per liter and a salinity similar to that of seawater. The salinity transition zone that separates these two zones is usually 150 feet or less in thickness. The altitude of the base of the brackish-water zone was mapped primarily using geophysical logs; it ranges from as shallow as 565 feet below sea level along the coast to almost 2,200 feet below sea level inland. This mapping indicated that the boundary represents a salinity interface, the depth of which is controlled by head in the brackish-water zone. Chloride concentrations in the upper part of the brackish-water zone range from 400 to 4,000 milligrams per liter. A large area of relatively low salinity in north-central Collier County and to the northwest, as defined by a 1,200-milligram-per-liter chloride-concentration line, coincides with a high area on the basal contact of the Hawthorn Group. As this contact dips away from this high area to central Hendry and southwestern Collier Counties, chloride concentration increases to 2,000 milligrams per liter or greater. However, the increase in salinity in these areas occurs only in the basal Hawthorn unit or Suwannee Limestone, but not in deeper units. In central Hendry County, the increase occurs only in the basal Hawthorn unit in an area where the unit is well developed and thick. These areas of higher salinity could have resulted from the influx of seawater from southwestern Collier County into zones of higher permeability in the Upper Floridan aquifer during high sea-level stands. The influx may only have occurred in structurally low areas and may have experienced incomplete flushing subsequently by the modern freshwater flow system. In an area in north-central Collier County, the altitude of the base of the brackish-water zone is anomalously deep given the position of this area relative to the coast. In this area, the base extends as deep as 2,090 feet below sea level, and the salinity transition zone is not present or is poorly defined. The origin of this anomalous area is interpreted to be related to the development of a unit containing thick dolomite and evaporite beds high in the middle confining unit of the Floridan aquifer system. The top of this dolomite-evaporite unit, which probably has very low permeability, occurs at the base of the brackish-water zone in this area. The axis of a high area mapped at the top of the unit trends to the northwest from central Collier County into north-central Lee County. This axis parallels and lies just to the west of the anomalous area, and it could have acted as an impermeable sill, preventing saline water from moving in laterally from the coast to the southwest and up from the Lower Floridan aquifer. Locating a Floridan aquifer system well field in or near this anomalous area could be optimal because of the lack of a salinity interface at depth.

Water-Resources Investigations Report↗
USGS1972

Determination of mass balance and entrainment in the stratified Duwamish River Estuary, King County, Washington

During a study of the effects of waste-water input on the stratified Duwamish River estuary, intensive water-velocity and salinity measurements were made in both the lower salt wedge and the upper fresher water layer for tidal-cycle periods. The net movement of water and salt mass past a cross section during a tidal cycle was determined from integration of the measured rates of movement of water and salt past the section. The net volume of water that moved downstream past the section during the cycle agreed with the volume of fresh-water inflow at the head of the estuary within (1) 3.8 and 7.2 percent, respectively, for two studies made during periods of maximum and minimum tidal-prism thickness and identical inflow rates .of 312 cfs (cubic feet per second), and (2) 15 percent for one study made during a period of average tidal-prism thickness and an inflow rate of 1,280 cfs. For the three studies, the difference between salt mass transported upstream and downstream during the cycles ranged from 0.8 to 19 percent of the respective mean salt-mass transport. Water was entrained from the .salt-water wedge into the overlying layer of mixed fresh and salt water at tidal-cycle-average rates of 30 and 69 cfs per million square feet of interface for the inflow rates of 312 cfs, and 99 cfs per million square feet of interface for an inflow rate of 1,280 cfs. At a constant inflow rate, the rate of entrainment of salt-wedge water in the Duwamish River estuary more than doubled for a doubling of tidal-prism thickness. It also doubled for a quadrupling of inflow rate at about constant tidal-prism thickness.

Water Supply Paper↗
USGS1982

Geohydrologic appraisal of water resources of the South Fork, Long Island, New York

The ground-water resources of the South Fork of Long Island, N.Y., were investigated from April 1974 to September 1977. The study area encompasses 137 square miles and includes the eastern part of the Town of Southampton and the entire Town of East Hampton. The South Fork consists of a Paleozoic basement complex that is overlain by Cretaceous and Pleistocene sediments. The surficial material is composed of Late Wisconsinan glacial and glaciofluvial deposits in association with beach and marsh deposits of Recent age. Till underlies most of the eastern part of the South Fork. Precipitation is the sole source of fresh ground water on the South Fork. Average annual precipitation recorded at Bridgehampton from 1931-76 is 45 inches; about half this amount reaches the ground-water reservoir. It is estimated that overland runoff amounts to 0.5 inches per year, and evapotranspiration is 23 inches per year. Thus, recharge equals approximately 22 inches per year. Hydraulic conductivity and transmissivity of the Magothy (Cretaceous) and upper glacial (Pleistocene) aquifers on the South Fork were estimated from aquifer tests and specific-capacity data. The average horizontal hydraulic conductivity of the Magothy aquifer is 70 feet per day, and of the upper glacial aquifer 350 feet per day. Transmissivity of the Magothy aquifer on the South Fork ranges from 600 to 24,100 feet squared per day; transmissivity of the upper glacial aquifer ranges from 5,400 feet to 22,700 feet squared per day. No potable water is available from the underlying Lloyd aquifer. The position of the freshwater to saline-water interface is depicted in maps. In the southern part of the area, the freshwater reservoir follows the Ghyben-Herzberg principle, but in the northern part, the depth to interface is less than expected owing to a greater degree of anisotropy of the geologic units. Total public-supply pumpage on the South Fork is estimated to be about 3 Mgal/day, (million gallons per day). Public-supply withdrawals in 1976 averaged 2.75 Mgal/day; of this amount, 2.55 Mgal/day was withdrawn from the upper glacial aquifer, and 0.17 Mgal/day from the Magothy aquifer. Ground water and fresh surface water on the South Fork are generally of suitable quality for drinking and most other uses. However, some substances, for example, iron, chloride, and nitrate, may occur locally in objectionable concentrations.

Water Supply Paper↗
USGS2020

Assessment of burrowing behavior of freshwater juvenile mussels in sediment

Standard laboratory sediment toxicity methods have been adapted for conducting toxicity tests with juvenile freshwater mussels. However, studies looking at juvenile mussel burrowing behavior at the water-sediment interface are limited. Juvenile mussels burrow in sediment for the first 0 to 4 yr of life but also may inhabit the sediment-water interface. The objective of this study was to evaluate burrowing behavior of various species and ages of juvenile freshwater mussels in three control sediments: West Bearskin Lake, Spring River, and coarse commercial sand. Species tested included (1) Fatmucket ( Lampsilis siliquoidea ), (2) Notched Rainbow ( Villosa constricta ), (3) Washboard ( Megalonaias nervosa ), (4) Rainbow ( Villosa iris) , (5) Arkansas Fatmucket ( Lampsilis powellii ), and (6) Oregon Floater ( Anodonta oregonensis ). Greater than 95% of the mussels burrowed into test sediment within 15 min. Across species, life stage, and substrate type, most mussels were recovered from the upper layers of sediment (91% at a sediment depth of 3.4 mm or less), and only 2% of the mussels were recovered at a depth >5.1 mm. No mussels were recovered from a depth >6.8 mm. There was no difference in mussel burrowing depth at 4 h versus 24 h across species, age, and sediment type. Two ages of Fatmucket burrowed to a significantly greater depth in the West Bearskin Lake sediment compared to the Spring River sediment or Coarse Sand. However, there was no significant difference in mean depth across sediment type with the other five species of mussels tested. Based on species and age of mussels tested, juvenile mussels up to an age of at least 20 wk and a length of at least 5 mm readily burrow into sediment and likely would be exposed to contaminants in whole sediment and associated pore water throughout a laboratory sediment toxicity test.

Freshwater Mollusk Biology and Conservation↗
USGS2014

Aragonite saturation states and nutrient fluxes in coral reef sediments in Biscayne National Park, FL, USA

Some coral reefs, such as patch reefs along the Florida Keys reef tract, are not showing significant reductions in calcification rates in response to ocean acidification. It has been hypothesized that this recalcitrance is due to local buffering effects from biogeochemical processes driven by seagrasses. We investigated the influence that pore water nutrients, dissolved inorganic carbon (DIC) and total alkalinity (TA) have on aragonite saturation states (Ω aragonite ) in the sediments and waters overlying the sediment surfaces of sand halos and seagrass beds that encircle Alinas and Anniversary reefs in Biscayne National Park. Throughout the sampling period, sediment pore waters from both bottom types had lower oxidation/reduction potentials (ORP), with lower pH relative to the sediment surface waters. The majority (86.5%) of flux rates (n = 96) for ΣNO x – , PO 4 3– , NH 4 + , SiO 2 , DIC and TA were positive, sometimes contributing significant concentrations of the respective constituents to the sediment surface waters. The Ω aragonite values in the pore waters (range: 0.18 to 4.78) were always lower than those in the overlying waters (2.40 to 4.46), and 52% (n = 48) of the values were <2.0. The DIC and TA fluxes at the sediment–water interface reduced Ω aragonite in 75% (n = 16) of the samples, but increased it in the remainder. The elevated fluxes of nutrients, DIC and TA into the sediment–water interface layer negatively alters the suitability of this zone for the settlement and development of calcifying larvae, while enhancing the establishment of algal communities.

Florida↗
USGS2000

Dynamics of nutrient cycling and related benthic nutrient and oxygen fluxes during a spring phytoplankton bloom in South San Francisco Bay (USA)

Benthic oxygen uptake and nutrient releases of N, P and Si were measured weekly at 2 sites in South San Francisco Bay around the 1996 spring bloom. Exchanges across the sediment-water interface were estimated from whole core incubations performed in the laboratory at in situ temperature and in dark. Fluxes changed significantly on a weekly time scale. Over a period of 15 wk the fluxes of dissolved inorganic N, P and Si ranged from -40 to +200, 0 to 13 and from 30 to 400 µmol m -2 h -1 respectively. Sediment oxygen demand increased from 10 before to 64 mg O 2 m -2 h -1 just after the bloom period. During the bloom, nutrient fluxes represented about 20, 16 and 9% of the Si, P and N requirements for primary production. Before and after the bloom period, Si fluxes contributed up to 30 and >100% of this requirement and P and N fluxes up to 15 and 50% respectively. Simple empirical models explain most of the spatial-temporal variability of benthic fluxes of Si, P and NH 4 (but not NO 3 ) from 3 predictor variables: sediment porosity, nutrient concentration in bottom waters and chlorophyll content of surficial sediments. These models show that algal blooms influence benthic-pelagic nutrient exchange through 2 processes: (1) depletion of nutrients from the water column (which enhances gradient-driven transports across the sediment-water interface) and (2) sedimentation of labile phytodetritus (which promotes remineralization in or on the surficial sediments). Rates and patterns of nutrient cycling were very different at the shallow and deep study sites, illustrating the challenge of extrapolating measurements of coupled algae-nutrient dynamics to whole ecosystems.

Marine Ecology Progress Series↗
USGS2021

Grassification and fast-evolving fire connectivity and risk in the Sonoran Desert, United States

In the southwestern United States, non-native grass invasions have increased wildfire occurrence in deserts and the likelihood of fire spread to and from other biomes with disparate fire regimes. The elevational transition between desertscrub and montane grasslands, woodlands, and forests generally occurs at ∼1,200 masl and has experienced fast suburbanization and an expanding wildland-urban interface (WUI). In summer 2020, the Bighorn Fire in the Santa Catalina Mountains burned 486 km 2 and prompted alerts and evacuations along a 40-km stretch of WUI below 1,200 masl on the outskirts of Tucson, Arizona, a metropolitan area of >1M people. To better understand the changing nature of the WUI here and elsewhere in the region, we took a multidimensional and timely approach to assess fire dynamics along the Desertscrub-Semi-desert Grassland ecotone in the Catalina foothills, which is in various stages of non-native grass invasion. The Bighorn Fire was principally a forest fire driven by a long-history of fire suppression, accumulation of fine fuels following a wet winter and spring, and two decades of hotter droughts, culminating in the hottest and second driest summer in the 125-yr Tucson weather record. Saguaro ( Carnegia gigantea ), a giant columnar cactus, experienced high mortality. Resprouting by several desert shrub species may confer some post-fire resiliency in desertscrub. Buffelgrass and other non-native species played a minor role in carrying the fire due to the patchiness of infestation at the upper edge of the Desertscrub biome. Coupled state-and-transition fire-spread simulation models suggest a marked increase in both burned area and fire frequency if buffelgrass patches continue to expand and coalesce at the Desertscrub/Semi-desert Grassland interface. A survey of area residents six months after the fire showed awareness of buffelgrass was significantly higher among residents that were evacuated or lost recreation access, with higher awareness of fire risk, saguaro loss and declining property values, in that order. Sustained and timely efforts to document and assess fast-evolving fire connectivity due to grass invasions, and social awareness and perceptions, are needed to understand and motivate mitigation of an increasingly fire-prone future in the region.

Arizona↗
USGS2017

Could changes in the agricultural landscape of northeastern China have influenced the long-distance transmission of highly pathogenic avian influenza H5Nx viruses?

In the last few years, several reassortant subtypes of highly pathogenic avian influenza viruses (HPAI H5Nx) have emerged in East Asia. These new viruses, mostly of subtype H5N1, H5N2, H5N6, and H5N8 belonging to clade 2.3.4.4, have been found in several Asian countries and have caused outbreaks in poultry in China, South Korea, and Vietnam. HPAI H5Nx also have spread over considerable distances with the introduction of viruses belonging to the same 2.3.4.4 clade in the U.S. (2014–2015) and in Europe (2014–2015 and 2016–2017). In this paper, we examine the emergence and spread of these new viruses in Asia in relation to published datasets on HPAI H5Nx distribution, movement of migratory waterfowl, avian influenza risk models, and land-use change analyses. More specifically, we show that between 2000 and 2015, vast areas of northeast China have been newly planted with rice paddy fields (3.21 million ha in Heilongjiang, Jilin, and Liaoning) in areas connected to other parts of Asia through migratory pathways of wild waterfowl. We hypothesize that recent land use changes in northeast China have affected the spatial distribution of wild waterfowl, their stopover areas, and the wild-domestic interface, thereby altering transmission dynamics of avian influenza viruses across flyways. Detailed studies of the habitat use by wild migratory birds, of the extent of the wild–domestic interface, and of the circulation of avian influenza viruses in those new planted areas may help to shed more light on this hypothesis, and on the possible impact of those changes on the long-distance patterns of avian influenza transmission.

Frontiers in Veterinary Science↗