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At least 397 records · Page 22Linked to original sources

USGS2004

The origin of high sulfate concentrations in a coastal plain aquifer, Long Island, New York

Ion-exchange batch experiments were run on Cretaceous (Magothy aquifer) clay cores from a nearshore borehole and an inland borehole on Long Island, NY, to determine the origin of high SO42- concentrations in ground water. Desorption batch tests indicate that the amounts of SO 42- released from the core samples are much greater (980-4700 ??g/g of sediment) than the concentrations in ground-water samples. The locally high SO42- concentrations in pore water extracted from cores are consistent with the overall increase in SO 42- concentrations in ground water along Magothy flow paths. Results of the sorption batch tests indicate that SO42- sorption onto clay is small but significant (40-120 ??g/g of sediment) in the low-pH (<5) pore water of clays, and a significant part of the SO42- in Magothy pore water may result from the oxidation of FeS2 by dissolved Fe(III). The acidic conditions that result from FeS2 oxidation in acidic pore water should result in greater sorption of SO42- and other anions onto protonated surfaces than in neutral-pH pore water. Comparison of the amounts of Cl- released from a clay core sample in desorption batch tests (4 ??g/g of sediment) with the amounts of Cl- sorbed to the same clay in sorption tests (3.7-5 ??g/g) indicates that the high concentrations of Cl- in pore water did not originate from connate seawater but were desorbed from sediment that was previously in contact with seawater. Furthermore, a hypothetical seawater transgression in the past is consistent with the observed pattern of sorbed cation complexes in the Magothy cores and could be a significant source of high SO42- concentrations in Magothy ground water.

Applied Geochemistry↗

USGS1977

Ground-water resources of the Riviera Beach area, Palm Beach County, Florida

The principal source of freshwater that has been developed in the Riviera Beach area is the so-called shallow aquifer, which is composed of sand, shells, sandstone, limestone, marl, and occasionally clay strata. Often a stratum contains mixtures of two or more of these materials and occasionally they are cemented. The aquifer ranges in thickness from approximately 300 feet at Lake Worth to less than 175 feet in the interior. The major water-bearing zone usually consists of cemented layers of sand and shells, about 100 feet thick, in the lower part of the aquifer. The quality of water in the shallow aquifer is generally suitable for municipal use except for an area along C-17 Canal where the dissolved solids concentration exceeds 500 milligrams per liter. The primary source of recharge to the shallow aquifer is rainfall. Discharge is mainly by evapotranspiration. Other discharges include seepage into drainage canals and Lake Worth, and pumpage. The configuration of the water table is greatly influenced by Lake Worth, C-17 Canal, West Palm Beach water catchment area, rainfall, and municipal pumpage. The major threat to development of water supplies, and possibly to the continuation of a current withdrawal rate of over 5 million gallons per day, is seawater intrusion. The municipal supply wells are almost 1 mile inland from the source of the seawater (Lake Worth), but the combined effects of increased pumpage, reduced recharge resulting from increased land development, and below normal rainfall, have caused seawater to advance inland in the aquifer. Additional supplies could be developed to the west, away from the threat of seawater intrusion.

Florida↗

USGS2009

Hydrogeologic and Hydraulic Characterization of the Surficial Aquifer System, and Origin of High Salinity Groundwater, Palm Beach County, Florida

Previous studies of the hydrogeology of the surficial aquifer system in Palm Beach County, Florida, have focused mostly on the eastern one-half to one-third of the county in the more densely populated coastal areas. These studies have not placed the hydrogeology in a framework in which stratigraphic units in this complex aquifer system are defined and correlated between wells. Interest in the surficial aquifer system has increased because of population growth, westward expansion of urbanized areas, and increased utilization of surface-water resources in the central and western areas of the county. In 2004, the U.S. Geological Survey, in cooperation with the South Florida Water Management District, initiated an investigation to delineate the hydrogeologic framework of the surficial aquifer system in Palm Beach County, based on a lithostratigraphic framework, and to evaluate hydraulic properties and characteristics of units and permeable zones within this framework. A lithostratigraphic framework was delineated by correlating markers between all wells with data available based primarily on borehole natural gamma-ray geophysical log signatures and secondarily, lithologic characteristics. These correlation markers approximately correspond to important lithostratigraphic unit boundaries. Using the markers as guides to their boundaries, the surficial aquifer system was divided into three main permeable zones or subaquifers, which are designated, from shallowest to deepest, zones 1, 2, and 3. Zone 1 is above the Tamiami Formation in the Anastasia and Fort Thompson Formations. Zone 2 primarily is in the upper part or Pinecrest Sand Member of the Tamiami Formation, and zone 3 is in the Ochopee Limestone Member of the Tamiami Formation or its correlative equivalent. Differences in the lithologic character exist between these three zones, and these differences commonly include differences in the nature of the pore space. Zone 1 attains its greatest thickness (50 feet or more) and highest transmissivity in coastal areas. Zone 2, the most transmissive and extensive zone, is thickest (80 feet or more) and most transmissive in the inland eastern areas near Florida's Turnpike. In this area, zone 1 is absent, and the semiconfining unit above zone 2 extends to the land surface with a thickness commonly ranging from 50 to 100 feet. The thickness of zone 2 decreases to zero in most wells near the coast. Zone 3 attains its greatest thickness (100 feet or more) in the southwestern and south-central areas; zone 3 is equivalent to the gray limestone aquifer. The distribution of transmissivity was mapped by zone; however, zones 2 and 3 were commonly combined in aquifer tests. Maximum transmissivities for zone 1, zones 2 and 3, and zone 3 were 90,000, 180,000, and 70,000 ft2/d (feet-squared per day), respectively. The northern extent of the area with transmissivity greater than 50,000 ft2/d for zones 2 and 3 in the inland northeastern area along Florida's Turnpike has not been defined based on available data and could extend 5 to 10 miles farther north than mapped. Based on the thickness of zone 2 and a limited number of aquifer tests, a large area of zone 2 with transmissivity greater than 10,000 ft2/d, and possibly as much as 30,000 ft2/d, extends to the west across Water Conservation Area 1 from the inland southeastern area into the south-central area and some of the southwestern area. In contrast to the Biscayne aquifer present to the south of Palm Beach County, zones 2 and 3 are interpreted to be present principally in the Tamiami Formation and are commonly overlain by a thick semiconfining unit of moderate permeability. These zones have been referred to as the 'Turnpike' aquifer in the inland eastern areas of Palm Beach County, and the extent of greatest thickness and transmissivity follows, or is adjacent to, Florida's Turnpike. Where it is thick and transmissive, zone 1 may be considered equivalent to the Biscayne aquifer. Areas

Scientific Investigations Report↗

USGS2001

Assessment of habitat, fish communities, and streamflow requirements for habitat protection, Ipswich River, Massachusetts, 1998-99

The relations among stream habitat, fish communities, and hydrologic conditions were investigated in the Ipswich River Basin in northeastern Massachusetts. Data were assessed from 27 sites on the mainstem of the Ipswich River from July to September 1998 and from 10 sites on 5 major tributaries in July and August 1999. Habitat assessments made in 1998 determined that in a year with sustained streamflow for most of the summer, the Ipswich River contains diverse, high-quality aquatic habitat. Channel types are predominantly low gradient glides, pools, and impoundments, with a sandy streambed and a forest or shrub riparian zone. Features that provide fish habitat are located mostly along stream margins; these features include overhanging brush, undercut banks, exposed roots, and woody debris. These habitat features decrease in availability to aquatic communities with declining streamflows and generally become unavailable after streamflows drop to the point where the edge of water recedes from the stream banks. The mainstem and tributaries were sampled to determine fish species composition, relative abundance, and length frequency. Fish sampling indicates that the fish community in the Ipswich River is currently a warm-water fish community dominated by pond-type fish. However, historical temperature data, and survival of stocked trout in the mainstem Ipswich into late summer of 1998, indicate that the Ipswich River potentially could support cold-water fish species if adequate flows are maintained. Dominant fish species sampled in the mainstem Ipswich River were redfin pickerel ( Esox americanus ), American eel ( Anguilla rostrata ), and pumpkinseed ( Lepomis gibbosus ), which together represented 41, 22, and 10 percent, respectively, of 4,745 fish sampled. The fish communities of the mainstem and tributaries contained few fluvial-dependent or fluvial-specialist species (requiring flow), and were dominated by macrohabitat generalists (tolerant of low-flow, warm-water, and ponded conditions). In comparison to a nearby river (Lamprey River, N.H.), and a reference fish community developed for inland New England streams, the Ipswich fish community would be expected to have appreciably higher percentages of fluvial-dependent and fluvial-specialist species were streamflows restored. Four riffle sites on the mainstem of the Ipswich River were identified as critical habitat areas because they are among the first sites to exhibit fish-passage problems or to dry during low flows. A watershed-scale precipitation-runoff model previously developed for the Ipswich River was used to simulate streamflows at these four sites for the period 196195 under no withdrawals (for water supply) and 1991 land use to evaluate habitat suitability under conditions that approximate the natural flow conditions. These simulated flows were used to calculate streamflow requirements by the Tennant and New England Aquatic-Base-Flow methods. Stream channels were surveyed at the critical riffle sites, and Water Surface Profile models were used to simulate streamflows and hydraulic characteristics needed for determining streamflow requirements by use of the Wetted-Perimeter and R2Cross methods. Normalized by drainage area to units of cubic feet per second per square mile, these methods yielded the following streamflow requirements: 0.50 cubic feet per second per square mile for the Tennant 30-percent Q MA method, 0.42 cubic feet per second per square mile for the wetted-perimeter value necessary to maintain wetted perimeter at three altered riffle sites, 0.42 cubic feet per second per square mile for the R2Cross value required to maintain R2Cross hydraulic criteria at a natural riffle site, and 0.34 cubic feet per second per square mile for the aquatic-base-flow median of monthly mean flows for August for the simulated 196195 period under no withdrawals and 1991 land use. The mean streamflow requirement determined from these four methods is 0.42 cubic feet per second per square mile. This flow would represent an average flow-exceedence value for the six study sites of about 77 percent under simulated flows with no withdrawals. For these flows, the 70-, 80-, and 90-percent exceedence flows averaged 0.59, 0.37, and 0.21 cubic feet per second per square mile, respectively, and the 7-day, 10-year low flow statistic at the two gaged sites averaged 0.08 cubic feet per second per square mile. Simulated flows under no withdrawals were used to determine monthly mean flows and other flow statistics used in the Range of Variability Approach to define a flow regime that mimics the river's natural flow regime.

Massachusetts↗

USGS2022

Oxygenation of a karst subterranean estuary during a tropical cyclone: Mechanisms and implications for the carbon cycle

Seasonal precipitation affects carbon turnover and methane accumulation in karst subterranean estuaries, the region of coastal carbonate aquifers where hydrologic and biogeochemical processes regulate material exchange between the land and ocean. However, the impact that tropical cyclones exert on subsurface carbon cycling within karst landscapes is poorly understood. Here, we present 5-month-long hydrologic and chemical records from 1 and 2 km inland from the coastline within the Ox Bel Ha Cave System in the northeastern Yucatan Peninsula. The record encompasses wet and dry seasons and includes the impact of rainfall during the development of Tropical Storm Hanna in October 2014 . Methane accumulated in highest concentrations at the inland site, especially during the wet season preceding the storm. Intense rainfall led to episodic increases in water level and salinity shifts at both sites, indicating a spatially widespread hydrologic response. The most profound storm effect was a ~ 0.8 mg L −1 pulse of dissolved oxygen that declined to zero within 2 weeks and corresponded with a reduction of methane. A positive shift in methane's stable carbon isotope content from −62.6‰ ± 0.6‰ before the storm to −44.0‰ ± 2.4‰ after the storm indicates microbial methane oxidation was a mechanism for the loss of groundwater methane. Post-storm methane concentrations did not recover to pre-storm levels during the observation period, suggesting tropical cyclones have long-lasting (months) effects on the carbon cycle. Compared to seasonal effects, mixing and oxygen inputs during storm-induced hydrologic forcing have an outsized biogeochemical influence within stratified coastal aquifers.

Ox Bel Ha Cave System, Yucatan Peninsula↗

USGS2013

Detection of salt marsh vegetation stress and recovery after the Deepwater Horizon Oil Spill in Barataria Bay, Gulf of Mexico using AVIRIS data

The British Petroleum Deepwater Horizon Oil Spill in the Gulf of Mexico was the biggest oil spill in US history. To assess the impact of the oil spill on the saltmarsh plant community, we examined Advanced Visible Infrared Imaging Spectrometer (AVIRIS) data flown over Barataria Bay, Louisiana in September 2010 and August 2011. Oil contamination was mapped using oil absorption features in pixel spectra and used to examine impact of oil along the oiled shorelines. Results showed that vegetation stress was restricted to the tidal zone extending 14 m inland from the shoreline in September 2010. Four indexes of plant stress and three indexes of canopy water content all consistently showed that stress was highest in pixels next to the shoreline and decreased with increasing distance from the shoreline. Index values along the oiled shoreline were significantly lower than those along the oil-free shoreline. Regression of index values with respect to distance from oil showed that in 2011, index values were no longer correlated with proximity to oil suggesting that the marsh was on its way to recovery. Change detection between the two dates showed that areas denuded of vegetation after the oil impact experienced varying degrees of re-vegetation in the following year. This recovery was poorest in the first three pixels adjacent to the shoreline. This study illustrates the usefulness of high spatial resolution airborne imaging spectroscopy to map actual locations where oil from the spill reached the shore and then to assess its impacts on the plant community. We demonstrate that post-oiling trends in terms of plant health and mortality could be detected and monitored, including recovery of these saltmarsh meadows one year after the oil spill.

Louisiana↗

USGS2006

Seasonal persistence and population characteristics of Escherichia coli and entercocci in deep backshore sand of two freshwater beaches

We studied the shoreward and seasonal distribution of E. coli and enterococci in sand (at the water table) at two southern Lake Michigan beaches—Dunbar and West Beach (in Indiana). Deep, backshore sand (∼20 m inland) was regularly sampled for 15 months during 2002–2003. E. coli counts were not significantly different in samples taken at 5-m intervals from 0–40 m inland (P=0.25). Neither E. coli nor enterococci mean counts showed any correlation or differences between the two beaches studied. In laboratory experiments, E. coli readily grew in sand supplemented with lake plankton, suggesting that in situ E. coli growth may occur when temperature and natural organic sources are adequate. Of the 114 sand enterococci isolates tested, positive species identification was obtained for only 52 (46%), with E. faecium representing the most dominant species (92%). Genetic characterization by ribotyping revealed no distinct genotypic pattern (s) for E. coli , suggesting that the sand population was rather a mixture of numerous strains (genotypes). These findings indicate that E. coli and enterococci can occur and persist for extended periods in backshore sand at the groundwater table. Although this study was limited to two beaches of southern Lake Michigan, similar findings can be expected at other temperate freshwater beaches. The long-term persistence of these bacteria, perhaps independent of pollution events, complicates their use as indicator organisms. Further, backshore sand at the water table may act as a reservoir for these bacteria and potentially for human pathogens.

Michigan, Indiana↗

USGS2011

Tidal Boundary Conditions in SEAWAT

SEAWAT, a U.S. Geological Survey groundwater flow and transport code, is increasingly used to model the effects of tidal motion on coastal aquifers. Different options are available to simulate tidal boundaries but no guidelines exist nor have comparisons been made to identify the most effective approach. We test seven methods to simulate a sloping beach and a tidal flat. The ocean is represented in one of the three ways: directly using a high hydraulic conductivity (high- K ) zone and indirect simulation via specified head boundaries using either the General Head Boundary (GHB) or the new Periodic Boundary Condition (PBC) package. All beach models simulate similar water fluxes across the upland boundary and across the sediment-water interface although the ratio of intertidal to subtidal flow is different at low tide. Simulating a seepage face results in larger intertidal fluxes and influences near-shore heads and salinity. Major differences in flow occur in the tidal flat simulations. Because SEAWAT does not simulate unsaturated flow the water table only rises via flow through the saturated zone. This results in delayed propagation of the rising tidal signal inland. Inundation of the tidal flat is delayed as is flow into the aquifer across the flat. This is severe in the high- K and PBC models but mild in the GHB models. Results indicate that any of the tidal boundary options are fine if the ocean-aquifer interface is steep. However, as the slope of that interface decreases, the high- K and PBC approaches perform poorly and the GHB boundary is preferable.

Ground Water↗

USGS2001

Simulation of ground-water discharge to Biscayne Bay, southeastern Florida

As part of the Place-Based Studies Program, the U.S. Geological Survey initiated a project in 1996, in cooperation with the U.S. Army Corps of Engineers, to quantify the rates and patterns of submarine ground-water discharge to Biscayne Bay. Project objectives were achieved through field investigations at three sites (Coconut Grove, Deering Estate, and Mowry Canal) along the coastline of Biscayne Bay and through the development and calibration of variable-density, ground-water flow models. Two-dimensional, vertical cross-sectional models were developed for steady-state conditions for the Coconut Grove and Deering Estate transects to quantify local-scale ground-water discharge patterns to Biscayne Bay. A larger regional-scale model was developed in three dimensions to simulate submarine ground-water discharge to the entire bay. The SEAWAT code, which is a combined version of MODFLOW and MT3D, was used to simulate the complex variable-density flow patterns. Field data suggest that ground-water discharge to Biscayne Bay relative to the shoreline is restricted to within 300 meters at Coconut Grove, 600 to 1,000 meters at Deering Estate, and 100 meters at Mowry Canal. The vertical cross-sectional models, which were calibrated to the field data using the assumption of steady state, tend to focus ground-water discharge to within 50 to 200 meters of the shoreline. With homogeneous distributions for aquifer parameters and a constant-concentration boundary for Biscayne Bay, the numerical models could not reproduce the lower ground-water salinities observed beneath the bay, which suggests that further research may be necessary to improve the accuracy of the numerical simulations. Results from the cross-sectional models, which were able to simulate the approximate position of the saltwater interface, suggest that longitudinal dispersivity ranges between 1 and 10 meters, and transverse dispersivity ranges from 0.1 to 1 meter for the Biscayne aquifer. The three-dimensional, regional-scale model was calibrated to ground-water heads, canal baseflow, and the general position of the saltwater interface for nearly a 10-year period from 1989 to 1998. The mean absolute error between observed and simulated head values is 0.15 meter. The mean absolute error between observed and simulated baseflow is 3 x 105 cubic meters per day. The position of the simulated saltwater interface generally matches the position observed in the field, except for areas north of the Miami Canal where the simulated saltwater interface is located about 5 kilometers inland of the observed saltwater interface. Results from the regional-scale model suggest that the average rate of fresh ground-water discharge to Biscayne Bay for the 10-year period (1989-98) is about 2 x 105 cubic meters per day for 100 kilometers of coastline. This simulated discharge rate is about 6 percent of the measured surface-water discharge to Biscayne Bay for the same period. The model also suggests that nearly 100 percent of the fresh ground-water discharge is to the northern half of Biscayne Bay, north of the Cutler Drain Canal. South of the Cutler Drain Canal, coastal lowlands prevent the water table from rising high enough to drive measurable quantities of ground water to Biscayne Bay. Annual variations in sea-level elevation, which can be as large as 0.3 meter, have a substantial effect on rates of ground-water discharge. During 1989-98, simulated rates of ground-water discharge to Biscayne Bay generally are highest when sea level is relatively low.

Florida↗

USGS2007

A simple model for calculating tsunami flow speed from tsunami deposits

This paper presents a simple model for tsunami sedimentation that can be applied to calculate tsunami flow speed from the thickness and grain size of a tsunami deposit (the inverse problem). For sandy tsunami deposits where grain size and thickness vary gradually in the direction of transport, tsunami sediment transport is modeled as a steady, spatially uniform process. The amount of sediment in suspension is assumed to be in equilibrium with the steady portion of the long period, slowing varying uprush portion of the tsunami. Spatial flow deceleration is assumed to be small and not to contribute significantly to the tsunami deposit. Tsunami deposits are formed from sediment settling from the water column when flow speeds on land go to zero everywhere at the time of maximum tsunami inundation. There is little erosion of the deposit by return flow because it is a slow flow and is concentrated in topographic lows. Variations in grain size of the deposit are found to have more effect on calculated tsunami flow speed than deposit thickness. The model is tested using field data collected at Arop, Papua New Guinea soon after the 1998 tsunami. Speed estimates of 14 m/s at 200 m inland from the shoreline compare favorably with those from a 1-D inundation model and from application of Bernoulli's principle to water levels on buildings left standing after the tsunami. As evidence that the model is applicable to some sandy tsunami deposits, the model reproduces the observed normal grading and vertical variation in sorting and skewness of a deposit formed by the 1998 tsunami.

Sedimentary Geology↗

USGS2012

Use of acoustic technology to define hydraulic characteristics of an estuary near the Mississippi Gulf Coast

An Acoustic Doppler Current Profiler (ADCP) was used on the Jourdan River at Interstate Highway 10 near Kiln, Mississippi, in 1996 to measure three-dimensional velocity vectors and water depths and in 1998, in combination with a global positioning system, to define channel bathymetry in the vicinity of the bridge. During a 25-hour period on September 19-20, 1996, 117 consecutive measurements of stage and discharge were obtained throughout a complete tidal cycle. These measurements were obtained during the time of year when headwater flows were minimal, and, therefore, the tidal-affected flow conditions were noticeable. The stage ranged from only 0.7 to 2.8 ft above sea level, but discharge ranged from 3,980 ft 3 /s flowing upstream to 5,580 ft 3 /s flowing downstream. The average discharge during the 25-hour period was only 80 ft 3 /s flowing downstream. By using the ADCP, full downstream flow, bi-directional flow, and full upstream flow conditions were identified. If conventional measurement techniques had been used, the bi-directional flow conditions could not have been detected since flow direction would have been based on what was seen at the water surface. These measurements were used to define the lower range of the stage-storage-volume relation inland of the highway. On June 10, 1998, the ADCP, in combination with a global positional system, was used to define channel bathymetry for the river reach from about 3,500 ft upstream to about 2,500 ft downstream of the bridge. The bathymetry was compared to past soundings obtained in the vicinity of the bridge; as much as 18 ft of total scour was indicated to have occurred at a bridge pier. Copyright ASCE 2004.

Conference Paper↗

USGS2019

Toward a theory of connectivity among depressional wetlands of the great plains

Functions of inland, freshwater depressional wetlands of the Great Plains are driven by natural disturbance in the form of fluctuating water levels or shifts between wet and dry ecological states. The geographically isolated prairie potholes and playas form broad-scale systems or networks that support biodiversity and provide ecological goods and services. Anthropogenic disturbance, primarily in the form of sediment accretion, results in the functional loss of individual wetlands from the system. The ecological value of individual depressional wetlands has been documented, but there has not been any assessment of the contribution of individual wetlands to the system. Network analysis can be used to prioritize the contribution of individual wetlands to the system for the purpose of conservation and management. We utilized the playas wetland system of the Southern High Plains to illustrate this concept. Playas form a redundant, resilient network based on natural disturbance (i.e., inundation patterns) across broad spatial and temporal scales that support biodiversity. Loss of individual playas to sediment accretion is causing the network to break down, resulting in the need for a greater proportion of inundated playas to provide the original level of ecological goods and services. The effects of decreased functional connectivity due to anthropogenic disturbance at the system scale portend negative effects on movement strategies, dynamics and persistence of local populations, decreased biodiversity, and, ultimately, the redistribution and system-wide extinction of playa wetland-dependent populations and loss of associated functions.

Book chapter↗

USGS2022

Hydrology of the Yucaipa groundwater subbasin: Characterization and integrated numerical model, San Bernardino and Riverside Counties, California

Executive Summary Water management in the Santa Ana River watershed in San Bernardino and Riverside Counties in southern California is a complex task with various water purveyors navigating geographic, geologic, hydrologic, and political challenges to provide a reliable water supply to stakeholders. As the population has increased throughout southern California, so has the demand for water. The Yucaipa groundwater subbasin (hereafter referred to as “Yucaipa subbasin”), one of nine groundwater subbasins in what the California Department of Water Resources (DWR) refers to as the Upper Santa Ana Valley groundwater basin (California Department of Water Resources, 2016; the DWR naming convention is used within this report), is no exception; steady population growth since the 1940s and changes in water use has forced local water purveyors to regularly adapt their water infrastructure to meet demand. Groundwater has historically been the dominant source of water in the Yucaipa subbasin although recently, imported water via the California State Water Project has augmented the total water supply. Despite the influx of imported water, overall demand for groundwater continues to rise, and there is concern by local water managers that groundwater levels may adversely impact water supply and (or) decline to a point where it will be uneconomical to produce water, severely limiting the ability of local agencies to meet water-supply demand. To better understand the hydrogeology and water resources in the Yucaipa subbasin, the U.S. Geological Survey (USGS) and the San Bernardino Valley Municipal Water District initiated a cooperative study to understand the hydrogeologic system of the Yucaipa subbasin and in the encompassing Yucaipa Valley watershed (YVW). A three-dimensional hydrogeologic framework model was constructed to quantify the structure and extent of hydrogeologic units. Historical and present-day groundwater conditions were characterized to evaluate the groundwater-flow system. Lastly, the Yucaipa Integrated Hydrological Model (YIHM) was developed to simulate the integrated surface-water and groundwater systems, including natural and anthropogenic (that is, human influenced) recharge and discharge throughout the study area from 1947 to 2014. The Yucaipa subbasin is an inland groundwater basin located about 12 miles (mi) southeast of the City of San Bernardino and about 75 mi east of Los Angeles, California. The subbasin encompasses about 39 square miles (mi 2 ), including the City of Yucaipa. The geographic extent of the Yucaipa subbasin was established by the California Department of Water Resources, who defined the boundaries of the subbasin based on hydrogeologic transitions between crystalline rock and basin-fill sediments, active fault strands, surface-water drainage divides, and a portion of an adjudicated groundwater management boundary. Two groundwater subbasins of the Upper Santa Ana Valley groundwater basin are adjacent to the Yucaipa subbasin, the San Bernardino groundwater subbasin to the west and the San Timoteo groundwater subbasin to the south. The Yucaipa subbasin is encompassed by the YVW, which is in turn comprised of three sub-watersheds that represent surface-water flow across and within the Yucaipa subbasin. Although the Yucaipa subbasin is the specific area of interest for this study, the entire YVW was considered for the purposes of characterizing the hydrogeology of the Yucaipa subbasin and for development of the YIHM. The purposes of this report are to (1) describe the hydrologic and hydrogeologic settings of the Yucaipa subbasin and aquifer system, (2) describe the construction and calibration of the fully coupled groundwater and surface-water flow model for the Yucaipa subbasin and the encompassing YVW, referred to as the YIHM, and (3) present numerical results, including water budgets and hydraulic heads, and the effect of pumping and climate stresses (precipitation and temperature) on water-budget components.

California↗

USGS2017

Vertical datum conversion process for the inland and coastal gage network located in the New England, Mid-Atlantic, and South Atlantic-Gulf hydrologic regions

Datum conversions from the National Geodetic Vertical Datum of 1929 to the North American Vertical Datum of 1988 among inland and coastal gages throughout the hydrologic regions of New England, the Mid-Atlantic, and the South Atlantic-Gulf have implications among river and storm surge forecasting, general commerce, and water-control operations. The process of data conversions may involve the application of a recovered National Geodetic Vertical Datum of 1929–North American Vertical Datum of 1988 offset, a simplistic datum transformation using VDatum or VERTCON software, or a survey, depending on a gaging network datum evaluation, anticipated uncertainties for data use among the cooperative water community, and methods used to derive the conversion. Datum transformations from National Geodetic Vertical Datum of 1929 to North American Vertical Datum of 1988 using VERTCON purport errors of ± 0.13 foot at the 95 percent confidence level among modeled points, claiming more consistency along the east coast. Survey methods involving differential and trigonometric leveling, along with observations using Global Navigation Satellite System technology, afford a variety of approaches to establish or perpetuate a datum during a survey. Uncertainties among leveling approaches are generally < 0.1 foot, and and Global Navigation Satellite System approaches may be categorized with uncertainties of ≤0.1 foot for a Level I quality category and ≥0.1 foot for Level II or III quality categories (defined by the U.S. Geological Survey) by observation and review of experienced practice. The conversion process is initiated with an evaluation of the inland and coastal gage network datum, beginning with altitude datum components and the history of those components queried through the U.S. Geological Survey Groundwater Site Inventory database. Subsequent edits to the Groundwater Site Inventory database may be required and a consensus reached among the U.S. Geological Survey Water Science Centers to identify the outstanding workload categorized as in-office datum transformations or offset applications versus out-of-office survey efforts. Datum conversions or datum establishment for the inland or coastal gaging network should meet datum uncertainty requirements among other Federal agencies. Datum uncertainty requirements are ±0.25 foot for U.S. Army Corps of Engineers water-control or construction projects and ±0.16 foot for Federal Emergency Management Agency field surveys and checkpoint surveys used for mapping. River level forecasts generally are defined as ± 0.10 foot among the National Oceanic and Atmospheric Administration–National Weather Service. Collaboration and communication among the cooperative water community is necessary during a datum conversion or datum change. Datum notification time-change requirements set by the National Oceanic and Atmospheric Administration–National Weather Service vary from 30 to 120 days, depending on datum conversion or datum-change case scenarios. Notification times associated with these case scenarios may be useful to the National Oceanic and Atmospheric Administration–National Weather Service and U.S. Army Corps of Engineers, because their daily operations are time sensitive, unlike the notification time change requirements of other entities that make up the cooperative water community. At the time of this writing, a future geopotential datum resulting from Gravity for the Redefinition of the American Vertical Datum is anticipated in 2022. A future version of VDatum and VERTCON is anticipated to provide a transformation among North American Vertical Datum of 1988 elevations to the new geopotential datum.

Techniques and Methods↗

USGS2006

Fish community structure in freshwater karstic water bodies of the Sian Ka'an Reserve in the Yucatan peninsula, Mexico

We evaluated the relationship between limnetic characteristics and fish community structure (based on species richness, abundance and individual size) in contrasting but interconnected inland aquatic habitats of freshwater karstic wetlands in the Yucatan peninsula, Mexico. In the western hemisphere, freshwater karstic wetlands are found in south-eastern Mexico, northern Belize, western Cuba, Andros Island, Bahamas and the Everglades of southern Florida. Only in the Everglades have fish communities been well described. Karstic wetlands are typically oligotrophic because calcium carbonate binds phosphorus, making it relatively unavailable for plants. Fourteen permanent and seasonally flooded water bodies were sampled in both wet and dry seasons in Sian Ka'an Biosphere Reserve, in the Mexican state of Quintana Roo. Water systems were divided by morphology in four groups: cenotes with vegetation (CWV), cenotes without vegetation (CNV), wetlands (WTL), and temporal cenotes (TPC). Discriminant analysis based on physical characteristics such as turbidity, temperature, depth and oxygen confirmed that these habitats differed in characteristics known to influence fish communities. A sample-based rarefaction test showed that species richness was significantly different between water systems groups, showing that WTL and CWV had higher richness values than CNV and TPC. The most abundant fish families, Poeciliidae, Cichlidae and Characidae, differed significantly in average size among habitats and seasons. Seasonal and inter-annual variation, reflecting temporal variation in rainfall, strongly influenced the environmental differences between shallow and deep habitats, which could be linked to fish size and life cycles. Five new records of species were found for the reserve, and one new record for Quintana Roo state. ?? 2006 by Verlag Dr. Friedrich Pfeil.

Ichthyological Exploration of Freshwaters↗

USGS2016

Characterizing supraglacial meltwater channel hydraulics on the Greenland Ice Sheet from in situ observations

Supraglacial rivers on the Greenland ice sheet (GrIS) transport large volumes of surface meltwater toward the ocean, yet have received relatively little direct research. This study presents field observations of channel width, depth, velocity, and water surface slope for nine supraglacial channels on the southwestern GrIS collected between 23 July and 20 August, 2012. Field sites are located up to 74 km inland and span 494-1485 m elevation, and contain measured discharges larger than any previous in situ study: from 0.006 to 23.12 m 3 /s in channels 0.20 to 20.62 m wide. All channels were deeply incised with near vertical banks, and hydraulic geometry results indicate that supraglacial channels primarily accommodate greater discharges by increasing velocity. Smaller streams had steeper water surface slopes (0.74-8.83%) than typical in terrestrial settings, yielding correspondingly high velocities (0.40-2.60 m/s) and Froude numbers (0.45-3.11) with supercritical flow observed in 54% of measurements. Derived Manning's n values were larger and more variable than anticipated from channels of uniform substrate, ranging from 0.009 to 0.154 with a mean value of 0.035 +/- 0.027 despite the absence of sediment, debris, or other roughness elements. Ubiquitous micro-depressions in shallow sections of the channel bed may explain some of these roughness values. However, we find that other, unobserved sources of flow resistance likely contributed to these elevated n values: future work should explicitly consider additional sources of flow resistance beyond bed roughness in supraglacial channels. We conclude that hydraulic modelling for these channels must allow for both sub- and supercritical flow, and most importantly must refrain from assuming that all ice-substrate channels exhibit similar hydraulic behavior, especially for Froude numbers and Manning's n. Finally, this study highlights that further theoretical and empirical work on supraglacial channel hydraulics is necessary before broad scale understanding of ice sheet hydrology can be achieved. This article is protected by copyright. All rights reserved.

Earth Surface Processes and Landforms↗

USGS1966

Salt-water encroachment in southern Nassau and southeastern Queens Counties, Long Island, New York

Test drilling, extraction of water from cores, electric logging, water sampling, and water-level measurements from 1958 to 1961 provided a suitable basis for a substantial refinement in the definition of the positions, chloride concentrations, and rates of movement of salty water in the intermediate and deep deposits of southern Nassau County and southeastern Queens County. Filter-press, centrifugal, and dilution methods were used to extract water from cores for chloride analysis at the test-drilling sites. Chloride analysis of water extracted by these methods, chloride analyses of water from wells, and the interpretation of electric logs helped to define the chloride content of the salty water. New concepts of environmental-water head and zerovels, developed during the investigation, proved useful for defining hydraulic gradients and ratee of flow in ground water of variable density in a vertical direction and in horizontal and inclined planes, respectively. Hydraulic gradients in and between fresh and salty water were determined from water levels from data at individual and multiple-observation wells. Salty ground water occurs in southern Nassau and southeastern Queens Counties as three wedgelike extensions that project landward in unconsolidated deposits from a main body of salty water that lies seaward of the barrier beaches in Nassau County and of Jamaica Bay in Queens County. Salty water occurs not only in permeable deposits but also in the shallow and deep clay deposits. The highest chloride content of the salty ground water in the main body and the wedges is about 16,000 ppm, which is about 1,000 to 2,000 ppm less than the chloride content of ocean water. The shallow salty water in the Pleistocene and Recent deposits is connected freely with the bays, tidal estuaries, and ocean. The intermediate wedge is found only in the southwestern part of Nassau County in the upper part of the Magothy (?) Formation, in the Jamneco Gravel, and in the overlying clay deposits. It extends from the seaward areas inland about 2 miles into Island Park. The deep wedge extends into southeastern Queens County and southern Nassau County principally in the deeper parts of the Magothy (?) Formation and in the underlying clay member of the Raritan Formation. The leading edge of the deep wedge is at the base of the Magothy (?) Formation. This edge is apparently at the shoreline east of Lido Beach and extends inland about 4 miles to Woodmere and about 7 miles to South Ozone Park. Zones of diffusion as much as 6 miles wide and about 500 feet thick were delineated in the frontal part of the salty-water wedges. These thick and broad zones of diffusion were probably formed during the past 1,000 or more years in heterogeneous unconsolidated deposits by long- and short-term changes in sea level and in fresh-water outflow to the sea and by dispersion caused by the movements of the water and its salt mass. Changes in sea level and fresh-water outflow together produced appreciable advances and recessions of the salt-water front. The chemical compositions of the diffused water in all wedges are modified to some extent by base exchange and other physical and chemical processes and also by diffusion. The intermediate wedge of salty water is moving landward at a rate of less than 20 feet a year in the vicinity of Island Park and, thus, has moved less than 1,000 feet since 1900. The leading edge of the deep wedge has advanced landward at about 300 feet a :ear in Woodmere in southwestern Nassau County and about 160 feet a year at South Ozone Park in southeastern Queens County, principally under the influence of local withdrawals near the toe of the wedge. Between Hewlett and Lido Beach, the deep wedge is moving inland at the rate of about 10 feet a year under the influence of regional withdrawals in inland areas. Regional encroachment of the deep wedge is apparently retarded appreciably by cyclic flow, that is, by the return seaward in the upper

Water Supply Paper↗

USGS1999

The effects of global climate change on seagrasses

The increasing rate of global climate change seen in this century, and predicted to accelerate into the next, will significantly impact the Earth's oceans. In this review, we examine previously published seagrass research through a lens of global climate change in order to consider the potential effects on the world's seagrasses. A primary effect of increased global temperature on seagrasses will be the alteration of growth rates and other physiological functions of the plants themselves. The distribution of seagrasses will shift as a result of increased temperature stress and changes in the patterns of sexual reproduction. Indirect temperature effects may include plant community changes as a result of increased eutrophication and changes in the frequency and intensity of extreme weather events. The direct effects of sea level rise on the coastal oceans will be to increase water depths, change tidal variation (both mean tide level and tidal prism), alter water movement, and increase seawater intrusion into estuaries and rivers. A major impact of all these changes on seagrasses and tidal freshwater plants will be a redistribution of existing habitats. The intrusion of ocean water into formerly fresh or brackish water areas will directly affect estuarine plant distribution by changing conditions at specific locations, causing some plants to relocate in order to stay within their tolerance zones and allowing others to expand their distribution inland. Distribution changes will result from the effects of salinity change on seed germination, propagule formation, photosynthesis, growth and biomass. Also, some plant communities may decline or be eliminated as a result of increased disease activity under more highly saline conditions. Increased water depth, which reduces the amount of light reaching existing seagrass beds, will directly reduce plant productivity where plants are light limited. Likewise, increases in water motion and tidal circulation will decrease the amount of light reaching the plants by increasing turbidity or by stimulating the growth of epiphytes. Increasing atmospheric carbon dioxide will directly elevate the amount of CO 2 in coastal waters. In areas where seagrasses are carbon limited, this may increase primary production, although whether this increase will be sustained with long-term CO 2 enrichment is uncertain. The impact of increases in CO 2 will vary with species and environmental circumstances, but will likely include species distribution by altering the competition between seagrass species as well as between seagrass and algal populations. The reaction of seagrasses to UV-B radiation may range from inhibition of photosynthetic activity, as seen for terrestrial plants and marine algae, to the increased metabolic cost of producing UV-B blocking compounds within plant tissue. The effects of UV-B radiation will likely be greatest in the tropics and in southern oceans. There is every reason to believe that, as with the predicted terrestrial effects of global climate change, impacts to seagrasses will be great. The changes that will occur in seagrass communities are difficult to predict; our assessment clearly points out the need for research directed toward the impact of global climate change on seagrasses.

Aquatic Botany↗