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Michael Turtora

Publications and source records attributed to Michael Turtora.

8 recordsLinked to original sources
USGS2015

Application of a coupled vegetation competition and groundwater simulation model to study effects of sea level rise and storm surges on coastal vegetation

Global climate change poses challenges to areas such as low-lying coastal zones, where sea level rise (SLR) and storm-surge overwash events can have long-term effects on vegetation and on soil and groundwater salinities, posing risks of habitat loss critical to native species. An early warning system is urgently needed to predict and prepare for the consequences of these climate-related impacts on both the short-term dynamics of salinity in the soil and groundwater and the long-term effects on vegetation. For this purpose, the U.S. Geological Survey’s spatially explicit model of vegetation community dynamics along coastal salinity gradients (MANHAM) is integrated into the USGS groundwater model (SUTRA) to create a coupled hydrology–salinity–vegetation model, MANTRA. In MANTRA, the uptake of water by plants is modeled as a fluid mass sink term. Groundwater salinity, water saturation and vegetation biomass determine the water available for plant transpiration. Formulations and assumptions used in the coupled model are presented. MANTRA is calibrated with salinity data and vegetation pattern for a coastal area of Florida Everglades vulnerable to storm surges. A possible regime shift at that site is investigated by simulating the vegetation responses to climate variability and disturbances, including SLR and storm surges based on empirical information.

Journal of Marine Science and Engineering↗
USGS2015

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

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

Florida↗
USGS2010

Seasonal and spatial distribution patterns of finfish and selected invertebrates in coastal lagoons of northeastern Florida, 2002-2004

The U.S. Geological Survey conducted a survey of juvenile fisheries resources, in cooperation with the St. Johns River Water Management District and Volusia County, to establish baseline data on spatial and temporal distribution patterns of estuarine fish. The survey was conducted from November 2001 to March 2005 and the baseline data established for the survey in the Northern Coastal Basins were collected from January 2002 to December 2004. The study area included the bar-built estuaries ranging from just north of St. Augustine, Florida, south to Ponce de Leon Inlet. Sampling protocols developed by the Florida Fish and Wildlife Research Institute for their statewide Fisheries Independent Monitoring (FIM) program were replicated to allow for comparability with FIM program results. Samples were collected monthly from randomly selected stations based on a geographically stratified design. Finfish and selected invertebrates were collected using a 21.3-meter center-bag seine with a 3-millimeter mesh, and a 6.1-meter otter trawl with a 3-millimeter mesh liner. Total estimated fish and selected invertebrate densities were similar to estimates from FIM projects in adjacent areas and were characterized by similar dominant species. Preliminary analysis indicates that observed species distribution patterns were mainly a function of proximity to the three inlets within the study area. The two regions encompassing the northern Tolomato River and the Tomoka River and Basin are farthest from inlets and appear to function as oligohaline nursery areas. Those two areas had the greatest estimated densities of shellfish and juvenile sciaenid (drum) species associated with oligohaline waters (for example, Micropogonias undulatus, Sciaenops ocellatus and Cynoscion nebulosus). Samples near inlets, and between the two northern inlets, had greater estimated densities of species limited to euhaline waters, including juvenile clupeids collected at relatively high abundance and species of marine strays collected in low abundance. Based on correspondence analysis, seasonal variation dominated the ordination of seine samples and spatial variation dominated the ordination of trawl samples; this was due to differences in the number and timing of taxa found near inlets versus oligohaline regions. The absence of seagrass habitat in the Northern Coastal Basins is reflected by the absence of a seagrass-fish assemblage.

Scientific Investigations Report↗
USGS1998

Water quality in the Georgia-Florida coastal plain, Georgia and Florida, 1992-96

This report is intended to summarize major findings that emerged between 1992 and 1995 from the water-quality assessment of the Georgia-Florida Coastal Plain Study Unit and to relate these findings to water-quality issues of regional and national concern. The information is primarily intended for those who are involved in water-resource management. Yet, the information contained here may also interest those who simply wish to know more about the quality of water in the rivers and aquifers in the area where they live.

Florida, Georgia↗
USGS1998

Stream habitat characteristics at selected sites in the Georgia-Florida coastal plain

Habitat characterization is part of a multidisciplinary approach to water-quality assessment implemented by the National Water-Quality Assessment Program. Habitat data were collected in the Georgia-Florida Coastal Plain study unit at 24 sites during 1993-95. Data were collected for habitat characteristics at three spatial scales: basin, segment, and reach. Basin data include physiography, land resource provinces, and land use, providing a description of the environmental setting at each site. Segment data include length, gradient, and sinuosity. A Kendall correlation analysis performed on segment characteristics and the log-of-basin area showed a correlation between segment gradient and the log-of-basin area and a correlation between sinuosity and segment length. Reach data consist of field-collected measurements of both instream and riparian habitats. Sand and detritus were the most common channel-bed substrates among the sampled sites. Measurements of channel width, water depth, and bank width and height were used to create cross-sectional profiles of each sampled area. Elevations of selected durations plotted on cross sections illustrated the percentage of time that the banks were inundated at each site. Sites were divided into two groups based on duration of bank inundation (less than or equal to 1 percent and greater than 1 percent). Bank woody vegetation was also sampled and a clustering algorithm known as Two-Way INdicator SPecies ANalysis (TWINSPAN) was used to analyze these data. TWINSPAN divided the sites into two groups based on their vegetation composition. A statistical comparison of the two types of site groups (duration of bank inundation and vegetation) was performed. The significant association between these groups was consistent with the hypothesis that inundation frequency affected riparian vegetation.

Florida, Georgia↗
USGS1996

Comparison of hydraulic conductivities for a sand and gravel aquifer in southeastern Massachusetts, estimated by three methods

Hydraulic conductivities of a sand and gravel aquifer were estimated by three methods: constant- head multiport-permeameter tests, grain-size analyses (with the Hazen approximation method), and slug tests. Sediment cores from 45 boreholes were undivided or divided into two or three vertical sections to estimate hydraulic conductivity based on permeameter tests and grain-size analyses. The cores were collected from depth intervals in the screened zone of the aquifer in each observation well. Slug tests were performed on 29 observation wells installed in the boreholes. Hydraulic conductivities of 35 sediment cores estimated by use of permeameter tests ranged from 0.9 to 86 meters per day, with a mean of 22.8 meters per day. Hydraulic conductivities of 45 sediment cores estimated by use of grain-size analyses ranged from 0.5 to 206 meters per day, with a mean of 40.7 meters per day. Hydraulic conductivities of aquifer material at 29 observation wells estimated by use of slug tests ranged from 0.6 to 79 meters per day, with a mean of 32.9 meters per day. The repeatability of estimated hydraulic conductivities were estimated to be within 30 percent for the permeameter method, 12 percent for the grain-size method, and 9.5 percent for the slug test method. Statistical tests determined that the medians of estimates resulting from the slug tests and grain-size analyses were not significantly different but were significantly higher than the median of estimates resulting from the permeameter tests. Because the permeameter test is the only method considered which estimates vertical hydraulic conductivity, the difference in estimates may be attributed to vertical or horizontal anisotropy. The difference in the average hydraulic conductivities estimated by use of each method was less than 55 percent when compared to the estimated hydraulic conductivity determined from an aquifer test conducted near the study area.

Water-Resources Investigations Report↗
USGS1994

A technique for estimating ground-water levels at sites in Rhode Island from observation-well data

Estimates of future high, median, and low ground-water levels in Rhode Island are needed for engineering and architectural design decisions and for appropriate selection of land uses. For example, the failure of individual underground sewage-disposal systems due to high ground-water levels can be avoided if accurate water-level estimates are available. Estimates of extreme or average conditions are needed because short-duration re-construction observations are unlikely to be representative. The technique described in this report utilizes a single water-level measurement at a site of interest, in combination with a long-term water-level record at an observation well, to estimate the long-term high, median, and low water levels at the site of interest. The transfer of information to the site of interest depends on four fundamental assumptions: (1) Water levels will fluctuate in the future as they have in the past, (2) Water levels fluctuate seasonally, (3) Ground-water fluctuations depend on site geology, and (4) Water levels throughout Rhode Island are affected by similar precipitation and climate. The technique is based on the equivalent relation between the ratio of potential water-level change to maximum annual water-level range at the site and the ratio of potential water-level change to annual water-level range at the observation well. Equations for estimating high, median, and low water levels, and graphs of probable annual water-level range are given for selecting representative ranges of water levels for sand and gravel and till in Rhode Island. The accuracy of the technique is evaluated by use of the equations to estimate water levels at long-term observation wells where high, median, and low water levels are known from monthly measurements over many years. As a test of the estimating procedure, 6,697 estimates each of high, median, and low water levels (depth to water level exceeded 95, 50, and 5 percent of the time, respectively) were compared with measured water levels exceeded 95, 50, and 5 percent of the time at 14 sites unaffected by pumping or other known factors. Mean squared errors (average differences squared, between estimated and measured water levels) for the estimates ranged from 0.34 to 1.53 ft 2 for high water levels, 0.30 to 1.22 ft 2 for median water levels, and 0.32 to 2.55 ft 2 for low water levels. All mean squared errors are less than the State required 3-foot separation between the bottom of the stone underlying the seepage system and the maximum altitude of the water table. This degree of accuracy is acceptable for many design purposes.

Rhode Island↗