Location of Taylor Slough in Everglades National Park and research sites. Topographic elevation is in meters and referenced to NAVD88 

Contexts in source publication

Context 1

... P is precipitation, Q in and Q out are surface-water discharge into and out of the basin, respectively, ET is evapotranspiration, Δ S is change in surface-water storage, and R is recharge. The sign convention used here was positive for water contributing to surface-water storage and negative for water leaving Taylor Slough. No additional variables were taken into consideration in this calculation such as possible sheet fl ow that could not be accounted for at the river gauging stations or submarine groundwater discharge into Florida Bay. The common way of estimating recharge by this method was the indirect or residual approach, whereby all the variables in the water-budget equation except R were measured, and R was set equal to the residual (Scanlon et al. 2002). A positive value of R indicated that groundwater discharged to the surface water, while a negative value of R corresponded with surface-water recharge to the aquifer. All the components of the water budget were calculated in rates of mm/day between January 2008 and July 2009. The natural basin boundaries of Taylor Slough were dif fi cult to determine due to its fl at topography. As a result, the physical boundaries of Taylor Slough as de fi ned for this study were the main park road to the north which served as a dam for surface-water fl ow from the north, a line following the L-31 W canal to the east which acted as a hydraulic boundary, and Florida Bay to the south. The boundary to the west was determined as best as possible using a topographic map ( Fig. 1). These physical boundaries enclosed an area approximately 450 km 2 . Most of the precipitation, surface-water level and discharge data used in this project were obtained from sites in and around the Taylor Slough basin maintained by different agencies including the US Geological Survey (USGS), Everglades National Park (ENP), and the South Florida Water Management District (SFMWD). Data from the USGS were obtained from the National Water Information System (NWIS) Web Interface (USGS 2009). The ENP data were obtained from the South Florida Natural Resources Center (SFNRC) DataForEVER Dataset (ENP 2009), while the SFWMD data were obtained from the DBHYDRO Environmental Database (SFWMD 2009). Data collected as part of this project as well as data from the USGS and SFWMD databases can be accessed through the FCE-LTER (2009) website. Fifteen USGS, ENP and SFWMD stations located within and nearby the de fi ned Taylor Slough basin boundaries were used to estimate P . Additionally, P was acquired directly at TSPh7b (FCE-LTER station) with a TE525 tipping bucket rain gage. The average depth of P across the Taylor Slough basin was estimated between January 2008 and July 2009 using the Thiessen polygon method (Fetter 2001). The number of Thiessen polygons differed between 2008 and 2009 due to the availability of data (Fig. 2). The sum of daily P values for each station multiplied by the area of the Thiessen polygon resulted in the weighted mean daily P for Taylor Slough. The daily P values were summed to determine monthly amounts. Monthly P amounts were compared to the long-term monthly average values reported for the Royal Palm (RPL) station located within the Taylor Slough basin (Fig. 1) with data available from 1949 to present from the National Climatic Data Center (NCDC 2009). A weather tower was constructed at TSPh7b for the collection of meteorological parameters needed for the estimation of ET. The tower was equipped with a Kipp and Zonen CNR1 net radiometer. Temperature and relative humidity were measured using a shielded Vaisala model HMP 45 sensor. Wind speed and direction were measured with an R. M. Young 05106 anemometer. A CR3000 Campbell Scienti fi c datalogger was programmed to record data every 10 min and averaged over 30-min intervals. ET rates were calculated using the Penman-Monteith combi- nation equation described by Shuttleworth (1992) ...

Context 2

... P is precipitation, Q in and Q out are surface-water discharge into and out of the basin, respectively, ET is evapotranspiration, Δ S is change in surface-water storage, and R is recharge. The sign convention used here was positive for water contributing to surface-water storage and negative for water leaving Taylor Slough. No additional variables were taken into consideration in this calculation such as possible sheet fl ow that could not be accounted for at the river gauging stations or submarine groundwater discharge into Florida Bay. The common way of estimating recharge by this method was the indirect or residual approach, whereby all the variables in the water-budget equation except R were measured, and R was set equal to the residual (Scanlon et al. 2002). A positive value of R indicated that groundwater discharged to the surface water, while a negative value of R corresponded with surface-water recharge to the aquifer. All the components of the water budget were calculated in rates of mm/day between January 2008 and July 2009. The natural basin boundaries of Taylor Slough were dif fi cult to determine due to its fl at topography. As a result, the physical boundaries of Taylor Slough as de fi ned for this study were the main park road to the north which served as a dam for surface-water fl ow from the north, a line following the L-31 W canal to the east which acted as a hydraulic boundary, and Florida Bay to the south. The boundary to the west was determined as best as possible using a topographic map ( Fig. 1). These physical boundaries enclosed an area approximately 450 km 2 . Most of the precipitation, surface-water level and discharge data used in this project were obtained from sites in and around the Taylor Slough basin maintained by different agencies including the US Geological Survey (USGS), Everglades National Park (ENP), and the South Florida Water Management District (SFMWD). Data from the USGS were obtained from the National Water Information System (NWIS) Web Interface (USGS 2009). The ENP data were obtained from the South Florida Natural Resources Center (SFNRC) DataForEVER Dataset (ENP 2009), while the SFWMD data were obtained from the DBHYDRO Environmental Database (SFWMD 2009). Data collected as part of this project as well as data from the USGS and SFWMD databases can be accessed through the FCE-LTER (2009) website. Fifteen USGS, ENP and SFWMD stations located within and nearby the de fi ned Taylor Slough basin boundaries were used to estimate P . Additionally, P was acquired directly at TSPh7b (FCE-LTER station) with a TE525 tipping bucket rain gage. The average depth of P across the Taylor Slough basin was estimated between January 2008 and July 2009 using the Thiessen polygon method (Fetter 2001). The number of Thiessen polygons differed between 2008 and 2009 due to the availability of data (Fig. 2). The sum of daily P values for each station multiplied by the area of the Thiessen polygon resulted in the weighted mean daily P for Taylor Slough. The daily P values were summed to determine monthly amounts. Monthly P amounts were compared to the long-term monthly average values reported for the Royal Palm (RPL) station located within the Taylor Slough basin (Fig. 1) with data available from 1949 to present from the National Climatic Data Center (NCDC 2009). A weather tower was constructed at TSPh7b for the collection of meteorological parameters needed for the estimation of ET. The tower was equipped with a Kipp and Zonen CNR1 net radiometer. Temperature and relative humidity were measured using a shielded Vaisala model HMP 45 sensor. Wind speed and direction were measured with an R. M. Young 05106 anemometer. A CR3000 Campbell Scienti fi c datalogger was programmed to record data every 10 min and averaged over 30-min intervals. ET rates were calculated using the Penman-Monteith combi- nation equation described by Shuttleworth (1992) ...

Context 3

... detailed explanation of all the variables in Eq. (2) can be found in Table 1. For the application of the Penman- Monteith equation, solar radiation recorded at TSPh7 was assumed to be uniform across the Taylor Slough basin. The Penman-Monteith method was based on the assumption that all the energy for ET was accessible by the plant canopy, and that water had to diffuse through leaves against a surface resistance before diffusing into the atmosphere against the aerodynamic resistance (Shuttleworth 1992). Besides the meteorological variables measured at TSPh7b, the Penman- Monteith equation included characteristics of the vegetation (Table 2). Two main land covers were identi fi ed as sawgrass and mangroves. Sawgrass was estimated to cover an area of 302,090,900 m 2 corresponding to 67 % of the basin and mangroves covered an area of 148,577,150 m 2 equivalent to 33 % of the basin (Fig. 1). The fi nal ET rates were calculated as a weighted average between the rates for mangroves and sawgrass. The meteorological station at TSPh7b operated from May 29, 2008 to July 31, 2009. During that timeframe two interruptions in the data logger occurred due to battery problems. Since the water-budget analysis required ET data between January 2008 and July 2009, the calculated ET values were correlated to ET values calculated at the USGS station JBTS (Fig. 1) and a linear interpolation was used to complete the ET time series for the days with missing data from the station at TSPh7b. Surface-water in fl ow ( Q in ) to the Taylor Slough basin occurs at the Taylor Slough Bridge along the main park road. Surface-water levels and fl ow at the bridge are monitored at the ENP station TS. Even though S332 and S175 hydraulic structures were considered in fl ow points to Taylor Slough, signi fi cant portions of these in fl ows seeped back into the canals because of the hydraulic gradient between the marsh and the adjacent canals (Genereux and Slater 1999). Consequently, the net in fl ows into southern Taylor Slough were assumed to be re fl ected in the measured fl ows at TS only. Surface-water out fl ows ( Q out ) were determined from the USGS stations McCormick Creek (MCC), Mud Creek (MUD) and Taylor River (TRE) (Fig. 1). All three creeks cut through the Buttonwood Ridge and are considered to be the major water discharges from Taylor Slough to Florida Bay (Sutula et al. 2001). Change in storage ( Δ S ) was calculated from 32 pre- existing surface-water stages located throughout the Taylor Slough Basin (Fig. 3) and monitored by both ENP and USGS. Surface-water stage data were analyzed with a geographic information system (GIS) and interpo- lated on a daily basis using a triangular irregular network (TIN). The TIN was a vector-based representation of the physical water-level surface, made up of irregularly distributed nodes (stages) and lines with three-dimensional coordinates (x, y and z) that were arranged in a network of nonoverlapping triangles. In this case, x and y were obtained from the UTM coordinates and z values were obtained from the daily average water elevation recorded at each stage. Later, each TIN obtained was transformed to grid raster data. The daily grids generated had a unit cell size of 100 x 100 m (10,000 m 2 ) and each cell contained a water-level elevation value. The difference between grids from two consecutive days provided the Δ S on a daily basis. The analysis was performed in MATLAB for data gathered between Jan. 1, 2008 and July 31, 2009. The hydraulic gradient method used Darcy s law for uid movement in a porous medium, assuming that the fl ow between the stream and shallow aquifer was entirely vertical (Fetter 2001). The rate and direction of water fl ow was estimated according to the ...

Context 4

... detailed explanation of all the variables in Eq. (2) can be found in Table 1. For the application of the Penman- Monteith equation, solar radiation recorded at TSPh7 was assumed to be uniform across the Taylor Slough basin. The Penman-Monteith method was based on the assumption that all the energy for ET was accessible by the plant canopy, and that water had to diffuse through leaves against a surface resistance before diffusing into the atmosphere against the aerodynamic resistance (Shuttleworth 1992). Besides the meteorological variables measured at TSPh7b, the Penman- Monteith equation included characteristics of the vegetation (Table 2). Two main land covers were identi fi ed as sawgrass and mangroves. Sawgrass was estimated to cover an area of 302,090,900 m 2 corresponding to 67 % of the basin and mangroves covered an area of 148,577,150 m 2 equivalent to 33 % of the basin (Fig. 1). The fi nal ET rates were calculated as a weighted average between the rates for mangroves and sawgrass. The meteorological station at TSPh7b operated from May 29, 2008 to July 31, 2009. During that timeframe two interruptions in the data logger occurred due to battery problems. Since the water-budget analysis required ET data between January 2008 and July 2009, the calculated ET values were correlated to ET values calculated at the USGS station JBTS (Fig. 1) and a linear interpolation was used to complete the ET time series for the days with missing data from the station at TSPh7b. Surface-water in fl ow ( Q in ) to the Taylor Slough basin occurs at the Taylor Slough Bridge along the main park road. Surface-water levels and fl ow at the bridge are monitored at the ENP station TS. Even though S332 and S175 hydraulic structures were considered in fl ow points to Taylor Slough, signi fi cant portions of these in fl ows seeped back into the canals because of the hydraulic gradient between the marsh and the adjacent canals (Genereux and Slater 1999). Consequently, the net in fl ows into southern Taylor Slough were assumed to be re fl ected in the measured fl ows at TS only. Surface-water out fl ows ( Q out ) were determined from the USGS stations McCormick Creek (MCC), Mud Creek (MUD) and Taylor River (TRE) (Fig. 1). All three creeks cut through the Buttonwood Ridge and are considered to be the major water discharges from Taylor Slough to Florida Bay (Sutula et al. 2001). Change in storage ( Δ S ) was calculated from 32 pre- existing surface-water stages located throughout the Taylor Slough Basin (Fig. 3) and monitored by both ENP and USGS. Surface-water stage data were analyzed with a geographic information system (GIS) and interpo- lated on a daily basis using a triangular irregular network (TIN). The TIN was a vector-based representation of the physical water-level surface, made up of irregularly distributed nodes (stages) and lines with three-dimensional coordinates (x, y and z) that were arranged in a network of nonoverlapping triangles. In this case, x and y were obtained from the UTM coordinates and z values were obtained from the daily average water elevation recorded at each stage. Later, each TIN obtained was transformed to grid raster data. The daily grids generated had a unit cell size of 100 x 100 m (10,000 m 2 ) and each cell contained a water-level elevation value. The difference between grids from two consecutive days provided the Δ S on a daily basis. The analysis was performed in MATLAB for data gathered between Jan. 1, 2008 and July 31, 2009. The hydraulic gradient method used Darcy s law for uid movement in a porous medium, assuming that the fl ow between the stream and shallow aquifer was entirely vertical (Fetter 2001). The rate and direction of water fl ow was estimated according to the ...

Context 5

... detailed explanation of all the variables in Eq. (2) can be found in Table 1. For the application of the Penman- Monteith equation, solar radiation recorded at TSPh7 was assumed to be uniform across the Taylor Slough basin. The Penman-Monteith method was based on the assumption that all the energy for ET was accessible by the plant canopy, and that water had to diffuse through leaves against a surface resistance before diffusing into the atmosphere against the aerodynamic resistance (Shuttleworth 1992). Besides the meteorological variables measured at TSPh7b, the Penman- Monteith equation included characteristics of the vegetation (Table 2). Two main land covers were identi fi ed as sawgrass and mangroves. Sawgrass was estimated to cover an area of 302,090,900 m 2 corresponding to 67 % of the basin and mangroves covered an area of 148,577,150 m 2 equivalent to 33 % of the basin (Fig. 1). The fi nal ET rates were calculated as a weighted average between the rates for mangroves and sawgrass. The meteorological station at TSPh7b operated from May 29, 2008 to July 31, 2009. During that timeframe two interruptions in the data logger occurred due to battery problems. Since the water-budget analysis required ET data between January 2008 and July 2009, the calculated ET values were correlated to ET values calculated at the USGS station JBTS (Fig. 1) and a linear interpolation was used to complete the ET time series for the days with missing data from the station at TSPh7b. Surface-water in fl ow ( Q in ) to the Taylor Slough basin occurs at the Taylor Slough Bridge along the main park road. Surface-water levels and fl ow at the bridge are monitored at the ENP station TS. Even though S332 and S175 hydraulic structures were considered in fl ow points to Taylor Slough, signi fi cant portions of these in fl ows seeped back into the canals because of the hydraulic gradient between the marsh and the adjacent canals (Genereux and Slater 1999). Consequently, the net in fl ows into southern Taylor Slough were assumed to be re fl ected in the measured fl ows at TS only. Surface-water out fl ows ( Q out ) were determined from the USGS stations McCormick Creek (MCC), Mud Creek (MUD) and Taylor River (TRE) (Fig. 1). All three creeks cut through the Buttonwood Ridge and are considered to be the major water discharges from Taylor Slough to Florida Bay (Sutula et al. 2001). Change in storage ( Δ S ) was calculated from 32 pre- existing surface-water stages located throughout the Taylor Slough Basin (Fig. 3) and monitored by both ENP and USGS. Surface-water stage data were analyzed with a geographic information system (GIS) and interpo- lated on a daily basis using a triangular irregular network (TIN). The TIN was a vector-based representation of the physical water-level surface, made up of irregularly distributed nodes (stages) and lines with three-dimensional coordinates (x, y and z) that were arranged in a network of nonoverlapping triangles. In this case, x and y were obtained from the UTM coordinates and z values were obtained from the daily average water elevation recorded at each stage. Later, each TIN obtained was transformed to grid raster data. The daily grids generated had a unit cell size of 100 x 100 m (10,000 m 2 ) and each cell contained a water-level elevation value. The difference between grids from two consecutive days provided the Δ S on a daily basis. The analysis was performed in MATLAB for data gathered between Jan. 1, 2008 and July 31, 2009. The hydraulic gradient method used Darcy s law for uid movement in a porous medium, assuming that the fl ow between the stream and shallow aquifer was entirely vertical (Fetter 2001). The rate and direction of water fl ow was estimated according to the ...

Context 6

... Eq. (3), the vertical rate of water ow q was determined by measuring the head difference ( δ h) between the stream level and the groundwater level, the vertical distance between the measuring point in the aquifer and the stream bed ( δ l), and the vertical hydraulic conductivity ( K v ) of the material. The use of Darcy ’ s law requires the assumption of a homogeneous aquifer and laminar fl ow conditions, which were assumed for the peat overlying the limestone bedrock. Two transects of piezometers at sites TSPh6b and TSPh7b were used for water monitoring ( Fig. 1). Piezometers consisted of 2.54 to 5.08 cm diameter PVC, ranging in depths from 0.5 m at TSPh6b to 1.0 m at TSPh7b, which corresponded to the thickness of the peat layer overlying the limestone bedrock. The vertical elevations of the tops of all piezometers were referenced to the North American Vertical Datum 1988 (NAVD88) using a Wild Nak-2 level and stadia rod. In-Situ Inc. Aqua Troll 200 pressure transducers (5 psi) were installed in TSPh7b piezometers (GWA1, GWA2 and GWA4), TSPh6b piezometer (GWC3) and at a surface-water site at both TSPH7b (SWCanoe) and TSPH6b (SWDock) (Fig. 1). The In-Situ Inc. Aqua TROLL 200 recorded water levels corrected for density differences due to changes in salinity and temperature every 30 min. The units were vented to the atmosphere, and therefore compensated for fl uctuations in barometric pressure. The overall accuracy of the water-level measurements was about 11.5 mm. Water-level records were gathered at TSPh7b between January 31 to July 31, 2009 and at TSPh6b from May 21 to July 31, 2009. Hydraulic conductivity of the peat overlying the limestone bedrock was estimated from slug tests performed in the piezometers with the slug-test data analyzed using the Bouwer and Rice (1976) method for an uncon fi ned aquifer using AQTESOLV (Fetter 2001). Surface-water and groundwater samples were collected monthly from April 2008 to July 2009. A total of eight surface-water (SWmouth, SWCanoe, SWA1, SWA3, SWDock, SWC1, SWC2, SWTSPh3) and eight groundwater stations (GWA1, GWA2, GWA3, GWA4, GWC1, GWC2, GWC3, GWTSPh3) were monitored (Fig. 1). The groundwater well GWTSPh3 has a 3.81 cm in diameter PVC pipe, with a depth of 4.6 m below the ground surface in the limestone bedrock. Prior to sampling, each well was purged of at least three well volumes using a peristaltic pump. A fi ltered sample was collected for chloride and alkalinity. Samples were fi ltered through a 0.45- μ m fi lter and stored in a refrigerator at 4 °C until analysis. Samples collected for cations were acidi fi ed to a pH of less than 2 using 10 % HCl. Total alkalinity was determined at Florida International University (FIU) by potentiometric acid titration to a pH near 2, while major anions (chloride and sulfate) and the major cations (calcium, magnesium, sodium and potassium) were determined by ion chromatography using a Dionex 120 instrument. As a check on the chemical analysis, a charge balance was performed. Charge balance errors ranged from 0 to 9.9 %. Errors of 5 % or less were considered acceptable and achieved in 147 out of 158 samples. Water chemistry data are included as electronic supplementary material. Surface water and soil (0.3 m depth) temperature measurements were recorded at the weather tower located at TSPh7b every 30 min using two Campbell Scienti fi c 107 L temperature sensors. Those measurements were combined with the air-temperature measurements recorded at the weather tower. Air, surface water and soil temperature were gathered in three different periods between May 29 and September 14, 2008; October 24 and December 17, 2008; and February 13 to July 31, 2009. By way of comparing the different temperature time series, the occurrence of groundwater/surface-water interactions was estimated qualitatively. During the 19 months of this research, approximately 69 % of the P occurred in the wet season (June-October) with the remaining 31 % in the dry season (November – May) (Fig. 4). From January 2008 until July 2009, the cumulative P measured in Taylor Slough was lower than the long-term average values for RPL (1416.75 mm annual and 760.08 mm for the fi rst 7 months of the year). The calculated daily ET rates varied between 1 and 6 mm with higher values (>4 mm/day) observed between May and August of both years 2008 and 2009, and the lowest rates observed between October and December 2008 (Fig. 5). The cumulative annual ET for 2008 and the fi rst 7 months of 2009 exceeded P by about 30 % (Table 3). Surface-water in fl ows at the Taylor Slough Bridge as recorded at the TS station, were minimal during the fi rst 5 months of 2008 and 2009, respectively (Fig. 6). During 305 out of 578 days, equivalent to 52.7 % of the time, fl ows registered at TS were lower than 0.1 mm/day. Positive surface-water in fl ow values were often recorded at TS during the rainy season months of June – October 2008 and June – July 2009. At the surface-water output stations, both positive and negative discharge values were observed (Fig. 6). Daily positive values meant water from Florida Bay entered Taylor Slough. In contrast, negative values represented water leaving Taylor Slough to Florida Bay. The total surface-water discharge from Taylor Slough during the 19 month study was 207.14 mm, or 89 % of the surface-water in fl ows measured at TS (Table 3). Surface-water stage levels in the Taylor Slough basin varied signi fi cantly on a daily time step and could change as much as 0.5 m to 1.0 m (Fig. 7). The observed daily variations in water levels resulted in daily reversals of water storage ( Δ S ) and recharge ( R ) within the Taylor Slough basin. Observing periods of groundwater discharge became dif fi cult at a daily time step, therefore, monthly totals were calculated for each of the water- budget parameters (Table 3; Fig. 8). The largest inputs of groundwater to the surface water occurred during the months of April, July and August 2008, and in May 2009 (Table 3). Between October 2008 and March 2009, surface water tended to recharge the aquifer. In general, groundwater and surface-water levels varied similarly throughout the study period (Fig. 9). Water levels for TSPh6b and TSPh7b were at their highest in the last week of May and June 2009 and at their lowest on May 21, 2009 at TSPh6b and end of January 2009 at TSPh7b. In an effort to minimize small fl uctuations in the difference between groundwater and surface-water levels, a daily average was computed from 30-min ...

Context 7

... Eq. (3), the vertical rate of water ow q was determined by measuring the head difference ( δ h) between the stream level and the groundwater level, the vertical distance between the measuring point in the aquifer and the stream bed ( δ l), and the vertical hydraulic conductivity ( K v ) of the material. The use of Darcy ’ s law requires the assumption of a homogeneous aquifer and laminar fl ow conditions, which were assumed for the peat overlying the limestone bedrock. Two transects of piezometers at sites TSPh6b and TSPh7b were used for water monitoring ( Fig. 1). Piezometers consisted of 2.54 to 5.08 cm diameter PVC, ranging in depths from 0.5 m at TSPh6b to 1.0 m at TSPh7b, which corresponded to the thickness of the peat layer overlying the limestone bedrock. The vertical elevations of the tops of all piezometers were referenced to the North American Vertical Datum 1988 (NAVD88) using a Wild Nak-2 level and stadia rod. In-Situ Inc. Aqua Troll 200 pressure transducers (5 psi) were installed in TSPh7b piezometers (GWA1, GWA2 and GWA4), TSPh6b piezometer (GWC3) and at a surface-water site at both TSPH7b (SWCanoe) and TSPH6b (SWDock) (Fig. 1). The In-Situ Inc. Aqua TROLL 200 recorded water levels corrected for density differences due to changes in salinity and temperature every 30 min. The units were vented to the atmosphere, and therefore compensated for fl uctuations in barometric pressure. The overall accuracy of the water-level measurements was about 11.5 mm. Water-level records were gathered at TSPh7b between January 31 to July 31, 2009 and at TSPh6b from May 21 to July 31, 2009. Hydraulic conductivity of the peat overlying the limestone bedrock was estimated from slug tests performed in the piezometers with the slug-test data analyzed using the Bouwer and Rice (1976) method for an uncon fi ned aquifer using AQTESOLV (Fetter 2001). Surface-water and groundwater samples were collected monthly from April 2008 to July 2009. A total of eight surface-water (SWmouth, SWCanoe, SWA1, SWA3, SWDock, SWC1, SWC2, SWTSPh3) and eight groundwater stations (GWA1, GWA2, GWA3, GWA4, GWC1, GWC2, GWC3, GWTSPh3) were monitored (Fig. 1). The groundwater well GWTSPh3 has a 3.81 cm in diameter PVC pipe, with a depth of 4.6 m below the ground surface in the limestone bedrock. Prior to sampling, each well was purged of at least three well volumes using a peristaltic pump. A fi ltered sample was collected for chloride and alkalinity. Samples were fi ltered through a 0.45- μ m fi lter and stored in a refrigerator at 4 °C until analysis. Samples collected for cations were acidi fi ed to a pH of less than 2 using 10 % HCl. Total alkalinity was determined at Florida International University (FIU) by potentiometric acid titration to a pH near 2, while major anions (chloride and sulfate) and the major cations (calcium, magnesium, sodium and potassium) were determined by ion chromatography using a Dionex 120 instrument. As a check on the chemical analysis, a charge balance was performed. Charge balance errors ranged from 0 to 9.9 %. Errors of 5 % or less were considered acceptable and achieved in 147 out of 158 samples. Water chemistry data are included as electronic supplementary material. Surface water and soil (0.3 m depth) temperature measurements were recorded at the weather tower located at TSPh7b every 30 min using two Campbell Scienti fi c 107 L temperature sensors. Those measurements were combined with the air-temperature measurements recorded at the weather tower. Air, surface water and soil temperature were gathered in three different periods between May 29 and September 14, 2008; October 24 and December 17, 2008; and February 13 to July 31, 2009. By way of comparing the different temperature time series, the occurrence of groundwater/surface-water interactions was estimated qualitatively. During the 19 months of this research, approximately 69 % of the P occurred in the wet season (June-October) with the remaining 31 % in the dry season (November – May) (Fig. 4). From January 2008 until July 2009, the cumulative P measured in Taylor Slough was lower than the long-term average values for RPL (1416.75 mm annual and 760.08 mm for the fi rst 7 months of the year). The calculated daily ET rates varied between 1 and 6 mm with higher values (>4 mm/day) observed between May and August of both years 2008 and 2009, and the lowest rates observed between October and December 2008 (Fig. 5). The cumulative annual ET for 2008 and the fi rst 7 months of 2009 exceeded P by about 30 % (Table 3). Surface-water in fl ows at the Taylor Slough Bridge as recorded at the TS station, were minimal during the fi rst 5 months of 2008 and 2009, respectively (Fig. 6). During 305 out of 578 days, equivalent to 52.7 % of the time, fl ows registered at TS were lower than 0.1 mm/day. Positive surface-water in fl ow values were often recorded at TS during the rainy season months of June – October 2008 and June – July 2009. At the surface-water output stations, both positive and negative discharge values were observed (Fig. 6). Daily positive values meant water from Florida Bay entered Taylor Slough. In contrast, negative values represented water leaving Taylor Slough to Florida Bay. The total surface-water discharge from Taylor Slough during the 19 month study was 207.14 mm, or 89 % of the surface-water in fl ows measured at TS (Table 3). Surface-water stage levels in the Taylor Slough basin varied signi fi cantly on a daily time step and could change as much as 0.5 m to 1.0 m (Fig. 7). The observed daily variations in water levels resulted in daily reversals of water storage ( Δ S ) and recharge ( R ) within the Taylor Slough basin. Observing periods of groundwater discharge became dif fi cult at a daily time step, therefore, monthly totals were calculated for each of the water- budget parameters (Table 3; Fig. 8). The largest inputs of groundwater to the surface water occurred during the months of April, July and August 2008, and in May 2009 (Table 3). Between October 2008 and March 2009, surface water tended to recharge the aquifer. In general, groundwater and surface-water levels varied similarly throughout the study period (Fig. 9). Water levels for TSPh6b and TSPh7b were at their highest in the last week of May and June 2009 and at their lowest on May 21, 2009 at TSPh6b and end of January 2009 at TSPh7b. In an effort to minimize small fl uctuations in the difference between groundwater and surface-water levels, a daily average was computed from 30-min ...

Context 8

... Eq. (3), the vertical rate of water ow q was determined by measuring the head difference ( δ h) between the stream level and the groundwater level, the vertical distance between the measuring point in the aquifer and the stream bed ( δ l), and the vertical hydraulic conductivity ( K v ) of the material. The use of Darcy ’ s law requires the assumption of a homogeneous aquifer and laminar fl ow conditions, which were assumed for the peat overlying the limestone bedrock. Two transects of piezometers at sites TSPh6b and TSPh7b were used for water monitoring ( Fig. 1). Piezometers consisted of 2.54 to 5.08 cm diameter PVC, ranging in depths from 0.5 m at TSPh6b to 1.0 m at TSPh7b, which corresponded to the thickness of the peat layer overlying the limestone bedrock. The vertical elevations of the tops of all piezometers were referenced to the North American Vertical Datum 1988 (NAVD88) using a Wild Nak-2 level and stadia rod. In-Situ Inc. Aqua Troll 200 pressure transducers (5 psi) were installed in TSPh7b piezometers (GWA1, GWA2 and GWA4), TSPh6b piezometer (GWC3) and at a surface-water site at both TSPH7b (SWCanoe) and TSPH6b (SWDock) (Fig. 1). The In-Situ Inc. Aqua TROLL 200 recorded water levels corrected for density differences due to changes in salinity and temperature every 30 min. The units were vented to the atmosphere, and therefore compensated for fl uctuations in barometric pressure. The overall accuracy of the water-level measurements was about 11.5 mm. Water-level records were gathered at TSPh7b between January 31 to July 31, 2009 and at TSPh6b from May 21 to July 31, 2009. Hydraulic conductivity of the peat overlying the limestone bedrock was estimated from slug tests performed in the piezometers with the slug-test data analyzed using the Bouwer and Rice (1976) method for an uncon fi ned aquifer using AQTESOLV (Fetter 2001). Surface-water and groundwater samples were collected monthly from April 2008 to July 2009. A total of eight surface-water (SWmouth, SWCanoe, SWA1, SWA3, SWDock, SWC1, SWC2, SWTSPh3) and eight groundwater stations (GWA1, GWA2, GWA3, GWA4, GWC1, GWC2, GWC3, GWTSPh3) were monitored (Fig. 1). The groundwater well GWTSPh3 has a 3.81 cm in diameter PVC pipe, with a depth of 4.6 m below the ground surface in the limestone bedrock. Prior to sampling, each well was purged of at least three well volumes using a peristaltic pump. A fi ltered sample was collected for chloride and alkalinity. Samples were fi ltered through a 0.45- μ m fi lter and stored in a refrigerator at 4 °C until analysis. Samples collected for cations were acidi fi ed to a pH of less than 2 using 10 % HCl. Total alkalinity was determined at Florida International University (FIU) by potentiometric acid titration to a pH near 2, while major anions (chloride and sulfate) and the major cations (calcium, magnesium, sodium and potassium) were determined by ion chromatography using a Dionex 120 instrument. As a check on the chemical analysis, a charge balance was performed. Charge balance errors ranged from 0 to 9.9 %. Errors of 5 % or less were considered acceptable and achieved in 147 out of 158 samples. Water chemistry data are included as electronic supplementary material. Surface water and soil (0.3 m depth) temperature measurements were recorded at the weather tower located at TSPh7b every 30 min using two Campbell Scienti fi c 107 L temperature sensors. Those measurements were combined with the air-temperature measurements recorded at the weather tower. Air, surface water and soil temperature were gathered in three different periods between May 29 and September 14, 2008; October 24 and December 17, 2008; and February 13 to July 31, 2009. By way of comparing the different temperature time series, the occurrence of groundwater/surface-water interactions was estimated qualitatively. During the 19 months of this research, approximately 69 % of the P occurred in the wet season (June-October) with the remaining 31 % in the dry season (November – May) (Fig. 4). From January 2008 until July 2009, the cumulative P measured in Taylor Slough was lower than the long-term average values for RPL (1416.75 mm annual and 760.08 mm for the fi rst 7 months of the year). The calculated daily ET rates varied between 1 and 6 mm with higher values (>4 mm/day) observed between May and August of both years 2008 and 2009, and the lowest rates observed between October and December 2008 (Fig. 5). The cumulative annual ET for 2008 and the fi rst 7 months of 2009 exceeded P by about 30 % (Table 3). Surface-water in fl ows at the Taylor Slough Bridge as recorded at the TS station, were minimal during the fi rst 5 months of 2008 and 2009, respectively (Fig. 6). During 305 out of 578 days, equivalent to 52.7 % of the time, fl ows registered at TS were lower than 0.1 mm/day. Positive surface-water in fl ow values were often recorded at TS during the rainy season months of June – October 2008 and June – July 2009. At the surface-water output stations, both positive and negative discharge values were observed (Fig. 6). Daily positive values meant water from Florida Bay entered Taylor Slough. In contrast, negative values represented water leaving Taylor Slough to Florida Bay. The total surface-water discharge from Taylor Slough during the 19 month study was 207.14 mm, or 89 % of the surface-water in fl ows measured at TS (Table 3). Surface-water stage levels in the Taylor Slough basin varied signi fi cantly on a daily time step and could change as much as 0.5 m to 1.0 m (Fig. 7). The observed daily variations in water levels resulted in daily reversals of water storage ( Δ S ) and recharge ( R ) within the Taylor Slough basin. Observing periods of groundwater discharge became dif fi cult at a daily time step, therefore, monthly totals were calculated for each of the water- budget parameters (Table 3; Fig. 8). The largest inputs of groundwater to the surface water occurred during the months of April, July and August 2008, and in May 2009 (Table 3). Between October 2008 and March 2009, surface water tended to recharge the aquifer. In general, groundwater and surface-water levels varied similarly throughout the study period (Fig. 9). Water levels for TSPh6b and TSPh7b were at their highest in the last week of May and June 2009 and at their lowest on May 21, 2009 at TSPh6b and end of January 2009 at TSPh7b. In an effort to minimize small fl uctuations in the difference between groundwater and surface-water levels, a daily average was computed from 30-min ...

Context 9

... mechanism by which water was lost from the Taylor Slough basin. The daily ET rates computed using the Penman-Monteith model (1 – 6 mm/day) were similar to values reported by others across the greater Everglades (Abtew 1996; German 2000; Nungesser and Chimney 2006) and for a wet prairie community in central Florida (Jacobs et al. 2002, 2004). Taylor Slough ET rates (~5 – 6 mm/day) were higher at the end of the dry season (May) and at the beginning of the wet season (June) when solar radiation, air temperature and wind speeds were high, while humidity was low ( Fig. 5). The lowest rates (<1 – 3 mm/day) occurred at the end of the wet season (October) and beginning of the dry season (November) when solar radiation, air temperatures and wind speeds were low. A similar seasonal pattern in evaporation was observed for other portions of the Everglades (Saha et al. 2012) and Florida Bay (Price et al. 2007). For 2008, ET (1295.8 mm/ year) was within the range of values reported by Abtew et al. (2003) based on lysimeter measurements (1,370 mm/ year) and Sutula et al. (2001) using the Bowen ratio method (1,620 mm/year). Although the total ET values exceeded P for the 19 month study, P exceeded ET for most of the rainy season months (May – September), allowing for an increase in storage in the basin. Between January 2008 and July 2009, Q in represented 9 % of the total input of water to Taylor Slough. Over the same time period, Q in (233.6 mm) roughly balanced Q out (207.1 mm). Similar results were reported more than a decade earlier by Sutula et al. (2001) for the years 1996 and 1997. A good correlation was obtained between Q in and Q out ( R 2 0 0.69), indicating that smaller and larger inputs and outputs were observed during the same time periods. In Taylor Slough, Q in represented managed water input from pumps located near the S-332 pump station (Fig. 1) that delivered water from the L-31 W canal to the northern reaches of Taylor Slough. Those pumps delivered no water to Taylor Slough for the rst 4 5 months of each year, or about 40 % of the time. The water that was delivered constituted only 15 % of the amount of water received by the basin via P between January 2008 and July 2009. With a 19 monthly sum of 164.4 mm, Δ S was the smallest component of the water budget and corresponded to 10 % of P . Despite such a low value, water levels (Fig. 7) and Δ S (Fig. 8) were highly variable on a daily or monthly basis. According to Davis and Ogden (1994), the balance of high P and ET rates causes a large inter-annual variation in water storage in the Everglades. Given that P has been shown to vary both spatially and on a daily basis across the Everglades (Duever et al. 1994), Δ S would be expected to vary accordingly. Furthermore, Q out was found to vary in direction from water fl owing out of Taylor Slough into Florida Bay, to times when estuarine waters from Florida Bay contributed to Δ S of the Taylor Slough basin. The contribution of Florida Bay water to Taylor Slough had been documented to be dominantly wind driven as opposed to tidal, occurring during times of strong southerly winds (Sutula et al. 2001) following the passage of winter-time cold fronts (Wang et al. 1994). During the 19 months of this research, R accounted for 668.95 mm (Table 3) of water input to Taylor Slough, equivalent to 27 % of the total water input or 42 % of P . Extreme R values were calculated for May 2008 and 2009 with values of 115.83 mm/month and 413.83 mm/month, respectively. These monthly R values were similar in magnitude to the 480 and 350 mm values reported by Sutula et al. (2001) for the 1997 dry and wet seasons, respectively. Although the four methods employed during this research were applied over different spatio-temporal scales, the results of each agreed well as to the timing of groundwater/surface-water exchange (Fig. 13). The water budget, hydraulic gradient, and temperature methods demonstrated that R varied on a daily time step. However, the longer trend in groundwater recharge by surface water occurred between October 2008 and March 2009 as indicated by the water-budget and temperature methods (Fig. 13). Conversely, upward fl uxes representing periods of groundwater discharge to the surface water occurred between June and September 2008 and after mid March 2009. Both salinity and Ca 2+ vs. Cl − plots from TSPh7b and TSPh6b concur as to the timing of groundwater discharge (Fig. 13). For instance, the black bars on Fig. 13f and g indicate the times when the chemistry of groundwater and surface water is similar as a consequence of groundwater discharging to the surface water. The variability in the timing and direction of R as measured in this investigation was observed by other researchers in the Everglades. For instance, Harvey et al. (2004) reported that R underwent reversals in direction during weekly, monthly and annual time scales between 1997 and 2002, within central Everglades wetlands located north of ENP. Their observed reversals in R seem to have been driven by the response of groundwater and surface-water levels to P events, ET and water-management releases. Previous researchers have suggested that groundwater discharge to Taylor Slough occurs dominantly in the dry season (November – May), when surface-water levels are low (Price et al. 2006; Sutula et al. 2001; Michot et al. 2011). The reasoning behind those statements is that high surface-water levels, which typically occur during the wet season (June – October), would suppress groundwater discharge. The results of the present investigation are contrary to those studies in that groundwater discharge dominates during the wet season months of June – September, when surface-water levels are high. This out of phase occurrence between groundwater/surface-water exchange, seasonal rainfall patterns, and surface-water levels, suggest a delayed response in the hydrologic system. Time lags amongst hydrologic variables in Taylor Slough have been observed by both Koch et al. (2012) and Michot et al. (2011) who reported the timing of surface-water runoff ( Q out ) to lag P inputs by 1 – 2 months. Saha et al. (2012) observed groundwater discharge in Shark Slough, ENP, to be highest in June, and lagging by 1 month the highest surface-water salinity levels. Despite the karstic nature of the underlying bedrock, groundwater fl ow through this system is expected to be slower than surface-water fl ow, and therefore would be expected to have a greater time lag in response to inputs to the basin than the overlying surface water. The time lag between the lowest observed surface-water levels (mid-March at TSPh6, and January at TSPh7) and the greatest groundwater discharge rates (end of March at TSPh6 and June at TSPh7) suggests that groundwater discharge to the basin lags low surface-water levels by less than 1 – 5 ...

Context 10

... 5 Daily a precipitation ( P ), b evapotranspiration ( ET ) and c P and ET together, in Taylor Slough from January 2008 to July 2009. The ET time series is a weighted average of the individual time series from mangroves and sawgrass regions depicted in Fig. 1  ...

Context 11

... groundwater/surface-water exchange in coastal wetlands is important for understanding their water, thermal energy and solute balance. To date, signi fi cant research has been conducted on groundwater/surface-water exchange in freshwater streams and lakes (Sophocleous 2002) as well as submarine groundwater discharge to seas and estuaries (Burnett et al. 2006; Li et al. 1999; Michael et al. 2005; Younger 1996), with few investigations into groundwater discharge to the coastal wetlands that occur between the fresh and saline environments. Of the few studies that have been conducted, results con fi rmed groundwater discharge to be a signi fi cant source of nutrients (Tobias et al. 2001), fresh water (Nuttle and Harvey 1995) and brackish water (Price et al. 2006) to coastal wetlands. In the case of the Florida Everglades, a large subtropical coastal wetland, groundwater/surface-water interactions were unintentionally enhanced by water- management practices that produced abrupt topographic and hydraulic head differences in what was originally relatively fl at terrain (Harvey and McCormick 2009). Beginning in the 1900s and continuing today, an extensive system of canals, levees, and water-control structures were constructed across the Everglades landscape for the purposes of drainage, fl ood control and reservoir management. Current water-management practices lead to storage of water in the Water Conservation Areas (WCAs) located north of Tamiami Trail (Fig. 1), with a reduction in water fl ow south of Tamiami Trail into Everglades National Park (ENP). Drier conditions currently prevail in the wetland areas of Shark Slough and Taylor Sloughs, the two dominant water fl ow ways within ENP (Fig. 1). Surface- water fl ows through Taylor Slough have been estimated to be 25 % less than what was expected during pre-drainage conditions (Light and Dineen ...

Context 12

... groundwater/surface-water exchange in coastal wetlands is important for understanding their water, thermal energy and solute balance. To date, signi fi cant research has been conducted on groundwater/surface-water exchange in freshwater streams and lakes (Sophocleous 2002) as well as submarine groundwater discharge to seas and estuaries (Burnett et al. 2006; Li et al. 1999; Michael et al. 2005; Younger 1996), with few investigations into groundwater discharge to the coastal wetlands that occur between the fresh and saline environments. Of the few studies that have been conducted, results con fi rmed groundwater discharge to be a signi fi cant source of nutrients (Tobias et al. 2001), fresh water (Nuttle and Harvey 1995) and brackish water (Price et al. 2006) to coastal wetlands. In the case of the Florida Everglades, a large subtropical coastal wetland, groundwater/surface-water interactions were unintentionally enhanced by water- management practices that produced abrupt topographic and hydraulic head differences in what was originally relatively fl at terrain (Harvey and McCormick 2009). Beginning in the 1900s and continuing today, an extensive system of canals, levees, and water-control structures were constructed across the Everglades landscape for the purposes of drainage, fl ood control and reservoir management. Current water-management practices lead to storage of water in the Water Conservation Areas (WCAs) located north of Tamiami Trail (Fig. 1), with a reduction in water fl ow south of Tamiami Trail into Everglades National Park (ENP). Drier conditions currently prevail in the wetland areas of Shark Slough and Taylor Sloughs, the two dominant water fl ow ways within ENP (Fig. 1). Surface- water fl ows through Taylor Slough have been estimated to be 25 % less than what was expected during pre-drainage conditions (Light and Dineen ...

Context 13

... reduction in surface-water ow throughout ENP allowed for an enhancement of seawater intrusion into the coastal aquifer along the entire coastline (Fitterman and Deszcz-Pan 1998). In the region of seawater intrusion, Price et al. (2006) con fi rmed that brackish groundwater discharged to the seasonally fresh coastal wetlands of the Everglades by a process termed coastal groundwater discharge (CGD). The CGD was found to be elevated in phosphorus, the limiting nutrient of the Everglades ecosystem (Noe et al. 2001). The extent of seawater intrusion and CGD co-occurred with the regional extent of the oligohaline ecotone, an area dominated by mangroves that marks a transition from freshwater to marine environments (Ewe et al. 2006; Childers 2006; Rivera-Monroy et al. 2011). The Everglades is currently at the center of one of the largest wetland restoration efforts as de fi ned by the Comprehensive Everglades Restoration Plan (CERP). One of the main objectives of CERP is to increase water fl ow through both sloughs in ENP ( Fig. 1). The increased freshwater fl ow is hypothesized to move the extent of seawater intrusion, CGD, and the oligohaline ecotone further seaward. In the case of Taylor Slough, quantifying the amount and location of groundwater discharge is essential to understanding nutrient cycling and ecosystem response to planned restoration efforts. The main objective of this research was to determine the timing and spatial distribution of groundwater and surface-water exchange in Taylor Slough. The objective was addressed using a variety of techniques across spatial and temporal scales. A water-budget was performed on a watershed scale at a daily time step over 18 months. Hydraulic-head measurements were monitored and logged at 30 min intervals in wells located along a salinity transect, while the geochemistry of groundwater and surface water was monitored on a monthly time step. Finally, temperature measurements were made at one location at 30-min intervals during three periods within the 18-month study. The results of this research provide baseline estimates of the major water-balance parameters, including groundwater discharge, in Taylor Slough prior to restoration efforts. Furthermore, the techniques used in this research may be applied to coastal wetlands world- wide such as the Sian Ka ’ an Biosphere reserve in Yucatan, Mexico, and the St. Lucia Isimangaliso wetland in South Africa. Taylor Slough is located at the southeastern end of the Everglades, which covers 10,000 km 2 of an elongated basin spanning 100 km from Lake Okeechobee to Florida Bay and sloping roughly 3 cm/km (Fig. 1). Taylor Slough occupies a slight depression in the underlying limestone bedrock and is bordered by broader areas 10 – 30 cm higher than the slough channel. The slough is dominated by emergent freshwater vegetation in the upper and intermediate portions and by mangroves in its lower part (Armentano et al. 2006). The southern section of Taylor Slough is characterized by a series of interconnected creeks and ponds. The boundary between Taylor Slough and Florida Bay is marked by a sediment laden ridge called the Buttonwood Embankment that is approximately 0.5 m high (Craighead 1971). This embankment restricts the overland fl ow of water to Florida Bay, making a few creeks, including the Taylor River mouth, the major discharges (Hittle et al. 2001). Sediments of Taylor Slough range in thickness from 0 to 150 cm and consist dominantly of Holocene age freshwater marls in the upland wetlands transitioning to mangrove peats in the southern region. Limestone bedrock of the Biscayne aquifer underlies the sediments but also crops out in places. The uncon fi ned Biscayne aquifer mainly consists of Fort Thompson, Key Largo and Miami limestone formations. Hydraulic conductivities exceed 3,048 m/day in the Biscayne aquifer (Fish and Stewart 1991). The climate in the region is humid, subtropical, and strongly in fl uenced by the western portions of the subtropical Azores-Bermuda high-pressure cells that de- velop over the ocean (Windsberg 2003). During most years, a rainy “ wet season ” extends from June through October while a “ dry season ” occurs from November to May (Chen and Gerber 1991). A bi-modal pattern in rainfall is often observed with peaks in June and September (Duever et al. 1994). Tropical, low pressure storms and cyclones from the Atlantic and Caribbean bring heavy rain in late summer and early autumn, while fronts from the North American continent bring radical swings in temperature and humidity in late fall, winter and early spring. Sampling was conducted at four sites located along a salinity transect of Taylor Slough and include TSPh3, TSPh6b, TSPh7b, and the mouth of Taylor River (TRE). These sites correspond to the research sites monitored as part of the FCE-LTER (Florida Coastal Everglades — Long Term Ecological Research Program) and the US Geological Survey (USGS) (Fig. 1). The northern site, TSPh3, is located in the freshwater marsh region and is vegetated mainly with sawgrass ( Cladium jamaicense ) and muhly grass ( Muhlenbergia fi lipes ). Some isolated and dispersed dwarf red mangroves also make their appearance in this landscape. The marsh at TSPh3 typically dries out for several months every dry season, and does not often experience salinity values greater than 1 practical salinity unit (PSU). Site TSPh6b is an estuarine site located within the oligohaline ecotone. Dwarf red mangroves dominate the landscape at this site, but freshwater marsh vegetation such as sawgrass and spikerush grow amongst the dwarf mangroves. Surface water at this site is fresh for most of the wet season, and becomes higher in salt content (30 – 40 PSU) in the dry season. The estuarine site, TSPH7b, is dominated by mangroves. Surface-water fl ow at this point is largely unidirectional during the wet-season towards Florida Bay but may fl ow in either direction in the dry- season when frontal passage winds cause water from Florida Bay to move upstream into Taylor Slough. The site TRE is located at the mouth of the Taylor River and marks the end of Taylor River and the beginning of Florida Bay. At this site Taylor River is overgrown with mangroves. At TRE, typical surface-water salinity values are above 30 PSU during the dry season and below 20 PSU during the wet season. A water-budget for the Taylor Slough basin was developed on the principle of conservation of mass according to the following ...

Context 14

... reduction in surface-water ow throughout ENP allowed for an enhancement of seawater intrusion into the coastal aquifer along the entire coastline (Fitterman and Deszcz-Pan 1998). In the region of seawater intrusion, Price et al. (2006) con fi rmed that brackish groundwater discharged to the seasonally fresh coastal wetlands of the Everglades by a process termed coastal groundwater discharge (CGD). The CGD was found to be elevated in phosphorus, the limiting nutrient of the Everglades ecosystem (Noe et al. 2001). The extent of seawater intrusion and CGD co-occurred with the regional extent of the oligohaline ecotone, an area dominated by mangroves that marks a transition from freshwater to marine environments (Ewe et al. 2006; Childers 2006; Rivera-Monroy et al. 2011). The Everglades is currently at the center of one of the largest wetland restoration efforts as de fi ned by the Comprehensive Everglades Restoration Plan (CERP). One of the main objectives of CERP is to increase water fl ow through both sloughs in ENP ( Fig. 1). The increased freshwater fl ow is hypothesized to move the extent of seawater intrusion, CGD, and the oligohaline ecotone further seaward. In the case of Taylor Slough, quantifying the amount and location of groundwater discharge is essential to understanding nutrient cycling and ecosystem response to planned restoration efforts. The main objective of this research was to determine the timing and spatial distribution of groundwater and surface-water exchange in Taylor Slough. The objective was addressed using a variety of techniques across spatial and temporal scales. A water-budget was performed on a watershed scale at a daily time step over 18 months. Hydraulic-head measurements were monitored and logged at 30 min intervals in wells located along a salinity transect, while the geochemistry of groundwater and surface water was monitored on a monthly time step. Finally, temperature measurements were made at one location at 30-min intervals during three periods within the 18-month study. The results of this research provide baseline estimates of the major water-balance parameters, including groundwater discharge, in Taylor Slough prior to restoration efforts. Furthermore, the techniques used in this research may be applied to coastal wetlands world- wide such as the Sian Ka ’ an Biosphere reserve in Yucatan, Mexico, and the St. Lucia Isimangaliso wetland in South Africa. Taylor Slough is located at the southeastern end of the Everglades, which covers 10,000 km 2 of an elongated basin spanning 100 km from Lake Okeechobee to Florida Bay and sloping roughly 3 cm/km (Fig. 1). Taylor Slough occupies a slight depression in the underlying limestone bedrock and is bordered by broader areas 10 – 30 cm higher than the slough channel. The slough is dominated by emergent freshwater vegetation in the upper and intermediate portions and by mangroves in its lower part (Armentano et al. 2006). The southern section of Taylor Slough is characterized by a series of interconnected creeks and ponds. The boundary between Taylor Slough and Florida Bay is marked by a sediment laden ridge called the Buttonwood Embankment that is approximately 0.5 m high (Craighead 1971). This embankment restricts the overland fl ow of water to Florida Bay, making a few creeks, including the Taylor River mouth, the major discharges (Hittle et al. 2001). Sediments of Taylor Slough range in thickness from 0 to 150 cm and consist dominantly of Holocene age freshwater marls in the upland wetlands transitioning to mangrove peats in the southern region. Limestone bedrock of the Biscayne aquifer underlies the sediments but also crops out in places. The uncon fi ned Biscayne aquifer mainly consists of Fort Thompson, Key Largo and Miami limestone formations. Hydraulic conductivities exceed 3,048 m/day in the Biscayne aquifer (Fish and Stewart 1991). The climate in the region is humid, subtropical, and strongly in fl uenced by the western portions of the subtropical Azores-Bermuda high-pressure cells that de- velop over the ocean (Windsberg 2003). During most years, a rainy “ wet season ” extends from June through October while a “ dry season ” occurs from November to May (Chen and Gerber 1991). A bi-modal pattern in rainfall is often observed with peaks in June and September (Duever et al. 1994). Tropical, low pressure storms and cyclones from the Atlantic and Caribbean bring heavy rain in late summer and early autumn, while fronts from the North American continent bring radical swings in temperature and humidity in late fall, winter and early spring. Sampling was conducted at four sites located along a salinity transect of Taylor Slough and include TSPh3, TSPh6b, TSPh7b, and the mouth of Taylor River (TRE). These sites correspond to the research sites monitored as part of the FCE-LTER (Florida Coastal Everglades — Long Term Ecological Research Program) and the US Geological Survey (USGS) (Fig. 1). The northern site, TSPh3, is located in the freshwater marsh region and is vegetated mainly with sawgrass ( Cladium jamaicense ) and muhly grass ( Muhlenbergia fi lipes ). Some isolated and dispersed dwarf red mangroves also make their appearance in this landscape. The marsh at TSPh3 typically dries out for several months every dry season, and does not often experience salinity values greater than 1 practical salinity unit (PSU). Site TSPh6b is an estuarine site located within the oligohaline ecotone. Dwarf red mangroves dominate the landscape at this site, but freshwater marsh vegetation such as sawgrass and spikerush grow amongst the dwarf mangroves. Surface water at this site is fresh for most of the wet season, and becomes higher in salt content (30 – 40 PSU) in the dry season. The estuarine site, TSPH7b, is dominated by mangroves. Surface-water fl ow at this point is largely unidirectional during the wet-season towards Florida Bay but may fl ow in either direction in the dry- season when frontal passage winds cause water from Florida Bay to move upstream into Taylor Slough. The site TRE is located at the mouth of the Taylor River and marks the end of Taylor River and the beginning of Florida Bay. At this site Taylor River is overgrown with mangroves. At TRE, typical surface-water salinity values are above 30 PSU during the dry season and below 20 PSU during the wet season. A water-budget for the Taylor Slough basin was developed on the principle of conservation of mass according to the following ...

Context 15

... reduction in surface-water ow throughout ENP allowed for an enhancement of seawater intrusion into the coastal aquifer along the entire coastline (Fitterman and Deszcz-Pan 1998). In the region of seawater intrusion, Price et al. (2006) con fi rmed that brackish groundwater discharged to the seasonally fresh coastal wetlands of the Everglades by a process termed coastal groundwater discharge (CGD). The CGD was found to be elevated in phosphorus, the limiting nutrient of the Everglades ecosystem (Noe et al. 2001). The extent of seawater intrusion and CGD co-occurred with the regional extent of the oligohaline ecotone, an area dominated by mangroves that marks a transition from freshwater to marine environments (Ewe et al. 2006; Childers 2006; Rivera-Monroy et al. 2011). The Everglades is currently at the center of one of the largest wetland restoration efforts as de fi ned by the Comprehensive Everglades Restoration Plan (CERP). One of the main objectives of CERP is to increase water fl ow through both sloughs in ENP ( Fig. 1). The increased freshwater fl ow is hypothesized to move the extent of seawater intrusion, CGD, and the oligohaline ecotone further seaward. In the case of Taylor Slough, quantifying the amount and location of groundwater discharge is essential to understanding nutrient cycling and ecosystem response to planned restoration efforts. The main objective of this research was to determine the timing and spatial distribution of groundwater and surface-water exchange in Taylor Slough. The objective was addressed using a variety of techniques across spatial and temporal scales. A water-budget was performed on a watershed scale at a daily time step over 18 months. Hydraulic-head measurements were monitored and logged at 30 min intervals in wells located along a salinity transect, while the geochemistry of groundwater and surface water was monitored on a monthly time step. Finally, temperature measurements were made at one location at 30-min intervals during three periods within the 18-month study. The results of this research provide baseline estimates of the major water-balance parameters, including groundwater discharge, in Taylor Slough prior to restoration efforts. Furthermore, the techniques used in this research may be applied to coastal wetlands world- wide such as the Sian Ka ’ an Biosphere reserve in Yucatan, Mexico, and the St. Lucia Isimangaliso wetland in South Africa. Taylor Slough is located at the southeastern end of the Everglades, which covers 10,000 km 2 of an elongated basin spanning 100 km from Lake Okeechobee to Florida Bay and sloping roughly 3 cm/km (Fig. 1). Taylor Slough occupies a slight depression in the underlying limestone bedrock and is bordered by broader areas 10 – 30 cm higher than the slough channel. The slough is dominated by emergent freshwater vegetation in the upper and intermediate portions and by mangroves in its lower part (Armentano et al. 2006). The southern section of Taylor Slough is characterized by a series of interconnected creeks and ponds. The boundary between Taylor Slough and Florida Bay is marked by a sediment laden ridge called the Buttonwood Embankment that is approximately 0.5 m high (Craighead 1971). This embankment restricts the overland fl ow of water to Florida Bay, making a few creeks, including the Taylor River mouth, the major discharges (Hittle et al. 2001). Sediments of Taylor Slough range in thickness from 0 to 150 cm and consist dominantly of Holocene age freshwater marls in the upland wetlands transitioning to mangrove peats in the southern region. Limestone bedrock of the Biscayne aquifer underlies the sediments but also crops out in places. The uncon fi ned Biscayne aquifer mainly consists of Fort Thompson, Key Largo and Miami limestone formations. Hydraulic conductivities exceed 3,048 m/day in the Biscayne aquifer (Fish and Stewart 1991). The climate in the region is humid, subtropical, and strongly in fl uenced by the western portions of the subtropical Azores-Bermuda high-pressure cells that de- velop over the ocean (Windsberg 2003). During most years, a rainy “ wet season ” extends from June through October while a “ dry season ” occurs from November to May (Chen and Gerber 1991). A bi-modal pattern in rainfall is often observed with peaks in June and September (Duever et al. 1994). Tropical, low pressure storms and cyclones from the Atlantic and Caribbean bring heavy rain in late summer and early autumn, while fronts from the North American continent bring radical swings in temperature and humidity in late fall, winter and early spring. Sampling was conducted at four sites located along a salinity transect of Taylor Slough and include TSPh3, TSPh6b, TSPh7b, and the mouth of Taylor River (TRE). These sites correspond to the research sites monitored as part of the FCE-LTER (Florida Coastal Everglades — Long Term Ecological Research Program) and the US Geological Survey (USGS) (Fig. 1). The northern site, TSPh3, is located in the freshwater marsh region and is vegetated mainly with sawgrass ( Cladium jamaicense ) and muhly grass ( Muhlenbergia fi lipes ). Some isolated and dispersed dwarf red mangroves also make their appearance in this landscape. The marsh at TSPh3 typically dries out for several months every dry season, and does not often experience salinity values greater than 1 practical salinity unit (PSU). Site TSPh6b is an estuarine site located within the oligohaline ecotone. Dwarf red mangroves dominate the landscape at this site, but freshwater marsh vegetation such as sawgrass and spikerush grow amongst the dwarf mangroves. Surface water at this site is fresh for most of the wet season, and becomes higher in salt content (30 – 40 PSU) in the dry season. The estuarine site, TSPH7b, is dominated by mangroves. Surface-water fl ow at this point is largely unidirectional during the wet-season towards Florida Bay but may fl ow in either direction in the dry- season when frontal passage winds cause water from Florida Bay to move upstream into Taylor Slough. The site TRE is located at the mouth of the Taylor River and marks the end of Taylor River and the beginning of Florida Bay. At this site Taylor River is overgrown with mangroves. At TRE, typical surface-water salinity values are above 30 PSU during the dry season and below 20 PSU during the wet season. A water-budget for the Taylor Slough basin was developed on the principle of conservation of mass according to the following ...