Estimation of Inputs to Florida Bay
Inputs from Florida Mainland - LoadsJuly 1998 Project Index | Estimation of Flows | Provide Comments Introduction | Methods | Preliminary Results | Additional Tasks This section develops preliminary estimates of nutrient loads from the Florida Mainland using flow estimates derived from ENP water balances and concentrations measured at ENP marsh and coastal monitoring stations. Supporting water quality data are displayed in the following forms:
The locations of all regional monitoring stations are shown on the attached map. Stations used in load calculations described below are shown on another map. Coastal stations (projects FLAB & TTI ) are operated by FIU. Structure stations (projects ENP & CAMP, station codes starting with 'S') and marsh stations (project EVER, station codes starting with 'P') are operated by SFWMD. Germain (1998) provides details on station locations, sampling procedures, and analytical procedures. Salinities were generally not reported at SFWMD stations and have been estimated from conductivities using the following equation calibrated to data from FIU stations: Salinity (ppt) = 0.00062 x Conductivity (micro-mhos/cm) Salinity values indicate that coastal stations (projects FLAB & TTI) are influenced to various degrees by seawater. Concentrations of nutrients and other water quality components measured at these locations partially reflect tidal exchanges between the mangrove areas and the Bay. As the flow leaves the ENP marsh areas and enters the coastal zone, concentrations of total phosphorus increase and total nitrogen decrease. Boyer & Jones (1998) describe similar patterns in the Ten Thousand Island / Whitewater Bay area. Some of the apparent increase in phosphorus concentrations may be attributed to differences in laboratory analytical procedures between the SFWMM and FIU labs. Nutrient cycling in the mangrove areas is another potential factor; Rudnick (1998) noted the tendancy for phosphorus concentrations in the mangrove regions of southern Taylor Slough to exceed those measured in the Everglades marshes and Florida Bay. Increases in phosphorus concentration may be partially attributed to ET rates exceeding rainfall in the mangrove areas; this mechanism would not influence phosphorus loads, however. Emergence of hypothetical "underground rivers" in these areas may also contribute to the changes in nutrient concentrations and loads (Brand,1998). Mainland -----> Mangroves <------> Bay <-------> Reef/Gulf Given the apparent tidal influences on the coastal stations and given the fact that the Florida Bay water quality model does not simulate nutrient transport from the Bay to mangrove areas, it does not seem appropriate to use concentrations measured at coastal stations to calculate loads from the Florida mainland. Concentrations measured at the southernmost ENP marsh station in each basin have been used as the primary basis for calculating net loads from the mainland. A secondary set of load estimates has been developed using coastal stations for use in sensitivity testing. These may reflect gross loads from the coastal areas to the Bay, not the net loads required by the water quality model. Preliminary results described below indicate that phosphorus loads entering the Bay from the mangrove areas are approximately three times those entering the mangrove areas from the Everglades marsh (assuming no net change in flow). The analysis does not quantify nutrient fluxes from the Bay to the mangrove areas, however. Given the significant changes in nutrient concentrations and loads moving through the mangrove areas, nutrient dynamics in these areas may have significant impacts on formulation of Bay nutrient balances. Comments, articles, supporting data, or alternative interpretations of the concentration patterns discussed above would be appreciated. The following algorithm has been applied to estimate monthly total loads for each water-quality component and ENP watershed:
Structure inflow loads to each ENP watershed are computed using the same algorithm. Measured daily flow time series are used for each structure. Total inflow loads to each watershed are computed by adding up the individual loads from each structure. The following table identifies the monitoring stations used in each watershed:
Stations in each category are identified on the attached map. Periods of record specified in the above table are determined by the durations of monitoring at marsh and coastal stations. Results will be extended through 1997, once flow estimates have been developed for 1996-1997. The following table identifies measured water quality variables in each set of stations:
Although TSS is routinely measured at ENP marsh stations, more than 50% of the observations are below detection limits, which range from 1 to 3 ppm. Concentration time series are not constructed for TSS. Instead, a constant inflow concentration of 1 ppm is assumed. An attempt can be made to construct concentration time series, if the water quality model is sensitive to TSS loads. The following table summarizes the equations and assumptions used to translate loads computed for the above measured water quality into loads required by the water quality model:
Sensitivity of model results to these assumptions should be determined. Software will be provided to generate load data files for alternative assumptions. Preliminary Results The following table summarizes calculated flow and nutrient balances for each ENP basin in Calendar Years 1995-1997. Outflows are reported using each set of monitoring stations (marsh, coastal). All stations were routinely operated over this period, with the exception of coastal stations used to calculate loads from the ENP West basin (Stations TTI61, 62, & 63) and Cape Sable basin (Stations FLAB44,45, 47), which were established in July 1996. Estimates for 1995 are based upon average concentrations in 1996-1997. These basins are relatively small and do not have structure inflows, so the impacts of missing concentration data for 1995 are likely to be small.
Another attached table (PDF format) contains yearly-average flows and flow-weighted-mean concentrations for each structure and ENP basin in 1995, 1996, & 1997. Preliminary results are displayed in the following formats: The following additional tasks are required to develop refined estimates of nutrient loads from the Florida Mainland:
http://www.wwwalker.net/flabay/enploads.htm Updated: 03/30/02 |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
