Lars Soderqvist
Hydrologic data will be used to: describe the hydrodynamic characteristics of the area; determine salinity patterns of rivers and estuaries; and provide baseline characteristics before the alteration related to ecosystem restoration efforts. This study also will provide data for the development and calibration of hydrodynamic/salinity models planned for the study area.
However, there is little information regarding the present-day quantity, timing and quality of fresh water flow to the Ten Thousand Islands. Current hydrologic models omit this area due to the complex nature of the hydrology and the lack of available data. The paucity of information poses a problem for the restoration with respect to identifying desirable surface water flow rates and assessing restoration success, as required under the Southwest Florida Feasibility Study and REstoration COordination & VERification (RECOVER).
Flow, salinity, and temperature stations have been constructed and instrumented at Blackwater River, Pumpkin River, Little Wood River, Faka Union River, and East River. One Water-level, salinity, and temperature station was constructed and instrumented at Faka Union Bay channel marker #6.
Continuous flow, salinity, temperature and water elevation at selected rivers flowing into the Ten Thousand Islands (10KI) will be measured by index velocity meters, water elevation sensors, and salinity-water temperature sensors that are permanently established at key locations for the duration of the data collection component of the study. These permanent stations will serve to provide a continuous, long-term record of change resulting from variation in flow. Regression analyses will be used to establish relations between flow at instrumented and non-instrumented rivers. These relations will be used to calculate discharge at all rivers within the study area.
Permanent stations can not be deployed to the extent necessary to adequately characterize all the 10KI bays and tributaries. Therefore, to achieve the greater aerial coverage necessary, individual boat surveys will be conducted. A flow-through chamber will be attached to the transom of a boat at 20 cm below the water surface, and a probe inserted in the chamber to measure salinity and temperature. The probe will be connected to a data logger with a Global Positioning Satellite (GPS) unit and record salinity, water temperature, time and location every 5 seconds (about every 5 to 10 meters) while the boat is moving. For every salinity survey, two boats will be used simultaneously to reduce the time required for data collection, and help to reduce the tidal data bias. The boats will travel from the lower bay area toward landward reach of coastal creeks, collecting thousands of individual data points that are used to create synoptic salinity maps representative of hydrologic conditions during the wet and dry season. This methodology has been used successfully in the Estero Bay Hydrologic and Salinity Evaluation Project. Multiple survey trips will provide an understanding of water quality conditions for the entire 10KI tributary and estuarine system that can be correlated to changes in measurements at the permanent stations.
We are performing 4 surveys per year (Wet Season, Transition to Dry Season, Dry Season, and Transition to Wet Season). Two (2) boat surveys (1 per season) will be conducted annually in conjunction with the operation of the permanent stations. Up to 2 addition surveys (1 per season) also are planned to typify extreme event conditions. These surveys will cover the areas from Everglades City to Goodland and from the rivers to the open waters of the Gulf of Mexico.
U.S. Department of the Interior, U.S. Geological Survey
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