Wenger 72944 Especificações descarregar pdf (Página 135)

Section 3 Future Without Project Conditions

EAA Storage Reservoirs Revised Draft PIR and EIS February 2006

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Assuming the successful implementation of all of these projects there would be a

continuing decline of TP concentrations within the surface waters of the EAA.

Several other water quality parameters could be expected to change in response

to anticipated activities and land use changes in the EAA over the planning

period. For example, concentrations of organic nitrogen could decrease in

response to the water quality programs being implemented in Lake Okeechobee,

in the contributing basins to the EAA, and within the EAA. Total nitrogen

concentrations have been declining in the EAA canals since at least the 1970s,

apparently in response to changing farming practices and BMPs. These nitrogen

concentrations should eventually level off at approximately 2 to 2.2 milligrams

per liter (mg/L) based on normal background concentrations typical of South

Florida wetlands.

Dissolved oxygen (DO) concentrations in the EAA canals have averaged between

3.9 and 4.8 mg/L over the past four decades with no clear temporal trends.

These concentrations could increase slightly as a result of decreased nutrients in

Lake Okeechobee. The water in the canals is largely from the lake. Lower

nutrients in the lake will result in reduced levels of algae. This in turn would

reduce the organic load to the canals allowing dissolved oxygen levels to rise

slightly in the future. However, due to the physical nature of the canals and

their position in an area of wetlands and organic soils, DO concentrations should

continue to be depressed below the 5 mg/L Class III water quality criterion. DO

concentrations within the STAs and within natural wetlands in the Holey Land

and Rotenberger WMAs should remain similar to current conditions (typically <

4 mg/L).

Specific conductance increased in the EAA canals until the 1980s to an average

of about 1,028 microSiemens per centimeter (μS/cm) and has been decreasing

since that time. This decreasing specific conductance trend should continue in

light of changing agricultural practices in the EAA to near historic levels,

approximately 600 μS/cm, by the end of the planning period.

Levels of turbidity and suspended solids have declined slightly in the EAA

canals in the past decade. A continuing trend of decreasing concentrations is

expected in light of the variety of water quality improvement projects in and

around the EAA. This trend could result in EAA canal concentrations of

turbidity and suspended solids less than 10 Nephelometric Turbidity Units

(NTU) and 10 mg/L, respectively.

Sulfate concentrations in the EAA canals increased from the earliest records in

the 1930s through the 1980s when they reached a maximum decade average

concentration of about 97 mg/L. Since 2000, average canal sulfate

concentrations have declined to 1930s levels (about 42 mg/L). Total mercury

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Wenger 72944 Especificações Página 135