Hydrology of the Everglades

Hydrology of the Everglades

Historically, Lake Okeechobee's water level would overflow during the wet season creating a sheetflow across the Everglades. Before water management projects started in the early 20th century South Florida was a vast and pristine landscape made-up of wetlands, dry prairies, sawgrass plains, swamps, mangrove forests and freshwater/salt water marshes (Renken, et al. 2005). The yearly sheetflow of surface waters through the Everglades from the south to southwest provided the Everglades ecosystem with a regular water supply. Precipitation and evapotransporation were the primary drivers of the hydrologic cycle of the pre-drainage Everglades . Sheetflow across the entire southern tip of Florida would discharged , toward the Gulf of Mexico and through the transverse glade areas springs reportedly discharged as freshwater boils (Genereux & Slater, 1999).

Evolution of the Hydro-ecological processes and the role of the surface water and groundwater interactions were a relatively small component of the Everglades water budget prior to its drainage in the early 1900’s.

The thin freshwater layer that lies over older groundwater not only plays a role in assisting the Everglades during a drought period but can also offer hints about the changing role of groundwater over a century of water management in the Everglades.(Harvey & McCormick, 2009)

Goal 1: Drain the land for Urban Development and Agriculture

About 1545 ha area was drained and farmed in the mid-1900’s, but was later returned to management as a constructed wetland.

Goal 2: Redirect Sheet flow

In the past the sheet flow moved through the wetland system moving south. Overtime canals and levees were added and narrowed the flow separated the Everglades into a series of water conservation areas, WCA’s.

Goal 3: Provide Flood Prevention for Agriculture/Urban Areas

Channelized Water From Lake Okeechobee now discharged into thee Atlantic Ocean/Gulf of Mexico for drainage and flood control were constructed in 1910.

Goal 4: Supply water for Agriculture/Urban Use

During the second half of the twentieth century the dependence on canals increased as the wetlands were converted to agriculture. As population increased the demand for water increased, leading to more municipal well fields and more drained land.

Goal 5: To Provide adequate water supply the the Greater Everglades Region

By 'storing' water in conservation areas the engineers of the time thought they were helping to maintain the helth of the ecosystem by maintaining a steady water level

The interactions between groundwater and surface water have increased due to water management and have caused less storage of fresh and uncontaminated water in the aquifer beneath the Everglades. Recharge and discharge could be effected by gravity waves which occur when water managers release surface water from upstream through control structures and send it to downstream basins. (Harvey, et al., 2004)

When the sudden discharges of freshwater occur they result in the rapid deaths of sea grasses and invertebrates. As saltwater continues to intrude we will see a steady loss of freshwater, mangrove forests and wading birds. As well as peat collapse and a redistribution of sediments.

Sources

Genereux, D., & Slater, E. (1999). Water exchange between canals and surrounding aquifer and wetlands in the southern everglades, USA. Journal of Hydrology., 219 (3-4), 153-168. Retrieved from http://ezproxy.fgcu.edu/login?url=http://search.proquest.com/docview/49150444?accountid=10919

Harvey, J. W., & McCormick, P. V. (2009). Groundwater's significance to changing hydrology, water chemistry, and biological communities of a floodplain ecosystem, everglades, south florida, USA. Hydrogeology Journal, 17(1), 185-201. doi:http://dx.doi.org/10.1007/s10040-008-0379-x

Harvey, J. W., Krupa, S. L., & Krest, J. M. (2004). Ground water recharge and discharge in the central Everglades. Ground Water, 42(7), 1090-1102.

Kisekka, I., Migliaccio, K. W., Munoz Carpena, R., Schaffer, B., & Li, Y. C. (2013). Dynamic factor analysis of surface water management impacts on soil and bedrock water contents in southern florida lowlands. Journal of Hydrology, 488, 55-72. doi:http://dx.doi.org/10.1016/j.jhydrol.2013.02.035

Renken, R.A., J. Dixon, J. Koehmstedt, A.C. Lietz, S. Ishman, R.L. Marella, P. Telis, J. Rogersand, & S. Memberg (2005). Impact of Anthropogenic Development on Coastal Ground-Water Hydrology in Southeastern Florida, 1900-2000: Reston, Va., U.S. Geological Survey Circular 1275, 77 p.

THE END

Historic Hydrology of the Everglades

Eric Frankovitch and Mackensea Larson

Everglades Book

Early 20th century Water Management Projects

Pre-drainage Post-drainage

Manipulating the Hydrodynamics of the Everglades Did What...?

(Renken, 2013)

Destroyed the historic sheet flow, altering the hydrologic cycle thus impacting the freshwater supply, hydraulic gradient and hydraulic conductivity, altered the soil composition, caused peat oxidation, increased saltwater intrusion,subsidence, and surface/groundwater interaction/contamination, and other hydro-ecological impacts that are still being investigated today.

The changes made to the Everglades had unpredicted consequences from altering the modern flow direction toward the east and south toward Florida Bay. As a result of the levees that were put in place to create water containment areas groundwater from the northern areas is transferred quickly to the south, bypassing the Biscayne Aquifer and its overlying wetlands. Much of this groundwater is taken from ENP, and is delivered back to the natural system (i.e. aquifer and marshes) at the southern tip of Florida close to the coast. This effect of the drainage canals (capturing groundwater and moving it south toward Florida Bay) may be good for flood control it creates problems for ecosystem restoration.(Harvey & McCormick, 2009)

Altered the Natural Hydro-period for the Region. The hydro-ecology of the Everglades is sensitive to its hydro-period and water depth. As the hydro-period grew shorter and water level got lower in some areas, other areas experienced prolonged hydro-periods and above average water levels. (Genereux & Slater, 1999)

(Renken, 2013)

Water Consumption

(Renken, 2013)

Restoring the Hydrology of the Everglades

The Everglades Nutrient Removal Project (ENR) was designed in the 1990’s to remove nutrients from agricultural drainage waters that move toward the Everglades.

In order to restore more natural flow patterns in wetlands then changes need to be made to infrastructure and operations. (water exchange between canals and surrounding aquifer)

In an attempt to correct the damages caused by human interference with the Everglades an environmental restoration project was established.

Called Comprehensive Everglades Restoration Plan (CERP)

Goals include reducing impacts on Everglades National Park (ENP) and Taylor Slough. (Dynamic factor analysis of surface water management impacts on soil)=(Kisekka, et al. 2013)

Transmissivity

The demand for fresh water to supply urban development and agriculture has nearly crippled the hydrology of the Everglades. If we continue to rely on canal drainage waters to meet our hydrologic goals than we may find that we will use up all of our drinkable water and we will have polluted the rest. (Harvey & McCormick, 2009)

The decrease in the hydraulic conductivity from the east to the west is caused by the changes from high-porosity limestones and coaser sands in the east to limestone that is more compacted and with finer sands in the western part of the Everglades. (Harvey & McCormick, 2009)

(Renken, 2013)

Saltwater Intrusion 1904-1995

(Renken, 2013)