Swamp and Circumstance

Planners hope the Natural System Model can help restore the Everglades. But will it survive politics?

"[The NSM] is very unprecedented," says Obeysekera. "We have never developed a model that tries to mimic what happened 100 years ago."

Modeling has come a long way in the century man has tried to engineer the Everglades. Hydrologists in the district's early years, before the advent of computers, used an analog model. It worked under the premise that electrical current could simulate the flow of Everglades water. They designed a giant circuit board to mimic the watershed: Resisters were supposed to behave like vegetation and delay the water, while capacitors served to store water, in the same way that current conservation areas do. Back then, to simulate the change in a canal, electrical engineers had to walk around circuitry mockups. Obeysekera says the U.S. Army Corps of Engineers even had huge adding machines that were hand-pulled to execute the massive calculations involved.

Today computer programmers and mathematicians input data in the form of algorithms, which are the basis for trillions of computer equations that make the Natural System Model move.

The 46-year-old Obeysekera arrived in the United States in 1978 from Sri Lanka. His work experience in the populous Third World island off the Indian subcontinent gives him a unique perspective on Everglades restoration. In his native land most rivers are diverted for irrigation. Flooding is common. There is little emphasis on environmental issues, and pollution is widespread. There are more problems in Sri Lanka than in Florida, he says. (Indeed many ecologists surveying the world's myriad environmental troubles believe that if a rich, technologically advanced nation such as the United States cannot restore the Everglades, the prospects for fixing similar problems throughout the world are grim.)

Obeysekera was teaching hydrology at Colorado State University when a colleague enlisted him to work on restoring Florida's Kissimmee River. The corps had straightened the meandering waterway in 1961 with ecologically disastrous results. (On June 5 the corps broke ground on a project to restore the river.) Even as a professor of hydrology, Obeysekera was not prepared for the complexity of the Everglades.

"We had textbooks and the normal hydrology that you teach and I come down here and I realize none of this hydrology is in textbooks," he still marvels.

Although the Everglades appears flat, it is in fact riddled with slight differences in elevation. Much of the original watershed was a vast system of interlaying ridges and channels called sloughs (rhymes with twos) through which water flowed. The changes in ground topography gently nudge water in certain directions and account for the diversity of plant and animal life. When the water level drops in the dry season, it concentrates in the sloughs. The shrunken pools of water increase the density of fish. Wading birds flock to these pools of water for an easy feast. Over millenniums the cycle of life evolved to follow the movement of water.

Some scientists believe the ridge and slough system is vital for the health of the Everglades. But these subtle changes in topography are a level of detail too small for the NSM to show. Perhaps the best-known example of this system is Shark River Slough, whose main path cuts through the northern end of Everglades National Park. Within this enormous slough are dozens of miniridges and sloughs. In the 1800s the closely held secret to Seminole and Miccosukee navigation was their knowledge of the ridge and slough system. Where whites saw impenetrable saw grass, the Indians knew how to follow the natural channels, the key to getting around the maze. Today the airboater who does not know ridges and sloughs may end up waist-deep in muck pushing his boat off a rise.

In order to model the flow of water, scientists must take into account the topography and the vegetation. In addition the southern third of the Everglades sits on porous limestone that covers a huge aquifer of water and acts like a giant sponge. The rate by which water disappears through movement, evaporation, and absorption must all be factored into the model.

Obeysekera admits the NSM is so new and complicated the modelers are unable to test for accuracy. "We are trying to find ways of doing uncertainty analysis for NSM correctly," he says.

The problem is too many variables. The NSM covers 9312 square miles broken into 2328 two-mile-by-two-mile computational cells. Each cell is interconnected to its neighbors in different ways. "You have to change the system many, many times to do an uncertainty analysis because to change one point in the system is to change everything," he explains.

Scientists hope to add data to the Natural System Model in an attempt to craft a more precise tool for policymakers.

One area that will make the NSM more reliable is soil analysis. For the past three years Christopher McVoy, a district ecologist, has sifted the layers of the Everglades earth in an enormous detective job. Through his research he reveals the alterations in soil before and after engineering met the natural system.

"The changes to the ecology of the area began almost immediately with drainage [in the late 1800s]," McVoy says.

Because ecologists know how some key vegetation thrives at various water levels, by looking at soil evidence dating back 100 years they can try to deduce how much water was once there. The implications are potentially enormous.

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