For the past several years, Floridians at all levels have talked extensively about restoring the Everglades.  Throughout these discussions, the fundamental process essential to the functioning of the Everglades ecosystem has been ignored, dismissed or rejected.  It is the basic physical process that historically nourished and sustained the Everglades. 

This process is evapotranspiration, or, as it is more commonly called, "ET".  ET is the Everglades' manifestation of the simple hydrologic cycle that every child learns about in school.  Water vapor evaporates from standing water and is transpired from plants into the air, rises into the sky, forms clouds, condenses and falls back to the earth.  This isn't a hard concept to understand.

What is harder to understand is how ET functioned in the historic Everglades, before they were ditched, diked and drained.  Florida, being surrounded by oceans, is the ideal place to collect moisture evaporated from the sea.  And for thousands of years, it worked fine.

Each day, as the sun warms the marsh, water vapor moves into the air above the marsh, making the air less dense, and therefore lighter. At the same time heat from the sun is absorbed by the earth's surface and re-radiated into the air above it.  The warmed air expands, and in the process becomes still lighter and floats upward.  As the mass of warmed air rises, cooler air flows under it onto the land from the surrounding sea, bringing with it more moisture that has evaporated into the oceanic air mass.  The rising columns of warmed air, cooling slowly as they rise, eventually reach an altitude, the cloud base, at which they can no longer hold the moisture they contain as invisible water vapor.  The water vapor condenses, forming clouds.  More oceanic air flows in on what we call the "sea breeze".  This air is in turn warmed and also rises, and the process is repeated continuously, all during the day. 

If there is enough moisture in the clouds that are formed, rain will fall from the clouds.  If and when the rain reaches the ground, if the soil is already flooded, it remains as standing water on the surface, from which it evaporates again into the atmosphere, and the process is repeated.  We call this process "The Rain Machine".   A particular water molecule brought from the sea on the sea breeze could be recycled through this process dozens of times before finally flowing back into the sea.

If on the other hand, the land has been drained, or paved over, or tilled for farming, when the rain reaches the land, it soaks into the soil, or runs off into ditches, and less of it is re-evaporated into the atmosphere.  Dry soil in the sun can become very warm, while pools of liquid water are seldom very warm, or if deep, tend to be even cooler.  Air rising above a dry field will contain less moisture than that which rises from the surface of a lake, pond or marsh, so it is more dense than moister air would be, creates smaller sea breezes, and brings less oceanic moisture onto the land.   Alternatively, when oceanic, moisture-carrying air flows over dry land, even though the air mass rises, the moisture levels may not be high enough to generate rainfall, or if rainfall is generated, it may re-evaporate before reaching the ground.  This is the condition being created when we drain large areas of former wetlands, such as the Everglades Agricultural Area, or "EAA".  In such a situation, even if water flows from the drained area when it does rain, that runoff is polluted by the activities on the area drained.  We understand how EAA runoff is polluted with phosphorus.  The result is that instead of clean rainwater falling and flowing through the system, the flow that does occur is contaminated industrial - agricultural - process water. 

One of the dangers of continued drainage of the EAA is that we are changing the overall amount of rainfall in the system, by eliminating the most productive source of rainwater, the flooded marshes of the area we now know as the EAA.  Long-time residents of South Florida are often heard to comment on the reduced frequency of afternoon thunderstorms in the summer.  They are not imagining this.  This is a serious issue, because both the natural system and the human cities surrounding the natural system require rainfall in order to have healthy populations of plants and animals, including people.  When the rainfall is reduced, the pressure on the natural system is increased, because human water requirements inevitably override the desire to protect the water supply for the natural system.

A few years ago, the late Arthur Marshall explained simply and clearly how important ET, and the rainfall that results from a flooded ecosystem, is to the human population of South Florida.  He listed all the surface inflows into Lake Okeechobee, quantified each of them, and added them up.  He then described the amount of evaporation that occurs from the surface of the lake.  The volume of the inflows were nearly equal to the evaporation from the surface of the lake.  The conclusion that flowed from these statistics was that the outflows from Lake Okeechobee were effectively due only to rainfall.  Without the abundant rainfall that historically existed before the system was modified by man, there would be two major results: first, water withdrawals from the lake will eventually consume all the water; and, second, nutrient levels in the lake will increase constantly through concentration resulting from evaporation.  There can be no flows out of the lake without either rainfall or back-pumping more contaminated water into the lake.  Therefore, without restoration of the Rain Machine, it is obvious that the natural system cannot be restored. 

The inherent defect of Aquifer Storage and Recovery, "ASR", is that water must be standing on the surface of the land, in the flooded marshes around Lake Okeechobee, in order to make the Rain Machine work.  But unfortunately, with ASR, the water necessary for this process is planned to be pumped far underground, where it cannot possibly contribute to the essential ET that makes the Rain Machine work. 

Every time the idea of reflooding the EAA and restoring the Rain Machine has been raised in recent years, both Water Management District and Corps of Engineers representatives have summarily dismissed it, citing unacceptable ET as the reason.  It is time to stop treating ET as an bad result of having standing water in the system.  ET, and plenty of it, is the beginning of a healthy Everglades ecosystem.  It is an essential component of the Everglades restoration.  We will not accomplish restoration until we come together to dispel the myth that ET is somehow harmful to restoration.  

The real, but unstated reason for objection to ET by the two key agencies in the Everglades restoration is that they live to build things, control water, and manage construction contracts, i.e., spend money.  The open-Everglades reflooding proposals, by their nature, don't need construction, won't provide a career for water managers to open and close floodgates, and don't give control of either water or vast sums of money to the agencies.  No wonder they don't support it.  If it is used, they don't have control of it, and Florida will have to live with the rainfall that nature provides, and survive on the water that falls outside the natural system.  But isn't that what restoration of the natural system implies anyway? 

There is another benefit of ET, and the Rain Machine, that so far has not been clearly stated.  It is FREE, that is, there are no operation costs.  Of course, the EAA land needed to make it work won't be free, but the cost of buying that land soon should be a lot less than perpetually paying to run pumps to pump water of uncertain quality up and down ASR wells and through other control structures.  Unlike the current restoration plan, ET requires no pumps, diesel fuel, gasoline, dredges, electricity, or any other artificial input.  It works on the solar energy which the Everglades receives in abundance.  Can we afford a restoration that requires constant inputs of money and expensive energy to sustain it?  We cannot.  The proposed restoration plan, as currently configured, is not sustainable and won't restore the Everglades.  Let's put ET, and the Rain Machine, back into our restoration plans as the essential elements without which we cannot restore the Everglades.

Michael Chenoweth
Former President and Special Advisor,
Friends of the Everglades