The importance of the water-energy nexus in Florida's future.

• Author: Baker, Keri-Ann C.

Florida has a long history and complex relationship with its most prominent resource: water. From the early efforts to drain swamps and channelize rivers, to the more modern efforts to restore habitat and preserve the natural environment, water is at the heart of what defines the state. Yet despite the apparent prevalence of water, increased urban development, utility demands, and the massive agriculture industry place demands on this ultimately finite resource.

The U.S. Government Accounting Office (GAO) has issued a series of reports that explore the critical interplay between water and energy production. These reports provide an important overview of how energy production utilizes significant amounts of water at every stage of the process. This article explores the findings of those reports, and discusses recent proposed legislation reflecting a growing understanding of the importance of this issue by our state legislators.

GAO's Findings on Energy and Water

There is significant interaction between energy and water demands because each requires varying inputs of the other to be viable. Water treatment, distribution, and disposal each generate different levels of energy demand. In areas with difficult terrain or where desalination is necessary, energy requirements escalate dramatically. At the same time, energy production has always required voluminous water availability. Thermoelectric power plants produce the majority of electricity in the U.S. These plants must have water available for cooling and steam generation. Similarly, the expansion of biofuel production has increased the demand for irrigation, which is already the largest consumer of water in the nation. Additionally, the new techniques developed for oil and natural gas extraction all rely on significant water inputs.

Thermoelectric Power and Water: GAO-10-23

The GAO first began to examine this issue in 2009 with the release of its report, "Energy-Water Nexus: Improvements in Federal Water Use Data Would Increase Understanding of Trends in Power Plant Water Use." (1) The report found that as of 2007, thermoelectric power plants generated approximately three-fourths of the electricity in the United States. These plants rely on massive water inputs to moderate temperatures during the power generation process. Although this water is not "consumed," but rather returned to the source at an elevated temperature, it nevertheless mandates an uninterrupted water source.

As with many water-energy issues, the location of a thermoelectric plant is a major determinant as to whether a current or future water constraint will exist. Because the cooling process can rely on virtually any water source, siting options vary. However, even when there is an adequate water supply, the use of the water can still have negative environmental impacts. For example, the cycling and increased temperature of the outflow can impact the surrounding water bodies.

There are alternatives to the current standard operational models that require less water, but these alternatives can be both costly and less efficient. Air-cooled steam cycling is one such alternative. However, because the heat density that air will readily absorb is much lower than that of water, the energy generation rates and the capital costs to implement this technology result in a higher energy-output cost. Another approach involves utilizing alternative water sources, such as treated effluent or groundwater that is...