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The Habitable Planet: A Systems Approach to Environmental Science 

Water Resources Interview with Wendy Graham

Interviewer: Can you tell us who you are and what you do?

WENDY: My name is Wendy Graham. I’m a professor and director of the Water Institute at University of Florida, and I hold the Swisher Chair in Water Resources.

I’m a hydrologist, and I study the timing, distribution and movement of water around the earth’s system, in particular, the terrestrial portion of the hydrologic cycle, which describes the way water moves about the earth’s system from the atmosphere through the earth to the oceans and back up into the atmosphere.

Interviewer: What got you interested in science?

WENDY: I grew up in the Bahamas and spent most of my time outdoors. There weren’t a lot of indoor distractions. Very few movie theaters, no shopping malls. So we spent our Fridays and Saturdays on sailboats in the ocean. And that crystal clear beautiful water with the abundant sea life was fascinating. Then we’d get home to shower and the water would be off, because we only had water from 6 am to 2 o’clock in the afternoon. We had very limited fresh water and very abundant salt water and I got interested in water resources thinking about that dichotomy.

Interviewer: Have you always had this idea of water as a limited resource?

WENDY: We knew it was limited; we lived on the little island and we had our well here, and then we had our septic tank here. And that proximity I always found kind of fascinating. There was the city water system that was on from 6 am to 2 pm, and then there was our personal well system, which we could use to supplement, but the water was brackish, so it wasn’t drinkable. We did shower with it and that sort of thing. Then when the electricity went off, the pump wouldn’t work, and we wouldn’t have water.

Interviewer: What is your fundamental research question?

WENDY: What we are trying to do is understand enough about the processes that control the movement of fresh water on and under the earth’s surface so that we can predict changes that will occur due to human pressures, land use development, and changes that may occur due to climate perturbations. We would like to understand the processes enough to be able to predict future outcomes of manipulations to the system. One of the biggest questions in the Suwannee River basin is trying to define what the hydrologic carrying capacity of that basin is. It’s one of the largest, unregulated rivers left in the US. It’s in a relatively underdeveloped region of Florida. There’s a lot of development pressure. There’s a lot of competition for those water resources. People in Tampa and Miami look up to north central Florida and think, “If California can move their water across the state, why we don’t go ahead and do that”? So we are interested in understanding what the requirements of the natural system are for the timing and distribution of water, how much water can be extracted from this system for human uses without interrupting the ecological function and also understanding how major land uses in that basin, particularly agriculture, affect the water quality in the river.

Interviewer: Is your research statewide, countrywide, and worldwide?

WENDY: Some of it is fundamental and it is not attached to any particular place right now. Most of the fieldwork I’m involved in is in Florida, but at times we’ve worked in Utah and Delaware and we hope to work internationally. But Florida is a very interesting place hydrologically. There’s a lot of fresh water and a lot of people and a lot of land use changes going on. Especially in this north central part of Florida, there is a lot of fresh water. There is the highest concentration of first order of springs in the world. It occurs right in north central Florida. There’s a huge reservoir of fresh water under the land surface that even in times of drought is emerging in the springs and flowing into the rivers. So we don’t get to the point here in this part of the state where we have utilized and over-utilized the resources so much that the Suwannee River itself would run dry. Some of the up line tributaries are probably dry now.

Interviewer: Much of your research relates to moving water, correct?

WENDY: Right. There are a lot of scientists that study various aspects of water. There are limnologists that study ecological process in lakes. There’s wetland scientists that study processes in wetlands, but what hydrologists do, what I do, is study the movement of water through the landscape and try to predict where it’s going to go and what it’s going to carry with it.

Interviewer: What is an “unregulated” river?

WENDY: An unregulated river flows according to gravity from its source to the mouth and is not interrupted by dams or hydroelectric power. It’s just allowed to flow freely in its natural state. And there aren’t too many rivers like that left in the US.

Interviewer: Is that why you’re studying the Suwannee?

WENDY: That makes it a little bit interesting, that it is closer to a natural condition than for example, South Florida, which is highly engineered and regulated. There are pumps and lift stations and locks that control where water moves and how it moves.

Interviewer: What human impact is there on the Suwannee?

WENDY: One of the most pressing changes that’s occurring in the Suwannee River basin is the increasing concentrations of nitrate in the springs that feed the river. And the source of that nitrate is human, saprogenic—either agricultural activities, or urban activities from waste water treatment plants or septic tanks. One of the questions we have been looking at over the last several years is how agricultural practices can be manipulated to minimize the loss of nitrate into the ground water, so we are looking at alternative irrigation practices, alternative fertilization practices, alternative cultural practices that keep most of the nutrients in the root cell where the plant can use them.

Interviewer: Can you describe the fresh water problems in this area?

WENDY: If you look at this north central part of Florida I think that major human influence has been in perhaps decreasing the levels of the aquifers in the Florida aquifer, which supplies the water for the region and also in enriching the natural sources of water with nutrients. I think those are two widespread issues that Florida is dealing with. Every water management agency in Florida is now charged with defining minimum flows and levels of all ground waters and rivers, lakes and wetlands. (The minimum flow or level is that level at which further extraction of water will harm the natural system.) There are two programs; the minimum flows and levels programs, which are trying to basically define the base level system to sustain the ecological framework, and then there’s the TMDL program, the Total Maximum Daily Load Program, which is trying to define the maximum contaminate concentration these water bodies can withstand without disrupting the natural system. The EPA mandated that these total maximum daily loads be implemented for all major water bodies in the country. And not much happened for a few decades. The heat is being turned up to go ahead and define these levels, and there’s not a lot of scientific information that already exists to help with that sort of thing, so we’re working to help them figure out what the minimum flows and levels are and what the maximum contaminant levels are that these ecosystems can withstand.

Interviewer: How do you define a “river basin”?

WENDY: Basically the river basin is that land area over which rainfall contributes to the river flow. Rainfall that falls within the river basin contributes flow to that river. If it falls outside the basin, it’s going elsewhere. It’s a topographical boundary that defines the source of water for the river. And it’s a scale-dependent thing. If you’re talking about a tiny stream, it’s fractions of a kilometer. If you’re talking about the entire Suwannee River, it’s 25 thousand square kilometers. We have a complicating factor here in that Florida is pretty flat and it’s not as easy to define those topographical boundaries. We also have an issue that the river has a major ground water source, and the ground water basin may not coincide with the river basin. Again, it’s the heterogeneity that makes the details so difficult to predict.

Interviewer: How does nitrogen get into the ground water?

WENDY: One of the driving forces for the loss of nitrogen to the natural system is irrigation. The sands in north central Florida have a very low water holding capacity. So when rainfall occurs or the field is irrigated, the nutrients move quickly below the root zone. So managing irrigation to only replace the water that’s lost by evapotranspiration is important.

Interviewer: What’s evapotranspiration?

WENDY: Evapotranspiration is the process by which water moves through the plant up into the atmosphere or from the solar surface to the atmosphere. The “evapo” part is from the cell surface and the transpiration part is through the plant. But both of them release water from the earth to the atmosphere.

Interviewer: In addition to managing irrigation, is there anything else you can do?

WENDY: Nutrient management—looking at the timing and placement of fertilizer to put it, first of all, at times of the years or the season where it’s unlikely to rain, or less likely to rain, so more likely to stay in the vicinity of the plant roots; formulations of fertilizer that are less soluble and less likely to leach; and placement—going from broadcast fertilization where you spread it over the entire land surface to very site-specific injection at the root zone. There are people that I work with that look at the plant response to the various ways of applying water and nutrients. They look at the engineered systems, how to control the water application based on solar moisture sensors. And what I do is take those inputs and try to predict the movement of the water and the nutrients into the environment.

Interviewer: Why should we be concerned about nutrient management?

WENDY: Anytime more nutrients than normal get into the natural system it disrupts the ecology and it changes the balance of flora and fauna and new things grow that weren’t there before. In particular, in the springs of north central Florida, they are evolved to have very nutrient poor water. So when this ground water is enriched and it emerges from the springs, it alters the ecology and increases the growth of algae and other organisms that aren’t naturally there. Eutrophication of the nation’s surface and ground waters is ubiquitous. In our particular area the country, the springs are a focal point. But in other areas it’s the Mississippi River, or it’s the Platte aquifer. It’s the most pervasive environmental water quality condition in a country.

Interviewer: How do you collect data?

WENDY: We use physical sensors to detect soil moisture in the root zone, and to observe the transport of water from the land surface to the ground water. We have pressure sensors within the ground water system that track the fluctuations of the water table and then stream gauges in the river that measure the flux of water through the river. We look at the response of ground water levels and river flows to the climatic forcing. There are other people that look at the chemistry of the water, so they look at the nutrient composition and the ionic composition of the water, and how that varies throughout the landscape. There are other people that look at the biology of the system and the ecology of the system, and look at how various parts of the landscape have different balances of various organisms.

Interviewer: What kind of multi-disciplinary collaboration exists in this research?

WENDY: Our research project is a collaborative effort throughout the watershed. We have geologists that are trying to understand the physical processes by which the water moves through the rock matrix. We have ecologists that are trying to understand how the differences in stream chemistry affect stream ecology. We have horticultural scientists who are trying to understand how the application of water affects plant growth and agricultural productivity. We have fish ecologists that want to understand how the timing and distribution of fresh water from the river affects the hatcheries in the Gulf of Mexico. There’s a wide variety of interdisciplinary work that goes on if you’re studying a watershed as a unit. We have engineers that are interested in storm water—how the cities control their storm water and how they release that back to the natural environment. In Florida we collaborate with Florida State University, which has a very strong meteorology department, so we work with them to understand the climatic and oceanographic influences. We work with FSUN, University of South Florida on that. There are collaborations that go across universities and with other regulatory and management agencies in Florida.

Interviewer: Where does the study of freshwater resources fit into a wider study of ecology?

WENDY: Our research in water resources fits into a larger context looking at the sustainability of human civilization on the earth, and how we can use our natural resources and manage our natural resources, and understand the influences of various actions we have on the natural system. We study water, but others study air and plants and animals and that sort of thing. Water is sort of the connector. Almost everything requires water, and is influenced by the timing and distribution of water delivery. The simple model that kids learn in the third grade is valid. They learn that water evaporates from the land surface, condenses in the atmosphere and returns to the earth’s surface as precipitation, and that is certainly what happens. But what’s complicated about hydrology is that the heterogeneity of the land surface makes it very difficult to predict where the rainfall is going to occur, where the evaporation is going to occur, and where the ground water is going to get recharged and how that water will emerge into the rivers. It’s a little simpler to predict how the water evaporates off an ocean surface because it’s homogeneous, it’s all ocean. And they have some waves, but compared to the heterogeneity on the terrestrial system, it’s not so difficult to predict.

Interviewer: Why did you choose to do this research?

WENDY: I think right now the biggest question that we don’t know the answer to is how far we can stress the system and not push it past the point of no return. How much water can be withdrawn from the Suwannee River basin and not cause ecological collapse? How can we allocate water among humans systems and agriculture and not end up with an 8 billion dollar restoration project in 20 years? We’re trying to understand the system and then water demands of all the users including the natural system so that we can manage the water more effectively and quickly. The Suwannee River basin in Florida is relatively underdeveloped, as opposed to South Florida, which was heavily developed in the 1950s after the huge drainage project that basically drained the Everglades and created agricultural land and urban lands for people to live on. But 20, 30 years after that process, people started discovering the harm that it was doing to the Everglade system. What we would like to do is understand the needs of the natural ecosystem as well as the needs of humans as well as the needs of agriculture so that we don’t pass that tipping point and have to spend 8 billion dollars for restoring the Suwannee River basin like we’re having to do in the Everglades.

Interviewer: How long will this research take?

WENDY: One thing about earth science research is that if you’re going out to study a drought, it’s going to rain and if you’re going out to study floods, there’s going to be a drought. So you really need to carry on the observations over an extended climatic record to really understand the system. Two or three year snapshots can be very skewed depending on the weather that occurs during that study. So it’s a long-term process, and I think most people understand that we’ll have to continuously monitor and adapt our management based on how the system responds.

Interviewer: An acceptable level of environmental impact can be difficult to agree upon.

WENDY: There’s really no one minimum flow for which the ecosystem can withstand water being extracted. But what we hope to do is to be able to understand the trade offs, because to have no impact, there would have to be no humans. All other organisms impact the environment where they live, so we are basically trying to understand those impacts, and understand the trade offs between more water extraction for agriculture versus more water for cities versus enough water for the ecosystem. And there’s no optimum solution, but there’s sort of a trade off curve where in the end people have to decide what kind of world they want to live in.

Interviewer: Of all those uses, which causes the biggest stress?

WENDY: The largest user of water in this region of Florida is agriculture. In fact, the largest user of fresh water is agriculture. But public water supply is a close second, and in the not too distant future I’m sure we’ll catch up and overtake agriculture as the major user. Beyond the use of water, the contaminants that that water is exposed to as it’s extracted and used and returned to the environment are also of concern. Those are different among urban and agricultural uses, but both users of water influence its quality.

Interviewer: What are the concerns related to public water use?

WENDY: Florida’s population is growing. There are about 16 million people that live in Florida now. It’s projected to go to 20 million by the year 2020, so as more people move into the area, there’s more demand for public water supply. Those people move into agricultural areas, shrinking both the agricultural areas and the efficiency with which agriculture uses water, so ultimately humans will become the largest consumer of water–for drinking–in this state.

Water is a finite resource. There’s no more water being created on the earth. We have all we’re going to have. So if human populations continue to grow, we will have to make some trade offs on what quality of water we use to bathe in, for example. Do we need drinking water quality to bathe in? Do we need drinking water quality to water our lawns? There are trade offs there.

Interviewer: What happens if we don’t make trade offs?

WENDY: If we just keep on going without worrying about it? Well, aquifers get depleted. Water quality becomes more and more expensive to provide water for human populations. I mean, we’ve got huge oceans that we can take the salt out to provide for drinking water, but that takes energy, that depletes oil or requires other energy sources. It’s definitely a balancing act, and if we don’t start thinking about it now earth may not be such a pleasant place to be.

I think if we control the population we’ll be in good shape. It cleanses itself. It’s just that when you overload it with too many people at a particular place, a particular time, those natural mechanisms break down or can’t keep up.

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