Our Cresting Water Crisis
Household water use accounts for a mere five percent of total water use. Agriculture, in comparison, comprises 70 percent of all fresh water withdrawn, according to the UN Global Compact CEO Water Mandate. Maintaining healthy water supplies is now among the greatest challenges facing the world and, as such, poses a great opportunity for engineers.
“For a healthy, sustainable future for the planet, developing methods of ensuring adequate water supplies pose engineering challenges of the first magnitude,” states the UN. Purdue engineers are responding to the call for help. Their work addresses the challenge on all levels, from quality to quantity, and on a scale ranging from remote satellite sensing to local hands-on sampling in the field.
While concerns about air quality and fossil fuel have gripped the American consciousness for decades, water is taken for granted by the average resident in most regions of the United States, the American Southwest being the biggest exception. Even in the research world, it has not received its due, according to Inez Hua, interim head of ecological and environmental engineering and professor of civil engineering.
“In the research world, water has not received as much attention as it should have in the last 15 years. There has been a lot of attention to climate change, but water has been folded into other areas, such as the transmission of disease,” observes Hua, whose research interests include water treatment, fate and transport of chemical contaminants, groundwater and soil remediation, and sustainability.
Purdue Engineering has had a standing presence in water-related research for many years, and the College is increasing its global standing with new faculty who bring additional perspectives to the discipline. Keith Cherkauer and Indrajeet Chaubey recently joined the agricultural and biological engineering faculty. Cherkauer, a hydroclimatologist, came with a background in aerospace engineering with a remote sensing focus. Chaubey is an ecohydrologist with an interest in nonpoint source pollution and watershed modeling. Other researchers around the College are tackling challenges at the municipal level: wastewater treatment; on an international scale: dryland hydrology in Tunisia; and in Space: water treatment technologies for space exploration.
Climate and water
Chicago, which claims to be an environmentally friendly city, recently completed a comprehensive study on climate impact that included input from researchers including Cherkauer. His particular interest in climate change and how evolving weather patterns influence water figured into the Chicago Climate Action Plan, which was unveiled in September and provides a comprehensive and detailed strategy to help lower greenhouse gas emissions and address climate change.
Cherkauer uses remote sensing information and hydrology models to study environmental change, land-atmosphere interactions, and the hydrologic cycle. His research on the impact of climate change, specifically precipitation and winter processes, has applications for infrastructure in areas like Chicago and for farmers who are increasingly affected by wet springs and dry summers. Engineers have traditionally designed bridges, dams, and levees based on 100-year flood levels. With changing rainfall amounts, however, the standard has changed. In the Southwest, increased drought is likely; in the Midwest, summers are becoming wetter, storms more intense, and flooding more common. Bridge design needs to anticipate this, Cherkauer says.
“We are confident that climate is changing,” Cherkauer says. “We design dams, bridges, and levees based on peak flow. That assumes nothing is changing. That no longer applies. If these structures are designed for the 100-year-flood, they may not be effective. Without estimates of what will happen in the future, it’s hard to know where to go.”
Cherkauer and the Hydrologic Impacts Group study areas ranging from the role of land management to hydrologic change in cold regions. In one study, Cherkauer and doctoral student Tushar Sinha used remote sensing information to study the impact of snow and soil frost on the surface water and energy balance in the upper Mississippi River basin. Using that data, they created models that show a trend of warming soils in the southern area and increasing soil frost in the north due to decreased snow pack, which is an insulator that has historically kept soil temperatures warmer. This information can be used by the construction industry, which has to accommodate for heaving soil. It can also predict potential flooding in areas where frozen soils are unable to absorb rainfall. Most flood forecasting does not take soil freeze into consideration, Cherkauer says.
“There is tighter collaboration with atmospheric scientists, studying vegetation growth, and soil mapping. It all leads to being able to improve long-range and short-term forecast work,” Cherkauer says. “With proper management, we can deal with the changes. We need to think about it as we design new infrastructures and methodologies.”
Clean water for all uses
Without water, agriculture is compromised. But with certain agricultural practices, water is compromised. It’s a cycle that Chaubey would like to see broken. His concern is water quality and nonpoint source pollution to ensure clean water, not just for human consumption but also for other ecosystems such as aquatic life and agriculture.
Among the challenges that motivate him are questions such as, “How can we optimize agricultural production but at the same time make sure water quality is unimpacted and good?”
Agricultural practice at a local level can have long-lasting and far-reaching effects. Much of the pollution in the Gulf of Mexico, for example, can be traced to fertilizers applied in the Midwest. Waters in the Gulf contain dangerously high nitrate levels. High nitrate levels contribute to increased algae growth, which then restricts the amount of oxygen available for fish and other life in the Gulf. The EPA Science Advisory Board’s Hypoxia Advisory Panel has recommended a 45 percent reduction of total nitrogen and total phosphorus flux if the size of the hypoxic zone in the Gulf is to be reduced. The panel feels that it is possible to shrink the zone from a current level of 22,000 square kilometers to 5,000 square kilometers. This brings Chaubey’s work into focus.
Ethanol production, while providing an alternative to fossil fuel, can have an environmental impact. Corn, the basis of ethanol, requires a lot of fertilizer. If uncontrolled, the fertilizer runs off fields and pollutes water sources. The answer is not to stop growing corn, Chaubey suggests. It is to institute management practices to minimize the loss of nutrients into water. This can be done by a variety of means, including injecting nutrients into the soil, using nitrate-removing wetlands that naturally process nitrates and then release them as nitrogen gas into the atmosphere, and building buffer strips at the ends of fields. Each of these has added cost for farmers and federal and local agencies, but resources are limited. “If you have only so many dollars to put into the field, where do you put them?” Chaubey asks. His investigation into how to protect water sources may help provide answers to that question.
Chaubey, who brought ecohydrology to Purdue when he arrived in 2007, conducts research in the field by examining how nutrients move through waterways. He is a principal investigator on a Conservation Effectiveness Assessment Project, one of 13 projects funded nationwide by the U.S. Department of Agriculture’s Cooperative State Research, Education, and Extension Service to evaluate how various management practices help improve water quality in agricultural watersheds and how the adoption of these best management practices (BMP) can be increased. The outcomes of this project should help various state and federal agencies, such as the National Resources Conservation Service and the EPA, to develop effective policy decisions on how agricultural watersheds should be managed.
Chaubey has also developed decision support tools to help users determine appropriate BMPs to reduce pollution. For example, he and his graduate students have developed methods to optimize selection and placement of BMPs that will maximize water quality improvement with minimum production and implementation cost. His team is currently using this tool to help various stakeholder groups determine various BMPs to control losses of nutrients, sediments, and pesticides from agricultural fields in Indiana.
Responding to a global challenge
In an address at the United Nations’ 2002 World Summit on Sustainable Development, Nitin Desai, secretary-general for the summit, spoke about the integral role that engineers could play in addressing the global water challenge:
“From digging wells to building dams, engineers have historically been prime providers of methods for meeting the water supply and quality needs of society. To meet current needs, which increasingly include environmental and ecosystem preservation and enhancement demands, the methods will have to become more sophisticated.”
Chaubey, Cherkauer, and their Purdue Engineering colleagues are not only providing tools that may improve the way that water is managed and protected but are also part of a growing global community putting their expertise to work on sustainable solutions. They are heartened to know that their work in sustainability will have an impact.
“It’s a complex problem, but it is very exciting because of the general awareness of the public and an increasing willingness to do the right thing,” Chaubey says. “Never before were so many aware of how our actions impact the environment and willing to do what it takes to minimize our footprint.”
– Linda Thomas Terhune