The High-Tech Way to Use Less Water
December 2004 / January 2005
Volume 2 Number 6
You might get some argument about what is the world's oldest profession, but farming would certainly be near the top of the list. Applying water and seeds to soil led to settled communities where people could cultivate the crops that allowed for more comfort and security than hunters and gatherers ever knew. Over time, managing water resources for efficiency and fairness led people to technological and social innovation. Irrigation and bookkeeping are the offspring of ensuring that the water is where you need it when you need it, the crops you plant receive their fair share of water and you receive a fair allocation in kind or cash for your planting and harvesting efforts.
When we learned that water can carry disease-causing microbes, another level of technological innovation opened up. Drinking water, which had never received much attention beyond there being enough of it to water our herds and refresh ourselves, became a medium for medical research. Identification of the role of water in the spread of diseases led to water-treatment technologies that have provided a measure of protection against many of the scourges, including cholera, typhoid and dysentery, that still can sweep through regions without adequate water safety facilities.
As climate change, deforestation, poor agricultural practices that diminish the land's productivity, population growth, and rural poverty and flight to the cities have reduced the arable land and the people willing to work it, water for agriculture and drinking is again seen a precious commodity, one worth fighting for. Access to fresh water is a critical international security issue. Experts predict that by 2015 nearly half the world's population—€”more than three billion people, mostly in Africa, the Middle East, South Asia, and China—€”will lack access to fresh water. This shortage can lead to increased frequency of international water-related disputes, conflicts and wars. Clearly, innovation in water security, safety and sustainability is even more important today than it was at the dawn of civilization as growing global population and increasing consumption puts greater stress on the available resources.
The Science of Water
Sandia National Laboratories is applying innovation to all aspects of water, including conservation, treatment, use and quality monitoring, infrastructure security and decision modeling. Scientists and engineers are developing dynamic simulation decision modeling software to help water managers integrate the complex relations between water supply, demand and quality as well as economic productivity, demographics, environmental impacts and social/cultural values. In partnership with the Environmental Protection Agency, water industry associations and water utilities, Sandia is developing a comprehensive program for protecting the water infrastructure, including its copyrighted Risk Assessment Methodology software for Water Utilities, RAM-W—„. The labs' efforts in use and quality monitoring reflect its expertise in microchemlab and other sensor technologies, as well as its international connections. Sandia, through its Cooperative Monitoring Center, has initiatives on environmental and water issues in South, Central and Northeast Asia, the Middle East, the Caucasus and the border region of the U.S. and Mexico. Water treatment programs include desalination technologies and nanoscale modeling and synthesis expertise for the removal of a wide range of contaminants, including arsenic, fluoride and perchlorate. But it is in agriculture that Sandia's science and technology could help make the greatest gains in water savings for global water conservation.
Old Technique, New Technology
Sandia researcher Ron Pate leads a team that is bridging the past and future with an old technique linked to the latest technology: the greenhouse. On the border between New Mexico and the Mexican state of Chihuahua, Pate and his colleagues Phil Pohl, Vipin Gupta, Ed Baynes, Nina Berry and Jesse Davis have collaborated with Mexican researchers, led by Hector Gallegos and forage greenhouse system fabricator Francisco Aguirre. They, along with other researchers at New Mexico State University and the University of Arizona, explored the performance, viability and ways to improve hydroponic greenhouses for growing livestock forage with very low water use. The system was developed by Gallegos and Aguirre for use in Chihuahua to help cattle growers survive the severe drought conditions of recent years. According to the Mexican team, these relatively low-tech forage production hothouses, along with Sandia-developed performance monitoring technologies, use roughly one or two percent of the fresh water otherwise needed to grow the same amount of open field forage crops.
According to Pate, the potential savings in water is particularly important in the American Southwest, Mexico and other water-parched regions like the Middle East and certain lands between India and Pakistan, where the majority of water use is for irrigated agriculture rather than direct human consumption or residential and industrial use. Thus a reduction in agricultural usage greatly increases the amount potentially available for other productive uses.
To put the potential water- and land-use savings into perspective, preliminary system performance indications suggest that, if all open-field alfalfa production in New Mexico were replaced with hydroponic forage greenhouses, the associated water use could be reduced from the current 800,000 acre-feet of water to 11,000 acre-feet to produce an equivalent amount of livestock forage and this could be done on less than 1,000 acres instead of the 260,000 acres currently used to produce alfalfa. Eighty percent of New Mexico's water use is agricultural, over half of which goes toward growing forage for livestock. Similar conditions of water use exist in many places in the world. Conventional farming methods in arid regions lose huge amounts of water through evaporation and over-absorption by soil. Over time, this can also result in soil salination and loss of agricultural productivity. Neither are factors in hydroponic greenhouses, which do not require high-quality arable land to function in the first place.
How it Works
In the 26 feet by 59 feet experimental greenhouse, a spatially distributed array of wirelessly networked sensors was used to monitor light, temperature, relative humidity and air pressure. The data, collected every few minutes, was sent by phone line to a remote computer for analysis. "We expect that environmental conditions in the [greenhouse] system will not be as slow-moving or spatially homogeneous as one might think in terms of environmental change," Pate says.
"Every time the water system pops on, the local temperature around the plants drops relatively quickly." In the current system, water sprays from quarter-inch nozzles for about 20 seconds into plants growing in a series of plastic trays stacked on metal racks whenever a humidity sensor or a back-up timer trips a control circuit. To lessen labor and also protect against mold, the researchers are exploring the development and use of trays that would be edible by livestock, thus making washing and sanitizing trays unnecessary. Such tray material, made from recycled agricultural waste materials like wheat straw, could also add nutrition content to the overall forage product, making it a more balanced ration for the livestock. Consumption of water, seed, and labor are also being monitored. In perhaps five to ten years, it is possible that very small, lightweight, inexpensive sensors could be put directly on the plants to more accurately monitor the crop's water status, temperature, growth rate, and other biophysical factors. These sensors could be linked together via wireless communications so that every monitored plant tells the control system directly what it needs, instead of relying on merely monitoring the air near the plants in the greenhouse at a few sparse locations.
Future hydroponic greenhouses can also more carefully control and modify the light reaching the plants. Experiments, including some with 3M Corporation using their films, limit the spectrum of light received by the plants to just that part of the spectrum required for photosynthesis. The experiments reduce the light intensity and restrict certain frequencies, using a variety of shading and spectrum-altering mechanisms to avoid overheating and improve plant growth.
Experiments are also planned that will use the blocked light to create another asset: solar-generated electrical power. Greenhouse pumps, fans, timers, and sensors are already powered by freestanding solar modules that change light into electricity, which is then stored in batteries for night-time use and during cloudy weather conditions. Greenhouses that are capable of generating excess solar-generated electrical power beyond their own needs could be a power source for other productive uses or sale to the grid because the intense sunlight in arid regions has to be filtered to prevent crop damage. The challenge is to create reliable, cost-effective materials to use that part of the spectrum the plant is not interested in using to produce power that can be put on a grid as well as operate the greenhouse.
Pate says that in recent years "all of us who live in the southwestern U.S. have experienced the growing competition for water, especially in the past six years or so of drought. Since irrigated agriculture is the major water user in our region, science and technology that could impact agricultural water use and productivity could make a significant positive impact. This is also a global issue, with water stress and the interdependency with agriculture and population growth of increasing concern and a source of potential future conflict in many parts of the world. From the standpoint of our national security and global stability, it seems worthwhile for a national lab to be thinking about such looming problems and the role that science and technology might be able to play to help address them."
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