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By Dan Rahn
drahn@uga.edu
Nobody knows how much water Georgia farmers pumped into their fields over the dry summer  of ’99--or, for that matter, over any other summer.
“We can make some educated guesses,” says state geologist Bill McLemore of the Georgia Geologic Survey, a branch of the Environmental Protection Division of the state’s Department of Natural Resources. “But there’s no question that’s the weak spot in our water use information system.”
With demands on water resources mounting, it’s a weakness the state can’t afford to carry into this millennium. So the DNR is funding a UGA project called Ag Water PUMPING (Potential Use and Management Program IN Georgia).
Industries and cities meter their water use, McLemore says. That allows for fairly accurate accounting. Farmers, though, don’t keep track of the water they use. The DNR figures its nearly 20,000 agricultural water-use permits closely reflect the number of irrigation systems out there.
“Agriculture is the second-largest user of water statewide,” McLemore says. “It’s the single largest user of groundwater.”
Farmers water during the growing season. For their biggest crops, that’s about six months. “For that period, they may be the biggest water user overall,” he says. “Some big farms use as much water as medium-size cities.”
The need to measure agricultural water use was clear by the mid-’90s, McLemore says. So the state asked UGA’s College of Agricultural and Environmental Sciences to devise a project to monitor a statistical sample of the irrigation systems.
“The U.S. Geological Survey had tried to get farmers to volunteer in a project like this,” he says, but the USGS approach didn’t elicit the needed data. “USGS has good planners in Atlanta, but doesn’t have a local presence, close to the farmers.”
The college, through the Extension Service, does have that local presence. Agents in every county work daily with farmers and have close links with college engineers and other
scientists.
“We put together a proposal to measure 400-plus systems across the state over five years and develop computer models to accurately estimate total water use,” says Dan Thomas, the professor of biological and agricultural engineering who heads the UGA team that began setting up the monitoring system last summer.
Using the state permits, the team came up with a sample of irrigation systems to monitor. They are working through county agents to contact each farmer on the list.
To include an irrigation system in the study, UGA engineers and technicians first check its water-flow rate. If the rig doesn’t already have an hour meter, the team installs one. Then technicians will check the meter monthly to see how long it pumped.
The project still requires farmers to volunteer. But so far, that hasn’t been a problem. “Most of our farmers understand the need for this study,” says David Curry, an extension agent in Toombs County.
Thomas says getting the monitoring part of the project in place will take two years. “About 170 systems are completed now,” he says. “We have three groups, and at times four, doing the installation.”
Water disputes in southwest Georgia and saltwater intrusion in groundwater along the coast make water-use data from those areas more critical. They were the first areas to be included, Thomas says.
The work will soon expand. In 2000, the team will not only put in the rest of the monitoring sites, but will start checking the ones already installed.
As the data begins to flow, the work on the computer models will grow. The models will provide accurate water-use data on many levels--by county, by drainage basin and by similar categories.
“Statewide, we’ve got pretty reasonable water-use estimates now,” Thomas says. “This will give us more precise data in local areas.”
That data is essential. “Natural resource management is based on good science and good engineering,” McLemore says. “And those depend on accurate numbers.”
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