Historic irrigation ditches in New Mexico benefit communities beyond just farming, according to recent studies by New Mexico State University researchers. Water leaking from unlined acequias shores up shallow aquifers, dilutes nitrates before the water returns to the river and supports riparian vegetation.

The research will be presented Wednesday at a daylong acequia symposium in Santa Fe.

The studies for the first time attempt to calculate how much water is lost from acequias and where it goes. The state has urged irrigators to line acequias with concrete to make water flows more efficient and reduce water losses from leaking irrigation ditches. The NMSU studies indicate there could be some negative consequences to shallow aquifers and riparian areas if all ditches were lined.

A seven-year study of acequias around Alcalde found an average of 7 percent of the water flowing down unlined acequias evaporated or was released as vapor from plants. The range of evapotranspiration was 1 percent to 16 percent depending on the soil's moisture, according to lead researcher Sam Fernald. Most of the water returned to the river as leftover irrigation water or infiltrated shallow groundwater and slowly seeped into the river. The water that filters underground during the irrigation season is protected further from evaporation, taking six to 10 weeks before reaching the river.

"The wisdom of the ancients was the starting point of our study," said Fernald, NMSU associate professor of watershed management. "For generations, people have believed that acequias are more important than just being used to water fields. They believed that the seepage affected groundwater quality and recharged the aquifer. But there were no supporting data."

Fernald and other researchers are looking for funding to test the acequia seepage model in other parts of New Mexico. In some cases, he said, it makes sense to line ditches. But to line them all could have unintended consequences. "We're just interested in knowing where the flow goes and helping people make informed decisions at the local level while keeping the big picture in mind," he said.

Fernald and associates are working with Sandia National Laboratories researcher Vince Tidwell on studying the sociological impacts of irrigation systems. "Urban development in Albuquerque could be impacted by how water is being managed upstream in the acequias," Fernald said.

He said they're also working with other researchers to study the interaction between humans and ecosystems in traditional irrigation communities around the world.

Other researchers are studying the social impacts on acequia communities as houses are built on irrigated lands and irrigation ditches fall into disuse. One NMSU master's degree student Ciara Cusack found the existing acequias are ideally situated in areas for restoring riparian areas, an important aspect of river ecosystem health.

Other presenters at the symposium include:

• Carlos Ochoa, a watershed management research specialist and a range science doctoral candidate at NMSU. Ochoa has studied surface water and vadose zone hydrology in Northern New Mexico since 2002.

• Quita Ortiz, who earned a Master of Applied Geography from New Mexico State University and works as a mapping specialist with the New Mexico Acequia Association in Santa Fe.

• José A. Rivera, a professor of planning at The University of New Mexico, who has researched water management institutions and water culture around the world.

• Michael Cox, a doctoral student at the Indiana University School of Public and Environmental Affairs, who uses geographic information systems and analysis to study human and environment interactions.

Contact Staci Matlock at 986-3055 or smatlock@sfnewmexican.com.

IF YOU GO

What: Acequia symposium
When: 7:30 a.m. to 5 p.m. Wednesday
Where: Santa Fe County Agriculture Extension Center, 3229 Rodeo Road.
Cost: $15
For more information and to register: http://aces.nmsu.edu/acequiahydrology/ or call Selina Trujillo at 505-852-4241.