Sandia LabNews

Computer models helping resolve conflicts over water

Last June, flows in the Rio Mimbres in southern New Mexico were insufficient to meet the demands of farmers. It had irrigators — those whose families have farmed the land along the river for centuries — wondering how they could keep their fields green until fall. Then the rains came.

Another couple of dry weeks and the courts would have refereed a dispute pitting farmers on the “senior ditch” (the senior water rights holders) with upstream farmers and domestic well owners, who likely would have had to severely curtail their water use to allow the downstream users access to water.

The worst did not come to pass last summer, though all agree that at some point the junior rights holders in the Mimbres basin will be ordered to cut back.

A familiar scenario

It is a scenario that is playing out across the western United States, portions of which are in an extended drought, says Vince Tidwell of Geohydrology Dept. 6313.

In several recent cases, Sandia computer models that simulate the complex interrelationships among surface flows, groundwater dynamics, and water demands, rights, and laws are being used to help locals determine which tradeoffs result in the best long-term outcomes.

To develop each model, the researchers work alongside local authorities, water users, and decision makers as part of a process known as computer-aided dispute resolution (CADRe). The project is a joint effort of Sandia, the US Army Corps of Engineers’ Institute for Water Resources, and several universities. Its funding, in part, was arranged by US Sen. Pete Domenici, R-N.M.

The models allow authorities to run hundreds of different versions of the future and see the effects of their choices decades away, says Vince. The simulations can be run on a PC, and each run takes 10-15 seconds after the inputs are set.

In the Mimbres basin, for example, models have helped create a “water bank” whereby local users trade credits with each other, not only within the same ditch but across ditches and with domestic well owners. A defined set of trading rules helps minimize conflict.

“It has allowed people to play a water trading game in a virtual environment to find out what will work and what won’t work without losing any real water,” says Vince.

The model incorporates a four-mile stretch of the Rio Mimbres, the associated groundwater system, nine acequias, a reservoir, and adjudicated water rights for the basin. Partners in the project include the New Mexico Office of the State Engineer, Mimbres Water Users Group, and the University of New Mexico.

Competing demands

In another project along the Middle Rio Grande Valley in central New Mexico, governments are grappling with the competing water demands of sprawling residential development, agricultural irrigation, and the needs of the endangered silvery minnow.

In 2001 Vince and Howard Passell (6313), with support from Sandia’s Small Business Assistance program, began working with the Middle Rio Grande Water Assembly to develop an integrated surface water and groundwater model addressing agricultural, urban, and environmental interests in a three-county region. The water plan resulting from the project was accepted by the state engineer’s office in late 2003 as part of a statewide water management plan.

More recently the Middle Rio Grande model was expanded to include 17 river reaches stretching from the Colorado state line to Elephant Butte Dam in south-central New Mexico, plus six reservoirs and three integrated groundwater basins. The plan is available to water managers as a tool to help them home in on regional water solutions.

Partners in the project include the New Mexico Interstate Stream Commission, US Bureau of Reclamation (USBR), Corps of Engineers, and US Geological Survey.

Similar Sandia projects are underway in Arizona, Texas, Oregon, and the Middle East. (See “Where models are helping set water management direction” above.)

Collaborative process

The greatest value of the computer models might be in the collaborative process itself, Vince says. Local decision makers are involved in building a model from the ground up for the specific water resource in question.

“We meet regularly with the stakeholders to discuss what’s important for the area, how decisions are made, and what the alternatives are,” he says. “When people see how the whole thing is built and how it works, they are more likely to accept its results.”

Helping develop the models forces many collaborators to confront inaccurate assumptions about water, he says. With a healthy level of disagreement at the table, participants often begin to understand the perspectives of those they are competing with.

“It forces them to look at water as a system and to deal with its physics,” he says. “Without somebody cramming it down their throats, they come to understand the complexities and the need for a multidisciplinary approach.”

The project is part of Sandia’s Water Program, which seeks to improve the water supply safety, security, and sustainability of US water resources through the development of technologies that create new sources of water, decrease demand through efficiency, and provide decision tools to the institutions responsible for balancing supply and demand.

Other Sandia contributors to the project include: Ray Finley, Tom Lowry, Amy Sun, Len Malczynski, Jesse Roach, Will Peplinski, Geoff Klise, Jim Brainard, Beth Richards, Amy Coplen, Chau Dam, Suzanne Pierce, Marissa Reno, and Alison Williams (all 6313).

Where models are helping set water management direction

As part of a project to allocate water awarded to New Mexico in the 2004 Arizona Water Settlements Act, Sandia worked with several stakeholder groups to develop and test a computer-aided decision tool for the Gila/San Francisco River basin that straddles the New Mexico/Arizona border.

The model is helping authorities put the water to the best long-term use while preserving environmental resources. The effort has generated interest in expanding the model to address water issues in southwestern New Mexico more broadly, says Vince Tidwell (6313).

Partners in the project include the New Mexico Interstate Stream Commission, US Bureau of Reclamation, US Fish and Wildlife Service, environmental organizations, and the Southwestern New Mexico Water Planning Group.

Near Austin, Texas, as part of a cooperative project with the University of Texas funded by the Laboratory Directed Research and Development program, Sandia researchers helped couple system-level models, which allow for rapid analysis, with a spatially detailed US Geological Survey groundwater model to study part of a major aquifer.

Joining the two modeling platforms allowed for collaboration by state and federal agencies and helped involve stakeholders in the decision process, says Vince.

Farther away, on the Willamette River in western Oregon, regulators, resource managers, city government representatives, industry officials, and environmentalists are using the models to devise a system of barter for “thermal credits” whereby heating of river water by communities and pulp and paper mills that use the water is traded for restoration projects that cool water elsewhere along the river, to improve salmon habitat.

The work has an international component as well. Howard Passell (6313) and a team of Sandia researchers are using common water concerns to foster cooperation among governments at international borders, particularly in the Middle East.