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Because Jacobs was a water manager with the Arizona Department of Water Resources for 23 years before joining the UA faculty as professor of soils, water and environmental science and specialist with the UA Water Resources Research Center, she suspected that such things as climate predictions and tree-ring data were not being included in river management decisions. "Very few agencies were using climate information as part of their day-to-day management," she says.

For years, personnel at the bureau have used historic river flow records, called hydrologic modeling, to predict shortfalls. "We all know that climate is changing, and so what happened in the past is not likely to be the same as what's going to be happening in the future," Jacobs says.

An example of the new data sources is the incorporation of tree-ring data from the upper Colorado River basin that help scientists understand what historic droughts and flood patterns look like. Seventy percent of the river’s flow originates in the upper basin. Dave Meko is working on the paleoclimate portion of the project. Meko, an associate research professor of dendrochronology with The University of Arizona’s Laboratory of Tree-Ring Research, also has been doing statistical reanalysis of existing data and studying how that affects the interpretation of past river flows.

Bart Nijssen, until recently an assistant professor in the departments of hydrology and water resources, and civil engineering, managed the hydrologic modeling component of the project.

Researchers want managers of other watersheds to use the management and modeling systems that are developed. Currently, other experts are developing a similar climate-based information model for the Santa Cruz River watershed south of Tucson.

Agriculture is still the primary user of Colorado River water, but increased development throughout the Southwest means that the balance is shifting. "By 2030 it's expected that agriculture won't take such a large percentage of Central Arizona Project (CAP) water," Jacobs says. "Over time, municipal uses will increase and become a larger fraction of the total delivery."

More precise predictions of water availability, for example, could lead to a system of dry-year options, which would pay select farmers in advance for the right to ask for their water allocation at some point in the future on a short-term basis with proper compensation. "We’re looking at what kinds of management practices can be put in place when you know you're going to have a shortage of a particular length on a particular segment of the river," Jacobs says. Monitoring reservoir levels and deciding on water releases during times of excess water also can help communities prepare for potential floods of normally dry tributaries.

The ability to predict how much water will be available and where the demands will be also includes how water managers will handle deliveries to Mexico. Being more precise by looking at seasonal or annual fluctuations ultimately could lead to better working relationships between the various entities vying for water.