After Four Centuries, Southwest US Irrigation System Faces Decline

Dwindling snowmelt runoff, combined with social and economic factors favoring modernism over tradition, has lead to the decline of communal irrigation systems known as acequias that have sustained farming villages in the arid southerwestern US for centuries, according to a Dartmouth College study.

The study, which appears in the journal of Global Environmental Change, reflects similar changes seen around the world in which isolated communities become integrated into a larger economy. This integration comes with benefits of modern living but also expose the communities to the economic shocks of large market fluctuations.

"The term acequia refers to both communities of farmers as well as engineered irrigation canals that carry snowmelt-driven runoff to farm fields as a way for the agricultural communities to share a scarce resource in arid regions. The acequias system, which is common in northern New Mexico and southern Colorado, provides a model of communal ownership that governs water rights, distribution, disputes and other issues," writes the press release announcing the findings.

Michael Cox, Dartmouth assistant professor and the study's author, examined the acequias of the Taos Valley in northern New Mexico. He found that they are declining in terms of agricultural productivity and have also mostly lost their communal pasturing system. A declining amount of snowmelt and a host of socio-economic factors, many resulting from population growth in the nearby city of Taos, have lead to the changes.

"The factors include state-level public policies that grant private water rights to individuals, which conflicts with the acequias' water sharing traditions; newcomers who are increasing demand for what water remains; increased tourism and land use development; and declining reliance on traditions in favor of modern, highly integrated economies," the statement said.

"While some of these changes can be attributed to declines in water availability, much of the change results from social drivers, including demographic changes, regional-to-global market forces and public policies," Cox said. "It thus seems quite unlikely that the acequias in Taos will return to their historical situation, meaning the acequia farmers must adapt to the current conditions."