Climate change, the Rio Grande forecast problem, and the death of stationarity

Laura Paskus takes us this morning to the mountains of northern New Mexico, where the snow is melting earlier than it used to, and less of the ensuing runoff is making it into our Rio Grande:

[A]s bleak as southwestern springtime stream flow forecasts have been in recent years, scientists at the University of New Mexico are now saying that actually, they’re probably not bleak enough.

“The warm spring temperatures are one of the clearest observed climate change signals in North America,” says David Gutzler, a professor in the University of New Mexico Earth and Planetary Studies Department.

Gutzler is part of the New Mexico Universities Working Group on Water Supply Vulnerabilities, which has been working on identifying points of vulnerability in our societal-ecosystem-water system. One of their key findings, developed by Gutzler’s student Shaleene Chavarria, is that changes in the climate weaken the old forecast tools, which are used to relate winter snowpack to runoff the following year.

This is the point Chris Milly, Julio Betancourt, and colleagues laid out in an important paper a few years back on “the death of stationarity” (pdf). “Stationarity” was a foundational assumption in water management – that the range of observed variability in the past provides a usable picture of the expected range of variability and system behavior in the future:

In view of the magnitude and ubiquity of the hydroclimatic change apparently now under way, however, we assert that stationarity is dead and should no longer serve as a central, default assumption in water-resource risk assessment and planning. Finding a suitable successor is crucial for human adaptation to changing climate.

The Paskus piece is part of a new reporting project being done by New Mexico In Depth, a non-profit news organization based here in New Mexico.