Colorado River Basin Managers are working on what they call a “Drought Contingency Plan” to reduce water use, but that’s probably a bad name to describe what’s going on, as the members of the Colorado River Research Group explain in a new white paper (pdf):
In current Colorado River water management, perhaps no word is used (and misused) more than drought. To most people, the word drought contains two concepts. The first is the lack of available water, primarily a function of below normal precipitation, but often exacerbated by management and water?use practices. Second is the notion that the condition is temporary—a deviation from a norm that is expected to eventually return. Aridity, in contrast, refers to a dryness that is permanent, and is a function of natural (and presumably stable) climatic conditions. While it is fair to say that the Colorado River Basin is in a period of drought (in that recent precipitation has lagged slightly below the long?term averages), and that much of the basin is arid (or semi?arid), neither term is adequate to accurately describe emerging conditions in the Colorado River Basin. For that, perhaps the best available term is aridification, which describes a period of transition to an increasingly water scarce environment—an evolving new baseline around which future extreme events (droughts and floods) will occur. Aridification, not drought, is the contingency that should guide the refinement of Colorado River management practices.
The underlying hydrologic problem is a decline in “runoff efficiency” – less water in the rivers for a given amount of rain or snow. That’s also the message in a new paper by the University of New Mexico’s Shaleene Chavarria and Dave Gutzler on the Rio Grande, where precipitation has actually gone up slightly, but river flows have nevertheless gone down.
Changes in the snowpack–runoff relationship are noticeable in hydrographs of mean monthly streamflow, but are most apparent in the changing ratios of precipitation (rain + snow, and SWE) to streamflow and in the declining fraction of runoff attributable to snowpack or winter precipitation.
So yeah, drought’s a less useful word. We don’t change language by publishing white papers and journal articles, but we can at least focus some energy on the conceptual problems.