Drought: The Supply and Demand Question

The latest drought monitor notes the current state of our reservoirs here in the western U.S.:

Despite the summer showers, many Western reservoirs remained unusually low, signaling ongoing hydrological drought.  At the end of July, reservoir storage stood at 82 percent of average for this time of year in Arizona.  Storage ranged from roughly two-thirds to three-quarters of average in several other Western states, including Idaho, Oregon, Utah, and Wyoming.

For New Mexico, the number at the end of July was 78 percent.

Tracking the supply side of this question – how much precipitation has fallen from the sky – is relatively straightforward. For the water year (meaning since Oct. 1), the key snowpack-producing areas of New Mexico are above normal. So why are our reservoirs so low? Is it lingering effects of prior years’ droughts? Go back two years. Three years. Four years. Five years. Not really much different – normal or above normal in all the key places.

This highlights the thing that’s not so easy to track: the demand side of the equation.