The Rio Grande through Albuquerque is likely to drop this summer to levels not seen for more than two decades.
Flows on the river are measured in cubic feet per second (cfs), an arcane but commonly used water flow metric on U.S. rivers. Normally* at this time of June, the Rio Grande at Albuquerque’s Central Avenue Bridge is flowing at a bit more than 2,000 cfs. As I’m writing this, the river’s flowing at 527 cubic feet per second.
But it will soon begin dropping significantly. Because of the drought, there is very little natural flow in the river. Most, if not all, of the river’s flow currently is water being released from storage behind dams on the Rio Chama. Without that, water managers say the river would be nearly dry by now in Albuquerque.
Since 2003, rules adopted by the U.S. Fish and Wildlife Service to protect the endangered Rio Grande silvery minnow required water managers to maintain a flow of 100 cfs at the USGS Central Avenue streamflow measurement gauge. But with supplies of supplemental storage water nearly exhausted, the river’s managers, with the concurrence of the FWS, have agreed to let the river drop to 50 to 60 cfs this summer.
The last time the river dropped below 100 cfs was late September and early October of 1989. The last time the river essentially went dry completely at Central was September of 1981.
(I thank the number crunchers at the U.S. Bureau of Reclamation and the New Mexico Interstate Stream Commission for help with the old river flow data.)
*For numbers nerds, by “normally” here I’m using the median for the period of record – essentially the mid point of the historical distribution of flows. The period of record in this case is 1942 to the present. This is one of those numerical distributions, like housing prices, where the mean is often higher than the median because wet years, like million-dollar houses, tug the numerical average toward the high side. The mean flow on June 14 is 2,580 cfs.