Sabino Creek, which was bone-dry for months due to an ongoing drought, is flowing again, thanks to runoff from melting snow in the Catalina Mountains.
Visitors to Sabino Canyon, northeast of Tucson, reveled in the flow this weekend - but it will dwindle again without a fresh infusion from winter storms.
"Right now, we're getting flow from that snowmelt, but the flow is declining" because the area has received no recent rain or snow, said Emmet McGuire, field office chief for the Arizona Water Science Center. The center monitors daily flows in Sabino Creek and other waterways.
"If we don't get more precipitation soon, the flow is going to continue to decline - and the creek could stop flowing again," McGuire said.
The flow had dropped to 2.99 cubic feet per second on Tuesday - below flow rates in late December as the creek was revived by valley rains and melt from mountain snow.
Pamela Selby-Harmon, officer in charge of the Mount Lemmon Post Office, estimated that 40 to 45 inches of snow has fallen in the Catalinas this winter - but accumulations vary widely depending on altitude and location.
A gauge on Sabino Creek recorded no stream flow in a continuous 73-day period from Oct. 4 through Dec. 15, according to daily flow measurements posted by the U.S. Geological Survey.
Survey records show the creek also had no flow in a continuous 69-day period from May 8 through July 15 last year - and for six days in August as well.
Those 75 days plus the 73-day dry period in the fall add up to 148 days of no flow in the creek.
McGuire and David Lazaroff, an author of books about Sabino Canyon, emphasize that the creek has experienced repeated no-flow periods over the past decade.
"It's not as unusual as we might think, at least in the 21st century," Lazaroff said in a December email in which he described extensive no-flow periods.
McGuire said he could provide no immediate data on the historical average of no-flow days in the creek.
But based on observations in recent years, "it seems that the intervals of no flow are increasing a bit," McGuire said.
For example, the autumn no-flow period was comparatively short in 2011.
"It stopped flowing Oct. 18 and started again on Nov. 13" that year, McGuire said. "In 2012, it was quite a bit longer. ... If we don't see increased precipitation for the next few months, we're probably looking at the interval of no flow to increase."
On StarNet: See more photos from Sabino Canyon at azstarnet.com/gallery
get to sabino dam
One place to get a good look at the Sabino Creek flow - while it lasts - is at Sabino Dam.
From the Sabino Canyon visitor center at 5700 N. Sabino Canyon Road, walk east from the parking lot on a broad path about 0.4 of a mile to a road. Turn right on the road and continue toward a bridge that crosses Sabino Creek. Before crossing the creek, go left on the Sabino Lake Trail or a parallel roadway and watch for the dam on the right.
From record lows to record highs in the span of about a week.
Tucson hit a record high Tuesday for the date when it reached 81 degrees, breaking the record of 80 set in 1986. Phoenix also hit a record high at 81 Tuesday.
Also, today's high in Tucson is expected to be near 80. If it does hit 80, that will tie the record high for the date, recorded in 1986.
A high-pressure system is keeping temperatures unseasonably warm. A slight cooling trend is forecast for the weekend, with chances of rain Friday night through Sunday.
Contact reporter Doug Kreutz at email@example.com or at 573-4192. On Twitter: @DouglasKreutz