Arizona’s Oak Creek overflows from heavy rain and snowmelt in winter
Flood warnings are in effect in northern Arizona as Oak Creek overflows due to heavy rain and the state’s snowmelt.
Rob Schumacher, Arizona Republic
A new storm system is on the way and the effects of a cold and wet winter are being felt across Arizona.
Statewide flood monitoring has been extended through Wednesday, with waterways dealing with potential surges.
Flooding in the valley is likely to worsen before it gets better, according to the Phoenix office of the National Weather Service, as additional rains are expected later Tuesday and then Wednesday morning.
“Given that the creek is flowing very high and this combination of additional precipitation, which is quite significant, in addition to more snowmelt, we have to consider that the snowpack is still well above average so more of that snow will flow away in the various rivers and streams. The situation is likely to get worse than it is now,” Weather Service meteorologist Gabriel Lojero told The Arizona Republic.
Winter Weather Closures
Winter weather conditions have already begun to weigh on highways in northern Arizona. with a list of closures that are already in effect. They include:
- State Route 260 in both directions east of Payson (MP 277-283).
- State Route 89A in both directions between Sedona and Flagstaff (MP 375-398).
- State Route 87 northbound at Payson.
- State Route 64 near the east entrance of Grand Canyon National Park (MP 244-261).
In addition, the Yavapai County Sheriff’s Office has placed Prescott residents at Granite Creek and Granite Gardens on “set status,” meaning those nearby should be prepared due to the increased flows on Granite Creek to evacuate due to the necessary water drainage from Watson Lake.
Mayer residents along Big Bug Creek on the East Stagecoach Trail and at Chimney Ranch RV Park have also been placed on “set status” due to rising water levels and should also be prepared for the evacuation.
As of this writing, the Phoenix Office of the Weather Service has issued multiple flood warnings along Bartlett Lake down to the confluence of the Gila River and in the Tonto Creek area.
“This will continue for the next few days and could continue at least early next week if not longer. We could extend these flood warnings until early next month,” Lojero said.
Additionally, according to Sgt. Joaquin Enriquez of the Maricopa County Sheriff’s Office, Tonto National Forest has been forced to close several recreational areas due to flooding, specifically the Granite Reef, Phon D Sutton and Coon Bluff areas.
“All of these low water crossings will be flooded over the next few days,” Lojero said.
Flood warnings throughout the Arizona highlands also remain in effect, with areas of Yavapai and Coconino counties being warned.
Forecast: More Snow for Northern Arizona; Rain in the Phoenix area
Tuesday’s central forecast has brought steady rainfall to parts of Yavapai County and northern Gila County, with a good chance it will spread to more areas by nightfall. The Weather Service is forecasting an average of 1 to 2 inches of rain in higher elevations, possibly even more in localized areas, with the main rainfall for the Phoenix area expected after midnight.
Snow in northern Arizona will be seen between elevations of 6,000 and 6,500 feet Tuesday, with the Flagstaff Weather Service Office having accumulated 6 inches of “heavy wet snow” so far.
“That means the moisture content in this snow is pretty high. Just a rough estimate, there’s somewhere between a half and three-quarters of an inch of liquid trapped in the fresh snowfall,” said Mark Stubblefield of the Weather Service’s Flagstaff meteorologist, the Republic Bureau said.
This, combined with snowmelt in the highlands and already elevated watercourses, could potentially force the Salt River project hand to release more water, which could cause even more severe flooding.
“It would require SRP to potentially make larger water deliveries along the various dams. Therefore, the flooding situation could get a little worse when we leave tonight and tomorrow,” Lojero said.
That being said, this approaching storm is well on SRP’s radar.
“We are monitoring this storm very closely. Looks like he’ll hit the waterhole tonight, tomorrow morning. It’s a warm storm, but it’s also a snow-rain mixed storm, which will do two things: It will add to the snow that’s up there in the Continental Divide, but it will also melt additional snow and increase inflows into the Verde River,” SRP spokeswoman Patty Garcia-Likens told The Republic.
The SRP plan
“We’ve been making releases every day since March 2 in anticipation of the fact that we’re going to have a very active, wet winter through March 2, by which time it was the second-highest snowpack in 30 years,” Garcia-Likens said. “However, it’s a good thing that we’ve been releasing all along.”
SRP’s argument for it being a “good thing” is that these storms will bring more snow that the utility knows will eventually melt, contributing to its Verde River reservoirs. This water must then be drained to make room.
“We need to make room and this is for the safety of the dams and the public. We need to make sure these dams can absorb all of the snow that will eventually melt over the next few weeks,” Garcia-Likens said.
Not only is this for safety, but the water seeps into the soil and aquifer, helping to sustain freshwater sources in urban areas as well as agricultural irrigation.
Well used: SRP releases stored water. But it is not wasted
How much water will SRP release?
“With the new storm approaching, we’re looking at increasing releases. Right now we’re at 11,000 cfs (cubic feet per second), but that could increase in the next 24 to 48 hours. It really just depends on how fast the snow melts and how much snow we get from the storm,” Garcia-Likens said.
Required release: The Salt River flows. Many open sluice gates
At the time of writing, that number has increased to approximately 12,073 cfs between Bartlett Dam and Stewart Mountain Dam (Saguaro Lake). However, total inflow is hovering around 7,000 cfs, down from Monday’s average of 9,037 cfs.
However, SRP’s primary concern is the Verde River.
“It’s the Verde system that we’re concerned about. Although it’s currently at 83% (capacity), that’s still very high considering we’ll be getting a lot more outflow as it gets warmer. We’re going to fill all of those systems by the end of the season,” Garcia-Likens said.
Looking at the numbers, the entire reservoir system with a capacity of nearly 2.3 million acre feet is currently 94% full. For comparison: The entire reservoir system was still at 71% a year ago.
Bartlett Dam renovations will come to hold more water
Over the decades, SRP has lost “a lot of capacity” to store water on the Verde side of the river due to increased sedimentation. In an effort to help with lost space, SRP is working to “modify” Bartlett Dam in hopes of alleviating these problems.
“We are in the process of working with the Bureau of Reclamation to modify the Bartlett Dam to hold more water,” Garcia-Likens said.
But it will still take some time.
“It’s a long process. In the next 10 years we hope to modify and make this dam bigger. If that was up there now, we wouldn’t be releasing that water,” Garcia-Likens said.