The Daily Courier
What a difference a few weeks makes, when it comes to the levels of Prescott’s Granite Dells-area lakes.
In early August, the level of Willow Lake had shrunk to its lowest point in years: Its granite shores showed chalky evidence of previous high marks, and its scenic bays were dry.
But this week, coming off a month of heavy monsoon rains, the levels in both Willow and Watson have climbed dramatically.
In fact, since Aug. 20, Watson Lake has been at or near full capacity every day.
And Willow Lake, which typically fills much slower than Watson, has risen about seven feet over the past month or so. Although still about seven feet from the top of the spillway, the rising level of Willow has helped to fill in some of the previously parched bays.
Helping to even things out between the two lakes has been the substantial amount of water that has been flowing from Watson to Willow.
Prescott Utilities Manager Joel Berman and Recreation Services Director Joe Baynes note that water has been flowing from Watson since Aug. 20 - the day after a monsoon deluge caused flooding along Granite Creek.
The entrance to the cross-cut ditch is located near the Watson Lake parking lot below the Highway 89 overlook. In order for water to reach the ditch, the level of Watson Lake must be within two feet of the spillway.
Records from Berman’s office show that Watson’s level stood at 2.8 feet below the spillway on Aug. 19, and at zero feet below the spillway on the 20th.
Over the past 23 days or so, the level of Watson Lake has ranged from between zero to 0.7 feet below spillway – keeping the cross-cut ditch flowing.
Although Berman and Baynes say there is no way to know exactly how much water has flowed through the channel, they say the flow has been having an obvious impact on Willow Lake.
Because Willow has a much smaller watershed area than Watson, the Willow Lake Road-area lake usually fills at a substantially slower rate than Watson. It typically is not until the transfer between the two lakes begins that Willow shows significant gains.
“We don’t have any sort of gauge on it,” Berman said Friday, pointing to the concrete channel just below one of Watson’s ramadas.
At a depth of about 18 inches, water from Watson continued to flow through the ditch on Friday. “It’s holding pretty steady right now,” Berman said. “And it’s flowing at a pretty good velocity.”
The flow is even more evident on the other side of the cross-cut ditch, which comes out near Willow Lake Road and Meadow Lane. There, the water runs swiftly on its way to Willow Lake, just a quarter-mile or so away.
And that is good news for the recreation potential at the lakes, Baynes said.
Prescott’s dry summer months tend to bring out weeds in the lakes, Baynes said, which makes it difficult for kayakers to navigate the waters of Willow and Watson. But as soon as the lakes rise, he said, the kayaks are back in force.
Along with its contributions to Willow Lake, Watson has also been adding to the city’s water portfolio.
When the city bought Willow and Watson from the Chino Valley Irrigation District in 1998, part of the plan was to regularly withdraw water from the lakes to increase the city’s recharge into the aquifer.
In turn, the city would receive credits in its water portfolio.
Through the years, the city has recharged thousands of acre-feet of lake water in its reclamation facility near the Prescott Airport.
To make the withdrawals, city workers open valves on the dams and allow water to flow out of the lakes and into a pipeline, which directs it to the airport facility where it is allowed to percolate into the ground.
The city has the right to withdraw from the lakes annually between April 1 and Nov. 30. Although no withdrawals have occurred on Willow Lake this year (or in the past three years), the city has taken advantage of the monsoons to draw considerably from Watson.
So far this year, Berman said the city has withdrawn and recharged about 245 million gallons (or 753 acre-feet) of water from Watson. About 50 million gallons (151 acre-feet) of the total occurred during the first 11 days of September, while 128 million gallons (392 acre-feet) were withdrawn in August.
Over the past several months, the city also has withdrawn about 31 million gallons (95 acre-feet) to satisfy its downstream delivery requirements, including an obligation to the Granite Dells Ranch.