Tag Archives: snowmelt

Water Conservation, City of Phoenix

SRP Water Supply Good after Sparse 2014 Runoff

In case anyone missed it, the five-month 2014 winter runoff season finished quite a bit like the previous three January-through-May periods: DRY.

In fact, this year’s five-month snowmelt season produced only 148,000 acre-feet _ the eighth-driest since Salt River Project has been keeping records for the last 116 years and the fourth consecutive year with below-median winter inflows into the SRP reservoirs.

The good news, however, is that the long-term forecast suggests the possibility of an El Niño event by the fall and winter of water year 2015. El Niño is characterized by warmer-than-normal ocean temperatures in the equatorial eastern Pacific. During El Niño events, the Pacific jet stream tracks farther south, with storms from the Pacific Ocean taking aim at the southwestern U.S. while, at the same time, the subtropical jet stream is displaced to the north, often leading to above-normal precipitation over Arizona.

Charlie Ester, SRP’s manager of Water Resource Operations, said that bodes well for a more active monsoon season followed by wetter conditions on the Salt and Verde watersheds next winter.

Ester said an “average” January-to-May runoff season would go a long way toward refilling the reservoirs on the Salt and Verde rivers that today stand at a healthy 53 perfect full with 1.22 million acre-feet stored – nearly the same percentage as one year ago. That followed the most productive runoff season — 444,788 acre-feet of stream flow accumulated in the first five months of 2013 – since 1,418,960 acre-feet of water was accumulated during the 2010 runoff season. The 30-year median runoff is 534,336 acre-feet.

“In spite of the consecutive dry winters, our reservoir system is in a good position to provide full allocation to our water customers because of SRP water resource management practices,” said Ester. “We’re keeping our fingers crossed for an active 2015 runoff season, and so far the early indications are good.”
SRP and central Arizona depend on wet winters and plentiful precipitation on the mountainous regions north and east of the Valley to replenish the reservoirs on the Salt and Verde rivers. Unfortunately, the watersheds contained in those mountainous regions received just 2.85 inches of precipitation from December 2013 through March 2014 — 37% of normal.

Overall, the SRP reservoir system has declined from completely full on May 1, 2010, to 56% full on May 1, 2014. Theodore Roosevelt Lake, which holds about two-thirds of the combined water stored on the Salt and Verde rivers, today stands at 42 percent full. Current storage on the Salt River system is 51 percent; the two reservoirs on the Verde River are a combined 66 percent of capacity.

SRP is the largest raw water supplier in the greater Phoenix metropolitan area, normally delivering about 1 million acre-feet annually.

roosevelt-dam-arizona

2013 Runoff Best in Last Three Years

While the early forecast of an El Nino season never materialized, the 2013 runoff season nevertheless produced just enough snowmelt to refill the reservoirs to near the previous year’s level on the Salt and Verde rivers going into the heaviest-use period of the calendar year.

And, after two of the driest La Nina winters on record, water managers at Salt River Project aren’t complaining with the 444,788 acre-feet of stream flow accumulated in the first five months of 2013, the January-through-May period that amounts to the year’s runoff season.

“We’re thrilled that the runoff we got this year put us back to where we were a year ago,” said Charlie Ester, SRP’s manager of Water Resource Operations. “That may not sound like a lot, compared to years such as 2010 when we filled our reservoirs, but essentially we have regained all of the water that we used the previous year.”

Thanks to another boost from a better-than-average monsoon season, the reservoirs on the Salt and Verde rivers today stand at 55 percent full with 1.28 million acre-feet stored – exactly the same percentage as one year ago following the 23rd and 16th driest runoff seasons among the 115-year-old records kept by SRP.

Theodore Roosevelt Lake, which holds about two-thirds of the combined water stored on the Salt and Verde rivers, today stands at 45 percent full. Current storage on the Salt River system is 54 percent; the two reservoirs on the Verde River are a combined 62 percent of capacity.

This year’s runoff season, while still below the 30-year median runoff of 534,336 acre-feet, was the most productive since 1,418,960 acre-feet of water was accumulated during the 2010 runoff season — the 20th most productive year on record. The snowmelt runoff in 2012 amounted to only about 196,064 acre-feet, which followed the 2011 runoff total of 222,907 acre-feet.

SRP is the largest raw water supplier in the Phoenix metropolitan area, normally delivering about 1 million acre-feet annually.