6/14/13: Fires impacting Arizona’s water

Fires impact Arizona's water

Bonnie Stevens
Flagstaff Business News
Friday, June 14, 2013

Few things are as refreshing as an ice-cold glass of water on a sizzling Arizona summer day. However, many of us do not look past the faucet to consider the journey water takes to quench our thirst. In fact, most of the water in Arizona’s reservoirs comes in as runoff from our forested uplands. Therefore, scientists say the quality, affordability and abundance of Arizona’s water are largely determined by the health of our high-country forests.

Scientists also say our forests are at risk, threatened by drought, massive insect infestations and intense firestorms like the Wallow and Schultz fires. And when our forests are at risk, so is our water.

“Catastrophic fires have a huge impact on the landscape and water that runs off,” said Salt River Project Senior Hydrologist Tim Skarupa. “On hillsides torched and depleted of vegetation, the rain no longer is absorbed by plants and soil. It can quickly build into a powerful raging river, eroding slopes and moving downed logs and sediment as we’ve experienced in Greer and Flagstaff. The debris is deposited into waterways. Tons of silt fill up reservoirs and clog water systems.”

In addition, Skarupa says these flood events elevate the levels of organic material in waterways below. Treating the water for harmful microorganisms and removing sludge and silt from reservoirs costs millions of dollars that will have to be paid by governmental agencies or, essentially, taxpayers.

With the increased size and intensity of Arizona wildfires in the last four decades, the costs to fight today’s fires and recover from the ensuing damage are enormous. A report by the Rural Policy Institute and Ecological Restoration Institute at Northern Arizona University estimates the total cost of the Schultz fire, including damage from post-fire flooding, to be between $133 and $147 million.

“Responding to catastrophic wildfire like the Schultz fire and subsequent flooding can cause financial chaos for local governments and financial devastation for affected property owners,” said Coconino County Supervisor Mandy Metzger.

So as the Forest Service embarks on the nation’s largest forest health project – the Four Forest Restoration Initiative (4FRI) – hydrologists with the ERI and SRP see an opportunity to study and compare the impact on water yield and infiltration into the soil for the benefit of the whole ecosystem, based on different levels of thinning and burning treatments.

“Because 4FRI treatments will be applied at a landscape scale and are expected to have significant effects on water quality and quantity for both ecological use and downstream water use by human communities, it is critical to quantify these effects in the early years of 4FRI,” said NAU Hydrogeology Professor Abe Springer, Ph.D. “We’ll be able to identify optimal forest patterns for the accumulation and retention of snowpack, and inform management decisions across the landscape.”

Thus, NAU and SRP are planning to engage in an extensive Paired Watershed Study to evaluate the effects of forest health treatments on surface water runoff, groundwater recharge, soil water storage and the evaporation of snow.

“We expect surface water and groundwater yield will increase significantly where basal area [tree density] is decreased by at least 30 percent,” said Springer.

ERI research shows southwestern ponderosa pine forests averaged 25 to 50 trees per acre before settlers arrived in the 1800s. Today’s forests can have hundreds of small trees packed into an acre. Excess trees fuel large wildfires while their overlapping treetops and branches keep sunlight and snow from reaching the ground.

“A lot of studies show reducing the canopy cover of the forest increases the water supply, but those studies were done on treatments that were not restoration treatments, which are based on the historic structure of the forest,” said Skarupa.

ERI Executive Director Wally Covington, Ph.D., has long promoted the need to return overcrowded and unhealthy forests to their pre-settlement condition so fire can perform its natural role as nature’s housekeeper, cleaning up debris on the forest floor and recycling nutrients.

“The Watershed Study with Salt River Project will help us better understand water and energy balances, as well as natural resource responses to restoration treatments,” said Covington. “Such information is essential, not only to ensure healthy forests and watersheds for current and future generations, but also to advance our fundamental understanding of ecological restoration.” FBN