Tuesday, December 31, 2013

Wetlands drying up in south valley

Low water table cited as probable cause

Express Staff Writer

    A series of beaver ponds and picturesque wetlands at the mouth of Croy Canyon near Hailey have gone dry, leaving frozen muddy puddles of water in their place.
     Several other wetlands in the area have also gone dry this year, leaving many valley residents to wonder what may be the causes.
    “Sometimes it can be a little bit of everything,” said Sean Vincent, hydrology section manager of the Idaho Department of Water Resources.
    The Croy Creek wetlands make up a nature preserve managed by the Wood River Land Trust. The site was once a city dump. Thanks to industrious beavers, spring creek flows and artesian springs, the area now encompasses several acres and is home to numerous bird and animal species.
    A boardwalk, built by the Land Trust to access the site, is now marked by signs stating that the drop in water level is due to an overall drop in the water table.
    “We anticipate that when the water table rises, the springs will begin filling the wetland again,” the signs state.
    Wood River Land Trust Executive Director Scott Boettger said in an interview that he believes a combination of extended drought conditions and “over-pumping” of groundwater from wells in the area has led to the drying of the wetlands.
    “Unfortunately, it is the wildlife that bears the brunt of it,” Boettger said.
    The Croy Creek wetlands went dry rapidly in September, after the Beaver Creek Fire raged through the hills above the west side of the Wood River Valley. The Big Wood River ran black with ash from rainwater runoff for weeks after the fire.

Unfortunately, it is the wildlife that bears the brunt of it.”
Scott Boettger
Wood River Land Trust

    Mudslides also followed the fire, perhaps altering the flow of water in springs.
    Wood River Land Trust staff, including hydrologist Wendy Pabich, walked the Croy wetlands in October. The area is held in trust under a conservation easement. They found that an artesian spring that usually flowed freely into the beaver ponds had gone dry.
    Vincent said wetlands are usually associated with groundwater resources.
    “It stands to reason that a slight decline in the water table could cause the small flow that is there to dry up,” Vincent said.
    Vincent said based on his study of aerial photographs from 2009 to 2013, there had not been significant enough increases in irrigation upstream of the Croy Creek wetlands, to have caused them to suddenly dry out.    
    District 37 Watermaster Kevin Lakey said at least two other wetlands south of Croy Canyon have also gone dry. One is west of the Star Bridge on Broadford Road and the other is at the south end of Broadford Road south of Bellevue.
    The wetland at the south end of Broadford Road had not been dry in 25 years, Lakey was told by a property owner.
    “It puzzled me, because the Big Wood River has been lower in other years when these [wetlands] did not go dry,” Lakey said.
    Lakey said he has heard speculation that the dry wetlands could be the result of the Beaver Creek Fire.
    “Some thought it was due to the silt that was in the river,” Lakey said.    
    Vincent said he had not heard of fire-caused silt causing a rapid drop in wetlands water levels.
    “But it is a plausible hypothesis,” he said.
    Vincent said the Big Wood River may have remained higher than usual late last summer because many irrigators did not divert as much water from the Big Wood River, due to the poor water quality.
    “There has been a drought, so despite the other causes, there could have still been a drop in the water table,” he said.    
Tony Evans: tevans@mtexpress.com

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