A program by Montezuma County Noxious Weed Department to reduce invasive tamarisk and Russian olive trees continues to expand, and has helped to prompt a national pilot program.
The nonnative, deep-rooted trees waste water, crowd out native grasses, willow and cottonwood, and increase wildfire danger, said department Director Bonnie Anderson during a meeting Wednesday at the Southwestern Water Conservation District offices in Durango.
Infestations congest river banks and canals, affect wildlife habitat, and can interfere with irrigation equipment.
Stands of tamarisk, also known as salt cedar, create an alkaline soil that blocks establishment of native plants and increases salinity to water and soil. High salinity levels are a problem for agricultural production.
Mapping shows tamarisk and/or and Russian olive trees occupy about 7,800 acres in the county, Anderson said.
The county noxious weed department treated 139 acres with tamarisk and Russian olives in 2022, up from 112 acres in 2021 and 106 acres in 2020.
From 2019 to 2022, the department, in cooperation with landowners, treated a total of 471 acres that included 45,028 Russian olive trees and 53,415 tamarisk trees.
Removal of tamarisk and Russian olives saves water and soil for native plants, keeps water in the ground and in waterways to benefit agriculture and ecology.
Potential water savings is important during the ongoing 20-year drought in the Four Corners, Anderson said.
Water consumption of tamarisk and Russian olives depends on many variables, and determining how much water is salvaged by their removal is difficult to assess.
U.S. Geological Survey and university studies indicate an average-size mature tamarisk may consume up to 32 gallons of water per day. Russian olives are believed to consume somewhat higher amounts of water.
Based on data from treatment plots, Anderson estimates that the invasive trees on the 471 acres treated in the past four years in Montezuma County consumed an average of 4.94 acre-feet of water per acre per year. Potential water loss per year from the invasive tamarisk and Russian olive is estimated at 35,956 acre-feet, dwarfing the capacity of Narraguinnep Reservoir, at 22,000 acre-feet.
The estimated water consumption of removed trees does not represent how much of the saved water made it to waterways, a difficult calculation because of all the variables.
Montezuma County has a robust noxious weed program and has been successful in finding funding outside its regular budget to fight tamarisk and Russian olives.
From 2019 to 2022, the department was awarded $352,000 in grants from state programs, Anderson said. Landowners provide matching funds. The grant funding has allowed the department to buy needed equipment and herbicide and hire two additional full-time workers.
Anderson was named Colorado’s 2022 Weed Manager of the Year for her determination and creativity in weed management.
The Colorado Department of Agriculture requires data from counties to estimate total population numbers.
Population estimates for tamarisk and Russian olives are incomplete statewide, Anderson said, because most counties lack the funding for mapping.
“Very few counties are able to accurately map and report populations,” she said.
Current CDA data shows 100,253 acres statewide with Russian olive and or salt cedar, representing 491,239 acre-feet of water loss per year, but it could be double that because of insufficient mapping data, Anderson said.
The county noxious weed department has been lobbying Congress to provide more funding and research to control the problem.
Information and presentations have been provided to U.S. Rep. Lauren Boebert, a Republican who represents Colorado’s 3rd Congressional District.
Boebert pointed out that the federal agencies introduced the invasive trees for stream bank stabilization and for wind rows in the 1930s.
“They need to help get rid of them now,” she said in an interview Wednesday with The Journal.
In an April 2022 letter to Congress, Boebert pushed for the establishment of a pilot program that instructs the Interior and Agriculture departments to provide an accurate inventory and funding to combat the tamarisk and Russian olive trees in the West.
“Salt cedar continue to cause significant damage to hundreds of thousands of acres throughout the country,” Boebert stated in the letter. “Salt cedar squander precious water resources and continue to create significant challenges for local communities already suffering from drought and abnormally dry conditions.”
In 2006, a bipartisan law was passed that recognized the need for taking action and removing salt cedar and Russian olive trees.
“Unfortunately, the implementation of this well-intentioned law missed the mark, and ultimately it did little to actually eradicate these invasive species,” Boebert stated. We need a coordinated, effective and efficient system in place to address the “salt cedar and Russian olive tree issues facing this country and to help protect precious water supplies.”
The pilot program was included in the 2023 Interior, Environment and Related Agencies Appropriations bill.