El Rio Pilot Project
 
Theresa Pinto1*, Spencer Bolen2, Kaylee Colter3, Tom Siegfried4
 
1 Flood Control District of Maricopa County, Phoenix Arizona;  tmp@mail.maricopa.gov
2 Flood Control District of Maricopa County, Phoenix Arizona;  spencerbolen@mail.maricopa.gov
3 Flood Control District of Maricopa County, Phoenix Arizona;  kayleecolter@mail.maricopa.gov
4 Flood Control District of Maricopa County, Phoenix Arizona;  tos@mail.maricopa.gov
 
 
The dense growth of salt cedar has led to the increased size of the floodplain in the lower Gila River west of Phoenix.  In response, the Flood Control District of Maricopa County (FCD) developed a Vegetation Management Plan (Plan) that if implemented would help reduce the floodplain through the removal of salt cedar and re-establishment of native vegetation for a 17-mile reach of the lower Gila River. The El Rio Pilot Project (Project) is the first salt cedar removal project that has been implemented from the Plan.  The goals of the Project are to track costs, test methods and techniques, document survivability rates of plantings, and other success, failures, and lessons that can be applied to other parts of the lower Gila River and potentially other ephemeral rivers in the southwest. 
 
About 24 acres of the site was cleared in December 2017 using a masticator that mulches the salt cedar in place; crews used heavy equipment to try to excavate most of the salt cedar root balls.   In January/February 2018, approximately 400 Freemont cottonwood (Populus fremontii) and Gooding’s willow (Salix goodingii) poles and 250 desert trees were planted on 4.5 acres; no supplemental irrigation was provided to the plants during or after planting.  Salt cedar regrowth was significant but managed using back-pack sprayers to test and apply different concentrations of Arsenal.  After a drier and hotter than normal summer, the survivability of the cottonwoods, willows, and desert shrubs was measured in October 2018 and was approximately 14% for cottonwoods and willows and 56% for desert trees.  In February 2019, FCD is planning to plant additional cottonwoods, willows, and desert trees.   Some of the lessons learned, next steps, issues, and up to date costs will be presented.