Mark L. Johnson
Guild Wash EA
Some Tortolita Alliance (TA) members might have received a postcard invitation (see invite left) to comment on the Guild Wash-Santa Cruz River Watershed Plan/Environmental Assessment (Guild Wash EA) and attend a meeting. The US Department of Agriculture Natural Resources Conservation Service is partnering with Pinal County Flood Control District to perform an EA for this critical watershed.
Guild Wash is a tributary to the Santa Cruz River. The watershed (brown line on map below) is extensive and encompasses 97,000 acres. The approximate Tortolita Preserve (TP) boundary is shown red on this map. TP is bisected by the Guild Wash watershed boundary line, i.e. about 50% of the TP is in the Guild Wash watershed. Dove Mountain communities including Del Webb Dove Mountain, Blue Agave, Golden Barrel, Los Saguaros and Boulder Canyon Pass III are located in Guild Wash watershed.
The Guild Wash is also part of the larger Tortolita Fan as shown on the map below. The TP boundary is shown in red.
Flooding, sediment control and soil erosion are the critical issues related to the Guild Wash EA. In 1983, Tropical Storm Octave caused widespread flooding in this watershed and along the Santa Cruz River. From September 27 to October 3, 1983, there was as much as 11 inches of precipitation, resulting in damaging floods. There were 8 lives lost and $226.5 million in damage. US Geological Survey-Floods of October 1983 In Southeastern Arizona Report calculated the flood return frequency of that event for the Santa Cruz River in Tucson and Marana to be greater than the 100-year flood (1% chance).
This study is coming at an opportune time. Although, we are in a 20-year drought, short-term high intensive rainfall events can occur. Especially, high intensity monsoonal rainfall events fueled by climate change. For example, back-to-back 300-year storm events occurred in 2014 and 2015 in La Quinta, CA (western end of the Great Sonoran Desert). Accordingly, TA wants to ensure that higher frequency flood events are analyzed to determine the impact on existing homes/businesses and whether it is prudent to build future homes/business in the flood impact portions of the Guild Wash.
TA will monitor the Guild Wash EA, provide comments and keep TA Members in the loop. We also suggest that TA Members sign-up for email communication at the project website at bit.ly/guild-wash . You can also get the on-line and call-in information for the April 29 meeting from the postcard (above) or the website.