HYDROLOGIC CHANGES IN THE C-AQUIFER OF NORTHEASTERN ARIZONA, 2005-2019

The Coconino aquifer (C aquifer) is a regionally extensive, multiple-aquifer system in parts of Arizona, New Mexico, and Utah that supplies water for municipal, agricultural, and industrial use. In northeastern Arizona, increases in groundwater withdrawals, coupled with ongoing drought conditions, have resulted in aquifer declines and the drying up of Obed Meadows, a natural peat deposit, and Hugo Meadows, a natural wetland, both south of Joseph City, Arizona. To monitor these changes, the U.S. Geological Survey’s C-Aquifer Monitoring program operates continuous groundwater level stations at five wells and measures discrete groundwater levels at another 12 wells in northern Arizona. Water levels in wells indicated little change to about two feet of decline from 2005 to 2019. Nine baseflow investigations during this same period were conducted on Clear Creek, Chevelon Creek, and a groundwater-fed portion of the Little Colorado River of northern Arizona to identify a hydrologic baseline and to track temporal changes. Highly conductive spring discharge along these reaches contributes to an increase in specific conductance and total discharge. Continued monitoring of the C aquifer in the study area will be essential in quantifying physical and chemical responses to continued stresses from withdrawals and drought on the aquifer.