C Aquifer Monitoring Program

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The Navajo Nation, the City of Flagstaff (COF), and the U.S. Geological Survey (USGS) maintain a cooperative monitoring program with other local and State agencies for groundwater in the C aquifer (Coconino aquifer) in the Little Colorado River Basin. The goal of this program is to determine baseline groundwater conditions in the C aquifer and other water-bearing zones before significant development in this area occurs and to monitor long-term changes in groundwater levels, water use, surface water, and water chemistry.

Site information and access to site data are available via the C-Aquifer Monitoring Program interative map. Data collected for the program  from 2005 to 2011 were published in Open-File Report 2012-1196 (Brown and Macy, 2012). Data collected for the program from 2012 to 2019 were published in Open-File Report 2021-1051 (Jones and Robinson, 2021). Additional reports evaluating data collected for this program will be produced as needed.

Groundwater resources of the C aquifer in the Little Colorado River Basin are already being affected by groundwater withdrawals for municipal, agriculture, and industrial water uses throughout the upper and middle parts of the basin (Hart and others, 2002). Proposed groundwater development from the C aquifer in the Leupp area includes: 1) the use of a potential well field to the south of Leupp by the Navajo Nation to supply water to southern and western reservation communities, 2) a future water supply for the City of Flagstaff at Red Gap Ranch adjacent to the Leupp wellfield, 3) a future water supply for the Navajo Twin Arrows Casino and new subdivisions east of Flagstaff, and 4) supporting continuing development along the Little Colorado River valley up gradient from Leupp. Additional development of groundwater resources in this area could also occur to improve water supplies for communities in the western part of the Navajo Nation (Leupp, Dilkon, Red Lake, Sebi Delka, etc.). Changing water levels could impact the base flow of lower Clear Creek, lower Chevelon Creek, and the Little Colorado River where riparian habitat support threatened and endangered species and other species of interest in addition to areas of cultural significance to the Navajo Nation and Hopi Tribe.


To establish current baseline information for the C aquifer before significant additional groundwater development occurs around the Leupp area, and to continue monitoring for long-term changes in groundwater levels, water use, and water chemistry.


A monitoring network has been established to collect hydrologic data from the C aquifer. Data are collected that describe the groundwater and surface-water systems. Continuous measurements of groundwater levels are made at 5 observation wells, and quarterly groundwater measurements are made at 12 additional wells. Water-level measurements from an additional 18 wells measured by the Arizona Department of Water Resources and the City of Flagstaff are also included when available. Discharge and water-quality field parameters are collected at springs and along Lower Chevelon Creek, and Lower Clear Creek to continue to document and characterize the quantity and quality of water resources at the western and southern end of the Navajo Nation. Seepage investigations are conducted on lower Clear Creek, lower Chevelon Creek, and the Little Colorado River to evaluate the base flow component of these streams.

Map showing approximate extent of the C Aquifer and location of the study area, northeastern Arizona.

Approximate extent of the C Aquifer and location of the study area, northeastern Arizona