Two Recent Developments in Managing the San Pedro River

Sept. 29, 2023
san pedro river

Image: Katja Schulz

The San Pedro River, running south to north from its headwaters in the mountains in northern Sonora, Mexico, to its confluence with the Gila River in Arizona, is a critical riparian corridor and hotly contested water resource. Recently there have been two noteworthy developments in the region’s management: a ruling from the Maricopa County Superior Court quantifying federal reserved water rights for the San Pedro River National Conservation Area (SPRNCA), and a petition sent to ADWR to designate the Upper San Pedro Basin as an Active Management Area (AMA).

On August 24, 2023, Maricopa County Superior Court judge Mark Brian issued an order quantifying federal reserved water rights for SPRNCA as part of the ongoing General Adjudication of the Gila River System. The order, which comes 35 years after Congress established the national conservation area, quantified rights to instream flow, flood flows, and groundwater to protect the “riparian area and the aquatic, wildlife, archeological, paleontological, scientific, educational, and recreational resources of the SPRNCA.” The rights are based on mean monthly surface water flow measured at four stream gages and groundwater elevations taken at nine monitoring wells within the conservation area. Water law expert Robert Glennon said in a recent article in the Arizona Daily Star that this decree is “an incredibly important step forward” for the conservation of the river.

On September 20, the San Pedro Alliance, a coalition of local, state, and international organizations, submitted a petition to ADWR to designate the Upper San Pedro Basin as an Active Management Area under the 1980 Groundwater Management Act. This is the third petition to be filed with the state, with the first filed by the Sierra Club in 1984, then again by the San Pedro Alliance in 2000. The first two petitions were denied because, according to a recent article on the Alliance’s petition, ADWR found an AMA designation wasn’t necessary because there was sufficient groundwater to meet future municipal, industrial, and agricultural needs. The recent petition argues that ADWR’s denial of the Alliance’s previous petition ignored federal water use in the SPRNCA (a point punctuated by the Maricopa County Supreme Court order) and describes the continued expansion of groundwater use in the basin since 2005.