International Waters 

Arizona and Sonora, Mexico share surface water and groundwater resources. The Santa Cruz and San Pedro Rivers flow north from Sonora into Arizona and Whitewater Draw in the Douglas Irrigation Non-expansion area flows intermittently south to Sonora.  All the groundwater basins along Arizona’s international boundary are shared with Sonora. From west to east these transboundary groundwater basins are the Yuma, Western Mexican Drainage, San Simon Wash, Tucson and Santa Cruz Active Management Areas (AMA), San Rafael, Upper San Pedro, Douglas and San Bernardino Valley Basins. Both the San Simon Wash and Western Mexican Drainage Basins are under federal ownership. Water use on either side of the border may impact the resource on the other side. Because of this shared resource it is important to understand the hydrology, water demand and water resource issues in the Mexican border region.

Binational issues related to the Colorado River are intimately connected with the Law of the River, including international treaties and are discussed in the Colorado River Management section. In general, water resource issues in the border region are related to declining supplies and increasing demand for water on both sides of the border due primarily to population increases.  More hydrologic information regarding water resource availability is needed in the border region including binational data sharing.

In the Santa Cruz AMA the department is involved with several binational activities.  These include efforts to develop an integrated groundwater model, discussions regarding future use of the effluent generated by Mexico and treated at the Nogales International Wastewater Treatment Plant (NIWWTP) in Arizona, discussion on development of an upgrade project for the NIWWTP to improve the quality of the wastewater effluent and participation in the binational pretreatment program technical committee that is essential to the effective operation of the NIWWTP.

In the Upper San Pedro Basin, as a member of the Upper San Pedro Partnership, the Department is involved in activities to facilitate cross-border cooperative efforts that may include data sharing, education and planning. 

The Department is an active participant in the EPA Border 2012 Arizona-Sonora Water Task Force www.epa.gov/usmexicoborder that includes the entire border region with the exception of the Colorado River area.  From the point of view of Arizona and Sonora, water quantity issues are a key component of the program. Meetings have been held in Agua Prieta, Bisbee, Hermosillo, Nogales Arizona, Nogales Sonora, and Sells to gather input on local water resource issues and needs in order to prepare a plan of work.  The meetings have improved communication and coordination between the U.S. and Mexico water and environment agencies, sharing of information about water management on each side of the border, a mission statement, identification of priorities, and a workplan for 2005-2006. Among the first of these activities is development of a binational water quality and quantity database with the goal of identifying data gaps in the Arizona-Sonora region.

The Border Governor’s Conference www.bordergovernorsconference.com Water Table is another forum for border cooperation.  At the 2005 conference in Torreon, Coahuila, the following declaration was adopted: “Establish a one-year work program among the ten border states, which provides an opportunity to each state to express issues, identify and promote water related initiatives and the permanent exchange of data and information regarding surface and groundwater along the border, empahasizing the extreme phenomena of drought and water excess, which also facilitates the interpretation and implementation of international agreements and treaties on the subject.”