PHOENIX - A report issued June 30 by the Arizona Department of Water Resources could eventually serve as a template of what's to come when the statewide adjudication of water rights moves to the Verde watershed.
The 1,300-page document defines the subflow zone within the San Pedro River watershed in southern Arizona. The report was created at the request of the Maricopa County court currently settling surface water rights throughout the state.
The subflow zone is the portion of a stream that flows beneath the ground. Delineating its boundaries is critical to resolving the issue of who has a right to use groundwater.
If water pumped from a well is determined to be surface water it is subject to having an established water right before it can be put to use. If water is determined to be groundwater, the owner of the property above can use the water without having a water right.
Wells within the subflow zone are generally considered to be pumping surface water.
"The subflow zone is a jurisdictional concept. It turns upside down the normal legal presumption that water pumped from beneath the ground is groundwater," says Jan Ronald, deputy counsel for ADWR,
"The concept of the subflow zone says that water pumped from a well within the lateral boundaries of the subflow is surface water, putting the burden of proof on the well owner to prove otherwise.
There are currently three unresolved cases in the Verde brought on by Salt River Project, involving the question of wells located within an area that SRP believes to be subflow of the Verde River.
The San Pedro subflow study, years in the making, took into consideration historical documents, scientific reports, geologic mapping, aerial photography and field investigations to determine the lateral extent of the San Pedro's subflow, along with the stream's two major tributaries, Aravaipa Creek and the Babocomari River.
The court has determined that subflow occurs within the geological formation known as the saturated floodplain Holocene alluvium, the porous alluvial deposits of sand, gravel and rock, adjacent to and beneath a stream, laid down over the last 10,00 years.
That, however, may not be the case with the Verde River.
"ADWR and others have said that what the San Pedro report says will not set a precedent for what happens throughout the rest of the state," says water attorney Lee Story. "Each hydrologic basin is unique."
Landowners within the San Pedro watershed who disagree with the methodology used to determine the subflow zone have until the end of the year to object to the ADWR determination.
"The judge will consider the objections, then we are not sure what will happen," Ronald says. "He could accept everything the department has done, or he may come back and have us redo parts of it. We just don't know."
