A team of Arizona Department of Water Resources field researchers recently completed a two-month-long “basin sweep” in the northwestern part of the state, intensively evaluating the underground water levels in the Northwest Basins Planning Area that surrounds the city of Kingman.
The area includes the Hualapai Basin, which the ADWR Director Tom Buschatzke designated as an irrigation non-expansion area (INA) in December 2022 after months of requests for the INA designation from the Board of Supervisors and residents of Mohave County. An INA prohibits landowners from building systems of irrigation on land that previously did not have irrigation.
A variety of agricultural groups and individual farm owners, such as the Arizona Farm Bureau Federation, opposed the INA designation due to what they called a lack of evidence to support the decision. In January, a Tucson-based law firm representing two out-of-state limited liability corporations filed a notice of appeal to the designation in Maricopa County Superior Court in Phoenix, as reported by Havasu News.
Ryan Mitchell, ADWR chief hydrologist, said that “for an INA, you can still pump the water, you can get your grandfathered right to irrigation, but you can’t expand the acreage.”
However, the nature of an INA does not necessarily equate to water savings. Different types of crops require varying amounts of water and often require more water as time passes and the crop ages, according to Mitchell.
“The small tree doesn’t use as much water as a 10-year-old tree, and so that water use, despite the irrigated acreage not changing, will likely be fluctuating and will likely be going up if the trees are maturing and need more water,” Mitchell said. “But (an INA) does help pump the brakes and kind of slow everyone down.”
“If (farmers) are staying within that irrigated acreage, the acreage doesn’t expand. They will satisfy the rules of the INA, but they’ll still be pumping more water,” Mitchell said.
ADWR conducts basin sweeps according to five- and 10-year scheduled plans, giving priority to INAs, Active Management Areas (AMAs) and other critical locations. Field researchers gather water data that helps to demonstrate trends in hydrology ¬– primarily how water is distributed underground and how water levels have changed over time.
According to Teri Davis, field services section manager for the ADWR Hydrology Department, the state’s water authority took over these hydrologic monitoring responsibilities from the U.S. Geological Survey, which had the responsibility of recording all water data prior to the establishment of ADWR in 1980.
ADWR assigns field workers who are not working in a specific area at the time of the basin sweep to survey the identified section of the state. The high number of researchers converging to work in one area allows for ADWR to quickly collect a large amount of data.
“Instead of one or two measurements in a basin every year, you end up getting like 30 or 40 measurements in about a one-week period,” Mitchell said. “We use that data for our models, we use that data for groundwater trends, and all of the stuff they collect eventually gets put into the GWSI (Arizona Groundwater Site Inventory).”
A typical basin sweep will take place over the course of four to six weeks. But according to Davis, ADWR often faces delays in the data collection process due to myriad reasons relating to well access.
Davis said that aside from well owners moving and wells sometimes collapsing, there are two distinct active well databases: Wells 55, ADWR’s registry mandated by statute, and the Arizona Groundwater Site Inventory, which labels wells differently with coordinates confirmed by a site visit.
“It’s just very difficult when we spend an excessive amount of time trying to match wells between Wells 55 and GWSI, making sure that we know what well we are at,” Davis said, explaining that a standardized system of wells in critical areas could streamline groundwater level monitoring.
ADWR sends researchers on site inventories prior to scheduled basin sweeps to remedy this often-delayed process, allowing for ADWR to confirm well location and method of construction.
“With AMAs and INAs, typically we have had more site inventories,” Davis said. “We can go quicker when we are familiar with the area.”
Davis said that “from planning a basin sweep, to organizing and ensuring that we have our equipment calibrated for our standards, to making sure our trucks are in working order,” ADWR’s data collection process is a meticulous and planned out sort of “clockwork.”
The ADWR Hydrology Department typically takes two to three weeks to complete quality assurance checks and enter the data into the GWSI – an interactive and multi-layered map on the ADWR website that allows users to view where basins, sub-basins and groundwater wells are located throughout the state.
A report explaining the findings of the data collection takes an additional two to three months to be compiled by the ADWR Hydrology Department. But results from the Northwest Basin Area sweep are unlikely to demonstrate the impact of the Hualapai Basin INA designation because of the drawn-out rate at which water moves through underground basins and aquifers – due to dirt and sentiment creating resistance for the flowing water, according to Mitchell. The effects of the INA designation are more long-term.