PHOENIX – One thing made clear in witness testimony in the trial over the U.S. water rights claim for the San Pedro Riparian National Conservation Area (SPRNCA) is modeling differences abound and results lie in the hands of the modeler.
Modeling is a process of feeding information into a program to assimilate certain contexts which can provide a forecast of future conditions. In the case of the water rights for SPRNCA, modeling has been performed for decades by numerous scientists, state and federal agencies and local governments. The U.S. Geological Survey has done numerous studies and modelings.
During Wednesday’s court hearing on the government’s water rights claims, another expert explained his modeling criteria. Certified professional hydrologist Dave Romero, president with Balleau Groundwater, Inc., has been active in groundwater assessments for the past 23 years and has performed many analyses for clients.
One of his tasks as requested by the U.S. was to determine the impact on the regional groundwater system if the Bureau of Land Management (BLM), which manages the SPRNCA, were to pump 300 acre feet, almost 98 million gallons, of water into the river in the Charleston reach of the San Pedro.
Under questioning by U.S. Department of Justice attorney Lee Leininger, Romero said if such “emergency” augmentation pumping was done for just one year in June or July over a period of 30 days, an additional 5 cubic feet per second would be added to the river’s flow. It would also draw the aquifer down 1 ½ feet and could create a lesser cone of depression which would easily be recovered in the monsoon.
However, if this was done annually, there could be problems, Romero added.
“It’s a balancing act,” he said. “It does represent a slight loss to the river flow, as groundwater which would support the river would be used for the stream flow. But, the stream would lose less than one-tenth of cubic flow per second.”
He reviewed modeling studies and statistics of the river in the Charleston reach as well as low-flow analyses and noted a decrease in flow over an 80-year period from 1935 to 2015.
The piezometers, which defense witness hydrologist Jeff Weaver said were insufficient to monitor depth to groundwater, Romero said were efficient and he was able to inspect a few while out on the SPRNCA. Piezometers monitor depth of groundwater and have transducers to collect data and are generally hand-rammed up to 30 feet into the ground. While they can get clogged with debris or sediment and knocked out in a flood, BLM has staff to handle such situations, Romero said.
Defense expert witness Amy Hudson’s modeling produced the same outcome as Romero’s. Groundwater pumping has captured groundwater that would be available to the river and riparian plants in the SPRNCA, Romero said.
He said pumping does impact the regional groundwater, the subflow zone and the river itself.
“Pumping changes the system,” Romero testified under direct questioning from Dave Gehlert, a U.S. Department of Justice attorney. “It can create a cone of depression. Water that would go to streamflow and transpiration will be affected.”
A review of a USGS model indicated it did not consider the calibration of streamflow or baseflow.
“It just assessed trends,” Romero said.
Romero also reviewed a study by hydrologist Laurel Lacher and reached the same conclusions on pumping effects on the aquifer.
“The effects of human development are affecting groundwater and the river,” he said.
Sierra Vista’s Environmental Operations Park (EOP) has helped decrease river flow loss, he noted. However, it does not overcome the effect of groundwater pumping for the public use of water, Romero said..
Romero chose Charleston for the area of study because of a study by federal witness William Miller, president and senior aquatic ecologist for Miller Ecological Consultants, Inc., who found more of the native desert sucker fish in the reach. In fact, the reach held 94 percent of the fish.
There is a problem with all the various modeling reviews and it is due to the lack of flood flows and bank storage being factored into the modeling programs, as defense attorney Sean Hood, representing Freeport Minerals, Inc., pointed out.
Romero agreed and said flood flows should be factored into an analysis.
He will be back on the stand Thursday and will be questioned by Deputy County Attorney Sara Ransom.