ONTARIO, CALIF. — CH2M Hill has unveiled the findings of a comprehensive year-long study measuring the vast scale and recharge rate of the Cadiz aquifer system. The study, presented this month at a conference of the Association of Ground Water Agencies and American Ground Water Trust, describes a groundwater basin consisting principally of an alluvial and carbonate aquifer ranging in size between 17 and 34 million acre-feet, a volume of water larger than Lake Mead, the nation’s largest surface reservoir.
The findings also confirm the presence of highly permeable limestone carbonate rock lying beneath the alluvium, which contributes significantly to the productivity of the aquifer system.
CH2M Hill’s findings have been peer-reviewed by leading hydrology experts and the results corroborated by extensive field research and pump testing involving the excavation of four borings and test wells to depths of between 1,000 and 1,947 feet beneath the earth’s surface.
Based on this study of natural recharge in the aquifer system, Cadiz Inc. will develop a groundwater management plan providing for the safe long-term annual withdrawal of 50,000 acre-feet of water each year, an amount that can sustainably supply the total water needs of 400,000 Southern California residents.
“This is the most comprehensive study of the hydrogeology of the watershed ever undertaken, based on recent field data and on the best and latest science,” said Terry Foreman, CH2M Hill’s senior hydrogeologist. “In the initial phase of the study, we’ve concentrated on developing a watershed model to determine the total volume of water in storage and the long-term yield that can be safely recovered on a sustainable basis. We had the benefit of a recently published U.S. Geological Survey (USGS) watershed model, fresh technical surveys conducted by the federal government, and an array of new data obtained from climate research. The application of the USGS model clearly supports the conclusion that the Fenner Valley includes a deep and dynamic aquifer system holding a significant and renewable water supply.”
To corroborate these findings researchers conducted a second phase of field work, which included a deep survey and pump test of the water table of the Fenner Valley. Test well data, including video taken to a depth of approximately 1,800 feet, confirmed the presence of water in the alluvial soils and deep into the carbonate units.
“The scientific debate about this aquifer system has always revolved around two questions: How deep is the water table beneath Cadiz, and does it extend way down beneath the alluvial soils into the underlying layers of carbonate rock,” said Dr. John Sharp, Carlton Professor of Geology at the University of Texas, and one of the nation’s leading experts on limestone carbonates. “These layers of dolomite, sandstone and limestone rock were laid down by an ancient seabed and are highly permeable. We now have new test well data, pumping results from the wells, and dispositive video evidence showing huge quantities of water flowing like a river through cavities 1,000 feet beneath the ground.”
Bob Ereth of Layne Christiansen, whose firm conducted the field tests, said in 43 years in the business, he has never seen a test well as productive as this one.
The findings were also independently analyzed and corroborated by Dr. Dennis Williams, who teaches ground water modeling and geohydrology at the University of Southern California and whose firm GEOSCIENCE Support Services Inc. previously conducted an exhaustive study of the Cadiz aquifer system for the Metropolitan Water District.
“These findings are entirely consistent with our earlier estimates of groundwater recharge into the Fenner, Bristol and Cadiz watershed areas,” said Williams.
There is undoubtedly a prolific aquifer system in the Fenner Valley, said Andrew Stone, hydrogeologist and executive director of the American Ground Water Trust. “CH2M Hill has systematically followed prudent and sound scientific methodologies in its comprehensive report characterizing the hydrogeology of the aquifer system.”
For more information about CH2M Hill or to view a video detailing the new findings and describing the extent of the water resource at Cadiz, please visit www. ch2mhill.com, or www.cadizinc.com/pureproof, respectively.