This spring, I was delighted to learn of the Hobbs administration’s intent to revoke water-pumping permits for the Saudi operators looking to raise alfalfa in La Paz County. It was a very welcome bold stroke that sent a clear message to “big ag” about our water priorities in Arizona.
The dewatering scheme of Australian mining company South32 for its Hermosa Project in the Patagonia Mountains is also a massive pumping plan—up to 4,500 gallons per minute, or 197 million gallons a year. Of course, the flat lowlands of La Paz County are very different from the tumble of mountain and valley land we enjoy in the Sky Islands and dewatering a mine is very different than irrigating a crop. The scope and effects of South32’s dewatering need a little explanation.
When the company first publicized their plans, I couldn’t quite comprehend the magnitude of the dewatering plan. It was a scene from the company’s three-minute promotional video (tinyurl.com/2r3joeqp) on their strategy of water management that truly terrified me.
High-volume drawdown from wells creates what hydrologists call a “Cone of Depression,” a curving funnel that would be dried out by massive 24/7 pumping, probably required for the life of the mine, now estimated at 60 years. In the South32 video, the funnel is shown as a blue mist, lying rather ephemerally over mountain terrain. A blue line spirals down to a drainage point right below the Hermosa Project. If wells were drilled to the bottom of the major deposits South32 seeks to mine, that drainage point could be more than 5,000 feet below the surface. With 5,100 feet above sea level being the approximate surface elevation of the Hermosa project, the bottom of the cone of depression can be visualized as roughly at sea level, around 4000 feet below the elevation of Patagonia. This is why the Cone of Depression is so extensive on the surface, so massive underground, and so terrifying when you figure out how more than half of the Patagonia Range north of the Mexico border could be impacted. I’d nickname the desiccated funnel the “Cone of Devastation.”
South32’s promotional video gives the blue mist of the Cone three seconds of screen time, long enough for a frame capture, but not long enough to visualize its real-world extent. Knowing the territory, I was able to add a dozen place labels that show the perimeter of the area that the company proposes to dry out. At about seven miles in diameter, it covers around 47 square miles. That’s roughly 70 times the 450-acre patented land area of the Hermosa project.
The perimeter of the Cone extends beyond the Coronado National Forest lands to include ranches like the Hale Ranch and private residences as well as a small vineyard, two historic settlements (Harshaw and Mowry) and their nearby graveyards. Over 90% of the proposed area of desiccation lies in Patagonia’s Designated Municipal Watershed (and yes, I’ve mapped them together.)
Sucking down all the water would be almost certain to dry up wells. It would also be very likely to dry up the dozens of seeps and springs now being mapped by Sky Island Alliance. It would be almost certain to kill the trees and other vegetation, which would promote wildfire, which would in turn promote erosion and possibly landslides. This spreading disaster would decimate the scenery and wildlife that the region’s growing – and sustainable – ecotourism industry depends on. When such a vast drawdown of groundwater gets to the surface, it would also decimate acreage now being grazed, whether in private ownership or BLM leases.
That haunting image of the cone is only the first half of the story. Downstream from the Hermosa Project, roughly six million gallons a day would pour down the generally rocky streambed of Harshaw Creek. All that gallonage has to drop about a thousand feet from mine site to Town elevation, so it would quickly the reach flat ground at the town. Near Sonoita Creek, the Town of Patagonia depends on two wells for its municipal supply, and they might be polluted if the groundwater rose substantially, or if flooding reached them. Built on a marsh, Patagonia is flood-prone already, as historic photos graphically show.
Present well levels in Town range from six to 40 feet. In one neighbor’s old hand-dug well near Fourth Ave. I was recently shown the water of this aquifer visible at 17 feet below ground surface. Directly, rather than through maps or data, I could see and feel the closeness of the aquifer to the surface, even smell it.
If local water levels increase because of aquifer absorption of mine-discharged water, and then a sizable monsoon storm adds a big slug of water, flooding in Patagonia would be almost certain. 60% of the town’s properties lie in the FEMA-designated 100-year flood zone, so a flood at or above the scale of 1938 or 1983 could disrupt the town’s water supply, cause major property damage and possibly loss of life. There could be ecological and flood effects downstream to the Lake and beyond. And we know that increasingly extreme weather – including both drought and precipitation “events” – is a primary feature of ongoing climate change.
These thoughts are not rocket science. The sheer scale of potential impacts from such massive drying and wetting is staggering. The mountains are at risk; Harshaw and Sonoita Creeks are at risk; the village of Patagonia is at risk. As now proposed, dewatering is a two-part catastrophe in the making.