Drought and overpumping push arsenic into San Luis Valley wells, threatening a poor community

The shrinking aquifer

The San Luis Valley aquifer, which supplies drinking water to thousands of people in southern Colorado, lost an estimated 1.2 million acre-feet of water between 1976 and 2013 [1]. That loss is accelerating as drought tightens its grip: Colorado's snowpack in 2026 is at the lowest level since record-keeping began in 1941 [2]. As farmers and residents pump more water from the ground, the aquifer's water level drops, concentrating naturally occurring heavy metals in the remaining water.

Heavy metals in the tap

Up to one in four private wells producing drinking water in the San Luis Valley contain elevated levels of heavy metals like arsenic and uranium [3]. Testing by SDC Laboratory in southern Colorado found that about 25 percent of well waters exceed the EPA's maximum contaminant level for arsenic [4]. The health risks are severe: exposure to arsenic in drinking water is linked to cancer, cardiovascular disease, diabetes, and impaired cognitive development in children [5].

A community at risk

Private wells are the main source of drinking water for 15 percent of Americans [6]. In the San Luis Valley, about a third of residents rely on private wells [7]. The population is largely Hispanic and poor: the valley has an estimated 21.4 percent poverty rate [8]. Many families cannot afford expensive treatment systems.

Costly and wasteful filtration

Household reverse osmosis systems can remove up to 99 percent of contaminants including arsenic [9]. But they come with a steep trade-off: reverse osmosis systems can waste up to 80 percent of the water that passes through them [10]. In a region where water is already scarce, that waste is unacceptable.

A new filter on the horizon

Researchers at Arizona State University are planning to field test a new filter that removes heavy metals from hard water without losing water [11]. The filter, developed by a startup called AmorPH2O, is expected to be commercially available in 2027 [12]. If it works, it could offer a lifeline to communities like the San Luis Valley that are caught between contaminated water and a drying aquifer.

What to watch next

The field trial in the San Luis Valley will determine whether the new filter can handle the region's hard, metal-laden water. If successful, AmorPH2O's technology could be deployed in other arid regions where groundwater depletion is concentrating contaminants.