Your Assimilative Capacity Has Been Reached

By Pam Lazos

On a recent excursion to Santa Fe, N.M. I was struck by how dry it was even in the late fall. Yes, the climate ranges from arid to semi-arid, but should snow feel dry? For me, it accentuated what’s true of much of the western half of our nation: they’re running out of water.

The Ogallala aquifer, a 10-million-year-old deposit, provides water to New Mexico and seven other High Plains states and is the most important water source in the region, serving an area of 174,000 square miles. Eighty-two percent of the people living in the High Plains get drinking water from this aquifer yet most of the Ogallala is used for agriculture. About 80 percent of the food grown in the U.S. comes from this part of the country.

No wonder the Ogallala is being depleted at a rate 14 times faster than it’s recharging. Population growth, and contaminants like pesticides and nitrates, have contributed to its decline.

Failure to recharge means not only less water but also degraded water quality. Recharge occurs through rainwater and snowmelt combined, a paltry one inch per year. With eight states tapping into one aquifer, at this rate of withdrawal and recharge the Ogallala will be depleted in a few decades and once depleted there is no turning back.

The main barrier to further recharge is impermeability. Currently, the specific yield of the Ogallala — meaning what’s available for use — is 15 percent. The rest of the water is locked up in the unsaturated zone where it’s inaccessible due to impermeability.

Until technology is developed to move this water to the saturated zone, the high quality Ogallala, once used for drinking without either filtration or treatment, will continue to degrade. If a water body is unable to refresh, the water quality tanks, or to put it in scientific parlance, its assimilative capacity, the level at which the water can no longer cleanse itself, has been reached.

Here in the water abundant eastern states drought conditions last seasons, but in the western higher elevations, arid land droughts can last for years, turning an acute issue into a chronic one. Without attention, chronic problems tend to become emergencies. While some inroads have been made regarding the impermeability puzzle, it’s only been achieved on a small scale. It’s time to focus our attention locally before our most valuable global natural resource is beyond recharging.

About the author: Pam Lazos works in Region 3’s Office of Regional Counsel chasing water scofflaws and enforcing the Clean Water Act. In her free time, when her family allows, she writes both fact and fiction, but mostly she likes to laugh.