Vanished Artesian Wells

Hilton A, Jasechko S. Widespread aquifer depressurization after a century of intensive groundwater use in USA. Sci Adv. 2023 Sep 15;9(37):eadh2992. doi: 10.1126/sciadv.adh2992. Epub 2023 Sep 13. PMID: 37703375; PMCID: PMC11006208.

Widespread aquifer depressurization after a century of intensive groundwater use in USA - PMC

Leonard O Ohenhen, Manoochehr Shirzaei, Patrick L Barnard, Slowly but surely: Exposure of communities and infrastructure to subsidence on the US east coast, PNAS Nexus, Volume 3, Issue 1, January 2024, pgad426, https://doi.org/10.1093/pnasnexus/pgad426

The article below is to a large extent excerpted and paraphrased from the paper cited above.

Flowing artesian wells are defined as wells where groundwater flows to the land surface without pumping. Flowing artesian conditions can arise in wells that tap unconfined aquifers or those that tap confined aquifers. Flowing artesian conditions were more widespread in the 19^th and early 20^th century than they are today, I am old enough to recall when an artesian well flowed not too far from where I sit now.

As our country developed these flowing artesian wells were used to supply water- irrigate farmlands, provide safe and inexpensive drinking water, and support businesses. This was the first groundwater we could tap without the available pumps and power of today. Groundwater sustains food systems and provides drinking water to millions of people in the US today, but most of the flowing artesian wells are gone.

Flowing artesian conditions indicate that there is a sufficiently high hydraulic head for upward-oriented groundwater flow. Upward-oriented groundwater flows may protect deep drinking water from downward transport of surface-borne pollutants (6). The loss of flowing artesian conditions and upward-oriented groundwater flows demonstrate depressurization of an aquifer. Depressurization can change groundwater flow patterns over large areas, affecting the solute distribution sin aquifers. Depressurization can also alter an aquifer’s skeletal structure by the compression and compaction of confining units, resulting in land subsidence and the loss of groundwater storage, especially in aquifer systems with fine-grained unconsolidated sediments.

Despite their importance to groundwater-dependent ecosystems and human water access, no continent-wide study had quantified how prevalent flowing artesian conditions once were or how they have changed over the last century. In the above cited study, the  researchers compiled thousands of water level measurements from US Geological Survey reports published in the early 1900s and compared these measurements to modern well water level measurements. They developed two complementary analyses to quantify change over time in flowing artesian conditions at the regional and continental scale and examined them for the eight regional aquifer systems of the continental United States.

In six of the eight regional aquifer systems, they found that flowing artesian conditions were common a century ago.  In the pre-1910 dataset 48% to 100% of wells were flowing artesian). Today, however, fewer than 10% of wells are flowing artesian (in our post-2010 dataset. These six systems are:

• Dakota Aquifer System (where the proportion of wells that exhibit flowing artesian conditions declined from 93% to 9% over the past century;
• North Atlantic Coastal Plain Aquifer System (declined from 83% to 0.8% over the past century;
• Mississippi Embayment Regional Aquifer (declined from 48% to 0.5% over the past century;
• Houston-Galveston area within the broader Gulf Coast Aquifer System (declined from 96 to 0% over the past century; 
• Roswell Artesian Basin in southeast New Mexico (declined from 100% to 0% over the past century; 
• California Central Valley (declined from 77% to 0.2% over the past century; 

Flowing artesian wells were also common over a century ago in the Floridan Aquifer System (58% of wells in our pre-1910 dataset). Contrasting the four above aquifer systems, the Floridan Aquifer System has retained an ability to support flowing artesian conditions at present day (17% of wells exhibit flowing artesian conditions in our post-2010 dataset). The wells that exhibit flowing artesian conditions are concentrated along the coasts, whereas flowing artesian wells are nearly nonexistent farther inland. The proportion of wells exhibiting flowing artesian conditions declined considerably from 58% of wells to 17% in our post-2010 dataset.

Flowing artesian wells were not common in the Columbia Plateau Regional Aquifer System before 1910. In our pre-1910 dataset, just 2% of wells that tap confined aquifers exhibit flowing artesian conditions, and 1% of wells are flowing artesian in our post-2010 dataset. The pre-1910 Columbia Plateau Regional Aquifer data shows that not all confined aquifers supported flowing artesian wells a century ago.

Flowing artesian wells have served humanity for centuries. In the US, flowing artesian wells enabled settlements, supported livelihoods, and provided safe and equally available drinking water supplies to settlers and indigenous peoples.  The analysis found a substantial reduction in the prevalence of flowing artesian conditions across the US (~61% in our pre-1910 dataset, to ~4% in our post-2010 dataset. The results provide evidence for a widespread depressurization of confined aquifer systems.

The decline in flowing artesian conditions may imply a reversal of groundwater flow directions from natural upward-oriented flow to the modern-era where there is a greater likelihood for downward-oriented flow. These reversed vertical groundwater flow directions and depressurized aquifer systems have likely increased the potential for contamination in deep aquifers and induced land subsidence. The analysis reveals that flowing artesian wells have been extinguished over a century of groundwater use in the US, affecting aquifer systems and humans that rely on artesian aquifers.