Ogallala Aquifer groundwater
Daily Earth Science Hydrosphere Repost

Ogallala Aquifer groundwater, sustaining life

One-sixth of the world’s grain production, and America’s breadbasket, depend on groundwater from the Ogallala Aquifer. However, we ask too much of this natural wonder that currently supplies 30 percent of all irrigation water in the United States. Water doesn’t magically appear in an aquifer. The aquifer must continually be recharged from surface water. Unfortunately, the rate of recharge for the Ogallala Aquifer groundwater is slower than the rate of water withdrawal.

The Ogallala Aquifer stores as much water as Lake Huron (29 billion acre-feet) and spreads out underneath eight states. Sadly, many parts of the aquifer are in decline, thus leading to falling water levels, dry wells, and failure of the aquifer to meet annual demand. Hence in western Kansas, aquifer water volumes are down by 60 percent from original levels.

The decline of the Ogallala Aquifer is not due to climate change. Instead, this is a case of insatiable demand and poor water management. If your home only uses water supplied through a large vat that collects rainwater, then you need to know your water budget. Assuming 5000 gallons of rainwater falls into the vat each year, you then know your maximum usage. If you use 6000 gallons a year, then eventually you will have a water supply problem. The Ogallala is no different.

Geology and recharge

The Ogallala Aquifer lies beneath the High Plains portion of the Mid-continent. The primary water-bearing unit in this High Plains aquifer is the Miocene Age Ogallala formation, a formation containing poorly sorted silts, sands, and gravels.  Aquifer thickness reaches up to 700 feet in some areas. The aquifer is generally overlain by unconsolidated Quaternary deposits of alluvial sediments, loess, and dune sands. 

Ogallala Aquifer groundwater hydraulically connects to the surface via the overlying Quaternary sediments. The term “hydraulically connects” means that water can pass from the ground surface through to the aquifer. So, this hydraulic flow connection allows the aquifer to recharged from rainwater falling on the surface of the earth. Water in the Ogallala formation moves slowly, generally flowing from the northwest to the southeast at about 1 foot per day.

The future

The Ogallala Aquifer is a valuable economic resource, and thus heavily monitored and studied. The depletion of the water reserves in the aquifer has been observed over many years. The most immediate effects of over-pumping in the aquifer are wells drying up, thus leading to the loss of water for irrigation and drinking. Less water for crops results in less food production and hence a loss of income for the region.

Below the ground, however, other changes take place. Because the aquifer is primarily composed of unconsolidated sediments, the water stored between sand and silt grains provides structural support. If enough water is removed, then the aquifer can collapse. The collapse process packs the sand and silt grains closer together, thus leaving less space for new water to fill. This process is irreversible, so even if the aquifer fills up again, it can never hold as much water as it initially did.

The recharge problem for the Ogallala Aquifer is related to not enough rainfall replacing what municipalities and commercial enterprises remove. Even though the Ogallala water crisis is human-made, climate change will impact the future of the High Plains. Current models predict a dryer, more arid future for the High Plains. So, the gap in accounting between deposits and withdrawals will grow larger if the region cannot adopt a more realistic water management policy.


ArcheanWeb:

Hot and dry in the Western USA, a megadrought in progress (Source: ArcheanWeb) – https://archeanweb.com/2020/04/21/hot-and-dry-in-the-western-usa-a-megadrought-in-progress/ Also:

The Colorado River is running dry (Source: ArcheanWeb) – https://archeanweb.com/2020/03/03/the-colorado-river-is-running-dry/ Also:

Sinking ground – Water in the American West (Source: ArcheanWeb) – https://archeanweb.com/2020/05/06/sinking-ground-water-in-the-american-west/ Also:

Sources:

Crisis on the High Plains: The Loss of America’s Largest Aquifer – the Ogallala (By Jeremy Frankel; University of Denver Water Law Review) – http://duwaterlawreview.com/crisis-on-the-high-plains-the-loss-of-americas-largest-aquifer-the-ogallala/ Also:

A Vanishing Aquifer (National Geographic) – https://www.nationalgeographic.com/magazine/2016/08/vanishing-aquifer-interactive-map/ Also:

High Plains Water-Level Monitoring Study (Groundwater Resources Program) (USGS) – https://ne.water.usgs.gov/ogw/hpwlms/hydsett.html Also:

Feature Image: Classic Kansas field of waving wheat (By Carol M. Highsmith) (Modified) – https://commons.wikimedia.org/wiki/File:Classic_Kansas_field_of_waving_wheat_LCCN2011632245.tif

William House
William is an earth scientist and writer with an interest in providing the science "backstory" for breaking environmental, earth science, and climate change news.