The Ogallala aquifer and other aquifers produce about one-third of america’s corn, wheat, alfalfa and other crops that feed both people and animals. They are being depleted rapidly and most wont’ be recharged until after the next ice age.
According to the USGS Groundwater Depletion in the United States 1900-2008:
- Groundwater depletion in the United States between 1900–2008 was 240 cubic miles (1,000 cubic km3).
- That’s twice as much water in Lake Erie (480 km3).
- For many areas the rate is unsustainable
- This rate increased dramatically after 1950
- The consumption rate nearly tripled from 2000-2008 over past rates. Some of this was due to drought and decreased snowmelt.
- In 2000-2008 about 25% of all water taken during the previous century was removed. This large volume of depletion represents a serious problem in the United States because much of this storage loss cannot be easily or quickly recovered and affects the sustainability of some critical water supplies and base flow to streams, among other effects
- The Ogallala aquifer won’t be replenished until after the next ice age and underlies 10 states (175,000 square miles). It is the main source of drinking and agricultural water. In 2000-2008, as much water was taken out as during the entire previous century from 1900 to 1999.
- Another dark side to depleting aquifers is that the extra water runs into the ocean and adds 2% of the global sea-level rise seen so far.
Map of the United States showing cumulative groundwater depletion 1900-2008 in 40 assessed aquifer systems or subareas. Colors are hatched in the Dakota aquifer (area 39) where the aquifer overlaps with other aquifers having different values of depletion (page 16).
Agricultural and Land Drainage in the United States
During the 20th century, many agricultural and civil engineering projects were completed for land reclamation, flood control, and agricultural drainage purposes in the United States. This led to significant losses of wetland areas throughout the Nation. On farms, crop yields can be increased by keeping the water table some distance below the land surface, thereby precluding waterlogging of land and allowing salts to be removed from the soil profile. Drainage projects can result in permanently lowered water-table elevations both locally and regionally. Where the seasonal or average annual position of the water table is permanently lowered, the net decline represents a long-term depletion of the volume of groundwater in storage below the land surface.
The first half of the 20th century was marked by emerging technologies for land drainage. Farmers joined together in drainage organizations to build drainage and flood control measures. Large-scale drainage projects backed by drainage organizations and Federal agencies affected both large and small wetland areas. Agricultural and urban expansion persisted throughout the United States. Use of drained lands usually occurred in a succession, from undrained wetlands to agricultural lands to urban areas. These factors led to the drainage of over 100,000 square miles of wetlands in the lower 48 states during the 20th century, which is about 55 km3 of permanently lost water.