Rocks and sediments that hold and transmit groundwater are called “aquifers.” Aquifers may be just beneath the land surface or very deep underground: water will continue to seep deeper underground until the rocks become too impermeable for the water to pass through. Groundwater that is recharged by surface water seeping through the ground is often fresh, but some groundwater is salty, either because the water originally came from the sea or because the groundwater dissolved minerals from the surrounding rock.
Groundwater is often a "transboundary" resource, shared by many groups of people across town, county, state, and international boundaries. Changes in groundwater resources can create unique challenges requiring high levels of cooperation and innovation amongst stakeholder groups, from individuals to state and federal government.
The High Plains Aquifer (HPA), which spans eight states from South Dakota to Texas, is overlain by about 20 percent of the nation’s irrigated agricultural land, and provides about 30 percent of the groundwater used for irrigation in the country according to the U.S. Geological Survey. Work by the Kansas Geological Survey indicates that some parts of the aquifer are already effectively exhausted for agricultural purposes; some parts are estimated to have a lifespan of less than 25 years; and other areas remain generally unaffected (Buchanan et al., 2015).
The 2016 Critical Issues Forum was a 1-½ day meeting covering multiple aspects of groundwater depletion in the High Plains. Presentations covered the current state of the High Plains Aquifer and water usage from scientific, legal, regulatory, economic, and social perspectives. State-specific perspectives were provided from Kansas, Nebraska, Texas, and Oklahoma, and a variety of issues were discussed surrounding communication, negotiation, policy, and the influence of climate change. Break-out sessions and participant discussions identified lessons learned and best practices from the High Plains Aquifer experience that might apply to other regions facing changes in the Earth system.
Widespread use of groundwater for irrigation in the United States emerged in the early- and mid-20th century, with withdrawals growing for decades subsequent as more — and higher capacity — wells were drilled. Access to abundant groundwater allowed farmers to grow more food on more land and to better withstand crop-withering droughts. The ensuing agricultural boom fed a growing U.S. population and fueled increasing national health, prosperity and food security. Today, roughly 11 percent of U.S.