Ephemeral Crossroads: November 2009

The Ogallala Aquifer underlies the heart of the Dust Bowl landscape. Catastrophic dust storms have subsided since the advent of irrigation technology and modern farming practices, yet dust bowl level droughts frequent the region still today. Without access to the irrigation from the aquifer cultivated top soil has little reason to stay put. In Oasis State Park, near Clovis New Mexico, blown top soil has settled due to sporadic trees and a lack of cultivation to create a entirely unique and foreign dune ecology.

Landscape - Sandplains

The Sand Hills of Nebraska is a region where the largest expanse of wind-blown sand deposits and dune topography in the Western Hemisphere (about 20,000 sq miles, USGS). The region supports mixed-grass prairie to take root in the shifting sand and stabilizing the dunes. Within these and hills, both ephemeral and permanent lakes and meadows occur between dunes where ground water is at or near the land surface. The World Wide Fund for Nature designated the Sand Hills as an ecoregion and according to their assessment as much as 85% of the land is intact natural habitat primarily due to the lack of cultivated agriculture and range cattle are managed in order to preserve the stability of the dunes. Throughout the High Plains dune sand soils are important recharge areas for the aquifer and the dune sand of the expansive Sand Hills specifically provides about 80% of the recharge for the aquifer. Consequently Nebraska has about 65% of the aquifer’s water (USGS publication).

Landscape - Playas

Playas are shallow depressions or playas that collect and store water during periods of runoff. Playas are most prevalent south of the Arkansas River and are critical areas of recharge for southern parts of the Aquifer. Playas are ephemeral closed-basin wetlands above the regional water table that have no external drainage and are critical habitat for birds and other wildlife in the otherwise ecologically vacant landscape dominated by the industry of agriculture production. Unlike the expansive dune sand of the Sandhills of Nebraska, playas are numerous but sporadic and geographically located in slight depression where the clay soil of the playa floor swell when wet and shrink when dry to form cracks. It is this soil dynamic which provides the unique areas of potential recharge through the cement like layer Caliche. 90% of the surface area of the southern High Plains drains into the some 66,000 playas, thus making playa important storage during floods and for irrigation and livestock, yet also potential concentrations for ground water pollutants.