Ground Water. Nebraska Department of Natural Resources.
The state agency website includes information on ground water statutes, use, contaminants, wells, and relationship to surface water.
https://www.dnr.state.ne.us/docs/groundwat.html
Groundwater Atlas of the United States: Kansas, Missouri and Nebraska
Now available online, this classic title describes "the location, the extent, and the geologic and hydrologic characteristics of aquifers" in the region.
https://pubs.usgs.gov/ha/ha730/ch_d/index.html