Groundwater Quality and Age of Secondary Bedrock Aquifers, Eastern Nebraska

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In eastern Nebraska, secondary aquifer systems are increasingly being considered to supplement growing municipal, domestic, and agricultural water demands. Within the Eastern Nebraska Water Resources Assessment (ENWRA) area, airborne geophysical surveys have mapped the thickness and extent of these aquifers over much of eastern Nebraska; however little is known about the age and quality of water in these secondary aquifers. We are sampling water from wells within the ENWRA for basic water chemistry, nutrients, stable isotopes and selected age tracers to aid water managers in determining if the secondary aquifer system is a usable resource.

In eastern Nebraska, secondary aquifer systems increasingly being considered to supplement growing municipal, domestic, and agricultural water demands. Within the Eastern Nebraska Water Resources Assessment (ENWRA) area, airborne geophysical (AEM) surveys have mapped the thickness and extent over much of eastern Nebraska; however, little is known about the age and quality of water in these secondary aquifers. We are supplementing the AEM surveys by providing key pieces of data intended to inform water managers of the sustainability of the secondary bedrock aquifers by determining the quality and age of groundwater.

Locations of wells that potentially utilize the secondary aquifer in eastern Nebraska
Well locations that potentially utilize the secondary aquifer in the ENWRA project area.

An improved understanding of the three-dimensional extent and quality of the aquifers is important in determining how increased development of the resource could impact the water quality. Furthermore, a better understanding of the age of the groundwater will show where recharge is occurring, and where anthropogenic compounds could be introduced into the system. Older groundwater may also indicate lower recharge rates, and potential sensitivity to future development.

Sampling

We are sampling water from existing wells (monitoring, domestic, or irrigation) for

  • basic water chemistry,
  • stable isotopes,
  • age tracers, and
  • anthropogenic compounds such as triazine.

Well Selection

Wells have been selected using the top and bottom of bedrock surfaces derived from AEM surveys and the screen information provided by the Nebraska Department of Natural Resources registered well database. Well selection is focused in areas where wells in close proximity are screened at differing elevations within the secondary aquifer. The purpose of sampling water from multiple wells in close proximity is to better understand how the quality and age changes within the aquifer by depth. Priority will be given to areas where little groundwater quality data has previously been collected, but development is occurring.

Data

Data we collect are being compiled with data collected during other water-quality studies focused on the secondary aquifers. The subsequent report will summarize the data collected to provide resource managers with concise data about the water quality of the secondary bedrock aquifers.