May 5, 2011

The methods used to research groundwater have evolved over the last few decades to provide better data for geologic models.  Learn more about current and historical research on ground in Nebraska's Panhandle at a May 13 seminar at UNL’s Panhandle Research and Extension Center in Scottsbluff.

Groundwater geologist Steve Sibray’s presentation will be at 3 p.m. in the Bluestem Room and cover both current and historical research.

Sibray has been conducting groundwater research in the Panhandle for more than 20 years. He will discuss methods of researching and characterizing the groundwater aquifer. Water quantity will be an important issue, Sibray said, and geophysics is a key method of answering questions about where water is located and how much is available.

These groundwater research methods are driven by the need for good predictive computer models, which require good geologic models.

One research method Sibray will discuss is resistivity, originally used in oil and mining exploration and adapted for groundwater study. Measuring resistivity with surface-based probes can identify water-bearing geological structures by the differences in their ability to conduct or resist electricity.

Water-bearing sand and gravel layers are resistant to electrical currents, but the Brule Formation common in western Nebraska is a good conductor. It’s composed of siltstone with a high percentage of clay. The Brule Formation does not give up groundwater, except where water collects in fractures and cracks. The North Platte Valley and Pumpkin Creek basin are well-suited to resistivity methods, Sibray said, because groundwater is typically contained in sand and gravel layers overlying Brule bedrock.

Another research method is borehole geophysics, also developed in the oil industry, but used for a long time in groundwater research.

Another method, aerial surveying, is relatively new to groundwater research. In western Nebraska, this has been carried out by a missile-shaped probe suspended under a helicopter. The helicopter flies transect lines at set intervals over the area under study. Sibray said the aerial method was first developed for mining. It allowed companies to search for base mineral deposits such as copper or lead. Aerial surveying also measures electrical conductivity of geological formations.

David Ostdiek
Communications Specialist, Panhandle Research and Extension Center