3125 Portia St
PO Box 83581
Lincoln, NE 68501
402.476.2729

kcameron_enwra@lpsnrd.org

 

News

The 2020 Airborne Electromagnetic (AEM) Survey Flight reports for the Nemaha and Papio-Missouri-River NRDs are complete! You can also click here for an updated location map of the eastern Nebraska 2006 to 2020 flight locations. A statewide interactive map of all flight lines is available here. Digital polyline files are available on the AEM tabs and at the bottom of the AEM Project Partners Tab. New tutorial video links demonstrating the download and use of the report deliverables are also availiable on the Media/Downloads Tab as well as other ENWRA project reports. Be sure to visit our other website tabs and the Nebraska GeoCloud website for more information on statewide AEM data availiability, guidelines and standards.

Groundwater elevation, weather station data and sampling results for ENWRA's 3 pilot study sites are now available under the Media/Downloads Tab. Click here for a link to download the 2008 to 2020 compiled datasets and graphs (345 MB).

 

 

Calendar

ENWRA's Spring Technical Committee Meeting is planned for May 17, 2021 via Zoom.

 

ENWRA Projects

Airborne Electromagnetic (AEM) Survey

AEM system flown October 2014/April 2015

AEM survey is a very rapid and efficient way of remotely sensing geology across an entire site without engaging in extensive drilling. In AEM surveys, a geophysical device (typically bullet or hoop-shaped) containing sensors is suspended beneath an aircraft (can be helicopter or fixed-wing). An electromagnetic field is continuously transmitted to the land surface (and subsurface) while the aircraft is in flight and the sensors carried under the aircraft receive the subsequent return of electromagnetic energy from the land surface.

Click here to watch an educational video produced by QUEST NEBRASKA

regarding AEM survey and Nebraska's groundwater. Please click here for a 2017 presentation of ENWRA AEM data by Aqua Geo Frameworks, LLC

2007 Helicopter Electromagnetic (HEM) Survey, Pilot Study Sites

Various technologies were applied to three geologically distinct pilot study sites (Ashland, Oakland, and Firth) to determine the most efficient way to characterize eastern Nebraska’s varied geology.

HEM over pivot

HEM system flown in 2007 and 2009

HEM survey (frequency domain electromagnetic geophysical method) was found to provide useful information in two of our three pilot study sites where there was little to moderate thicknesses of glacial till.

For more information and videos of the 2006-2007 HEM data, visit our Media/Downloads page (converted by AGF in 2016, the pilot study HEM datasets are also available in Google Earth .kmz format).

2009 HEM Surveys, Sprague and Swedeburg Areas

Lower Platte South and Lower Platte North budgeted $240,000 in 2009 for additional HEM flights outside of the pilot study areas. These areas are of special interest to their Natural Resources Districts because of water quality and quantity issues. The Nebraska Environmental Trust has contributed an additional $200,000 toward processing the data generated by the flights (reports are available for download on Media/Downloads page - converted by AGF in 2016, the Sprague dataset is also available in Google Earth .kmz format).

2013 AEM Surveys, Clarkson-Howells & Dwight-Valparaiso-Brainard Areas

In 2013, the Lower Elkhorn and Lower Platte South contracted approximately 190 square miles (combined) of additional AEM flights to learn more about areas in their respective Natural Resource Districts with water quantity issues in the 2012 drought season. These surveys employed the time domain electromagnetic geophysical method (TDEM), an AEM method capable of resolution below the thick glacial tills common in eastern Nebraska. Click here for a copy of the Lower Elkhorn report for the Clarkson-Howells area. Click here for a copy of the Lower Platte South AEM report for the Dwight-Valparaiso-Brainard survey. The 2006 to 2013 reports, including Google Earth .kmz file deliverables, are available for download on Media/Downloads page.

2014 to 2020 AEM Surveys

2014/2015 AEM results are posted under the 2015 AEM tab, the 2016 AEM results are posted under the 2016 AEM and AEM Partner Projects tabs, the 2018 AEM results are posted under the 2018 AEM tab. The Nemaha NRD and Papio-Missouri River NRD each were awarded WSF grants in 2019 for additional flights conducted in August 2020.

Digital version of Flight Lines used in the map below: PDF Shapefile Download (5.4 MB) PDF kmz file Download (5.2 MB)

 

Test Hole Drilling

Logging test hole

Drilling and logging a test hole

ENWRA drilled approximately 40 test holes total across the three pilot study sites. The test holes provide high-quality geologic data and are required in order to make a direct association between HEM survey results and subsurface geology. Downhole geophysical tools are used to log both electrical resistivity and gamma-ray emissions of the geologic materials encountered in the test holes. Test hole drilling continues today under ENWRA to both ground truth AEM survey areas and provide additional borehole contraint on future AEM data processing. Click here for a link to the University of Nebraska, School of Natural Resources, Conservation and Survey Division's Statewide Test-hole Database.

Estimating Recharge

Firth Uplands

Vadose zone equipment and weather station

ENWRA uses heat-dissipation sensors, soil moisture probes, and weather stations (air and soil temperature, precipitation, humidity, wind speed, solar radiation, and potential evapotranspiration) to continuously collect data regarding groundwater recharge at each of the pilot study sites. This information contributes to understanding the volume of precipitation recharging the underlying aquifer at a specific site, how fast that recharge occurs, and the importance of vertical and horizontal flow paths. Click here for a link to download ENWRA's recharge station locations and associated 2008 to current compiled weather station datasets and graphs (65 MB).

Water Chemistry and Age Dates

Water Chemistry

Collecting a water quality sample

ENWRA collects annual water quality samples at the Pilot Sites: Oakland, Ashland and Firth (approximately 75 monitoring wells targeting multiple levels of the aquifers/different aquifer units) and has the samples analyzed to determine general water chemistry. By comparing water chemistry, hydrogeologists can assess the extent of connection between aquifers and surface water and potential flow paths. In cases where general water chemistry does not provide a clear answer regarding connections, additional ground water samples will be collected and age dated. In addition to providing information about aquifer connections and flow paths, water sampling provides site specific information that will likely be useful in the future for water quality conservation purposes. Click here for a link to download ENWRA's 2008 to current compiled datasets and graphs (291 MB).

Water Level Monitoring and Aquifer Tests

Aquifer Test

Aquifer test at Logan East Rural Water System

In addition to the fleet of 60 transducers collecting continuous water levels in various aquifer units at the ENWRA Pilot Sites ENWRA conducted two aquifer tests, one near Hickman and another near Oakland. Aquifer tests are performed to assess the aquifer extent, amount of water in storage, the rate of water movement, and its potential hydraulic connection to other aquifers. To perform an aquifer test, hydrogeologists use a high-capacity production well installed in the aquifer they are studying. Observation wells are then installed at selected distances and in different directions outward from this pumping well. These observation wells are designed to monitor water levels within, above, or below the pumped aquifer.

Water is pumped from the production well at a constant rate over a period of multiple days. The amount of water level decline in each observation well (drawdown) provides hydrogeologists with the information they need to estimate the transmissivity and storativity of the aquifer. Changes in the rate of water-level decline allow hydrogeologists to assess flow boundaries and the potential connections between aquifers.