Map Shows Groundwater Decline Slowed

LINCOLN, Neb. -- Groundwater levels in Nebraska slowed their rate of decline and actually increased in some areas of the state last year, according to the latest map released by University of Nebraska-Lincoln researchers.

Above-normal precipitation after seven years of drought, well-timed rains and more efficient irrigation practices may all be factors in the relatively good news reflected on the one-year map, said Mark Burbach, an assistant geoscientist in UNL’S School of Natural Resources (SNR).

One-year rises were particularly notable along the Platte River from Columbus to Fremont, south into Butler and Saunders Counties and north into Dodge County. Other areas of recorded rises were in central Nebraska along the Platte and Republican rivers.

Mike Jess, associate director of the UNL Water Center, said that the groundwater level maps produced annually by SNR’S Conservation Survey Division are like a report from the doctor after a checkup. White areas indicate no change, or stable groundwater levels, with oranges and reds indicating declines and greens and blues showing increases.

"These maps are the way we check the health of our hydrologic resources at annual intervals,” Jess said. “We would like to see the map look white. Instead, if you look at the series of maps over time, you see areas that start out lighter and then get darker and finally red.”

Maps can be downloaded free on the SNR's web site at (http://snr.unl.edu/information/GroundwaterMaps.asp). The most recent groundwater level monitoring map shows groundwater level changes from Spring 2006 to Spring 2007. Otheres record levels from the earliest records to Spring 2007, and from 2000 to Spring 2007, and an updated map of the density of irrigation wells across the state is also available. Maps from previous years are archived there, too, dating to 1954. A multi-year drought started in 2000 and subsided last year for all but western Nebraska.

Over the long term, Jess said, areas of declining groundwater stand out:

Box Butte, Chase, Perkins and Dundy counties show drops of more than 40 feet in some areas, comparing the earliest measurements with this year’s. Along the Platte River, extending south between the Big Blue and Little Blue rivers, and north to the South Loup River, declines are generally less than 20 feet.

Burbach noted that western Nebraska has not benefited in the short-term from the above-normal rains that have helped the rest of the state, and that after the 1980s and 1990s, two of the wettest decades on record, groundwater levels in eastern Nebraska were mostly back to where they were when measurements were first recorded.

Some of the areas on the map showing the most dramatic long-term increases in groundwater levels reflect surface water diversions, either canals or irrigation, that have increased groundwater recharge, Burbach and Jess said. Other areas reflect a positive balance between recharge and use.

Burbach compiled data for the maps based on measurements recorded from nearly 6,000 wells taken by 27 organizations: Nebraska’s 23 Natural Resources Districts, the U.S. Geological Survey, the Central Nebraska Public Power and Irrigation District, the U.S. Bureau of Reclamation, and UNL.

The map is based on readings as close to April 1 as possible, before the start of the irrigation season. Although it is possible to measure the distance from the surface of the ground to the water table, reliable data does not exist to show the overall depth of Nebraska’s aquifers, Burbach said.

Although the Ogallala is the best known, Nebraska has numerous aquifers.

Efforts by NRDs, the state, and other organizations are underway to provide information, incentives and management that will lead to reduced water use by irrigators. Irrigation also becomes more expensive as water has to be pumped a greater distance. However, Jess observed, the groundwater level maps seem to indicate that the economic pressures to irrigate are still strong.

"This is not saying we’re going to run out the year after next,” he added. “We can sustain this for a long, long time. There are vast quantities of groundwater.”

Writer:

• Kelly Helm Smith, School of Natural Resources, ksmith2@unl.edu, 402-472-3373

Sources:

• Mark Burbach, Ph.D., assistant geoscientist, School of Natural Resources, 402-472-8210
• J. Michael Jess, associate director of UNL’s Water Center, 402-472-7570