Managing the aquifer means funding balance for water use

This is the FOURTH in a series of stories reporting on the water conference held in Imperial on March 27.

By Russ Pankonin

Imperial Republican

Using allocations to manage groundwater use serves as a favorable method to protect the Ogallala aquifer. 

University of Nebraska Professor Derrel Martin likes the method which has served as an effective tool in the Upper Republican Natural Resources District (URNRD) to manage the aquifer. 

Martin was among the keynote speakers at the URNRD’s second annual water conference in Imperial March 27.

The URNRD is one of only two NRD regions in Nebraska where groundwater has shown a decline from pre-irrigation development. 

Use of allocations and other rules has helped stem those declines over time. Areas in western Chase and Dundy Counties experienced declines of 40 feet or more.

But as a state, the aquifer under Nebraska actually gained 1.1 million acre feet (AF)  from 1950 to 2011. 

Martin said the largest declines have occurred in Texas and Kansas. 

Texas has depleted 60 percent of the total volume of the aquifer underneath it. Kansas is next with a 26 percent decline. 

Streamflow depletion

Martin, PhD, PE, serves as professor of Biological Systems Engineering and is an Extension specialist in Irrigation and Water Resources Engineering at UNL.

He said there’s no question of the hydrologic connection that groundwater pumping adversely affects the amount of water available as stream flow. 

As groundwater pumping occurs, the level of the aquifer declines. This results in less water coming into the stream. 

Wells near streams and rivers have more immediate effect than wells further away. But over time, both play a role in declining streamflow. 

However, groundwater pumping can’t be singled out as the only factor. 

In the Republican River Basin, 2.13 million acres of land are terraced to hold back water. 

This is water that never makes it back to the stream, Martin said, noting it’s no small number. 

Calculation shows these terraces hold back 125,000 AF, which results in a 100 percent impact on streamflow. 

Of those 125,000 AF, evaporation consumes 42,000 AF with 83,000 AF seeping back into the ground as recharge. 

Conservation tillage, which conserves soil moisture, accounts for additional decreases in streamflow, he added. 

Martin also noted that technological changes adopted by farmers have resulted in more efficient use of groundwater. 

Improvements to irrigation application have reduced runoff and reduced loss to evaporative transpiration. 

Other advances include genetically-modified crops that use less water, better plant soil moisture monitoring and variable rate irrigation. 

Martin said it’s important to create a water balance to manage use throughout the entire watershed. 

That will create a healthy ecosystem that benefits all users, he noted.