SCOTTSBLUFF - There's simple math involved in measuring the value of irrigation water in farm country. It's needed more in places that get less precipitation.

 

"Our water needs are higher out here than to the east," said Steve Sibray, a geoscientist and hydrogeologist with the University of Nebraska-Lincoln's Panhandle Research and Extension Center at Scottsbluff.

Average annual precipitation around Scottsbluff is just 15 inches. Farmers have been lucky to see even that much during the past several years of drought.

While much of Nebraska no longer is painted with the colors of drought on U.S. Drought Monitor maps, after receiving good rains in 2007, the Panhandle and points west remain dry.

There are other ways in which farming is different than in south-central Nebraska.

Some differences were discussed last week by farmers on the Central District Water Users tour as the bus rolled down country roads and past miles and miles of irrigation canals.

They saw pale, sandy soils and many small, misshaped crop fields. Some wondered aloud if the water could be better used in places with richer soils and "big squares" to irrigate.

Other differences are below the ground, Sibray said.

Panhandle farmers don't benefit from the huge Ogallala Aquifer, but some can tap into narrow, often thin aquifers in places with the required sands and gravels.

In area such as the Pumpkin Creek watershed south of the North Platte River in Banner and Morrill counties, some groundwater is pumped from fractures in Brule clay, which is the material found in Chimney Rock and other western Nebraska natural monuments.

"Groundwater is very spotty," Sibray said, with little saturated thickness in the Scottsbluff area.

Describing a conversation with new property owners who were disappointed when they couldn't get a well, he said a buyer can't assume there is water under a property. "Don't assume you're gonna have groundwater out here in the Panhandle."

Irrigation has changed the natural way of things in the region.

Sibray and Mike Jess, a water resources engineer with UNL's Conservation and Survey Division and former state water engineer, said Panhandle streams that were intermittent before settlement now carry water year round because of surface water irrigation projects.

Jess said they became perennial streams in the 1920s, or about 10 years after all the projects were completed.

"The south side of the river is much different, hydrologically, than the north side," he said, because its alluvial area has more potential for groundwater use.

Groundwater use in the Pumpkin Creek watershed is the focus of a lawsuit of interest beyond the watershed. Surface water right holders say pumping from groundwater hydrologically connected to the stream has caused Pumpkin Creek to go dry and resulted in the "taking" of return flows needed downstream.

"Aquifers are not buckets," Sibray said. In the Panhandle, they're irregular and some reach a limit where, economically, landowners can't continue to irrigate.

A stream's depletion as a result of groundwater pumping depends on the well's distance from the stream and the geology (types of materials involved). Sibray added that watersheds today respond differently to precipitation because of irrigation.

He said the basics people need to know are: groundwater is a limited resource, especially in the Panhandle; groundwater has affected surface water; and conservation is important.

Science can help to better understand water issues, Sibray said, "but it cannot solve the legal problems."
"There's always a lot of politics in water, especially in Nebraska because it's publicly owned," he added.
Central Water Users President Dave Dahlgren of Holdrege asked Sibray if people in the Panhandle believe Lake McConaughy is dry only because of drought, not because groundwater pumping interferes with return flows.

Sibray replied that some believe drought is at least partly to blame and others say it's the only cause.
He said it reflects a quote by author Upton Sinclair: "It is difficult to get a man to understand something when his salary depends upon his not understanding it."