|Mapping for the future
January 27, 2003
By Shirley Wentworth
Tri-City Herald (Basin bureau)
P.O. Box 2608
Tri-Cities, Wash. 99302
509-582-1500 or 1-800-874-0445
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The same thing that made many Columbia Basin homesteaders go bust in the 1880s can also bring down modern farmers.
Lack of water.
Now the Ground Water Management Area organization hopes to answer critical questions about the sources and availability of water in the Basin with recently completed three-dimensional computerized maps showing the underground geology of the Columbia Basin.
The project began a few years ago as a means of identifying areas in Adams, Grant and Franklin counties with ground water contaminated by high nitrate levels. The idea was to help develop agricultural practices to reduce nitrate pollution.
But the project gradually grew more ambitious, taking on the study of the aquifer itself -- to show points of pollution, the layers of water and their sources and destinations.
Terry Tolan and Kevin Lindsey, two Kennedy/Jenks geologists hired by the Ground Water Management Area to conduct the study, don't think they have all the answers yet.
But the data they've collected about the aquifer and well locations in the three-county area is now available at the Franklin County Conservation District office in Pasco, much of it in three-dimensional map form in a formidable computer system.
There are no printed maps available for people to look at yet, but Mark Nielson, conservation district manager, said he's close to having the information available for the public to review. He added that there already have been numerous requests to view the data.
The three-dimensional maps show not only the layers of the aquifers, but also which layers the wells are plugged into. They can also tell which wells have high nitrate levels and why, and answer the question of whether drilling deeper will help.
"It shows how fragile the porous layers are," Nielson said. "The lights are going on with farmers."
"If you don't figure out how the ground water works, you'll never manage it," Tolan said. "We don't want to promise people we'll find more water, but that we can manage it."
The data can keep farmers from repeating some of the mistakes of the early homesteaders, who often stopped and built where they found water. But in a few years, their water source went dry and it was time to move on.
"People would homestead anything back then, then find out in a few years it couldn't be done," Lindsey said.
Some of those mistakes are still being made, as at a dying cherry orchard that Lindsey pointed out that had been planted in dune sand on top of flood gravel. Because the soil is so porous, water quickly drains away.
The mystery of ground water is inextricably tied to the mystery of geologic formations, the consultants said.
Ground water comes primarily from rain and snow. Where it goes and where it can be accessed is determined mainly by underground rock layers and their permeability.
What's important about the Columbia Basin aquifer is the nature of the basalt rock that lava flows created 15 million years ago. The flows cover 200,000 square miles in Washington, Oregon, Idaho, Nevada and California.
Because the lava flows came at different times over thousands of years, a series of layers formed one on top of another. Air pockets formed as the rock cooled, caused by bubbles in the lava.
"This has profound implications," Tolan said. "Because of the special nature of these lava flows, it really controls ground water."
The layers are full of holes that water can run through. Seep lines, as indicated by horizontal lines of green vegetation growing across an outcrop, indicate the presence of water. Geologists can follow those green lines of moss and shrubs to water sources.
It's not as easy as that, however. There are many tricks to finding water.
Geologists look at the sequence of the rock layers and analyze their chemical and physical properties to get an idea of what kind of layer it is and where the water is going.
"We can reliably identify the flows over large areas because of the chemistry of the layers. A lot of people have a hard time understanding this," Tolan said. "The basalt flows are what make this region special."
Still, what's taking place in one part of the Columbia Basin can be entirely different from what's occurring in another place.
For instance, 15 million years ago a basalt flow dammed off the river and formed a large lake that extended from Othello to Quincy to Ellensburg.
Lava flows later entered the lake, ultimately leaving layers of sand and rubble-sized chunks of glassy basalt through which water now easily flows. Geologists have found the best aquifers in the Basin are those where the lake was deepest, because that's where porous layers of rubble were produced.
Such information helps geologists pinpoint the best well locations and best depths to drill.
"We're trying to use what we know about basalt to find out more about the aquifer, and trying to use what we know about the aquifer to better understand basalt," Lindsey said."
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