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<H1 class=rdheadline>Columbia plateau aquifer levels dropping</H1>
<P class=rdbyline>By KEVIN MCCULLEN<BR>TRI-CITY HERALD</P><!--BEGIN ARTICLE-->
<P>TRI-CITIES, Wash. -- Ground water levels declined over the past
quarter-century in 83 percent of 470 wells measured in the sprawling Columbia
Plateau Regional Aquifer system in southeastern Washington, northeastern Oregon
and western Idaho, a new report from the U.S. Geological Survey found.</P>
<P>The steepest drops occurred in the deepest basalt aquifer in the
44,000-square-mile plateau. Smaller declines were recorded in shallower aquifers
that receive recharge water from irrigation, precipitation or discharge from
rivers or wells, according to the survey.</P>
<P>Hydrologists compared readings taken in 1984 with measurements recorded in
2009 for the report, which was released this week.</P>
<P>Declines were reported throughout the Columbia Plateau, but were more
widespread in parts of the Yakima River Basin, in western Lincoln, eastern Grant
and southwestern Adams counties, and in the Pullman-Moscow area.</P>
<P>Average annual declines over the 25 years in the Moscow-Pullman area, which
taps ground water for municipal water supplies, averaged more than 1 foot per
year, the survey found.</P>
<P>Irrigation accounted for much of the use elsewhere, the survey said.</P>
<P>The average annual decline in the Grande Ronde basalt unit - the oldest and
deepest level of the aquifer tapped for water use - averaged 2 feet a year over
the period. Thickness of the basalt in the Grande Ronde may be greater than
15,000 feet near the central part of the basin, according to the survey.</P>
<P>Declines also occurred in the Yakima River Basin because of heavy pumping
from the Wanapum basalt unit, which averages up to 1,200 feet thick, the survey
said.</P>
<P>But the drop was less in the shallower Overburden unit, at less than 0.3 feet
per year, the survey said.</P>
<P>Overall, results of the study - launched to assess ground water levels in the
plateau and identify trends in storage and use - came as no surprise to
hydrologists for the U.S. Geological Survey, said Sue Kahle, project manager for
the agency.</P>
<P>"Water level declines have been tracked for many years in smaller (areas).
This the first time we looked at the Columbia Plateau as a whole," Kahle
said.</P>
<P>Historically, ground water levels in the regional aquifer system have dropped
since the 1930s.</P>
<P>The study "confirms some of the concerns swirling around for years," said
Joye Redfield-Wilder, a spokeswoman for the Washington Department of Ecology in
Yakima.</P>
<P>Darryll Olsen of the Columbia-Snake River Irrigators Association, which
represents agricultural interests and irrigation districts in Eastern
Washington, said the most interesting part of the survey is the decline in water
levels in the Grande Ronde unit.</P>
<P><STRONG><FONT color=#ff0000>Water levels dropped by more than 100 feet in
some of the 136 Grande Ronde unit wells where measurements were taken, with
declines greater than 25 feet measured in 60 percent of the wells, the survey
said.</FONT></STRONG></P>
<P>"I'd like to know what is going on in the Grande Ronde," Olsen said.</P>
<P>One explanation may be the depth of the formation, said Guy Gregory,
hydrogeologist with Ecology's water resources program in Spokane. He supervised
a group of scientists involved in the study.</P>
<P>"Recharge has a hard time getting there and there is not a lot of recharge to
begin with," Gregory said. "We're using more of (the recharge water) and it's
harder to get more to it because of its depth."</P>
<P>The study will help scientists develop a ground water-flow simulation model
that water managers hope to use to test ways of managing the region's ground
water supplies under different development and climatic conditions, Kahle
said.</P></DIV></BODY></HTML>