Ground-Water Hydrology of the Upper Klamath Basin, Oregon and ...

Ground-Water Hydrology 59
Long-term water-level trends in northwest Langell Valley
and east of Lorella indicate that pumping stresses in those
areas are periodically greater than average (for the area),
probably resulting from the occasional use of supplemental
ground-water rights. The water level in the observation well
in northwest Langell Valley (39S/11E-26ABD) apparently
responded to increased pumping during the 1970s, again in the
early 1990s, and again starting in 2001 (fig. 36). The groundwater
flow system nearly recovered after each of the earlier
cycles. In 2005, the water level was about 13 ft below the level
measured during 1998, the most recent wet period. A trend
similar to that observed in the Langell Valley well, but with
a smaller amplitude of fluctuation, is seen in the long-term
record at well 39S/12E-35ADD, just east of Lorella (fig. 36).
The 2005 water level in the Lorella well was only about 4 ft
below the 1998 measurement. Recharge from canal leakage in
the area may also be influencing the water-level trend in the
Lorella well (Grondin, 2004).
Recent pumping stresses in the Klamath Valley area
are reflected in water levels measured in observation well
41S/09E-12AAB (fig. 37). With the exception of a sharp
decline in 1970, the water-level trend in the well appears to
have been in dynamic equilibrium until 2001. The increased
pumping stresses combined with drought contributed to a
water-level decline of about 12 ft between 2001 and 2004.
Fluctuations in Hydraulic Head in Response to
Recent Increases in Ground-Water Pumping
Prior to 2001, the ground-water system in most of the
upper Klamath Basin was in a state of dynamic equilibrium,
under which water levels rose and fell in response to climate
cycles and seasonal pumping, but generally without chronic
long-term declines. (Water levels in some wells near the town
of Sprague River [fig. 33] are an exception.) Historically,
water levels declined for several years during droughts, but,
with local exceptions, water levels eventually rose to (or
nearly to) predrought levels during subsequent multiyear
wet periods. Wells generally have been drilled deep enough
and pumps set low enough to accommodate these historical
water-level fluctuations. Pumping in the upper Klamath Basin
increased an estimated 50 percent starting in 2001 in response
to changes in water management and a prolonged drought. The
ground-water system has responded to the increased pumping
with water levels showing acute, seasonal, and long-term
effects.
Acute effects occur close to pumping wells, generally
within hundreds to thousands of feet. These effects typically
are the result of the cone of depression of the pumping
well spreading to neighboring wells, resulting in a decline
in the static water levels, sometimes referred to as “well
interference.” These effects typically have a rapid onset and
dissipate relatively soon after pumping ends.
0
10
39S/11E-26ABD
20
30
DEPTH TO WATER, IN FEET
40
50
30
40
50
60
70
80
1950
39S/12E-35ADD
1955
1960
1965
1970
1975
1980
1985
1990
1995
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2005
Figure 36.
Water-level fluctuations in wells 39S/11E-26ABD and 39S/12E-35ADD in the western Langell Valley, Oregon.