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

50 Ground-Water Hydrology of the Upper Klamath Basin, Oregon and California
wells were measured quarterly during this study by the USGS
for periods ranging from 1 to 6 years (fig. 22). Nineteen wells
were instrumented with continuous recorders, devices that
measure and record the water-level elevation every 2 hours.
Graphs of water-level fluctuations in all of the wells monitored
by the USGS are available on the USGS web site (http://
waterdata.usgs.gov/or/nwis/gw). Not all wells monitored in
the upper Klamath Basin are shown in figure 22. Scores of
additional wells have been or currently are monitored by the
CDWR and the OWRD for specific purposes. Data from the
wells shown in figure 22, which includes all wells monitored
by the USGS, provide a comprehensive picture of the dynamic
nature of the regional ground-water system.
Climate-Induced Fluctuations
Water levels in most wells fluctuate in response to natural,
climate-induced changes in recharge. The greatest response
to climate-induced water-level fluctuations in the upper
Klamath Basin occurs in the Cascade Range. The response to
diminished precipitation (and hence recharge) in the Cascade
Range during the current drought cycle is exemplified by the
hydrograph of well 30S/07E-06AAA on the lower eastern
flank of the Crater Lake highlands (fig. 23). The water level in
that well has declined approximately 12 ft since 2000 because
of climate-related decreased recharge. On the eastern side of
the basin, a similar post-2000 trend exists in well 36S/14E-
25BCB (fig. 24), but the magnitude of the recent decline is
less. A comparison of these water-level fluctuations with
precipitation at Crater Lake in the Cascade Range (fig. 24)
shows that periods of rising ground-water levels generally
correspond to periods of increasing precipitation, and falling
water-levels correspond to periods of decreasing precipitation.
Figure 24 also shows that the decadal drought cycles are
responsible for the largest water-level fluctuations. During
periods of abundant precipitation, the rate of ground-water
recharge exceeds, at least temporarily, the rate of discharge.
When ground-water recharge exceeds discharge, the amount of
ground water in storage must increase, causing the water table
to rise. During dry periods, in contrast, the rate of discharge
exceeds the rate of recharge, and ground-water levels decline
as a result.
Water table fluctuations in response to variations in
recharge are most prominent in the Cascade Range, the
primary recharge area. Climate-related fluctuations may be
difficult to discern in some interior parts of the basin, for
two reasons. First, precipitation and, hence, recharge are
comparatively small in the interior parts of the basin, so
climate-induced water-level fluctuations are correspondingly
small. Second, water levels in these areas are affected by
ground-water pumping, canal operation, and irrigation, the
effects of which can mask the climate signal.
186
188
190
DEPTH TO WATER, IN FEET
192
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J M M J S N J M M J S N J M M J S N J M M J S N J M M J S N J M M J S N
2000 2001 2002 2003 2004 2005
Figure 23.
Water-level fluctuations in well 30S/07E-06AAA near Bear Creek northeast of Crater Lake, Oregon.