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

Ground-Water Hydrology 53
35
37
Depth to water in well 40S/9E-28ADB01
Discharge in North Canal
40
35
DEPTH TO WATER, IN FEET
39
41
43
45
30
25
20
15
10
DISCHARGE, IN THOUSANDS OF ACRE FEET
47
5
49
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 0
2000 2001 2002 2003 2004 2005
Figure 27. Water-level fluctuations in well 40S/09E-28ADB on the southwest side of the Klamath Hills, Oregon, and
monthly discharge in the nearby North Canal.
The upper interval, which responds primarily to the canal
operation, is open from 92 to 516 ft below land surface. The
main water-bearing zone is in pyroclastic material between
305 and 360 ft below land surface, and is overlain by lava
flows. The water level in the upper interval of this well
responds in a matter of days to the operation of the Langell
Valley Irrigation District canal system (fig. 28). The water
level starts to rise shortly after the canals start flowing,
peaking late in the irrigation season, and dropping soon after
canals are shut off for the season. The rapid response of the
water table to canal leakage at such depth likely is due to rapid
downward movement of water through interconnected vertical
fractures in the lava flows. The lower water-bearing interval in
the observation well is open from 950 to 1,005 ft below land
surface, and is not influenced by canal operation. Both the
upper and lower water-bearing zones in this well respond to
the pumping effects of nearby wells (fig. 29). Individual wells
can respond to both canal operation and pumping.
Response to Lake Stage
As previously discussed, ground water discharges to
Upper Klamath Lake. The lake, therefore, represents a local
boundary to the regional ground-water system. As a result,
water levels in most wells near the lake track variations in
lake stage. The water-level in well 35S/06E-10ACC (fig. 30),
drilled on the lower northeast flank of Pelican Butte, closely
follows the stage in Upper Klamath Lake. The well, about
OR19-0048_fig27
3,500 ft from the shoreline of the lake, is constructed into
layered lava flows that are saturated below a depth of about
470 ft (altitude 4,140). Well 38S/09E-17CBC, located near the
Oregon Institute of Technology campus in Klamath Falls, also
fluctuates with the stage of Upper Klamath Lake (fig. 31). The
well is about 5,200 ft from the lake, and is constructed into
interbedded sediment and lava to a total depth of 425 ft.
Long-Term Water-Table Fluctuations
Water levels in wells in the upper Klamath Basin that
have been monitored for several decades show fluctuations in
response to many of the stresses just discussed. In addition,
measurements in most of the wells also reflect decadal scale,
wet-dry climate cycles, with some showing the effects of
multiyear pumping stresses. Water level trends observed near
Bly (well 36S/14E-25BCB), Bonanza (well 39S/11E-20AAD),
and the southern Langell Valley (well 41S/14E-08CAA)
exemplify areas where ground-water levels are responding
mostly to variations in recharge (climate) (fig. 32), showing
decadal scale fluctuations of 4–5 ft.
The ground-water flow system appears to be responding
to prolonged pumping stresses in several other areas in
the upper Klamath Basin, including the area between the
communities of Sprague River and Beatty, parts of Butte
Valley, south Poe Valley and the area of the Shasta View
Irrigation District just north of Malin, parts of west Langell
Valley, an area east of Lorella, and the Klamath Valley.