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

62 Ground-Water Hydrology of the Upper Klamath Basin, Oregon and California
DEPTH TO WATER, IN FEET
0
10
20
30
40
50
48N/04E-35L02
60
1985 1990 1995 2000 2005
Figure 39.
Water-level fluctuations in well 48N/04E-35L02 near the town of Tulelake, California.
The year-to-year water-level declines can be evaluated
by observing the changes in water levels between spring 2001
and spring 2004 (fig. 40). Although data are sparse in the
northern part of the area, measurements show that over the
3-year period, water levels declined more than 10 ft in deep
water-bearing zones (primarily basalt underlying basin-filling
sediments) over more than 135 mi 2 of the Klamath Valley
and northern Tule Lake subbasin. Declines exceed 15 ft over
an area of about 37 mi 2 encompassing the State line in the
Tule Lake subbasin and extending southward to the town of
Tulelake and northward to Malin. Declines of 10–15 ft during
this period are common north of Malin. Declines of 5 to 10 ft
are common in the southeast part of the Tule Lake subbasin.
Levels in three wells on the Modoc Plateau southeast of the
Tule Lake subbasin declined 5 to 10 ft (fig. 40). The decline in
this southernmost area, where no new pumping has occurred,
is somewhat enigmatic, but may indicate that effects are
propagating southeastward from pumping centers in the Tule
Lake subbasin.
If the post-2000 pumping rates continue in the future, the
regional ground-water system possibly will eventually achieve
a new state of dynamic equilibrium. This will occur when
the depression in the water table is large enough to redirect
sufficient regional ground-water flow into the area to offset
the increased pumping. At equilibrium, however, the increased
discharge in the area of pumping must be offset by decreased
discharge elsewhere, likely manifesting itself as a combination
of decreased discharge to adjacent basins and decreased
discharge to streams, lakes, and wetlands.
Certain details are readily apparent from the recently
collected data and existing knowledge of the area. Groundwater
pumping is accompanied by declines in water levels that
occur at a variety of temporal and spatial scales. The amount
of ground water that can be pumped in a period of time will
be determined in part by how much drawdown water users
and regulatory agencies will tolerate, and in part by how
much interference with streams and lakes will be considered
acceptable. The drawdown can be easily measured. Where
drawdowns acutely affect individual springs, the effects on
discharge may be easy to measure. However, where the effects
are to larger streams or lakes and represent a small part of the
overall flow, they usually are difficult to discriminate from
other fluctuations by measurement. Such effects, however, can
be calculated using computer models or analytical methods.
OR19-0048_fig39