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

Ground-Water Hydrology 31
Upper Klamath Lake Subbasin—Temporal Variations in
Ground-Water Discharge
Temporal variations in ground-water discharge to Annie
Spring can be evaluated using data from the gaging station
(11503000) that has been operated on Annie Creek just below
the spring since 1977 (fig. 13). The discharge from Annie
Spring is small, averaging about 3 ft 3 /s. It is included here to
illustrate the behavior of smaller flow systems. Annie Spring
shows temporal variations that are different from those of the
large-scale systems discussed previously. The lowest flows
of large-scale spring systems are typically August through
September. The lowest flows of Annie Creek, in contrast, are
January through March. The likely cause is that Annie Spring
is fed by ground water recently recharged and following very
short flow paths, and consequently much of the water feeding
the springs is frozen as snow during the winter months. The
annual low flows of large-scale systems typically increase
each year during periods of successive wetter-than-average
years. This is less pronounced with Annie Creek. A graph of
monthly and January to March mean flows of Annie Spring
(fig. 13) shows that it peaks before the cumulative departure
from average precipitation curve. This is because of the lack
of storage effects in the small flow system. Annie Spring and
similar small-scale flow systems in the upper Klamath Basin
have the characteristics of runoff-dominated streams.
Gaging stations have been operated intermittently on
the Wood River since 1913. However, data are not easily
compared because the stations have been operated at different
locations that are affected differently by tributary inflow,
return flow, and diversion, and the periods of record are short,
ranging from roughly 1 to 14 years. Although the gaging
station data do not provide a continuous long-term record of
ground-water discharge, they do provide useful information
on the magnitude and timing of ground-water discharge
fluctuations. A USGS gaging station at Fort Klamath
(11504000) operated intermittently from 1913 to 1936 shows
a probable drought-related decrease in annual mean flow from
approximately 310 to 140 ft 3 /s during its period of operation
(fig. 14). Another USGS gaging station operated 4 mi south
of Fort Klamath (11504100) from 1965 to 1967 shows a
climate-related decrease in annual mean flow from 350 to
290 ft 3 /s during that period. A gaging station was operated in
the early 1990s, and recently near the headwaters springs of
the Wood River (about 1 mile downstream at Dixon Road)
by Graham Matthews and Associates (GMA). Variations
in ground-water discharge to the Wood River headwater
springs can be evaluated using the GMA data (provided by
Graham Matthews, written commun., May 13, 2003) along
with a multitude of miscellaneous instantaneous discharge
measurements made over several decades by USGS and
OWRD (fig. 14). The measurements near the headwaters
DISCHARGE, IN CUBIC FEET PER SECOND
16
14
12
10
8
6
4
2
Monthly mean discharge
January to March mean discharge
Cumulative departure from average precipitation at Crater Lake (1932-2005)
0
1975 1980 1985 1990 1995 2000
150
100
50
0
-50
-100
CUMULATIVE DEPARTURE FROM AVERAGE PRECIPITATION, IN INCHES
Figure 13. Monthly mean discharge and January to March mean discharge of Annie Spring near Crater Lake,
Oregon (USGS gaging station number 11503000), and the cumulative departure from average precipitation at Crater
Lake.