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

Ground-Water Hydrology 25
TOTAL WATER-YEAR PRECIPITATION, IN INCHES
120
100
80
60
40
20
Average annual
precipitation
66.7 inches
Values estimated
from other sites
Total water-year precipitation at Crater Lake
Cumulative departure from average precipitation (1932-2005)
120
100
80
60
40
20
0
-20
CUMULATIVE DEPARTURE FROM AVERAGE, IN INCHES
0
1932 1940 1950 1960 1970 1980 1990 2000
-40
2005
WATER YEAR
Figure 8. Annual precipitation at Crater Lake National Park, Oregon, and the cumulative departure from average
precipitation from 1932 to 2005. (Data from Western Regional Climate Center, 2006.)
The Sprague River responds relatively quickly to precipitation
and snowmelt events, with peaks commonly exceeding
2,500 ft 3 /s in April or May at the gaging station near Chiloquin
(station 11501000). Mean monthly discharge at this location
averages 1,300 ft 3 /s during April and 300 ft 3 /s during October.
Major hydrologic features of the subbasin include the North
and South Forks of the Sprague River, the Sycan River and
Marsh, and Kamkaun Springs.
The Sprague River originates along the flanks of
Gearheart Mountain and Coleman Rim in the highlands along
the central-eastern edge of the upper Klamath Basin. From
these highlands, the North and South Forks gain water from
numerous tributaries as they flow down mountain canyons
to the upper Sprague River Valley, above Beatty Gap. The
hydrologic regimes of the North and South Forks have a
pronounced runoff component and similar hydrographs near
the uplands, with peaks occurring during snowmelt in the
spring. However, above the Sprague River Valley, the North
Fork gains significant ground water, whereas the South Fork
does not.
From the confluence of the North and South Forks, the
Sprague River meanders downstream through the narrowing
upper Sprague River Valley, until it passes through Beatty
Gap into the lower valley. Gains due to ground-water inflow
occur in the upper valley, which contains both drained and
un-drained wetlands. More ground-water discharge occurs to
a spring complex (locally known as Medicine Springs) just
downstream of Beatty Gap. From here, the Sprague River
meanders through the lower Sprague River Valley for 75 mi, to
its confluence with the Williamson River.
OR19-0048_fig08
Aside from the runoff-driven Sycan River, tributaries
north of the river and downstream of Beatty Gap are limited to
a few unnamed ephemeral creeks draining the Knot Tableland
and a few small springs near the mouth of the Sycan River.
South of the river are four perennial and several ephemeral
creeks. Three of the perennial creeks (Spring, Brown, and
Whisky Creeks) are largely ground-water fed and lack a
significant runoff component (fig. 7). (Note: The Spring Creek
that is tributary to the Sprague River is too small to show at the
scale of figures in this report. It enters the Sprague River just
east of Brown Creek. The other Spring Creek mentioned in
this report is tributary to the Williamson River.) An additional,
but smaller amount of ground water discharges to Trout Creek
as well as a few small springs near the mouth of Whisky
Creek. Two large, isolated spring complexes, Kamkaun-
McReady and Whitehorse, farther downstream, are the only
other ground-water discharge areas in the lower valley.
Ground-water discharge to the North and South Forks
of the Sprague River (above the valley) was estimated using
data from gaging stations with short periods of record and
miscellaneous measurements made from 1992 to 2002.
The spatial distribution of gains is relatively well known
in the reaches and main tributaries of the North and South
Forks (fig 7). However, the locations of specific springs
have not been identified in either subbasin. Continuous and
miscellaneous streamflow measurements were analyzed using
index regression techniques on the North and South Forks to
improve understanding of the temporal variability of groundwater
discharge. Gains to the South Fork above the valley are