Geography and Climate
Location
The 920-mi2 ground water investigation area is limited to the eastern portion of
the Lost River sub-basin, east of Klamath Falls in southeast Klamath County (fig.
3). The investigation area includes the Town of Bonanza and the communities of
Dairy, Yonna, and Lorella.
Figure 3. Ground water investigation location (eastern Lost River sub-basin)
Physical Geography
Northwest trending uplands separate interconnected Langell, Yonna, Poe, and
Swan Lake Valleys and Pine Flat lowlands (fig. 4 and pl. 1). Upland elevations
range from 4,300 ft on eastern plateaus to more than 6,000 ft in the west and
north. The western uplands peak at 6,475 ft, and the northern uplands peak at
7,226 ft at Yainax Butte. Valley floor elevations range from 4,100 to 4,200 ft.
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Figure 4. Geography of the eastern Lost River sub-basin
Gaps in the upland topography interconnect the lowlands. A mile-wide gap at
Bonanza occurs between Langell Valley and Yonna Valley. Harpold Gap occurs
between Yonna and Poe Valleys. Un-named gaps occur between the Swan Lake
Valley-Pine Flat lowland and Yonna Valley to the east and Poe Valley to the
south. At the west end of Poe Valley, Olene Gap occurs at the boundary between
the eastern Lost River sub-basin and the western Lost River sub-basin.
The Lost River is the primary stream in the sub-basin. It flows north through
Langell Valley from Clear Lake, California to Bonanza, and then flows west from
Bonanza to Olene Gap via southern Yonna and northern Poe Valleys. Miller
Creek in Langell Valley and Buck Creek in Yonna Valley are the primary
tributaries. Bonanza Big Springs at Bonanza and un-named springs in western
Poe Valley make important contributions to river flow. Surface drainage from
Swan Lake Valley and Pine Flat to the Lost River is largely through constructed
drains and pumpage.
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Climate
Climate analyses in this report used data from the Klamath Falls climate station as
reported by the State Climatologist (2002) for the 1920 through 2000 calendar
years. Klamath Falls is the station closest to the eastern Lost River sub-basin that
has long-term climate data, and it has an elevation similar to the sub-basin
valleys. This investigation organized the data by water year for the analyses
conducted. A water year captures the entire annual wet season from October 1
through September 30 rather than split it between two calendar years. For
example, water year 2000 ran from October 1, 1999 to September 30, 2000.
The area is semi-arid. The average annual precipitation in Klamath Falls by water
year from 1921 to 2000 is 13.7 inches with a minimum of 6.6 inches and a
maximum of 22.8 inches (fig. 5 and app. 3).
A graph of cumulative departure from average water year precipitation shows wet
and dry period trends (fig. 5). Above average precipitation trends occurred during
the early 1940s, most of the 1950s, early 1980s, and late 1990s. Below average
precipitation trends occurred during the early 1930s, late 1970s, and late 1980s to
early 1990s. Periods of nearly average precipitation occurred through the 1940s
and through the 1960s to the early 1970s.
On average, the wettest months in Klamath Falls are November through January,
and the driest months are July through September (fig. 6 and app. 3). The
average monthly precipitation in November, December, and January is about twoinches. In July, August, and September, it is about a half-inch or less. Monthly
extremes range from no precipitation to nearly nine-inches.
Total annual precipitation in the eastern Lost River sub-basin varies by
topography and location. Results of Spatial Climate Analysis Service (2001) use
of a PRISM climate modeling system first described by Daly and Neilson (1992)
and Daly and others (1994) indicate annual average precipitation on the valley
floors is 12 inches in Yonna Valley, 13 inches in Langell and Poe Valleys, and 14
inches in Swan Lake Valley. The results indicate greater annual average
precipitation occurs in the uplands, generally exceeding 20 inches.
Temperatures vary greatly. The overall average in Klamath Falls is 48 oF.
However, daily temperatures averaged by month from 1971 to 2000 ranged from
40oF maximum and 22oF minimum in December and January to 85oF maximum
and 50oF minimum in July and August (fig. 7 and app. 4). Extreme temperatures
exceeded 100oF during the summer and minus 10oF during the winter.
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Figure 5. Total precipitation and cumulative departure from average by water
year at Klamath Falls from 1921 to 2000
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Figure 6. Monthly maximum, minimum, and average precipitation at Klamath
Falls from 1921 to 2000
Figure 7. Daily maximum, minimum, and average temperatures averaged by
month for Klamath Falls from 1971 to 2000
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Land Ownership and Use
Both private and public land ownership occurs in the sub-basin. Private land
dominates the valleys and exists in some upland areas. Public land is generally
limited to upland areas.
Public land holdings include U.S. Forest Service and U.S. Bureau of Land
Management. The public lands are managed for timber, livestock grazing,
wildlife, and recreation. The U.S. Bureau of Reclamation’s Gerber Reservoir and
many private reservoirs reside on U.S. Bureau of Land Management administered
land.
Agriculture is the predominant private land use. Agricultural activities include
cattle and sheep ranching, dairies, and irrigated crop production. Crops irrigated
during the investigation included alfalfa and grass hay, potatoes, sugar beets, and
frost-resistant strawberry plants.
Irrigation water used in the sub-basin comes from surface and ground water
sources allocated by Oregon water rights. Most of the surface water comes from
U.S. Bureau of Reclamation Klamath Project impoundments at Clear Lake,
Gerber Reservoir, and Upper Klamath Lake. Klamath Project water delivery
occurs via irrigation districts. Figure 8 shows areas enclosed by the boundaries of
irrigation districts supplied by Klamath Project water. Areas where irrigation
independent of Klamath Project water can occur under existing Oregon surface
water and/or ground water rights is shown in figure 9. Some overlap occurs
between figures 8 and 9. These overlaps exist because landowners obtained the
right to a supplemental source of surface or ground water for the times their
primary source of surface or ground water is not available.
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Figure 8. Areas enclosed by the boundaries of irrigation districts relying upon
U.S. Bureau of Reclamation Klamath Project surface water
(Irrigation district boundaries from U.S. Bureau of Reclamation,
1997)
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Figure 9. Areas where irrigation independent of the Klamath Project water can
occur under existing Oregon surface water and ground water rights
(adjudication claims not shown)
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