The Klamath River basin, including the adjacent Lost River basin, includes about ?,5>OO square miles of plateaus, mountain-slopes and valley plains in south-central Oregon* The valley plains range in altitude from about U,100 feet in the south to more than li,500 feet at the northern end; the mountain and plateau lands rise to an average altitude of 6,000 feet at the drainage divide, some peaks rising above 9*000 feet. The western quarter of the ba3in is on the eastern slope of the Cascade Range and the remainder consists of plateaus, mountains, and valleys of the basin-and-range type* The rocks of the Klamath River basin range in age from Recent to Mesozoic* At the southwest side of the basin in Oregon, pre~Tertiary metamorphic, igneous, and sedimentary rocks, which form extensive areas farther west, are overlain by sedimentary rocks of Eocene age and volcanic rocks of Eocene and Oligocene age* These early Tertiary rocks dip east toward the central part of the Klamath River basin. The complex "volcanic rocks of high Cascades" include three units: The lowest unit consists of a sequence of basaltic lava flows about 800 feet thick5 the medial unit is composed of volcanic-sedimentary and sedimentary rocks?the Tonna formation-200 to 2,000 feet thick; the uppermost unit is a sequence of basaltic lava flows commonly about 200 feet thick. These rocks dip east from the Cascade Unpublished records subject to revision 2 Range and are the main bedrock formations beneath most of the basin. Extensive pumice deposits, which emanated ^?^ ancestral Mount Mazaraa, cover large areas in the northwestern part of the basin* The basin has an overall synclinal structure open to the south at the California boundary where it continues as the Klamath Lake basin in California* The older rocks dip into the basin in monoclinal fashion from the adjoining drainage basins* The rocks are broken along rudely rectangular nets of closely spaced normal faults* the most prominent set of which trends northwest* The network of fault displacements includes two main grabens, the Klamath and the Langell, which were downthrown approximately ?00 and 1,000 fast, respectively* The average annual precipitation varies with the altitude, the higher parts of the Cascade Range getting more than 60 inches, and the semierid valley plains receive as little as 13 inches in some places* Most precipitation occurs in the winter. \ The principal tributaries, Williamson and Sprague Rivers, rise near the higher parts of the eastern rim of the basin, flow through narrow valley plains to the western part, and discharge into Upper Klamath Lake* Wood River and associated creeks also empty into Upper Klamath Lake after draining southward along the eastern foot of the Cascade Range* The Klamath River receives the outflow from Upper Klamath Lake, via Lifak River and Lake Ewauna, and flows southwestward through Keno Gap and hence through a youthful canyon, to its lower valley in California* The ground water occurs largely in an unconfined, or water-table, condition, though areas of local confinement are present* The regional Unpublished records subject to revis&oa is graded to water table / a base level about equal to that of the major drainage* where water is confined, on the valley plains. The slope of the water tafele, ~ of/the piezomstric surface is downstream at about the same grade as that "of the surface drainage in each of the larger valleys, attd groufid*water divides occur between the upper parts of adjacent major valleys* The principal water-bearipg units are.the'lower lava rocks and upper lava rocks of the "volcanic rocks of high Cascades,* the pumice of Quaternaryage, and the allusriTuju In places layers of coarse flagmental material in the Tonna formation (Newcorub, 1958) also transmit water* The water-bearing units, especially the breccia layers of the lava rocks and the pumice, yield large amounts of water to wells and provide natural discharge outlets for the ground water. The spring outflows to the Williamson and Wood Rivers-Crooked Creek drainage, measured in September and October 1955, were at a rate equivalent to about 700,000 acre-feet per year. The spring outflows into the Sprague River were at a rate equal to 2l;5>000 apre-feet per year* Large springs occur along the edges of Upper Klamath Lake but their discharges could not be measured, and the known spring discharge from the lower lava rocks in the river canyon below Keno was not measured. The spring discharge into Lost River in the reach ?rom Bonanza to Harpold Bridge was at a rate equivalent to 75,000 acre-feet per year. Much of the water discharged from springs is used for irrigation during the growing season, but ground water has not been extensively Unpublished records subject to revision developed by means of wells except in the'Yonna Valley and other local areas. The total withdrawal of ground water from wells in 1951? was only about 30,000 acre-feet, of which 27,000 was used for irrigation* The ground water is of excellent quality in general, but sodium sulfate water occurs in the belts of warm rock along some faults and alkali bicarbonate water is present in the main evapotranspiration basins. Unpublished records subject to revision
Open file report; subject to revision; "Prepared in cooperation with the Oregon State Engineer, the U.S. Bureau of Reclamation, and the California Division of Resources."; "July 1958."