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U.S. GEOLOGICAL SURVEY
Scientific Investigations Report 2007–5050
Version 1.1, April 2010

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Introduction

The upper Klamath Basin spans the Oregon-California border from the flank of the Cascade Range eastward to the high desert. Although much of the basin is high desert, the region receives considerable runoff from the Cascade Range and uplands to the east. As a result, the area has numerous perennial streams, large shallow lakes, and extensive wetlands, and the Klamath River has historically supported anadromous fish runs. Water in the basin is used for agricultural irrigation, for extensive waterfowl refuges, and to support aquatic wildlife in lakes and streams in the upper basin and downstream.

The agricultural economy of the upper Klamath Basin relies on irrigation water. Just over 500,000 acres are irrigated in the upper Klamath Basin, about 190,000 acres of which are within the Klamath Project developed and operated by the Bureau of Reclamation (Reclamation) (Burt and Freeman, 2003; Natural Resources Conservation Service, 2004). The principal source of water for the Bureau of Reclamation Klamath Project is Upper Klamath Lake. In recent years, Endangered Species Act biological opinions have required Reclamation to maintain certain lake levels in Upper Klamath Lake to protect habitat for endangered fish (specifically the Lost River and shortnose suckers) and at the same time maintain specified flows in the Klamath River below the lake and project diversions to provide habitat for listed salmon. This shift in water management has resulted in increased demands for water. Owing to the limitations of other options, the increased demand has resulted in increased use of ground water in the basin. The problems associated with increased demands are exacerbated by drought.

The upper Klamath Basin has a substantial regional ground-water system, and ground water traditionally has been used for irrigation for many decades in certain areas. The changes in water management described above coupled with a series of dryer than average years have resulted in an approximately 50 percent increase in ground-water pumping in the basin since 2001. Most of this increase is focused in the area of the Klamath Project. Increased pumping has caused local water-level declines that have been problematic for some ground-water users and generated concern among resource management agencies and the community. In addition to the measured effects, the basic principles of hydrology require that the volume of ground-water pumped and used consumptively must be offset by changes in flow to or from other boundaries including streams.

The effects of large-scale ground-water pumping can spread beyond the pumping centers to other parts of the regional ground-water system. Prior to this study, the ground-water hydrology had been studied only in separate parts of the basin, with many areas left undescribed. Therefore, there was no basic framework with which to understand the potential regional effects of ground-water development in the basin and the broad ramifications of water-management decisions. In 1999, the U.S. Geological Survey (USGS) and the Oregon Water Resources Department (OWRD) began a cooperative study to (1) quantitatively characterize the regional ground-water flow system in the upper Klamath Basin and (2) develop a computer model to simulate regional ground-water flow that can be used to help understand the resource and test management scenarios. This report summarizes efforts to quantitatively characterize the ground-water hydrology.

Study Area

The upper Klamath Basin (fig. 1) comprises the entire drainage basin above Iron Gate Dam, including the internally drained Lost River and Butte Creek subbasins, and encompasses about 8,000 mi² (square miles). Study-area boundaries were defined to correspond to hydrologic boundaries across which ground-water flow can be estimated or assumed negligible. The southwestern boundary near Iron Gate Dam was selected because it corresponds with the transition from a geologic terrane dominated by permeable volcanic rock to a terrane dominated by older rock with much lower permeability. It is not likely that significant regional ground-water flow crosses this geologic boundary. The boundary between the regional flow systems in the upper Klamath Basin and the Deschutes and Fort Rock Basins to the north (not shown on fig. 1) is defined by a surface-water divide that roughly corresponds to the ground-water divide. This boundary is likely permeable. The boundary between the ground-water system of the upper Klamath Basin and that of the Pit River Basin to the south also is defined by a surface-water divide in most places. The southern surface-water divide does not correspond to a ground-water divide in all places, as hydraulic head data indicate that there is southward flow of ground water from the upper Klamath Basin south of the Tule Lake subbasin toward the Pit River Basin. The eastern study-area boundary corresponds to a surface-water divide and is characterized in many places by a transition to older geologic strata.

The upper Klamath Basin occupies a broad, faulted, volcanic plateau that spans the boundary between the Cascade Range and Basin and Range geologic provinces. The basin is bounded by the volcanic arc of the Cascade Range on the west, the Deschutes Basin to the north, the internally drained Silver Lake, Summer Lake, and Goose Lake Basins to the east, and the Pit River Basin to the south. The altitude of the Cascade Range along the western margin ranges from 5,000 to 7,000 ft (feet) with major peaks such as Mount McLoughlin and Mount Thielsen exceeding 9,000 ft. The interior parts of the basin are dominated by northwest-trending fault-bounded basins, typically several miles wide, with intervening uplands. Basin floors range in altitude from roughly 4,000 to 4,500 ft, and adjoining fault-block upland altitudes range from 4,500 to more than 5,000 ft. The northern and eastern parts of the upper Klamath Basin consist of a volcanic upland with numerous eruptive centers, including Yamsay and Gearhart Mountains, both of which exceed 8,000 ft. The southeastern margin of the upper Klamath Basin consists of a broad, rugged, volcanic upland known as the Modoc Plateau, where most of the land surface ranges from 4,500 to 5,000 ft. The southern margin of the basin is marked by the broad shield of Medicine Lake Volcano, which reaches an altitude of 7,913 ft.

The upper Klamath Basin is semiarid because the Cascade Range intercepts much of the moisture from the predominantly eastward moving Pacific weather systems. Mean annual precipitation (1961–90) ranges from 65.4 inches at Crater Lake National Park in the Cascade Range to 13.5 inches at Klamath Falls (fig. 2). Most precipitation occurs in the fall and winter. November through March precipitation accounts for 71 percent of the total at Crater Lake and 64 percent of the total at Klamath Falls. Most precipitation falls as snow at higher elevations. The interior parts of the basin are very dry during the spring and summer; mean monthly precipitation at Klamath Falls is less than 1 inch from April through October. Winters are generally cold, with January mean minimum and maximum temperatures of 20.3°F and 38.8°F, respectively, at Klamath Falls and 17.5°F and 34.5°F, respectively, at Crater Lake. Summers, in contrast, are warm, with July mean minimum and maximum temperatures of 50.8°F and 84.6°F, respectively, at Klamath Falls and 39.8°F and 68.0°F, respectively, at Crater Lake.

Principal streams in the upper Klamath Basin include the Williamson River, which drains the northern and eastern parts of the basin; the Sprague River (a tributary to the Williamson) which drains part of the eastern side of the basin; the Lost River, which drains the southeastern part of the basin; and the Klamath River (fig. 1). The Lost River subbasin is actually a closed stream basin. Prior to development, the river flowed to internally drained Tule Lake, although it occasionally received flow from the Klamath River during floods. The Lost River is now diverted just below Olene into a channel across a low divide to the Klamath River. Generally, little water from the Lost River drainage above the diversion channel now flows to the Tule Lake subbasin. The largest lake in the basin is Upper Klamath Lake, which has a surface area between 100 and 140 mi² (including non-drained fringe wetlands) depending on stage (Hubbard, 1970; Snyder and Morace, 1997). Principal tributaries to Upper Klamath Lake include the Williamson River, the Wood River (which originates at a series of large springs north of the lake), and several streams emanating from the Cascade Range.

The 250-mi (mile)-long Klamath River begins at the outlet of Upper Klamath Lake, which is controlled by a dam. For the first mile downstream of the lake, the river is known as the Link River. About 1 mi below the dam, the river flows into a 20-mi-long narrow reservoir behind Keno Dam known as Lake Ewauna. The dam for another impoundment, John C. Boyle Reservoir, is about 10 mi below Keno Dam. Below John C. Boyle Dam, the river enters a narrow canyon and flows freely about 20 mi to Copco Lake (a reservoir) and immediately below that, Iron Gate Reservoir. Iron Gate Dam, at about river mile 190, marks the downstream boundary of the upper Klamath Basin. There are no impoundments on the Klamath River below Iron Gate Dam.

The surface hydrology of the upper Klamath Basin has been extensively modified by drainage of lakes and wetlands for agriculture and routing of irrigation water. Prior to development, the Tule Lake and Lower Klamath Lake subbasins contained large lakes fringed by extensive wetlands. Under natural conditions, the Lost River flowed from the upper Lost River subbasin through the gap near Olene and then south to Tule Lake. The Lost River system received flow from the Klamath River system during periods of flood. Prior to development of the Bureau of Reclamation Klamath Project, the high stage of Tule Lake was about 4,060 ft (La Rue, 1922). At this stage, the lake would cover an area exceeding 96,000 acres. Historical accounts indicate that at high stage Tule Lake drained into the lava flows along the southern margin. In the early 1900s, the U.S. Reclamation Service (predecessor to the Bureau of Reclamation) experimented with augmenting this subsurface drainage in early attempts to drain the lake. La Rue (1922) argued that the fact that the water of Tule Lake was fresh, and not saline, was proof that the lake “in the past had an outlet.” Subsurface drainage is also suggested by the hydraulic head gradient that slopes southward away from the Tule Lake subbasin toward the Pit River Basin. In 1912, a canal and dam were completed that allowed the diversion of water from the Lost River to the Klamath River, cutting off the supply of water to Tule Lake. Most of the Tule Lake Basin was drained and is now under cultivation. The only remnant of the lake is the Tule Lake Sump in the southern and western parts of the basin that collect irrigation return flow. Since 1942, water from the sump has been pumped via tunnel through Sheepy Ridge into the Lower Klamath Lake subbasin. The Lower Klamath Lake subbasin once held a large lake-marsh complex that covered approximately 88,000 acres, about 58,000 acres of which were marginal wetlands with the remaining 30,000 acres open water (La Rue, 1922). Lower Klamath Lake was connected to the Klamath River through a channel known as the Klamath Strait, and probably through the expansive wetland that separated the lake from the river elsewhere. In the early 1900s, a railroad dike was constructed across the northwestern margin of the Lower Klamath Lake subbasin, cutting off flow between the lake and river except at the Klamath Strait. In 1917, the control structure at the Klamath Strait was closed, cutting off flow to the lake. As a result, Lower Klamath Lake is now largely drained, with much of the former lake bed and fringe wetlands under cultivation. Areas of open water remain in the Lower Klamath Lake Wildlife Refuge in the southern part of the subbasin.

Currently (2007), about 500,000 acres of agricultural land are irrigated in the upper Klamath Basin, roughly 190,000 of which are included in the Bureau of Reclamation Klamath Project (fig. 3) (Carlson and Todd, 2003; Natural Resources Conservation Service, 2004). This total does not include wildlife refuge areas within the Project.

The upper Klamath Basin is mostly forested (Loy and others, 2001). Forest trees in upland areas east of the Cascade Range are predominantly ponderosa pine, with areas of true fir and Douglas fir on Yamsay and Gearhart Mountains. Forests in the Cascade Range are composed primarily of mountain hemlock and red fir. Lower elevation uplands are dominated by lodgepole pine. Lowland forests consist largely of juniper and sagebrush with some juniper grasslands. Stream valleys and the broad, sediment-filled structural basins generally have extensive marshes, such as Sycan Marsh and Klamath Marsh, except at lower elevations, where the basins have been mostly converted to agricultural land (for example, the Wood River Valley, and the Lower Klamath Lake and Tule Lake subbasins).

The population of the upper Klamath Basin is approximately 70,000. Klamath County, most of which is in the upper Klamath Basin, had a population of 64,600 in 2003, most of which live in the Klamath Falls area (Oregon Blue Book, 2006). Few people live outside Klamath County in the Oregon part of the basin. The population in the California part of the upper Klamath Basin is difficult to estimate. Population in the block groups from the 2000 census that include the populated parts of Modoc and Siskiyou Counties in the basin is slightly more than 3,000. Some small settlements and ranches may not be included in these block groups.

Principal sectors of the economy in the upper Klamath Basin, in terms of output and employment, include forest products, agriculture, construction, retail, health care, and services (Weber and Sorte, 2003). In the agricultural sector, principal crops include (in approximate order, with largest acreages first) alfalfa hay, irrigated pasture, grains, and potatoes (Carlson and Todd, 2003; Siskiyou County, 2003). The proportions vary slightly between land inside and outside the Bureau of Reclamation Klamath Project, and between land in Oregon and California. Project lands in California tend to include more grains than alfalfa. Most agricultural land in the upper Klamath Basin (not including rangeland) is irrigated. A substantial part of the local economy, therefore, relies on irrigation water.

Irrigation water comes from a variety of sources in the upper Klamath Basin. Upstream of Upper Klamath Lake, in the Williamson, Sprague, and Wood River drainages, private (non-Project) irrigation water comes primarily from diversion of surface water from the main-stem streams or tributaries. A smaller amount of irrigation water is pumped from ground water, particularly in the Sprague River Valley and Klamath Marsh areas. In the Langell and Yonna Valleys of the upper Lost River subbasin, irrigation water comes from Clear Lake and Gerber Reservoirs. Irrigators use ground water and some surface water in Swan Lake Valley. Ground water is used for irrigation in areas not served by irrigation districts and to supplement surface-water supplies throughout the area.

South of Upper Klamath Lake, most irrigation water comes from the lake, which is the largest single source of irrigation water in the upper Klamath Basin. This area is the main part of the Bureau of Reclamation Klamath Project. Water is stored in and diverted from the lake to irrigate land south of Klamath Falls, including the Klamath Valley, Poe Valley (in the Lost River subbasin upstream of Olene Gap), and the Tule Lake subbasin. Irrigation return flow (water that originates in Upper Klamath Lake) that ends up in the Tule Lake Sump is pumped through Sheepy Ridge and used for irrigation and refuge use in the southern part of the Lower Klamath Lake subbasin. Water diverted from the Klamath River several miles downstream of the lake also is used for irrigation and refuges in the Lower Klamath Lake subbasin. Irrigation and refuge return flow in the Lower Klamath Lake subbasin is routed back up the Klamath Strait drain through a series of pumping stations to the Klamath River.

A certain amount of ground water is used for irrigation on land surrounding the Klamath Project upslope of the major canals. Principal areas of ground-water use surrounding the Project area include the southern end of the Klamath Hills, parts of the Klamath Valley, and the northern and eastern margins of the Tule Lake subbasin (fig. 1). Some ground water traditionally has been used for supplemental irrigation in the Project area. Increased water demand due to drought and requirements for a 100,000 acre-ft pilot water bank placed on Reclamation by the National Oceanic and Atmospheric Administration (NOAA) Fisheries 2002 biological opinion (National Marine Fisheries Service, 2002) have resulted in a marked increase in ground-water pumping in and around the Klamath Project since 2001.

Purpose and Scope

This report summarizes the present understanding of regional ground-water flow in the upper Klamath Basin resulting from the USGS–OWRD cooperative study. The report provides a description of the ground-water hydrology for resource managers, water users, and those with a general interest. It is also intended to provide sufficient quantitative information useful to hydrologists working in the basin, and to provide background for subsequent reports and investigations.

The report is regional in scope. Thus, data and analysis presented herein are intended to provide an understanding of the ground-water hydrology at a regional scale. Although the information and interpretations are useful for understanding the hydrologic setting of smaller areas, the ground-water hydrology of local areas is generally not discussed in detail.

The report covers many key aspects of the regional ground-water system. A summary of the geologic framework of the regional ground-water system is presented that is based on existing geologic mapping, field reconnaissance, radiometric age dates, and interpretation of lithologic data from more than 1,000 wells. A regional ground-water budget (including recharge and discharge), calculated from precipitation data, streamflow data, measured and estimated ground-water discharge to streams, and estimated evapotranspiration, also is provided. The distribution of hydraulic head, which controls ground-water flow directions, was estimated from water-level measurements in more than 1,000 wells, altitudes of gaining stream reaches, and altitudes of hundreds of springs mapped on USGS quadrangle maps. The response of the flow system to climate variations and pumping stresses was determined by using time-series water-level measurements from wells throughout the basin, with frequencies ranging from hours to months and periods ranging from years to decades, and from streamflow data.

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