Scientific Investigations Report 2006–5036
U.S. GEOLOGICAL SURVEY
Scientific Investigations Report 2006–5036
Demand for water in the semiarid upper Klamath Basin of southern Oregon and northern California has increased in recent years, resulting in the need to better quantify water availability and use in and around the Bureau of Reclamation Klamath Project. Most of the water entering the Lower Klamath and Tule Lake National Wildlife Refuges originates from the Project. In 2005 the Bureau of Reclamation asked the U.S. Geological Survey Oregon Water Science Center to evaluate and better quantify water use and flow data to and from the refuges.
Located south of the Project and mostly in California, the Lower Klamath and Tule Lake refuges encompass approximately 46,700 and 39,100 acres, respectively. Roughly one-third of the combined refuge surface areas are leased to farmers for cereal grain and alfalfa production. Since the early 1900s, surface-water flow to and from the refuges has developed into a highly regulated system.
The Lower Klamath refuge receives most of its water from the D Pumping Plant via a tunnel under Sheepy Ridge, Ady Canal, and precipitation. Additional, smaller quantities of water enter the refuge from springs that supply flow to Sheepy, Willow, and Cottonwood Creeks. Most of the water leaves the refuge through open-water evaporation, evapotranspiration from vegetated wetlands, and the Klamath Straits Drain. Water is pumped through the Klamath Straits Drain into the Klamath River.
Water enters the Tule Lake refuge from Project return-flow canals, the Lost River, the N Canal, precipitation, and ground-water seepage. Water leaves the refuge through the D Pumping Plant, open-water evaporation, evapotranspiration from vegetated wetlands, and ground-water seepage. The Tule Lake refuge is composed of four major sumps, which include Sumps 1A, 1B, 2, and 3. Sumps 1A and 1B usually are year-round open-water bodies, whereas Sumps 2 and 3 usually are leased for agriculture.
Annual water-use estimates for the refuges were computed using separate open-water evaporation and evapotranspiration rates and acreage for four land-use categories. On the basis of local climate data and data from previous studies, the estimated combined annual open-water evaporation and evapotranspiration rates for grain fields, seasonal wetlands, emergent vegetation wetlands, and open-water bodies were, for this study, 2.5, 2.9, 2.63, and 4.07 ft, respectively. Total water use was estimated as the sum of the products of each rate and the number of acres in its associated land-use category. Because the number of acres in each land-use category changes each year, total water use was computed separately for 2003, 2004, and 2005 and then averaged to approximate current conditions. Mean annual (2003–2005) water use for the Lower Klamath and Tule Lake and refuges was approximately 124,000 and 95,900 acre-ft, respectively. To estimate needed water deliveries for each refuge, annual precipitation for 2003, 2004, and 2005 was subtracted from the annual water use estimate for those years. Twenty percent of those totals was then added to the estimates to account for long-term salinity flushing over time. The 2003–2005 mean annual estimated needed water deliveries for the Lower Klamath and Tule Lake refuges were 107,000 and 82,800 acre-ft, respectively.
Using estimated and measured surface-water inflows and outflows for 2003–2005, mean annual net inflow to the refuges was computed by subtracting outflows from inflows. Computed 2003–2005 mean annual net inflow for the Lower Klamath refuge was approximately 73,700 acre-ft. This volume was computed by subtracting flow at Klamath Straits Drain at State Line Road from the sum of D Pumping Plant and Ady Canal at State Line Road flows. However, that value can be compared only to estimated water use in refuge units located south of State Line Road served by Project water. The estimated needed water delivery for those units is approximately 77,600 acre-ft (in contrast to the estimated needed water delivery for the entire refuge of 107,000 acre-ft) and comparable to the mean annual net inflow estimate above. For the Tule Lake refuge, mean annual 2003–05 net inflow was approximately 76,100 acre-ft, which was comparable to the estimated annual needed water delivery of 82,800 acre-ft.
For 1962–2005, mean annual net inflow to the Lower Klamath refuge was approximately 49,800 acre-ft, about 23,900 acre-ft less than for 2003–2005. Although mean April–September net inflows for 1962–2005 and 2003–2005 have remained fairly constant, mean October–March net inflows were greater during 2003–2005 than during 1962–2005. Increased autumn and winter flow deliveries starting in the mid-1980s reflected a significant change in refuge management: More units currently are managed as seasonal wetlands than were in the 1960s and 1970s.
Flow records for the Ady Canal at State Line Road, Klamath Straits Drain at State Line Road, and D Pumping Plant were evaluated for their data quality. On the basis of USGS flow-record criteria, all three flow records were rated as “poor.” By definition, 95 percent of the daily flows in a record having this rating could be in error by more than 15 percent.
Improvement in the streamflow-data collection network at refuge boundary locations can be achieved through (1) data collection by a single agency—the Bureau of Reclamation, U.S. Fish and Wildlife Service, or U.S. Geological Survey, (2) better data documentation and archiving, (3) equipment modernization, (4) more frequent check measurements, and (5) new flow-measurement locations near the boundaries of both refuges.
For more information about USGS activities in Oregon, visit the USGS Oregon Water Science Center home page.
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