HR: 08:00h
AN: H31H-01 INVITED     [Abstracts]
TI: Overview of Hydrologic Issues in the Upper Klamath River Basin, Oregon
AU: * Lynch, D D
EM: ddlynch@usgs.gov
AF: US Geological Survey, 10615 SE Cherry Blossom Drive, Portland, OR 97216 United States
AB: The geologic setting of the upper Klamath Basin makes it a naturally arid landscape with eutrophic water bodies. Anthropogenic alterations of the land and hydrology over the past 100 years have put large demands on water supplies and further enriched water bodies with nutrients. Major changes to the upper basin include diking and draining lakes and wetlands for agricultural and grazing land, modifying lakes to increase the supply of summer irrigation water, clearing land and harvesting timber, and installing hydropower dams on the mainstem Klamath River that has blocked salmon passage above Iron Gate Dam. These alterations have contributed to diminished populations of endangered shortnose and Lost River suckers in the upper basin and threatened Coho salmon in the lower Klamath River. Upper Klamath Lake (UKL), with an average depth of 2.5 meters and a surface area of 310 square kilometers, is the primary water-supply reservoir for the Bureau of Reclamation's Klamath Project, which services about half (97,000 ha) of the irrigated agriculture in the upper Klamath Basin. The lake is also the primary habitat for the two endangered suckers. Because of the nutrient enrichment of UKL, the development of large summer blooms of Aphanizomenon flos-aquae, and the periodic crash of these near monoculture blooms, the magnitude and frequency of large sucker die-offs from hypoxia have increased. The relation between management of the lake and surrounding wetlands and algal ecology is not well understood. It is clear, however, that runoff from drained wetlands upstream and around UKL have enriched the lake water and its bottom sediments with phosphorus for many decades. Internal loading from enriched bottom sediments triples the summer phosphorus concentration in UKL and fuels the problematic algal blooms from June through October. An ongoing pattern of below-average precipitation has increased demands from UKL and generated concern. Two recent Biological Opinions aimed at protecting threatened and endangered fish call simultaneously for downstream water deliveries from UKL to provide salmon habitat while maintaining water levels in UKL for shoreline spawning and rearing of suckers. These demands cannot be met during extended droughts if full water deliveries are made to farms and several National Wildlife Refuges. Attempts to increase water supplies through land idling, increased ground-water pumping, and conservation have met with mixed success. The hydrologic issues surrounding the water controversy in the upper Klamath Basin will be expanded upon in this presentation along with an introduction to some of the past, ongoing, and future studies aimed at bringing science and data to the critical decisions being made to recover species and manage scarce water resources.
DE: 1803 Anthropogenic effects (4802, 4902)
DE: 1829 Groundwater hydrology
DE: 1845 Limnology (0458, 4239, 4942)
DE: 1871 Surface water quality
DE: 1890 Wetlands (0497)
SC: Hydrology [H]
MN: Fall Meeting 2005