Submitted to: American Water Resources Association Conference Proceedings
Publication Type: Other
Publication Acceptance Date: 6/1/2005
Publication Date: 11/4/2005
Citation: Geffen, B., Clifton, C., Webster, J., Williams, J.D. 2005. Total maximum daily load water quality monitoring for sediment in Wildhorse Creek, northeast Oregon. In Proceedings of the American Water Resources Association Conference, November 1-4, Seattle, WA. CDROM.
Technical Abstract: In 1998 over 40 stream segments in the Umatilla River Basin were listed as “water quality limited” on Oregon Department of Environmental Quality’s (ODEQ) 303(d) list under the Clean Water Act. A unique multi-agency cooperative effort led to the Umatilla River Basin Total Maximum Daily Load (TMDL) and Water Quality Management Plan (WQMP), approved by the Environmental Protection Agency in 2001. Sediment loads, (total suspended solids, total dissolved solids, conductivity, and turbidity), were monitored with to: 1) determine the relationship between landuse and sediment delivery to streams, 2) determine quantity and variability of seasonal sediment loads, and 3) identify sediment loads from selected tributaries of the Umatilla River. Automated sediment samplers collect daily composite, 6-hour interval samples at 11 sampling stations on the Umatilla River and its major tributaries, which are analyzed in USDA-FS water lab in Pendleton OR. Seven years of data show highly variable daily, seasonal and annual sediment concentrations and loads in the mainstem Umatilla and tributaries. Spatial patterns of turbidity are seen in calculated sediment duration curves demonstrating increasingly higher frequencies of turbidity standard exceedance in the lower river. Detecting and linking change in sediment loads specific to management changes at the scale of the Umatilla Basin is problematic because of variability in soils and climate, and lag time in stream morphological and water quality responses. Focused monitoring within a high priority watershed has been implemented to improve our ability to link management activities to instream sediment loads.