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United States Department of Agriculture

Agricultural Research Service

Title: Spatial and Temporal Contributions to Variability in Sediment Loads of the Umatilla River, Oregon

Authors
item Williams, John
item Robertson, David
item Geffen, Brook - UMATILLA CO. SWCD
item Webster, James - CONFEDERATED TRIBES UMATI
item Clifton, Catherine - USDA-FS

Submitted to: Soil and Water Conservation Society
Publication Type: Abstract Only
Publication Acceptance Date: January 30, 2006
Publication Date: June 24, 2006
Citation: Williams, J.D., Robertson, D.S., Geffen, B.A., Webster, J.G., Clifton, C.F. 2006. Spatial and temporal contributions to variability in sediment loads of the Umatilla River, Oregon. In Proceedings of the SWCS International Environmental Management Conference, July 22-26, Keystone, CO. 2006. CDROM.

Interpretive Summary: Oregon has been producing Total Maximum Daily Load and Water Quality Management Plans (TMDL/WQMP) in compliance with the US Clean Water Act. The Umatilla River TMDL/WQMP was completed and accepted by the USEPA in 2001. A number of the stream segments in the Umatilla River subbasin were identified as water quality impaired. Water quality impairment is related to flow and sediment from soil erosion. Our goals are to: 1) determine the relationship between land use and development on sediment delivery to streams, 2) determine variation and quantity of sediment during seasonal events, and 3) identify sediment load contributions from tributaries to the mainstem Umatilla River. Analysis and summary of seven years of data show highly variable daily, seasonal and annual sediment loads in the mainstem Umatilla and tributaries. Detecting and linking change in sediment loads specific to management changes at the scale of the Umatilla Subbasin is problematic because of variability and lag time in responses. As a result of these early findings, the Umatilla TMDL/WQMP technical committee is focusing monitoring efforts on a high priority tributary to improve the potential for linking upland and riparian management to instream sediment transport.

Technical Abstract: Forty stream segments in the Umatilla River Subbasin in Oregon were designated water quality limited and placed on the US Clean Water Act’s 303(d) list, in 1998. A unique cooperative effort of local, county, state, tribal, and federal agencies and private citizens developed the Umatilla River Basin Total Maximum Daily Load and Water Quality Management Plan (TMDL/WQMP), which was approved by the USEPA in 2001. Sediment data is being used to establish a baseline for determining progress in meeting sediment targets in the TMDL/WQMP. Our goals are to: 1) determine the relationship between land use and development on sediment delivery to streams, 2) determine variation and quantity of sediment during seasonal events, and 3) identify sediment load contributions from tributaries to the mainstem Umatilla River. There are currently 11 sampling stations in the Umatilla River and major tributaries. Daily composite samples are collected with automated pumping samplers, at 6-hour intervals, and analyzed for total suspended solids, total dissolved solids, conductivity, and turbidity. Analysis and summary of seven years of data show highly variable daily, seasonal and annual sediment loads in the mainstem Umatilla and tributaries. Detecting and linking change in sediment loads specific to management changes at the scale of the Umatilla Subbasin is problematic because of variability and lag time in responses. We are focusing monitoring efforts on a high priority tributary to improve the potential for linking upland and riparian management to instream sediment transport.

Last Modified: 7/31/2014
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