HR: 0800h
AN: H11C-0667    [Abstracts]
TI: Fingerprinting Persistent Turbidity in Sheep Creek Reservoir, Owhyee, Nevada
AU: * Ransom, R N
EM: RANSOMRN@uwec.edu
AF: University of Wisconsin - Eau Claire, Department of Geology, Eau Claire, WI 54701, United States
AU: Hooper, R L
EM: HOOPERRL@uwec.edu
AF: University of Wisconsin - Eau Claire, Department of Geology, Eau Claire, WI 54701, United States
AU: Kerner, D
EM: dkerner@brncald.com
AF: Brown and Caldwell, 600E. Riverpark #210, Boise, ID 83706, United States
AU: Nicols, S
EM: dkerner@brncald.com
AF: Brown and Caldwell, 600E. Riverpark #210, Boise, ID 83706, United States
AB: Sheep Creek Reservoir near Owyhee, NV is historically a quality rainbow trout fishery. Persistent high-turbidity has been an issue since a major storm event in 2005 resulted in surface water runoff into the Reservoir. The high turbidity is adversely impacting the quality of the fishery. Initial turbidity measurements in 2005 were upwards of 80NTU and these numbers have only decreased to 30NTU over the past two summers. Field parameters indicate the turbidity is associated with high total suspended solids (TSS) and not algae. Five water samples collected from around the reservoir during June, 2007 indicated uniform TSS values in the range of 5 to 12mg/L and oriented powder x-ray diffraction(XRD) and transmission electron microscopy(TEM) analyses of suspended sediment shows very uniform suspended particulate mineralogy including smectite, mixed layer illite/smectite (I/S), discrete illite, lesser amounts of kaolin, sub-micron quartz and feldspar. Diatoms represent a ubiquitous but minor component of the suspended solids. Six soil samples collected from possible source areas around the reservoir were analyzed using both XRD and TEM to see if a source area for the suspended solids could be unambiguously identified. Soils on the east side of the reservoir contain smectite and mixed layer I/S but very little of the other clays. The less than 2 micron size fraction from soils collected from a playa on the topographic bench immediately to the west of the reservoir show a mineralogic finger-print essentially identical to the current suspended sediment. The suspended sediment probably originates on the bench to the west of the reservoir and cascades into the reservoir over the topographic break during extreme storm events. The topographic relief, short travel distance and lack of a suitable vegetated buffer zone to the west are all consistent with a primary persistent suspended sediment source from the west. Identification of the sediment source allows for design of a cost effective remediation plan that includes minimizing future loading of the reservoir with soils capable of producing extended turbidity.
DE: 1850 Overland flow
DE: 1871 Surface water quality
DE: 1895 Instruments and techniques: monitoring
DE: 4558 Sediment transport (1862)
SC: Hydrology [H]
MN: 2007 Fall Meeting