RESEARCH BRIEFS
Wyoming Water Resources Center

The Influence of Channel and Riparian Zone Types on Muddy Creek's Water Discharge and Sediment Transport (1986-1991)

Investigators: Chris M. Goertler, Wyoming Water Resources Center; Thomas A. Wesche, Wyoming Water Resources Center and Department of Rangeland Ecology and Watershed Management; and Quentin Skinner, Department of Rangeland Ecology and Watershed Management, University of Wyoming.

Purpose: The value of healthy stream channels and their associated riparian zones is widely recognized, yet little scientific information is available quantifying the amount of suspended sediment deposited within these areas. This is especially important as suspended sediment is considered a major nonpoint source pollutant in Wyoming streams. Consequently, this research was conducted on Muddy Creek, a Wyoming cold-desert perennial stream considered by the U.S. Environmental Protection Agency as a major contributor of sediment to downstream systems in the Upper Colorado River Basin (Figure 1). The research goal of this study was to compare streamflow and suspended sediment transport through degraded, improved, and improving stream channel segments of Muddy Creek where each supported different types of riparian vegetation.

Background: Research began in 1983 with funding from the U.S.D.A. Cooperative Research Service, Wyoming Southwestern Livestock Grazing Board, U.S. Bureau of Land Management (BLM), Wyoming Water Development Commission, and Wyoming Water Resources Center. Our research was part of an overall program designed to evaluate differences in riparian vegetation and groundwater storage found in the selected degraded, improved, and improving stream channel segments. Early in this study, 14 different user groups (state agencies, federal agencies, landowners, and the University of Wyoming) signed a Memorandum of Understanding to provide project advice and begin a goal setting process for managing the Muddy Creek watershed. The BLM identified our research area as being of national importance and named it a Riparian Zone Demonstration Area.

Methods: The Wyoming Water Resources Center established the hydrologic and suspended sediment transport monitoring network within the ten mile long Riparian Zone Demonstration Area. Data were collected at five stations established above and below the degraded, improved, and improving stream segments to estimate surface water discharge and suspended sediment load for each of these areas. These data were then compared to help characterize sediment transport within: a) the degraded segment (a U-shaped channel without a well-developed floodplain where little or no riparian vegetation grew); b) improved segment (a shallow and braided channel supporting a relatively level one-half mile wide grass and willow covered riparian zone created by man-made diversion dikes); and c) improving segment (a single channel with floodplains along each bank where small, wire dams were placed to promote sediment deposition, increase the growth of riparian grass and willow, stabilize the channel, and add streamflow to groundwater supplies).

Results: Streamflow-- Runoff in the Muddy Creek watershed is snowpack dominated and highly variable, commencing normally in March, peaking during late March or April, and usually continuing until ice conditions prevail. Runoff during summer can be greatly influenced by thunderstorm events. Muddy Creek runoff patterns appear to be typical of other perennial cold-desert streams of the semi-arid west.

We estimate that 10,000 acre feet of streamflow in Water Year 1987 were stored and then lost to the groundwater supply, and/or to evapotranspiration, within the improved segment because contribution of this water to late summer streamflow was not evident (Figure 2). Periods of zero flow were recorded during the late summer and fall in the drier water years and most prevalent through the degraded segment. Water stored during low flow years behind wire dams in the improving segment remained available for use by both wildlife and livestock although Muddy Creek above and below this segment was dry.

Suspended Sediment Concentration and Load--Suspended sediment concentrations in Muddy Creek are highly variable, both spatially and temporally, with the greatest concentrations corresponding with peak streamflow resulting from spring snowmelt and thunderstorm runoff. Concentrations were greatest through the degraded segment and significant decreases were observed below the improved segment.
Over 95 percent of the suspended sediment load is transported through Muddy Creek during the spring season; however, high amounts for short periods were recorded during some thunderstorms. Estimates of suspended sediment load were highest in the degraded segment with peaks occurring during wet spring and fall periods. The greatest suspended sediment load was recorded for the wettest year in 1987, but this was effectively filtered out by the riparian zone vegetation growing within the improved segment downstream. We, therefore, conclude that the improved segment is effective in controlling nonpoint pollution produced from the upper portion of the Muddy Creek watershed. Approximately 2.6 million tons of sediment were stored in the improved segment during the wet year of 1987 (Figure 3).

Continued Activity on Muddy Creek: University research initiated by the 1983 group was discontinued in 1991, at which time the Little Snake River Conservation District led an effort to form a Muddy Creek Cooperative Resource Management (CRM) program. This active program s goal is to promote best practices for managing the Muddy Creek watershed. All user groups and interested parties of the CRM continue to focus their attention on promoting best management of the headwater uplands and riparian zones of Muddy Creek.

Publications:
Goertler, C.M. 1992.Sediment Dynamics Within Channel and Riparian Zone Types Along a Cold-Desert Wyoming Stream. MS Thesis, University of Wyoming, Laramie, WY. 205 pp.

For further information on this or other research projects or for a list of Wyoming Water Resources Center publications, please write or call the WWRC at:
Wyoming Water Resources Center, P.O. Box 3067, University Station, Laramie, WY 82071-3067 (307) 766-2143 Fax: (307) 766-3718
RESEARCH BRIEFS are published by the Wyoming Water Resources Center with funds provided in part by the US Geological Survey, Department of Interior, as authorized by the Water Resources Research Act of 1984. The research on which this report is based was financed in part by the US Geological Survey, Department of Interior, and Wyoming Water Resources Center. The views expressed do not necessarily represent those of the Department of Interior or the WWRC. Persons seeking admission, employment, or access to programs at the University of Wyoming shall be considered without regard to race, color, national origin, sex, age, religion, political belief, handicap, or veteran status.

RB95-01

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