Final Project
Middle Popo Aggie River
Embedded Files
Introduction into the Middle Popo Aggie River
Introduction into the Middle Popo Aggie River
Part of the Popo Aggie River Watershed
Part of the Popo Aggie River Watershed
HUC: 1008000302
HUC: 1008000302
Watershed Location and Drainage (Figure 1)
Watershed Location and Drainage (Figure 1)
Middle Popo Aggie River is part of the Popo Aggie River Watershed HUC:1008000302. This watershed is located in central Wyoming, Fremont County. This watershed is apart of the larger Wind River Basin 6 Digit HUC. Closet major town nearby is Lander, Wyoming.
The Middle Popo Aggie River drains into in these in this order: Wind River, Bighorn River, Yellowstone River, Missouri River, Mississippi River, Gulf of Mexico
Figure 1: Major WY rivers that Middle Popo Aggie connects to. The 10 digit HUC is the Popo Aggie River Watershed. The 6 digit HUC is the Wind River Basin. Data derived from Cybercaster (2024a, 2024b) and Arc GIS.
Catchment map with locations of study reaches (Figure 2)
Catchment map with locations of study reaches (Figure 2)
Figure 2: Project site locations for my confined, laterally unconfined and partially confined planform-controlled sites. Included is the perrenial drainage network, elevation, and watershed/basin location. Data derived from Cybercaster (2024a, 2024b) and Arc GIS.
Climate
Climate
Climate is semi-arid continental climate
Average annual precipitation: Wind River Range: 20-40 inches (mostly as snow), Surrounding Basin: 10-14 inches
Temperature range: Summer highs: 80-90°F (27-32°C) Winter lows: 0-20°F (-18 to -6°C)
Flow Regime
Flow Regime
The primary water source for the Popo Agie River watershed (HUC 1008000302) is snowmelt from the Wind River Range, particularly from glaciers and snowpack in the high elevation areas above 10,000 feet.
Popo Aggie River Watershed is a snowmelt-dominated system and experiences annual variation based on snowpack.
Flow Pattern:
Winter low flow (ice-affected)
Spring snowmelt is peak flow
Summer recession of flow
Baseflow occurs in the fall
Geologic Setting
Geologic Setting
Wind River Mountains
Precambrian granite and metamorphic rocks
Extensive glacial features
Sharp elevation changes
Wind River Basin
Sedimentary deposits
Tertiary and Cretaceous formations
Alluvial deposits in valley bottoms
(Vandeberg & VanLooy, 2014)
Physiographic Setting
Physiographic Setting
Ecoregion: The Popo Agie River is located in the Wyoming Basin ecoregion which is considered a semi-arid climate of grasslands and sagebrush by the Environmental Protection Agenecy (EPA). The section of river we are focusing on is considered a sub irrigated high valley level IV ecoregion by the EPA (Chapman et al. 2004). The ecoregion means that this area has higher moisture levels than surrounding ecoregions and experiences seasonal flooding. Also, sub-irrigated high valley ecoregions can support more biodiversity and are great areas to implement river management to prevent flooding downstream.
Vegetation Communities
Vegetation Communities
Alpine Zone (>10,000 ft)
Alpine tundra
Limited vegetation
Subalpine Zone (8,000-10,000 ft)
Engelmann spruce
Subalpine fir
Lodgepole pine
Montane Zone (6,000-8,000 ft)
Douglas fir
Aspen groves
Mountain meadows
Basin Zone (<6,000 ft)
Sagebrush steppe
Mixed grasslands
Riparian corridors with cottonwood
Photo of Middle Popo Aggie: Taken from a reach in sinks canyon, this area is partially confined margin controlled.
Watershed Morphometrics
Shape: Elongated, roughly rectangular
Area: 1077 km^2
Length: 60 km
Width: 30 km
Elevation Range:
Maximum: 13,000 ft (Wind River Peak area)
Minimum: 5,400 ft (near Lander)
Mainstem Characteristics
Main Channel: Popo Agie River
Length: Approximately 25-30 miles
Major Tributaries:
Middle Fork Popo Agie
North Fork Popo Agie
Little Popo Agie
Current Land Use: The upper mountainous areas is proctected and there is agriculture/infrastructre in the basin. Lots of recreation and forest managament within Sinks Canyon.
Laterally Unconfined Riverscape
Laterally Unconfined Riverscape
Laterally Unconfined Reach: Above you can see this reaches extent within the Valley Bottom (pink line). This area has numerous point bars and an active floodplain, signaling a zone with potential for continued meandering and possible braiding patterns. Mid-channel bars are also present along this reach. On river right, abandoned old channels are visible, indicating historical river migration. This area marks the confluence where the Middle Popo Agie connects to the Wind River. While nearby infrastructure and farming activities limit the river's ability to migrate across its entire valley bottom, the large valley width in this area still provides significant potential for future channel movement within these constraints.
River Type:
Likely a gravel-bed river
Mixed with sand in some sections
Minimal bedrock control due to being laterally unconfined
Flow Characteristics:
Annual spring snowmelt brings peak flow rates (typically May-June)
Bankfull flows occur approximately every 1.5-2 years
Floodplain inundation happens during spring runoff events
Lower flows during late summer and winter months
Channel & Floodplain Adjustment:
Banks are typically non-cohesive to mixed meaning there is high potential for lateral migration due to being unconfined.
Channel can/will adjust through:
Lateral migration
Bar formation
Avulsion during high flow events
Sediment deposition and erosion (cut-and-fill alluviation)
Channel Characteristics:
Generally wide and shallow profile
Multiple channels possible (anastomosing patterns)
Pool-riffle sequences common
Sediment Load:
Mixed load system
Gravel and cobbles as bedload
Sand and finer materials as suspended load
High sediment transport during spring runoff
Geomorphic Units Present: Point bars, mid-channel bars, secondary channels, abandoned channels, floodplain surfaces at various elevations
Future Predictions:
Continued lateral migration
Braided river system
Potential for high amounts of avulsion
Channel pattern could become less meandering if upstream daming increases or nearby infrastrcutre/ farming expands in valley bottom
Sediment Composition:
Bars: Gravel and cobble with sand matrix
Floodplain: Mixed layers of sand, silt, and gravel
Channel bed: Predominantly gravel and cobble
Vegetation:
Riparian: Cottonwoods, willows, sedges and rushes in wet areas
Wood structures include: Natural log jams, fallen trees, sccumulated woody debris on bars and banks
Confined Riverscape
Confined Riverscape
Pictured is a view overlooking the valley bottom of Sinks Canyon. This photo is roughly one mile downstream of the confined site. In the photo, you can see how the valley bottom is confined by the steep surrounding valley slopes. Also, in the distance, you can see where the river gets its primary snowpack runoff from (the Wind River Range).
Confined Reach: This area is laterally confined by the surrounding hillsides and banks, which are composed of larger sediments such as cobbles/boulders and bedrock.
River Type: This confined river reach is predomisanlty a bedrock-dominated system. This area is channelized adn confiedn deu to the valley setting.
Flow Characteristics:
Annual spring snowmelt brings peak flow rates (typically May-June)
Limited floodplain inundation due to confinement
Flow concentrated in main channel
Channel & Floodplain Adjustment:
Very limited lateral adjustment due to bedrock confinement
Banks predominantly bedrock (non-cohesive)
Vertical adjustment limited by bedrock control
Minimal floodplain development
Channel Characteristics:
Narrow and deep profile
Step-pool morphology can be common
Bedrock-controlled pools and cascades
Sediment Load: It is predominantly bedload transport consisting of large boulders or cobbles. The area is very limited in the capacity in which sediment can be deposited. During large floods, the only likely deposits are large cobbles/boulders, and lots of sediment will move through this reach but not be deposited.
Geomorphic Units Present: Bedrock outcrops (forms forced pools) and boulder cascades.
Little to no bars present and the river formed primarly thorugh plunge pool development and bedrock incsion.
Future Predictions:
Relatively stable planform
Slow vertical incision
Limited lateral change
Changes mainly during extreme events
Sediment Composition:
Channel bed: Boulder, cobble, bedrock
Limited bars: Coarse material (boulder/cobble)
Pocket deposits: Mixed gravel and sand
Bedrock exposure common
Vegetation: Conifers on canyon walls and small and very few riparian areas as valley walls limit space for riparian growth.
Wood structures: Are limited due to high flows and channelization. Most wood is transported through system and not deposited
The confined reach located in Sinks Canyon is the least dynamic river system out of all the reaches discussed. The reach is controlled by the bedrock, which causes the area to be channelized and lack stability, leading to frequent high-energy sediment transport events. Also, its structure limits its storage capacity, thus limiting the ability for floodplains to form and bars
Ponderosa Pine along Middle Popo Aggie. Photo taken about 0.5 miles downstream of the confined reach. Notice the lack of sediment deposition around tree and current erosion.
Partly-confined Riverscape
Partly-confined Riverscape
(Planform Controlled)
Confinement & Control:
Unlike the unconfined area, this reach has significant bedrock control. The reach is partially confined and planform-controlled because only about 20-30% of this reach is confined due to hillslopes. This area will still likely experience some geomorphic change, but it will be a more stable process. While this area's confinement does limit its ability to meander, it can store sediment and build features such as the point bars seen above.
The sediment type in this reach is predominantly larger cobbles and stones on river left, but on river right, there are some areas that are not confined and experiencing some lateral movement, such as the areas around the island. Over time, erosion continues to occur on either side of the bar while vegetation has developed
Channel Pattern
Most areas channelized wiht some expreicening aggradaing and widening
Stable planform due to bedrock
Narrower active corridor than the unconfined reach (limits the lateral movment and active valley bottom)
Geomorphic Units
Some mid-channel bars and point bars are primarily lateral bars due to their lack of sinuosity.
Some bedrock-forced pools
Discontinuous floodplain pockets, unlike the continuous floodplain pockets of the unconfined reach.
Channel Adjustment
Limited lateral migration potential
Vertical adjustment controlled by bedrock
Less susceptible to avulsion
More stable long-term position
Vegetation Patterns
More confined riparian corridor
Vegetation limited to floodplain pockets
Mixed conifer on valley walls
Less extensive cottonwood/willow communities
Future Trajectory: The reach of the active channel is limited. There is some slight lateral movement, but the presence of bedrock limits areas where lateral movement can occur. The area will have limited lateral adjustment, but if the bends keep forming, it has the potential to continue to be an area of moderate sediment deposition.
References
References
Vandeberg, G. S., & VanLooy, J. A. (2014). Continental glaciers of the Wind River Range, Wyoming—Future survival under a warming climate (Scientific Investigations Report 2014–5118). United States Geological Survey. https://pubs.usgs.gov/sir/2014/5118/
(Chapman et al. 2004) Chapman, S.S., Bryce, S.A., Omernik, J.M., Despain, D.G., ZumBerge, J., and Conrad, M., 2004, Ecoregions of Wyoming (color poster with map, descriptive text, summary tables, and photographs): Reston, Virginia, U.S. Geological Survey (map scale 1:1,400,000).
Cybercastor. (2024a). Hydrologic Context for Popo Agie River. A Riverscapes Project data set of type: Hydrologic Context. Owned by: BLM Riverscapes. Available from: https://data.riverscapes.net/p/5fe391ba-20d0-41c7-a81e-4e85c096437f/
Cybercastor. (2024b). Riversapes Context for Popo Agie River. A Riverscapes Project data set of type: Riverscapes Context. Owned by: BLM Riverscapes. Available from: https://data.riverscapes.net/p/8dc94d99-24b7-4643-804b-8cf7541cb5d5/
Page updated
Google Sites
Report abuse