Powder River: Data for Cross-Channel Profiles at 22 Sites in Southeastern Montana, 1975 through 2019 Active

Introduction

Sources/Usage: Public Domain.

Powder River rises in the Bighorn Mountains of Wyoming and flows northward through a semi-arid landscape in Wyoming and Montana to the Yellowstone River. The river drains an area of 34,700 square kilometers and has an average discharge of about 500 million cubic meters per year (or 16 cubic meters per second).

The river in the adjacent photo is at about bed-full flow (12 m³ s^-1, Moody and others, 1999), and several riffles with disturbed water can be seen downstream between smooth glassy reaches of the river. A narrow band (~2-4 m wide) of reddish sedge (Scirpus spp.) grows just above the bed-full level along the edge of water with a wider band of mixed grasses (Agropyron repens, A. pauciflorum, Bromus inermis, Elymus canadenis, Spartina pectinata, and S. cynosoroids), willow (Salix exigua), tamarisk (Tamirix ramosissima) and small cottonwood seedlings and trees (Populus sargentii) on the flood plain. Three terrace levels have been identified along the river (Leopold and Miller, 1954; Moody and Meade, 2008). The first is the Lightning Terrace with small cottonwood trees (seen here without leaves) adjacent to the floodplain in the right-center of the photo. The second is the Moorcroft Terrace seen best forming the left bank and extending as a flat surface to the left (west) with a few large cottonwood trees still retaining their green leaves. The third is the colluvial Kaycee Terrace that grades slowly upwards and meets the hills of the Fort Union Formation. It can be seen on the right side at the base of the hills and in the far distance on the left side, west of the white ranch buildings.

Powder River has no dams or other large-scale human modifications, which, combined with its substantial suspended-sediment load (2-3 million metric tons per year), makes it an optimal outdoor laboratory for studying natural fluvial processes (Moody and Meade, 1990; Hubert, 1993; Moody and others 2002). A research program was started in 1975 and, by 1977, 20 channel cross sections had been established in the 93-km reach, with the uppermost (PR113) just upstream from the Moorhead gage and the lowermost (PR206, see map) just downstream from the Broadus gage. Cross section PR120 crosses the river in the above photo at a point near where the shadows from the large cottonwood trees on the left bank meet the river downstream from the apex of the nearer bend (Moody and others 1999; Pizzuto and others, 2008). An extreme flood in 1978 (779 m³ s^-1) (Moody and Meade, 2008; Meade and Moody, 2013) was a major disturbance that widened the channel, caused two meander cutoffs (not visible in this photo), and deposited fresh sediment on the Lightning and Moorcroft terraces. Two additional cross sections (PR 122A and PR141A) were established on the cutoffs in 1979, and the post-flood response has been monitored at most channel cross sections through 2012. Elevation datum is NGVD29, and all cross-sectional data (1975-1998) also are available in the Results tab of this page.

Sources/Usage: Public Domain.

Current Discharge Data 

• USGS National Water Information System, Station 06324500, Powder River at Moorhead MT
• USGS Surface-Water Daily Statistics for the Nation Station 06324500, Powder River at Moorhead MT

Citation For This Dataset

Moody, J.A., and Meade, R.H., 2014, Powder River: Data for cross-channel profiles at 22 sites in southeastern Montana from 1975 through 2014, Washington: U.S. Geological Survey Data Set, doi:10.5066/F70Z719C.