The purpose of this report is to document current conditions in the Dearborn River watershed on behalf of the Montana River Action Network (MRAN). [Ed. note: The organization name is now Montana River Action] MRAN, a non-profit advocacy organization, is building a network of volunteers to report on the health of Montana’s rivers. The report consists of the following components: 1) this text; 2) an annotated aerial photograph log; 3) a photo log from a spring 2007 float trip; 4) water quality, temperature, and discharge data; and 5) several customized maps based on data obtained from the Montana Natural Resource Information System (NRIS). The information presented in the report derives largely from two recent river trips and data from NRIS.
The headwaters of the Dearborn River drain the eastern half of the Scapegoat Wilderness in the heart of the Rocky Mountain Front. The Front, also known as the Sawtooth Range, marks the transition between the Rocky Mountains and the Great Plains. The stream’s headwaters lie at about 6000 feet above mean sea level. The Dearborn then flows for approximately 67 miles before adding its flow to the Missouri River at an elevation of about 3420 feet. The Dearborn is more remote than many streams in western Montana; only a few bridges cross its banks. Except for U.S. Forest Service holdings in the upper watershed, most land along the river corridor is privately owned. According to the MRAN, 44 miles of the river are chronically dewatered during each irrigation season. This means that the streamflow may not be adequate for use by fish.
River Corridor Description
The following discussion relates to a multi-day spring float trip down the river (Table 1). The accompanying photo logs document the trip. We launched our boats at noon on Saturday, May 26, 2007. Upstream, a recent storm had the blasted the Scapegoat Wilderness and the Rocky Mountain Front. During the first day, the mountains, laden with new snow, jutted up into the sky behind us and were clearly visible from the river. The effects of the storm would become apparent toward the end of the trip when streamflow had increased by over 100 cubic feet per second (cfs).
Read the rest of the 34-page report, which includes photos, maps, tables and graphs.
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