Historic changes and water quality characteristics of off-channel habitats on the 59-mile segment of the Missouri National Recreational River (MNRR)

• Main Author: Yager, Lisa A
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2010
• Subjects: Ecology; Geomorphology; Limnology
• ISBN: 1124389636; 9781124389639

Using historical and current aerial imagery, I was able to quantify changes in the number, size, and shape of off-channel habitats, specifically backwaters and side channels, from 1941 (pre-dam), 1983-85, and 2008 (post-dam). The overall number of features increased slightly from 1941 (30) to 1983-85 (35), but declined steeply by 2008 (20). Total and mean areas of off-channel features declined by 70% and 55%, respectively, and mean length decreased by 54% from 1941 to 2008. A clear proportion shift from side channels to backwaters was also observed pre- to post-dam, highlighting the change in channel-floodplain connectivity and the impacts to off-channel habitats. Current restored backwaters are considerably larger, both in area and length, than natural backwaters in 1983-85 and 2008, but were comparable in size to those found in 1941. Potential areas for further backwater restoration were also identified. Three backwater habitats have recently been restored within the 59-mile segment of the MNRR. Monitoring of water quality, benthic invertebrates, and terrestrial vegetation at the Gunderson Backwater (RM 777) was conducted in 2008 and 2009. Additionally, two other restored backwaters at Ponca State Park (RM 754) and Yankton, SD (RM 806), as well as two naturally occurring backwater complexes at RM 774 and RM 766 were added to the monitoring program in 2009. The water quality of these backwaters differed significantly from the adjacent main channel, specifically suspended solids (40% less within backwaters, p=0.0929), total dissolved solids (9.6% greater, p=0.0949), and alkalinity (14% greater, p=0.0644). When the flow through backwater at RM 766 was excluded, temperature was also significantly different (roughly 1°C warmer, p=0.043). Spatial and temporal trends and water quality patterns with individual backwaters were also examined. These backwater features provide a valuable and unique habitat not found within the main channel of the river and the continued loss of this habitat could be detrimental to the overall river ecosystem. Continued restoration and research are crucial to these endangered habitats.