Abstract
Loss of shallow water habitat (SWH) is hypothesized as a factor contributing to the decline of native Missouri River fishes, including the endangered pallid sturgeon. As a result, the restoration of SWH is a high priority in this large river system. Restoration activities often include constructing side channel chutes; however, limited information exists on the potential negative, unintended effects of chute construction activities on water quality. This study was designed to better understand the possible effects of chute construction, both initially and as chute development continues, on Missouri River nutrient concentrations. Our first objective was to determine if the addition of sediment from proposed chute locations to river water samples (i.e., elutriate samples) increased nutrient concentrations relative to water-only river samples collected just upstream of the proposed chute locations or river water samples collected from eight long-term water quality monitoring stations. Our second objective was to determine if nutrient concentrations of river samples monitored during 2009 and 2010 increased after water passed through previously-constructed chutes. Nutrient concentrations of elutriate samples were not significantly higher than river water samples collected just upstream of the proposed chute locations; the same was true for Missouri River water samples collected from seven of eight long-term water quality monitoring stations. Furthermore, monitoring of nutrient concentrations collected from water samples at the outlet of previously-constructed chutes were not significantly higher than water samples collected at the upstream inlet of these chutes. Our results suggest that individual SWH chute construction projects designed to restore some of the natural form and function of the Missouri River are unlikely to significantly increase Missouri Rivernutrient concentrations initially or as these chutes continue to develop.
Highlights
During the 20th century, the Missouri River was dramatically altered for the purposes of flood control, hydropower generation, water supply, and commercial navigation
Our results suggest that individual shallow water habitat (SWH) chute construction projects designed to restore some of the natural form and function of the Missouri River are unlikely to significantly increase Missouri River nutrient concentrations initially or as these chutes continue to develop
In contrast to Total nitrogen (TN) and NO3-NO2, no monitoring stations had significantly lower total phosphorus (TP) or total orthophosphorus (TOP) concentrations compared to elutriate concentrations (Figure 3)
Summary
During the 20th century, the Missouri River was dramatically altered for the purposes of flood control, hydropower generation, water supply, and commercial navigation. These alterations included the construction of six mainstem reservoirs in the upper Missouri River basin and extensive channelization and bank stabilization below Sioux City, IA as part of the Bank Stabilization and Navigation Project (BSNP) [1,2,3,4,5]. Missouri River mainstem dams trap 100 - 150 million metric tons of sediment per year (about 50% of the historic sediment load), while major and minor engineering projects and soil-retention measures account for the rest of the trapped sediment [4]
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