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Suzanne Walther

University of San diego | Assistant Professor

Subject Areas: Geomorphology

 Recent Activity

ABSTRACT:

This study focused on the geomorphological, ecological, and sedimentological impacts of the Jordanelle Dam Provo River, Utah. This particular study site provides a unique opportunity because the Jordanelle dam was put in place in 1992 and a large scale restoration project was completed in 2008, allowing for high resolution imagery and observations prior to dam placement and restoration. To monitor these effects, we established cross section study sites along the Provo River, with 5 above the dam and 5 below the dam. At each cross section, we measured baseline channel morphology characteristics via surveying and sediment size distribution via sediment collection and lab grain size analysis processing. We also inventoried vegetation characteristics along the river to monitor differences upstream and downstream of the dam. This data, combined with analysis of historical imagery and current high resolution imagery, enables us to identify geomorphic changes over time and evaluate the impacts of those changes on the post-engineered river system as it applies to current and future watershed management. Post-impoundment, we find that channels downstream of the dam have become more stable, allowing for vegetation colonization, as exhibited in land cover changes from bare soil to grass. This results in greater species richness owing to colonization of a more stable riparian zone, ultimately changing habitat conditions. Grain size increases below the dam, which is a known dam impact. This data is particularly important as Utah faces climate change and population growth, both of which stress water availability, and has the potential to inform and improve watershed management practices to result in both a healthy fluvial system and a sustainable water resource.

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ABSTRACT:

Sediment cores were collected (GPS coordinates taken) at three transects, one at the north end of Utah Lake and two within a kilometer of the Lake on the Jordan River. The cores were sub-sampled at 5 cm resolution for sediment grain size, C and N stable isotope and C/N ratio, and lead-210 analyses. All sampling was standardized. Sampling data is one time data (summer field collection). Carbon and nitrogen stable isotope compositions show a 4 per mil and a 2 per mil positive shift, respectively, as a depth of 55cm. C/N ratios show large variations (9-18) at depths shallower that 55cm, but are more stable (11-14) with greater depth. These results indicate a shift in organic matter sources to Utah Lake at a depth of 55cm, which likely represents the boundary between pre- and post-pioneer settlement in the valley around 1847. At depths greater than 55cm, the major contribution of soil organic matter was likely terrestrial C3 and autochthonous native C4 plants, whereas at depths shallower than 55cm terrestrial vegetation, manure/sewage-derived matter, and lake algae were the major lake organic matter sources. From this information, we approximate the post-settlement sedimentation rate in the lake to be 3.3mm/yr. Students and leads were responsible for data collection, data analysis, and data interpretation of the project.

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ABSTRACT:

Sediment cores were collected (GPS coordinates taken) at three transects, one at the north end of Utah Lake and two within a kilometer of the Lake on the Jordan River. The cores were sub-sampled at 5 cm resolution for sediment grain size, C and N stable isotope and C/N ratio, and lead-210 analyses. All sampling was standardized. Sampling data is one time data (summer field collection). Carbon and nitrogen stable isotope compositions show a 4 per mil and a 2 per mil positive shift, respectively, as a depth of 55cm. C/N ratios show large variations (9-18) at depths shallower that 55cm, but are more stable (11-14) with greater depth. These results indicate a shift in organic matter sources to Utah Lake at a depth of 55cm, which likely represents the boundary between pre- and post-pioneer settlement in the valley around 1847. At depths greater than 55cm, the major contribution of soil organic matter was likely terrestrial C3 and autochthonous native C4 plants, whereas at depths shallower than 55cm terrestrial vegetation, manure/sewage-derived matter, and lake algae were the major lake organic matter sources. From this information, we approximate the post-settlement sedimentation rate in the lake to be 3.3mm/yr. Students and leads were responsible for data collection, data analysis, and data interpretation of the project.

Show More
Generic Generic

ABSTRACT:

This study focused on the geomorphological, ecological, and sedimentological impacts of the Jordanelle Dam Provo River, Utah. This particular study site provides a unique opportunity because the Jordanelle dam was put in place in 1992 and a large scale restoration project was completed in 2008, allowing for high resolution imagery and observations prior to dam placement and restoration. To monitor these effects, we established cross section study sites along the Provo River, with 5 above the dam and 5 below the dam. At each cross section, we measured baseline channel morphology characteristics via surveying and sediment size distribution via sediment collection and lab grain size analysis processing. We also inventoried vegetation characteristics along the river to monitor differences upstream and downstream of the dam. This data, combined with analysis of historical imagery and current high resolution imagery, enables us to identify geomorphic changes over time and evaluate the impacts of those changes on the post-engineered river system as it applies to current and future watershed management. Post-impoundment, we find that channels downstream of the dam have become more stable, allowing for vegetation colonization, as exhibited in land cover changes from bare soil to grass. This results in greater species richness owing to colonization of a more stable riparian zone, ultimately changing habitat conditions. Grain size increases below the dam, which is a known dam impact. This data is particularly important as Utah faces climate change and population growth, both of which stress water availability, and has the potential to inform and improve watershed management practices to result in both a healthy fluvial system and a sustainable water resource.

Show More