Event Title

The Influence of Watershed Complexity on Downstream Biotic Productivity in Small Mountain Watersheds

Presenter Information

Michelle Kang

Location

Eccles Conference Center

Event Website

http://water.usu.edu/

Start Date

4-2-2009 10:35 AM

End Date

4-2-2009 10:40 AM

Description

Lakes are frequently studied as individual units but the degree of watershed complexity above them may also be an important factor influencing their overall biotic productivity and stability. In this study, phytoplankton abundance (chlorophyll a) and nutrient level of five inflows and lakes in the Sawtooth Mountains (ID) was assessed from May-October, 2008. The abundance and seasonal variation in phytoplankton were examined in relation to the percentage of the upstream watersheds composed of lakes. Mean chlorophyll a concentrations of the final lakes decreased 44% as the upstream lake cover of the watershed increased from < 0.6 % to > 3 %. Nutrient measurements from inflows suggest that this was due to upper lakes in the watershed trapping nutrients before they reached the final lake. The mean total phosphorous concentrations decreased from 5.6 ug/L to 2.6 ug/L as upstream lake area relative to the watershed increased from 0 % to 4 %. Although upper lakes may have decreased downstream productivity, they may also have stabilized it, as the temporal variability in chlorophyll a within lakes with more upstream lake cover was 45% less than in watersheds that had few or no upstream lakes. The results indicate that upstream watershed complexity likely influences downstream productivity and stability.

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Apr 2nd, 10:35 AM Apr 2nd, 10:40 AM

The Influence of Watershed Complexity on Downstream Biotic Productivity in Small Mountain Watersheds

Eccles Conference Center

Lakes are frequently studied as individual units but the degree of watershed complexity above them may also be an important factor influencing their overall biotic productivity and stability. In this study, phytoplankton abundance (chlorophyll a) and nutrient level of five inflows and lakes in the Sawtooth Mountains (ID) was assessed from May-October, 2008. The abundance and seasonal variation in phytoplankton were examined in relation to the percentage of the upstream watersheds composed of lakes. Mean chlorophyll a concentrations of the final lakes decreased 44% as the upstream lake cover of the watershed increased from < 0.6 % to > 3 %. Nutrient measurements from inflows suggest that this was due to upper lakes in the watershed trapping nutrients before they reached the final lake. The mean total phosphorous concentrations decreased from 5.6 ug/L to 2.6 ug/L as upstream lake area relative to the watershed increased from 0 % to 4 %. Although upper lakes may have decreased downstream productivity, they may also have stabilized it, as the temporal variability in chlorophyll a within lakes with more upstream lake cover was 45% less than in watersheds that had few or no upstream lakes. The results indicate that upstream watershed complexity likely influences downstream productivity and stability.

https://digitalcommons.usu.edu/runoff/2009/AllPosters/6