The Effect of Submerged Aquatic Vegetation Expansion on a Declining Turbidity Trend in the Sacramento-San Joaquin River Delta |
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| Authors: | Erin Lee Hestir David H Schoellhamer Jonathan Greenberg Tara Morgan-King Susan L Ustin |
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| Institution: | 1.Marine, Earth, and Atmospheric Sciences,North Carolina State University,Raleigh,USA;2.Center for Spatial Technologies and Remote Sensing,University of California,Davis,USA;3.Department of Civil and Environmental Engineering,University of California,Davis,USA;4.California Water Science Center,United States Geological Survey,Sacramento,USA;5.Geography and GI Science,University of Illinois at Urbana-Champaign,Champaign,USA |
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| Abstract: | Submerged aquatic vegetation (SAV) has well-documented effects on water clarity. SAV beds can slow water movement and reduce bed shear stress, promoting sedimentation and reducing suspension. However, estuaries have multiple controls on turbidity that make it difficult to determine the effect of SAV on water clarity. In this study, we investigated the effect of primarily invasive SAV expansion on a concomitant decline in turbidity in the Sacramento-San Joaquin River Delta. The objective of this study was to separate the effects of decreasing sediment supply from the watershed from increasing SAV cover to determine the effect of SAV on the declining turbidity trend. SAV cover was determined by airborne hyperspectral remote sensing and turbidity data from long-term monitoring records. The turbidity trends were corrected for the declining sediment supply using suspended-sediment concentration data from a station immediately upstream of the Delta. We found a significant negative trend in turbidity from 1975 to 2008, and when we removed the sediment supply signal from the trend it was still significant and negative, indicating that a factor other than sediment supply was responsible for part of the turbidity decline. Turbidity monitoring stations with high rates of SAV expansion had steeper and more significant turbidity trends than those with low SAV cover. Our findings suggest that SAV is an important (but not sole) factor in the turbidity decline, and we estimate that 21–70 % of the total declining turbidity trend is due to SAV expansion. |
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