Abstract
Water quality data collected between 2007 and 2014 within the Allen Creek Watershed were used to: (1) determine the factors controlling the temporal variations in turbidity and suspended sediment concentration (SSC) within a representative, high-gradient headwater basin in the Southern Appalachians; and (2) assess the recovery of water quality following extensive logging operations during the early to mid-1900s. Regression analysis suggests that suspended sediment is primarily derived from upland areas and variations in concentration reflect rainfall intensity and total event precipitation. Overall, SSC and turbidity were low in stream waters in comparison to both reference values for stable streams and more developed basins in the region. Some floods were characterized by high SSC values, but limited turbidity and vice versa. Differences in measured SSC and turbidity between storms reflect different controls on the two parameters, and the apparent influence of natural organic matter on turbidity during rainfall events that are incapable of transporting sediment to the channel via overland flow. Low SSC and turbidity values are presumably related to the reforestation of hillslopes and riparian buffers following the cessation of logging operations. They also are due to a historical reduction in the sedimentological connectivity of hillslopes and tributaries with the axial channel that occurred during logging operations.
Highlights
Excessive sediment in rivers is often considered to be one of the most significant threats to aquatic ecosystems [1,2,3,4]
The analysis provides insights into the potential degree to which headwater basins in the southern Appalachians and other temperate mountainous regions may recover over the decadal time scale to extensive anthropogenic disturbance, data that are important to both river restoration science and the establishment of total maximum daily load targets for fine-grained sediment
Several years of data were collected at each site, it was inadequate to directly estimate flood recurrence intervals for the largest events contained within the data set
Summary
Excessive sediment in rivers is often considered to be one of the most significant threats to aquatic ecosystems [1,2,3,4]. The National Water Quality Inventory, a program in the U.S developed to assess the current condition of the nation’s water resources, indicates that sediment is second only to pathogens The potential impacts of sediment, many of which are related to anthropogenic activities, include rapid episodes of reservoir sedimentation, reduced reservoir storage capacity, degraded water distribution systems, increased turbidity resulting in a reduction of light penetration, degraded aquatic habitats, the burial and/or smothering of benthic organisms, and a decline in the aesthetic quality of the riverine environment. Significant effort has been devoted in recent years to:
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