Spatial and isotopic analysis of watershed soil loss and reservoir sediment accumulation rates in Lake Anna, Virginia, USA

Abstract

Soil erosion and associated sedimentation are a threat to the sustainable use of surface water resources through the loss of volume storage capacity and conveyance of pollutants to receiving water bodies. The RUSLE2 empirical model and isotopic sediment core analyses were used to evaluate watershed erosion and reservoir sediment accumulation rates for Lake Anna, in Central Virginia. A sediment flux rate of 66,000 Mg/year was estimated from the upper basin and land use was determined to be the primary factor contributing to soil erosion. Barren lands and agricultural activities were estimated to contribute the most sediment ([20 Mg/ha/year), whereas forested and herbaceous landscapes were less likely to erode (\0.3 Mg/ ha/year). Eleven separate 210 Pb-based estimates of sediment accumulation were used to construct reservoir-scale sedimentation rates. Sedimentation rates in the upper reaches of the reservoir were variable, ranging from 2.3 to 100 Mg/ha/year, with a median rate of 8.4 Mg/ha/year. Historical sedimentation showed an increase in annual accumulation from 1972 to present. Based on these data the reservoir has experienced a 2% loss of volume storage capacity since impoundment in 1972. Results from this study indicate that Lake Anna is not currently experiencing excessive sedimentation and erosion problems. However, the predominance of highly erosive soils (soil erodibility factor [0.30) within the watershed makes this system highly vulnerable to future anthropogenic stressors.

The impact of urban expansion and agricultural legacies on trace metal accumulation in fluvial and lacustrine sediments of the lower Chesapeake Bay basin, USA

“…The samples were compressed in a hydraulic press (3000 psi) to form disks approximately 2.2 cm in diameter so as to standardize the density of the sediment. Counts occurred over approximately 22 h. Sediment 210 Pb based chronology and accumulation rates in lacustrine cores were based on a regression model assuming both 210 Pb input to the sediments and sediment accumulation rates are constant over the time interval being considered (Odhiambo and Ricker, 2011;Matsumoto and Wong, 1977).The constant rate supply (CRS) model was also applied, which accounts for variable sedimentation rates at different depths and dates. This model assumes a constant supply of 210 Pb to the sediment-water interference, which allows for the variable accumulation rates with depth in a core (Appleby and Oldfield, 1978;Nriagu, 1979;Odhiambo and Ricker, 2012).…”

“…The aquatic systems of the southern Chesapeake Bay watershed display disrupted sedimentation, declining water quality, and altered ecologies resulting from anthropogenic alterations (Yesilonis et al, 2008;Dauer and Alden, 1995;Conrad and Chisholm-Brause, 2004;Conrad et al, 2007;Odhiambo and Ricker, 2011). These environmental aquatic degradations will continue to be exacerbated as basin's human population and urban expansion modify fluvial aggradation, degradation and contaminant dispersal processes.…”

Recent Sedimentation Rates of Shallow Lakes in the Middle and Lower Reaches of the Yangtze River: Patterns, Controlling Factors and Implications for Lake Management

“…Furthermore, human activities have been recognized as a key driver of sedimentation processes in the past century due to sewage input, land use changes and hydrological regulation [4,14,20]. Combined with natural environmental changes, human impacts pose a greater threat to the functioning of lake ecosystems by creating unfavorable lake environments such as increased sedimentation, reduced storage capacity, widespread flooding, often accompanied by enhanced nutrient levels and metal pollution [12,16,[21][22][23][24][25][26].…”

Spatial and temporal analysis of lake sedimentation under reforestation

“…A study in the United Kingdom (Lexartza-Artza and Wainwright, 2011) identified areas within a catchment that are most susceptible to erosion from land use changes. Odhiambo and Ricker (2012) found that land use changes primarily in areas cleared for agricultural fields contributed the most sediment to the Lake Anna watershed in Virginia, US.…”