期刊
ENVIRONMENTAL SCIENCE & TECHNOLOGY
卷 50, 期 4, 页码 1877-1886出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.est.5b04073
关键词
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资金
- Maryland Sea Grant [NA10OAR4170072, NA14OAR1470090]
- Maryland Water Resources Research Center [2015MD329B]
- National Science Foundation [CBET-1360415]
- U.S. Geological Survey Chesapeake Bay Ecosystem Program
- Directorate For Engineering
- Div Of Chem, Bioeng, Env, & Transp Sys [1360415, 1360345] Funding Source: National Science Foundation
- Directorate For Engineering
- Div Of Chem, Bioeng, Env, & Transp Sys [1360424, 1360395] Funding Source: National Science Foundation
Reduction of suspended sediment (SS), total phosphorus (TP), and total nitrogen is an important focus for Chesapeake Bay watershed management. The Susquehanna River, the bay's largest tributary, has drawn attention because SS loads from behind Conowingo Dam (near the river's mouth) have been rising dramatically. To better understand these changes, we evaluated histories of concentration and loading (1986-2013) using data from sites above and below Conowingo Reservoir. First, observed concentration-discharge relationships show that SS and TP concentrations at the reservoir inlet have declined under most discharges in recent decades, but without corresponding declines at the outlet, implying recently diminished reservoir trapping. Second, best estimates of mass balance suggest decreasing net deposition of SS and TP in recent decades over a wide range of discharges, with cumulative mass generally dominated by the 75 similar to 99.5th percentile of daily Conowingo discharges. Finally, stationary models that better accommodate effects of riverflow variability also support the conclusion of diminished trapping of SS and TP under a range of discharges that includes those well below the literature-reported scour threshold. Overall, these findings suggest that decreased net deposition of SS and TP has occurred at subscour levels of discharge, which has significant implications for the Chesapeake Bay ecosystem.
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