IAN Seminar Series 2017

The goal of the IAN seminar series is to provide concise, thought-provoking ideas relating to Chesapeake Bay science and management. Short presentations (15 minutes maximum length) are immediately followed by a lunchtime discussion of the topics raised by the presenter. The discussion is summarized and is posted along with a pdf version of the seminar slides. The seminars are captured on video and posted under a Creative Commons license so they can be freely shared.

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DateSpeakerSeminarSeries
Thu 27
Oct
2016
http://ian.umces.edu/seminarseries/
Decadal-scale Changes in Sediment and Nutrient Delivery from Conowingo Reservoir to Chesapeake Bay: Statistical Evaluations of Reservoir Trapping using Long-Term Monitoring Data - Qian Zhang (UMCES IAN) - IAN Seminar Series
2016-10-27T12:00:00-04:00 2016-10-27T13:00:00-04:00
Macknis Room, Chesapeake Bay Program Office, 410 Severn Avenue (Suite 109), Annapolis MD
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 75th~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 sub-scour levels of discharge, which has significant implications for the Chesapeake Bay ecosystem.
Qian Zhang
UMCES IAN
qzhang@umces.edu
Decadal-scale Changes in Sediment and Nutrient Delivery from Conowingo Reservoir to Chesapeake Bay: Statistical Evaluations of Reservoir Trapping using Long-Term Monitoring Data

Science for Citizens
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Abstract

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 75th~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 sub-scour levels of discharge, which has significant implications for the Chesapeake Bay ecosystem.



Time and Venue

Seminars start at 12 noon, scheduled for 45 mins (15 mins plus 30 min question/discussion time).

Science for Citizens seminars are held in the Joe Macknis Conference Room (Fish Shack) at the Chesapeake Bay Program Office, 410 Severn Avenue, Annapolis MD 21403, immediately following the monthly meetings of the Science Technical Analysis and Reporting (STAR) team meetings.

Citizens for Science seminars are conducted at the UMCES Annapolis Office, 1 Park Place, Suite 325, Annapolis, MD 21401.



Inquiries

If you have any queries or would like to contribute to next year's seminar series, please contact:

Jane Thomas ()
Bill Dennison ()