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posted by janrinok on Monday November 18 2019, @07:17PM   Printer-friendly

Arthur T Knackerbracket has found the following story:

University of Maryland Center for Environmental Science researchers have completed a study on the impact of Conowingo Dam on water quality in Chesapeake Bay. Scientists synthesized field observations, model results, and long-term monitoring data to better understand the potential impacts of nutrient pollution associated with sediment transported from behind the Dam to the Bay.

"This synthesis is important for bringing the best science to Bay management decisions by considering the entire Susquehanna-Conowingo-upper Bay system and integrating insights from several related studies," said Peter Goodwin, president of the University of Maryland Center for Environmental Science. "Since most rivers around the world are dammed, understanding potential impacts to adjacent estuaries is highly relevant to international scientific and management communities."

Dams initially starve downstream ecosystems of both sediments and particulate nutrients by trapping them in upstream reservoirs. Eventually, however, these reservoirs fill, increasing the delivery of sediment and nutrients to downstream ecosystems, especially during storm events when stored sediments can be scoured. Since its construction in 1928, Conowingo Dam has trapped most of the Susquehanna River watershed sediment and associated particulate nitrogen and phosphorus before they enter Chesapeake Bay. However, its storage capacity has significantly decreased, raising questions of potential impacts to Bay ecosystems.

Scientists found that most sediment and particulate nutrient impacts to the Bay occur during high-flow events, such as during major storms, which occur less than 10% of the time. Loads delivered to the upper Chesapeake Bay during low flows have decreased since the late 1970s, while loads during large storm events have increased. Most of these materials are retained within the upper Bay but some can be transported to the mid-Bay during major storm events, where their nutrients could become bioavailable.

Sediment and particulate nutrient loads have decreased since the late 1970s for normal river flows and increased for storm flows. During non-event flows, most sediment delivered past Conowingo comes from the Susquehanna watershed. Sediment and attached nutrient loads have declined since 1978 (first complete year of monitoring data) for non-event river flows. This decrease reflects efforts to reduce watershed loads through BMP installation.

[...] While large events can have significant short-term impacts, the Bay is resilient over the long run due to ongoing restoration and time gaps between events. Major storm events can deliver enormous amounts of sediment to the Bay, but they occur infrequently (less than 10% of the days since 1978). Sediment delivery to the mid-Bay region, where waters are saltier and more conducive to nutrient releases from sediment, is relatively small in magnitude, minimizing potential impacts to Bay water quality.


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  • (Score: 0) by Anonymous Coward on Monday November 18 2019, @09:36PM

    by Anonymous Coward on Monday November 18 2019, @09:36PM (#921689)

    The researchers found a bunch of empty soda bottles in the sediment, tried to return them for deposit to fund further studies, and got shot by a cop outside the grocery store.