Friday, December 1, 2023

It’s been a rainy July


Bad news for the environment: historic rainfall totals, not just in Baltimore but all along the East Coast, have caused flooding and a significant increase in the level of pollution flowing into the Chesapeake Bay, the Baltimore Sun reports.

(NASA/JAXA, Hal Pierce)

In the graphical analysis above, meteorologists at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, show rainfall totals during the period July 19–26. The highest totals were over the Outer Banks, in central Maryland, and in central Pennsylvania. Shown in purple are areas where more than 180 mm (about 7 inches) of rain fell in those seven days.

BWI Thurgood Marshall Airport reported 4.79 inches of rain on just July 21 and 4.07 inches on July 24. A stalled weather pattern led to persistent showers and thunderstorms moving up the eastern seaboard during the week of July 22, resulting in significant rainfall amounts and numerous flood warnings.

According to an article from the Bay Journal, republished on Maryland, oxygen levels and submerged aquatic vegetation in the Chesapeake Bay were recovering nicely. But the flooding and increased runoff of pollution these latest rains have brought—July was the second-wettest month ever for many areas inside the Chesapeake Bay watershed—could be a setback that takes months to fully measure or analyze.

A recent report from the US Army Corps of Engineers and the Maryland Department of the Environment examined the impact of excessive flooding from the Susquehanna River on the Chesapeake Bay during storms like the latest deluge.

Storms, the report concludes, have “adverse impacts to water quality, habitat, and living resources.” Potential impacts of freshwater surging into the Bay include:

  • Large freshwater flows can lead to long periods of low-salinity water that could kill oysters, particularly in the Upper Bay.
  • Sediment associated with high flows can bury oyster reefs and bottom-dwelling organisms.
  • Sediment and nutrient-fueled algae blooms block sunlight from reaching underwater grasses, which could devastate grass beds, whose acreages hit record highs last year.
  • Nutrients accompanying the flows could fuel expanded algae blooms during the second half of the summer.
  • Oxygen-starved “dead zones” in deep areas of the Bay could worsen as that algae die, sink to the bottom, and decompose in a process that depletes oxygen.
  • In some places, high flows could flush juvenile fish out of optimal nursery habitats.
Paul Katula
Paul Katula is the executive editor of the Voxitatis Research Foundation, which publishes this blog. For more information, see the About page.

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