Page 28 - aruba-today-20190708

A28 SCIENCE
Monday 8 July 2019

Experts warn of ‘dead zone’ in Chesapeake Bay from pollution

By DAVID McFADDEN launched in 1983 that put tial threat, asserting the noting that most of the change could result in wet-
Associated Press an end to unbridled pol- massive deposit of reservoir pollutants flowing into the ter conditions in the region
CONOWINGO, Md. (AP) lution. But the 200-mile muck would devastate the Chesapeake come from make it all the more im-
— When the Conowingo (325-kilometer) long bay is bay if ever released down- upstream, particularly in portant that the upstream
Dam opened to fanfare sources of river pollution in
nearly a century ago, the the Susquehanna be ad-
massive wall of concrete dressed,” Exelon said in a
and steel began its job of statement.
harnessing water power in Pennsylvania routinely
northern Maryland. It also pushes back against the
quietly provided a side criticism, noting that it has
benefit: trapping sediment a whopping 33,000 farms
and silt before it could flow and more than 350 munici-
miles downstream and pol- palities in the watershed.
lute the Chesapeake Bay, The state says it’s commit-
the nation’s largest estuary. ted to meeting pollutant
The old hydroelectric dam reduction targets.
spanning the lower Susque- “The momentum in Penn-
hanna River is still produc- sylvania has never been
ing power, but its days of stronger,” said Deborah
effectively trapping sedi- Klenotic, a spokeswoman
ment in a 14-mile (22.5-ki- for Pennsylvania’s Depart-
lometer) long reservoir ment of Environmental Pro-
behind its walls are over. tection.
Behind the 94-foot (29-me- But the warning signs are
ter) high barrier lies a mas- clear. Environmental scien-
sive inventory of coal-black tists are predicting a 2-mile
muck — some 200 million (3-kilometer) swath of low-
tons (181 million metric Water flows through Conowingo Dam, a hydroelectric dam spanning the lower Susquehanna to-no oxygen in the bay this
tons) of pollutants picked River near Conowingo, Md., on Thursday, May 16, 2019. summer, making it one of
up over decades from Associated Press the biggest “dead zones”
farmlands, industrial zones in nearly 20 years.
and towns. increasingly being ravaged stream in a major storm. Pennsylvania. Most of the This year’s particularly
How big a threat this sedi- by runoff-triggering down- They note that sediment nitrogen pollutants reach- damaging dead zone is
ment stockpile poses to pours, including record-set- freely flows over the dam ing the bay, for instance, believed to be caused
the Chesapeake Bay or ting rainfall in 2018 and this during downpours, turning travel there as dissolved ni- by nitrogen-laden runoff
whether anything can year’s soggy spring. the upper bay’s waters a trate and are not affected into rivers and tributaries,
even be done about it de- Intense cycles of down- murky brown. at all by the Conowingo’s mostly from the Susque-
pends on who one talks to. pours are washing pollut- “The situation behind sediment storage. They hanna, which supplies the
With Maryland pushing to ants into the Chesapeake the dam is a ticking time say mitigating the impacts most freshwater to the bay
curb pollution in dam dis- from municipal sewer bomb,” said Genevieve from the huge infill behind while also being its biggest
charges, the issue has be- overflows, subdivisions and Croker, spokeswoman for the Maryland dam is part source of sediment and nu-
come a political football farms where manure often the Clean Chesapeake of the puzzle but hardly the trient loads.
as Conowingo’s operator isn’t effectively handled Coalition, a grouping of ru- keystone piece in the resto- In recent days, the Environ-
seeks to renew its federal li- and nitrogen and phos- ral Maryland counties that ration strategy. mental Protection Agency
cense to operate the dam phorous-rich fertilizers are have Republican Gov. Lar- “The most effective ap- released its evaluations of
for 46 more years after its used. Experts say climate ry Hogan’s ear. proach has always been to bay states’ roadmaps to
old license expired. change is accelerating the Qian Zhang, an assistant re- better manage upstream reduce pollution under the
And as negotiations drag environmental decline, po- search scientist at the Uni- sources,” said William Ball, Chesapeake Clean Wa-
on, the lack of agreement tentially leading to more versity of Maryland Center a scientist who directs the ter Blueprint by 2025. The
about curbing runoff pol- damaging algae blooms for Environmental Science, Chesapeake Research Chesapeake Bay Founda-
lutants following the wet- and dead zones in the confirms that the sediment Consortium. tion, an influential watch-
test year on record imperils Chesapeake and coastal does flow freely. Chicago-based Exelon dog group, says that while
hard-won gains in restoring waters. “The reservoir is no lon- Corp., the dam’s operator, Maryland and Virginia’s
the Chesapeake Bay. Maryland politicians and ger capable of trapping stresses that the Conowin- draft plans are on track,
The iconic estuary famed watermen who make their sediment and sediment- go itself is not a source of Pennsylvania’s fell “dras-
for its blue crabs and oys- living off the bay’s fragile associated nutrients. It pollution and agrees the tically short.” It said the
ters has been gradually bounty portray the sedi- will release sediment dur- problem lies upstream. It EPA’s assessment failed to
rebounding under a fed- ment stored behind the ing storm events, creating suggests that more sedi- press for more pollution re-
eral cleanup program Conowingo as an existen- room for sediment to de- ment could wash through ductions or spell out if there
posit in subsequent days. the dam in coming years, would be consequences
However, from a long-term since sustained downpours for failure.
mass-balance perspective, lead to high river flows and Fearing a cascade of eco-
the reservoir is essentially at require more crest gate logical decline, foundation
a stage where sediments openings. president Will Baker argues
entering the reservoir equal In 2018, there were 157 days the stakes couldn’t be
sediments leaving,” Zhang when at least one crest higher for the decades-old
said. gate was open, compared environmental effort.
But he and numerous oth- to 25 days in 2017 and 17 “If EPA doesn’t fully exer-
er bay-area scientists say days in 2016, according to cise its oversight responsibil-
nutrient pollution, not sedi- company data. ity, efforts to save the Bay
ment, is the major threat, “The possibility that climate will be lost,” Baker warns.q