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What is a Watershed?
A Story of a Raindrop
Imagine a spring day. A warm wind blows a bank of clouds in from the west, blanketing the region
with a soft gray sky. A raindrop falls. This first drop catches the wind before falling toward a parking
lot in Randallstown, just north of Liberty Road. The drop settles on a slope east of a small ridge for just a
moment. Gravity then pulls it downhill to the northeast and toward a small stream known as the Scotts
Level Branch.
As the raindrop rolls across the open pavement, it encounters a spot of oil deposited by a leaky car.
The oil swirls over the drop, making it shimmer with a spectrum of colors. A passer-by takes note of the
wet pavement and quickens her pace to avoid the coming shower. More rain falls and joins our drop on the
pavement, each picking up bits of oil. The water starts to flow.
Our raindrop joins a million other drops in what is known as the Scotts Level Branch Watershed. All
the water in this watershed – from surface and groundwater sources alike – will eventually flow to the Scotts
Level Branch. From there, the water makes its way into the Gwynns Falls stream under I-695, and eventually
empties into the Chesapeake Bay via the Middle Branch of the Patapsco River. This means that the Scotts
Level Branch, along with a number of other “tributaries” (smaller streams that empty into larger ones), is
part of the Gwynns Falls stream system. The watersheds of each tributary are considered sub-watersheds of
the Gwynns Falls. They combine to make up the larger Gwynns Falls Watershed, which in turn is a part of
the larger Chesapeake Bay Watershed.
Our raindrop flows downhill and into a storm drain near an elementary school. From there it reaches
the swelling Scotts Level Branch, then joins the main stem of the Gwynns Falls. It meets other drops that
have come from Owings Mills, Woodlawn, and Soldiers Delight Natural Area. These drops have
carried to the stream not only oil from the streets, but trash left on roadsides, pesticides and fertilizers
sprayed on lawns, and sediment from construction sites upstream. In the future, the nutrients from lawn
fertilizers may cause increased algae growth and decreased oxygen in the stream system. The pesticides may
be ingested by a fish that is then caught on a line by a father and daughter fishing near Gwynns Falls/Leakin
Park. Certainly, most of the trash and debris will end up near the Baltimore Harbor.
Soon, the rain ends and the rivers settle down. Our raindrop reaches the Middle Branch of the Patapsco
and flows past the Resco Incinerator. In a few days, it will find its way into the Chesapeake Bay itself.
The story of a raindrop reminds us of this: every plastic bag, every trace of pesticide, every raindrop
that falls anywhere within our watershed, and everything that the water carries, ends up in our streams, our
rivers, our Bay, and eventually our own lives.
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