TYPHOID FEVER IN WASHINGTON AND ITS RELATION TO THE 
POTOMAC WATER SUPPLY. 
WASHINGTON’S WATER SUPPLY. 
The city of Washington now receives its water supply from the 
Potomac River. The intake is at Great Falls, about 14 miles above 
the city. At this point a masonry dam extends across the river from 
the Maryland to the Virginia side. 
From 1859 to 1888 Washington received its water supply from Lit- 
tle Falls Branch, a tributary of the Potomac. A dam was thrown 
across this little stream about 4^ miles from Washington, forming 
Dalecarlia reservoir. At the same time (1859) the Georgetown dis- 
tributing reservoir was put into service. 
Dalecarlia reservoir is an unlined storage basin with a capacity of 
about 150,000,000 gallons, and was originally constructed to collect 
the surface water from the drainage area of Little Falls Branch. The 
constant turbidity and impurities introduced from the inhabited 
watershed draining into the Dalecarlia basin, especial!}^ from Tenley- 
town, led to a discontinuance of this source of supply in 1888, when 
this reservoir was put out of service and not again used until 1896. 
In the meantime the land immediately draining into Dalecarlia 
reservoir was purchased and controlled, and the waters of Little Falls 
Branch diverted through a tunnel, and the conduit from the Potomac 
at Great Falls was connected with the Dalecarlia reservoir, so that 
in 1896, when Dalecarlia reservoir was again put into service, it 
received water from the Potomac and not from Little Falls Branch. 
The Georgetown reservoir and storage basin has a capacity of about 
150,000,000 gallons. It was put into service in 1859, and was used 
as a distributing reservoir from that date to November, 1905, since 
when it has served as a settling basin. 
The conduit from Great Falls to Georgetown reservoir was com- 
pleted in 1863, and has furnished the city continuously with Potomac 
River water from that date to the present time. In order to avoid 
the impurities from the Little Falls Branch this conduit was built 
around Dalecarlia reservoir. This section of the conduit now acts as 
a b}^-pass, so that whenever the water in the river is clearer than the 
water in the Dalecarlia reservoir — which not infrequently happens — 
the by-pass is used and the reservoir closed. 
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