Geoscience Reference
In-Depth Information
in Brazil was proposed to expand the upstream
navigation of large vessels (Alho 2005). This
project would have had a signii cant environ-
mental impact on the Pantanal wetlands. After
much discussion and opposition from environ-
mental and other groups, the project has been
set aside for now due to the many ramii cations
on the l ow regime of the river and its adjoining
wetlands (Alho 2005).
Canals have been constructed since ancient
times for irrigation and navigation. Canals and
navigable rivers are subject to the same laws of
nature that govern uncontrolled streams. Water
l ow, sediment erosion, l ooding, transport of
pollutants, and related issues are of great impor-
tance for long-term maintenance and operation
of canals. Canals also have special circum-
stances, as they often require dedicated water
sources, and they may connect drainage basins
of dissimilar type. Migration of exotic aquatic
species, such as the zebra mussel (see chapter
7.4) has occurred in some canals.
The old Erie Canal was the i rst major water-
works project in the United States, built in 1817-
1825. The canal connected Lake Erie to the
New York harbor tidewater in a multi-level route
that followed the local terrain and was fed
by local water sources. Water l ow in the canal
was required for several purposes (Langbein
1976):
• Filling the canal at the beginning of each
spring season.
• Water for lockage to replace water lost from
higher to lower levels.
• Water lost by seepage through the berm and
towpath banks.
• Water diverted for industrial power usage.
The canal was initially a great economic success,
which led to a boom in canal building. The Erie
Canal was enlarged twice in 1836-1862 and
1905-1917. It is now known as the New York
State Barge Canal, and is used today mainly for
recreation (Fig. 11-13). In general, canals in the
Figure 11-13.
Canals in western New York, United States and southern Ontario, Canada (see Color Plate 11-13).
The Welland Canal is nowadays the primary shipping connection between lakes Ontario and Erie. The New York
State Barge Canal (NYSBC) is utilized mainly for recreational purposes. Landsat false-color composite; TM bands 2,
3 and 4 color coded as blue, green and red. Active vegetation appears red and pink. Acquired June 1983; adapted
from NASA Goddard Space Flight Center.
