International Rainwater Catchment Systems Conference
Catchment: An Answer to the Water Scarcity of the Next Millennium."
Petrolina, Brazil - July 1999
Section 4: Technology of Rainwater Catchment Systems
Rock Tanks, Dugouts and Riverbed Dugouts: Three Traditional
Systems of Rainwater Catchment in the Brazilian Northeast
IRPAA (Instituto Regional da Pequena Agropecuária Apropriada)
C.P.21, 48900-000 Juazeiro-BA, Brasil
In the Brazilian Northeast, a large area of approximately
900,000 km2 receives a classification as being semiarid. In this
region however, one does not find traditional water catchment systems typical
of semi-arid regions, such as wells, cisterns, etc. This could be due to the
level of technological development of the native population, prior to the
arrival of the Portuguese colonizers, but also to the simple fact of lack of
need. The semiarid Brazilian northeast has many humid areas, and neighboring
areas have regular rainfalls. Large parts of the dry interior region have a
short history of settlement by people of European origin, too short for the
development of empirical spontaneous technologies.
A large part of the Northeast semiarid region has a crystalline
sub-soil, highly adequate for natural water reservoirs of the "caldeirão" type,
for the escavation of dugouts and for the construction of riverbed dugouts.
The caldeirão (rock water tanks): are natural holes in
granite rock that, when escavated, represent excellent reservoirs for
The caxio (dugout): weathering transforms the granite rock
in such a manner that it may be dug manually, with relative facility, but that
preserves a total impermeability.
The original measurements are 4.40 m. The construction of a
dug-out is a task that takes various years and, has two separate parts, one may
use first the water of the shallow area and continue to deepen it during the
annual dry season.
Riverbed dugout: is constructed in the bed of one of the
many streams and rivers. To avoid the riverbed sand from caving into the area,
today it is common to construct, on a firm base, a brick wall, or concrete
rings, to a level a little lower than the river or stream bed.
Access to water, a basic right of being a citizen.
The construction of independent water sources, under the
control of the rural population, has demonstrated its effectiveness in the
increase in the consciousness and civic activity, creating independence from
the traditional rural powers that be, and has resulted in an increase in
production in the rural area and a reduction in rural migration.
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