9th International Rainwater Catchment Systems Conference
"Rainwater Catchment: An Answer to the Water Scarcity of the Next Millennium."
Petrolina, Brazil - July 1999

Section 4: Technology of Rainwater Catchment Systems

Paper 4.21

Rock Tanks, Dugouts and Riverbed Dugouts: Three Traditional Systems of Rainwater Catchment in the Brazilian Northeast

Haroldo Schistek
IRPAA (Instituto Regional da Pequena Agropecuária Apropriada)
C.P.21, 48900-000 Juazeiro-BA, Brasil
E-mail: irpaa@ax.apc.org

Resumo

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 rainwater.

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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