Accepted Papers - 3.pdf - UNESCO

shapes and sizes are built underground or over
ground to collect rainwater for drinking purposes.
These are constructed in a variety of places like
court yards, in front of houses and temples, in open
agricultural fields, barren lands etc. These are built
both for individual households as well as for village
communities using locally available materials.
While some structures are built in stone masonry
with stone slab coverings, others are built with only
rudimentary plastering of bare soil surfaces of the
tank with cement or lime and covering with
Zizyphus Numularia thorns. Some Kuccha
structures have a convex covering of local wood
with mud plaster. Inlet holes are provided in the
convex covering at the ground level to facilitate
entry of rainwater into the tank. In case of Pacca
structures the wall of the tank is kept projecting
above the ground to provide inlet hole below :
Roof catchments, for instance, are not suitable
in small adivasi villages, as their huts have
roofs, which are not suitable for collecting water.
For these villages, the most appropriate solution is
to construct paved ground catchments connected
with underground storage tanks. Other rainwater
harvesting technologies such as rock catchments and
paved catchments could be appropriate in water
scarcity villages. The catchments are connected with
a storage tank as illustrated in the picture.
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In constructing ground catchments, it will
be necessary to take into consideration a number of
factors, such as the rainfall regime, the number of
days in a year that rain harvested water is required,
number of users, appropriate catchments and
reservoir design, operation and maintenance.
Ground catchments are costly to install and require
a careful maintenance. They provide fairly good
quality water and satisfy the water needs of the
entire community. To construct a ground catchments
require, relatively large plots of land that may not
always be available in hilltop villages. The size of
the area to be cleared depends on the factors
mentioned for the roof catchments. The cleared area
should be graded to reduce losses due to evaporation
and infiltration, to avoid soil erosion and to prevent
silt content in the water. The type of paving and its
cost depends on the type of material used (concrete,
tiles, plastered flat stones, etc.) and its local
availability. In USA chemicals are used for this
purpose, such paraffin wax shredded and spread on
the ground surface. Wax is melted by sunlight and
seals soil pores, making a water repellent surface.
Reinforced asphalt membranes are also used where
this material is cheap. In Arizona, USA, the ground
catchment is made impervious by lying polyethylene
sheets covered with gravel for protection against
damage and sunlight. Catchments are generally
fenced.
Ponds / Tanks
This is by far the most commonly used
method to collect and store rain water in dug ponds
or tanks. Most ponds have their own catchments,
which provide the requisite amount of water during
the rainy season. Where the catchments are too small
to provide enough water, water from nearby streams
is diverted through open channels to fill the ponds.
Spring Water Harvesting System
Spring water is a highly desirable source
of community water supply. Since the water emerges
at the ground surface through cracks and loose joints
in rocks under internal pressure of the ground water
system, no pumping is required. More over the water
is fresh and free from pollution obviating the need
for artificial purification. However, such sources are
available mostly in hilly terrain, foothill areas or
intermontane valleys.