Page 16 - Water Every Drop Counts

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Supply of Water

Approaching Limits

90% of earth’s total precipitation falls directly into oceans. As if this was not
enough, precipitation over land is very unevenly distributed over space and
time. But requirements of water do not vary much over seasons. This makes
it critical to first impound and store water and then, to regulate its distribution
for meeting human needs.

Until the 1980s, the prevailing approach to water management was to focus on taming of the natural
hydrological cycle through construction of physical infrastructure (dams and barrages), reservoirs for water
storage and new aqueducts/pipelines for inter basin transfers.
With large scale supply side opportunities having been largely exhausted, and given the resistance
encountered by large scale water storage/diversion projects on environmental grounds, planners now
recognize the need for a shift from supply side management to optimisation of demand.

HYDROLOGICAL CYCLE : THE ETERNAL WATER WHEEL

Water on the earth
is continuously in
Rain clouds
circulation. Solar heat
and action of the winds
causes evaporation.
Once in the atmosphere
and subject to right
conditions water vapor
condenses to form
clouds. In turn, and
again if the conditions
are right, the water
contained in clouds falls
back on earth as rain,
hail or snow.
Of the precipitation that
falls on earth, some

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