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ural water supply programmes) to be entirely
benign, it is clear they can have a big impact on
the viability and utility of traditional tank systems
and on patterns of water availability and use
within a tank catchment and command area.
This impact appears to be most marked in low
rainfall years and when increased water harvesting
in the tank catchment area is coupled with
increased groundwater extraction. The changed
pattern of water use and associated changes in
access to water for domestic and productive
purposes results in trade-offs and distinct winners
and losers. Although these trade-offs might be
acceptable and, in some circumstances highly
desirable, they should be considered explicitly in
strategic-level and village-level decision making
processes which, ideally, should be based on
principles of integrated and adaptive water
resource management (Batchelor et al, 2001).
It is clear also that programmes of tank
rehabilitation should consider the multiple tradeoffs
both within the individual tank system
(i.e. catchment area, command area and the tank
itself) and the larger macro-catchment before
decisions are taken on whether rehabilitation of
individual tanks is needed. It is clear also that
programmes of tank rehabilitation must be
careful to differentiate between symptoms and
causes of decline in tank utility and to be sure to
address causes such as those affecting tank
inflows.
regard water harvesting as a totally benign
technology. In contrast in semi-arid areas,
downstream communities are becoming
increasingly aware of the problems caused
by intensive drainage-line treatment in
upstream areas.
4.4 Annual water balances
Figure 33 presents indicative estimates of the
components of the annual water balance for
Dhone and Kalyandurg at the macro-watershed
scale. These estimates have been produced on the
assumption that, on average, storage terms will be
insignificant. This figure shows that evaporation
from rainfed arable areas is the largest component
of the water balance. In both mandals,
evaporation from different surfaces or land uses is
the fate of approximately 95% of the rainfall.
These figures contrast with the statewide water
balance figures of the Andhra Pradesh Water
Conservation Mission (Anon, 2003) which
suggest that the fate of annual rainfall is as
follows: evapotranspiration – 41%, surface runoff
– 40%, percolation to groundwater bodies – 9%
and retained as soil moisture – 10%.
Kalyandurg
23%
4% 1%
3% 1%
13%
The following points provide a summary of the
main findings of analysis relating to the
impacts of water harvesting on patterns of
availability and use:
55%
. In the study mandals, water harvesting and
groundwater-based irrigation have in
recent years had a major impact on patterns
of access and use of water for irrigation.
This has led to major improvements in
the livelihoods of many households once
they have paid off the debt incurred in the
process of becoming irrigator farmers
(e.g. borewell construction).
. In many areas, intensive water harvesting
coupled with over-exploitation of
groundwater is impacting on downstream
water availability and, in particular the
utility of tank systems. Hence, significant
negative trade-offs are often associated
with the changed pattern of use.
Dhone
1% 3% 1%
17%
17%
Runoff
Urban water use
ET (irriga ted area s)
ET (rainfed arable areas)
ET (non-arable a reas a nd e phe me ral wate r bodies)
ET (forest areas)
GW recession
9%
52%
. With a few notable exceptions, government
and NGO watershed development or rural
water supply source protection programmes,
Figure 33. Annual macro-watershed or basin
scale water balances
56