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Remote Sensing and GIS tools and techniques were employed to assess
the tanks in the Adakkal region to suggest a plan for combating
drought.
The study assessed individual tanks that are
connected to a group, their degradation status, and feasibility
of restoration and benefit of restoration for 62 tanks in parts
of Addakkal region. Status of degradation was assessed in terms
of surface area, silt thickness, encroachments on the reservoir
bed and blockage / impediments along the inward channels.
Thematic maps (survey of India) prepared during 1966, 1987 &
2000 and Indian Remote Sensing satellite data of 1992 and 2003
were used for the this purpose (in addition site verification
was carried out in March 2005). Status of outward channels and
the probable areas for rainfall fed agriculture was estimated in
calculating the restoration benefits. Annual (40 years), monthly
(10years) and daily (5 years) rainfall records were used in
understanding the rainfall intensity and time series pattern.
Further, run-off from the tank catchment for a range of rainfall
scenarios was calculated in meeting the human, animal and
crop-irrigational requirements of villages that are located in
the vicinity. Deficiency of water availability from the tanks
towards the winter and summer crops and ground water extraction
requirements were estimated.
This information was collated in the
preparation of tank improvement scheme as a macro level drought
management program (asset generation). This map indicates the
Degradation status – low (<10%), Moderate (10-30%), High
(30-50%) and Very High (>50%); restoration benefit that was
calculated based on the quantity of silt to be removed from the
lake bed, length of in-ward and outward channel to be restored
etc. and grouped into 3 categories. This information could form
the basis for micro level planning in combating drought. Based
on this model, a range of vulnerability scenarios for different
rainfall regimes have been developed as color-coded maps (see an
example in Figure above). The usefulness of such maps has been
discussed with the communities to assess their response to the
interpretation of experts. Initial responses have been positive,
and the testing process continues. In the mean time, a group of
researchers of the Indian National Remote Sensing Agency (NRSA),
an institute having mandate to apply space technology and remote
sensing information for natural resource management, has come
forward to join such a study.
Click the year for
vulnerability maps (2007)
(2008)
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