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Groundwater Draft
During the earlier periods,
the net ground water draft for irrigation was taken for computation,
where as, the present methodology recommends that the gross ground water
draft shall be considered for computation.
Domestic draft
The domestic draft was computed based on the rural population
who are mostly dependent on ground water. The population figure as on
1999 was computed and an amount of 100 litres per capita per day was
taken for computation of the domestic draft. This also was computed for
each block separately.
Irrigation draft
The irrigation draft were computed based on the number of structures
cleared by various departmental agencies.
The data were collected from
various organisations and was used for this. The data mainly includes;
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All
structures cleared by NABARD
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Structures constructed
under community irrigation project by state ground water department.
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Structures constructed by
Kerala Samuhya Jalasechana Samithi in Trichur district
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The bore well details in
Palghat district collected by CGWB during the studies
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The bore well details
supplied by the Irrigation Department.
The unit draft was taken as
per the standards recommended by NABARD, which is in close agreement
with the recommended figures in the methodology. However, the
recommended draft for energised wells is taken as 0.0054 MCM while draft
for non-energised wells is taken as 0.0012 MCM. The available block
wise statistics of energised and non-energised wells are taken from
Govt. agencies, reports and it needs proper validation for realistic
estimation. It is assumed that the irrigation draft during monsoon
season is negligible.
Industrial draft
The details of ground water structures constructed by Ground
Water Department and details from the industrial department were
collected for computing the industrial draft. The Industrial Department
has given the district wise figures and this was distributed block
wise. The tube wells constructed by the Ground Water Department in
Alleppey and Quilon districts were not taken since they tap mostly the
deep aquifers. For calculation, unit draft of 0.036 MCM was taken for
bore wells (10000 L for 10 hours pumping per day) and 0.018 MCM was
taken for other structures. This was computed block wise depending on
the data available.
Gross ground water draft
The gross ground water draft was calculated by adding the domestic
draft, industrial draft and the irrigation draft.
Annual Net Ground Water
Available
The annual net ground water available was calculated from the recharge
figures after deducting the unaccounted natural losses. As per the norms
given, it is 10% if the monsoon recharge was computed based on rainfall
infiltration method and 5% if it is based on water level fluctuation
method. This was computed for each block separately.
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