With the shifting positions of WAPDA in respect of criterion
for water availability from 4 out of 5 years (80% probability) to
average year (50% probability), it is necessary to understand
precisely the concept and the implication of these criteria. It may be
stated that the storage dams already constructed in Pakistan and the
proposed Kalabagh Dam are designed to store water from the flow
available during a particular year after meeting the current
requirements and the balance water of high floods is spilled over in
to the sea. This water which escapes to sea is not available for use
in subsequent years, in the absence of a carry over dam which can
store the surplus flow of high flood years for subsequent use. Under
the circumstances it must be clearly understood that if the criterion
of mean year availability is adopted, water available will be less
than this figure for 50% of the time. Is it practicable to conceive
a huge project of storage dam with over Rs. 250 billion
investment, knowing that
water may not be available for storage for 50% of the time? How can
such a project be feasible and economically viable?