RAISING the Wyangala Dam wall by 10 metres will add 650 gigalitres of storage capacity to the reservoir but historical data suggests that capacity will rarely be used.
The dam has filled only four times since 2000 and according to government modelling the raised wall would yield just 21GL annually.
Construction of the dam began in 1928.
It was completed in 1935 and then extended in 1971, tripling its capacity to about 1200 gigalitres.
For the proposed extension there is no concept design, business case or feasibility study. The expansion is a 650GL capacity, but will yield only 21.02GL on an annual long-term average. That is, it will fill only about once every 25 years.
That the extra room in the dam will rarely be used angers Upper Lachlan…