The Federal Government is now claiming (Penny Wong ABC AM 03/02/10) up to 20,000 megalitres of water returned to the Darling River as a consequence of the Government's purchase of Bourke's iconic Toorale Station. A few weeks ago they claimed 11,000 megalitres, so presumably this new figure is additional?
The irrigation water storage on Toorale (Ross' Billabong) is estimated to hold approximately 10,000 megalitres and this is the only irrigation storage on the Station and apart from any water that may have gone direct on to irrigation fields, this is the maximum amount that can be claimed as being "returned to the Darling" from the current event. Water for this storage can be pumped from the Darling or diverted from the Warrego.
The Warrego River, which is mostly not flowing and is only a shallow gutter, runs through the property from north to south. It has five dams on it, all of which have two four foot diameter pipes (and gates) in the bed of the river. These allow smaller flows to pass through to the Darling. They are/were closed towards the end of a flow so as to retain water for livestock and domestic purposes,both for Toorale and neighbours, not for irrigation.
When there is too much Warrego water for the pipes to carry the river spills out to the west and runs down a natural flood plain, flooding over 20,000 acres before entering the Darling downstream of the main Warrego/Darling junction.
The original dams on the Warrego were built in the late 1890's by the legendary Sir Samuel McCaughey and apart from providing livestock and domestic water storages, one was designed to push smaller flows out on to the western flood plain where the water stimulates the most prolific growth of natural pasture, ideal for livestock fattening.
The very reasonable requirement of the NSW Government, in the second half of last century, to place the pipes in the bed of the river and allow smaller flows to pass through to the Darling, effectively means that natural conditions have been replicated. If there is too much water for the open pipes to carry the river would have spilled to the west anyway.
Thus, the Government cannot claim any additional "savings" as a consequence of the purchase of the irrigation licenses other than the water which could be stored for irrigation purposes in Ross' Billabong-10,000 megalitres.
The conversion of the whole property to a National Park has taken Bourke's most productive station out of production with all of the harmful impact this has on the Bourke economy and the local Mayor's call for the property to again be used as a grazing enterprise should be heeded. Toorale used to pay 10% of Bourke's total Shire rates, now it pays nothing.
The only environmental "benefit" that can be claimed as a consequence of the two Governments(Federal and State) purchase of Toorale, as demonstrated by the current flow event in the Warrego and the Darling, is the aforementioned 10,000 megalitres.Since the Ist January when the Darling commenced to flow again at Louth some 1,163,964 megalitres has flowed past Louth. An investment of $23.75m. for 0.86% of the flow (with plenty more to come)doesn't sound like good economics to me. Particularly when you consider that most of the water flowing past will be diverted in to the Menindee Lakes Storage Scheme where around 50% of it will evaporate.