Independent analysis of Lower Lakes needed to improve the Basin plan

It’s time to let saltwater into the Lower Lakes to save freshwater evaporation, argues Mike Erny.

HAVING been involved in water management for more than 30 years, I believe an opportunity exists to help the Murray Darling Basin Plan increase environmental allocation without further take from irrigation communities by making changes to the Lower Lakes water storage.

The Lower Lakes is being totally manipulated to be a freshwater storage, with a loss of some 900 gigalitres to evaporation annually.

Compare this to the other MDBA storages, with Dartmouth losing one gigalitre in evaporation, Hume 82GL, Menindee 426GL and Lake Victoria 165GL

The evaporative loss from the Lower Lakes is about 1.5 times the combined total of the other storages.

Rather than focusing on the likes of Menindee Lakes, there would be greater potential if management of the Lower Lakes water storage could be improved to reduce this very large volume. It also needs to be remembered that one megalitre saved in the Lower Lakes would equate to maybe double saved in upper an Murray-Darling catchment.

Surely there is an opportunity to reinstate some tidal inflow into the Lower Lakes to substitute some freshwater. If even the 900GL was reduced to 600GL it would provide a huge relief to basin communities currently under pressure for further savings.

How perverse the planning has become when upstream storages are drained or will be by the end of summer and the Lower Lakes sit above the nominal full supply level.

Surely it is far more prudent for water during drought to be held in the upper storages and look to allow some sea water into what was a tidal estuary.

There may be positive outcomes for estuarine plant and animal species with a change back to a tidal estuary, but there would be a need for an alternative water supply for a small number of people drawing water directly from the Lower Lakes. But this needs to also be balanced against the long term significant environmental impacts to Basin communities and environment upstream.

Surely, we don’t need more mass fish kills, abandoned irrigation communities, impacted indigenous communities, and environmental impacts to see the current mode of operation is not delivering the right outcomes.

Rather than build more dams at the top of the system, a fully independent analysis of an improved alternative management regimen for the end of system could deliver far better outcomes for an improved Basin Plan by reconfiguring the Lower Lakes.

●  Mike Erny was NSW DPI Menindee Lakes water savings project manager