Innovative solutions

I thought I’d expand on the RWA’s “innovative solutions to reduce on-farm evaporation” because, while it’s not relevant as regards the town water supply, it will be of interest to many of you out there.

Evaporation is a key problem when it comes to water planning in the Granite Belt.  No matter how big your dam, in an extended drought they’re all dry.  The RWA cites multiple studies by CSIRO and USQ that conclude that up to 40% of on-farm dam storage capacity is lost in evaporation each year.  It’s why Stanthorpe can’t just build an extra dam to use when the first one runs out: whether you use it or it evaporates, the water is gone just the same. 

From the RWA analysis, it is estimated that up to 4,500 megalitres of evaporation could be saved annually, if half the on-farm storages in the Granite Belt are covered.

To put that in context, that is more than the annual take for Emu Swamp Dam (which is 3,900 megalitres).

Both shade cloth ($120,000 to $190,000 per ha) and floating covers ($110,000 to $180,000 per ha) are identified, with shade cloth being the preferred design approach.

At this cost, the benefit cost ratio is positive for apples, strawberry runners and green vegetables.  It is much higher for tomatoes and even higher for strawberries.

The RWA has recommended that this option be progressed by engagement by the Department with interested landholders on the Granite Belt.

This is a positive program, because while you can’t control how much rain you get, it would be fantastic for landholders to be able to take steps to control how much is lost to evaporation.  And if that’s equal to one Emu Swamp Dam each year, then it would be a win for all participating irrigators right across the district. 

26 September 2023