Woes continue

By Country News

I congratulate and thank the efforts of Country News staff, together with so many correspondents, who have valiantly highlighted local water issues of more immediate concern over the past year. If only we could say it has all been worthwhile.

Analysis beyond the more immediate issues shows the enormity of our emerging water problems. There is no evidence that policy makers intend to even comprehend these problems. Those with some concern seem overwhelmed with more immediate social and economic issues related to water.

So what are these bigger, less immediate, issues?

Firstly, about 1000Gl of irrigation water once used in our more temperate districts is now used in the arid parts of the Murray-Darling Basin.

This water is about half as effective in generating plant growth for two simple reasons: evapotranspiration and rainfall.

Comparison of Shepparton and Sunraysia districts shows annual differences of around 400mm and 250mm in evapo-transpiration and rain. With 100mm being equivalent to 1Ml/ha this translates into about 6.5Ml/ha annually. In other words it can take an extra 6.5Ml/ha in arid zones to make soil moisture adequate for good year-round plant growth.

How stupid it is to have policies that decrease the nation’s plant production from the increasingly limited water in the basin.

Secondly, in conveying water to irrigation areas in the arid zone, rivers are being subjected to maximum out-of-season flows.

These flows are causing major damage to river and bank ecosystems. A stage has now been reached where even these flows cannot satisfy the usual spikes in arid zone demands for irrigation. Such is this problem that temporary draw-downs of lock weir pools will be used together with water storage in shallow side lakes and billabongs newly commissioned for the purpose. Some people even talk of dredging the Barmah Choke.

Additionally, conveyance losses go unrecognised with a megalitre at Albury still being a megalitre at Renmark.

Thirdly, the energy demands for irrigation are changing dramatically.

The extra 1000Gl used in arid districts of Victoria, NSW and SA are beyond our gravity flow irrigation schemes. Rather than using gravity, developers install their pumps. If diesel alone was the fuel used, perhaps 30litres per megalitre of water is needed — 30million litres (for 1000Gl of water). So much for the risk this policy has created for arid zone irrigators who operate in a nation that has only a couple of weeks’ petroleum supply in reserve.

Fourthly, the Murray-Darling Basin Plan focuses on the Lower Lakes. Historically these are part of the Murray River’s estuary.

Barrages modified the situation, stopping inward movements of sea water and holding back river water, in an attempt to establish freshwater lakes. Maintenance of these lakes demands about 1000Gl annually to replenish evaporation losses.

This is similar to GMID irrigation usage. Furthermore, significant flushing flows are used to reduce salt concentration. Moreover, large proportions of the basin’s environmental flows are used for these purposes.

Meanwhile projections for sea level rises indicate just how inadequate the barrages will be in three or so decades’ time.

How absurd is the politics of the Murray estuary when it defends present Lower Lakes policies?

In all probability we can look forward to suffering another year of denial of fundamentals. Our policy makers, intent on debating today’s apparent issues, seem to make no attempt to view these in the context of the bigger long-term picture.

The four issues mentioned above will be impacted by climate change. Despite this, we continue to disregard the unequivocal actual happenings and projections in reports from our planet’s Intergovernment Panel on Climate Change.

Politicians who defend current water rules that protect the rights of individuals and corporations in areas more dependent on irrigation water on the basis that ‘‘they vote too’’ guarantee the continuance of current predicaments.

— Barry Croke