FIONA SIMSON says we need an open talk about the water needs of the Lower Lakes.

The Murray River's Lower Lakes are the "elephant in the room" in the conversation about the Murray Darling Basin Plan.

Few groups have been prepared to raise the issue but NSW Farmers believes it's too important a subject to remain taboo just because it is politically sensitive.

For too long it has been accepted that the problems of sedimentation at the mouth of the Murray River and salinity in the southern lagoon of the Coorong are the result of insufficient flows from upstream.

We believe the situation is far more complicated and we want the facts discussed openly.

In the proposed basin guide, the MDBA stipulated that a minimum of almost 2000 gigalitres of additional water purchases was required to meet the needs of the Lower Lakes in South Australia.

That's two thirds of the total minimum purchase requirement outlined in the guide.

The problem with the artificial environment in the Lower Lakes is that it requires a constant supply of fresh water every year. This does not reflect the reality of the Australian climate.

Most environmental needs in the basin have adapted themselves to receive periodic watering as would occur naturally, but the Lower Lakes - in no small part because of their artificial status - require large volumes of water, every year, regardless of climatic conditions.

When the MDBA's 2000-gigalitre figure is viewed in the context of different climatic scenarios, the potential impacts on communities can begin to be understood.

The social and economic report released by the MDBA recently says that supplying an additional 2000 gigalitres to the Lower Lakes during drought years would require 60 per cent of the high-security entitlements from the entire southern connected system.

The impacts on communities would be devastating.

The NSW Farmers Association is calling for an independent inquiry into the management of the Lower Lakes. We're not suggesting we have the answers. We don't.

But you cannot take almost 2000 gigalitres out of rural and regional communities without considering what this water is being used for and whether this requirement could be reduced.

Investments in environmental infrastructure can save significant volumes of water, but to date the MDBA and Government seem to have ignored the Lower Lakes and opportunities for reducing their reliance on fresh water solutions.

This is not about pitting state against state in the basin plan discussion; it is about open and transparent discussion in the national interest. No issue should be left off the table, no matter how sensitive the politics.