Water productivity is in strongly correlated to land productivity.

In general, farmers are not concerned with water productivity as they still see land and labour as key limiting resources. Crop production functions show that whilst water is the most important factor of land productivity, there are multiple factors of water productivity (fertilizer uses, salinity, soil type, farm management practices).

Improvements across the board in farm management are the factors that will allow current levels of physical water productivity to be improved.

The physical water productivity of wheat is high, but in value terms it is low in comparison to rice and sugar cane.

Physical water productivity of pastures and fodders is relatively poor (as they are often grown in more saline conditions), but the value added through livestock production results in higher dollar value WP.

Analysis of the gross margin per unit of water used ($/m3) gives additional insight into farmer choices and strategies, particularly in relation to the costs of achieving greater water productivity.

At basin or full system scale, it may be possible to re-allocate water to better optimize groundwater use, but the long term impacts on salinity and salt mixing between fresh and degraded parts of the aquifer is a crucial factor of long term sustainability. A groundwater model was built to investigate this over 30-50 year scenarios, but the results are not conclusive due to poor calibration of the salt model, due to data limitations.

The adoption of resource conserving technologies is increasing rapidly (mainly zero tillage and laser land leveling). These have been claimed to save water at field scale, and detailed measurements confirm that one early irrigation for wheat is saved by more timely sowing following rice, which makes better use of residual soil moisture. Surveys of farmer perceptions and practices revealed that medium and large farmers used this "saving" to establish larger areas of wheat, and then subsequently pumped more groundwater - we estimated a net minor increase (3-4%) in total annual water use as a result.

We can conclude that water savings do not materialize from increasing water productivity per se, but from policies that re-allocate water or limit water use and require farmers to improve water productivity in response.