Water

Efficiency target looming

By Geoff Adams

The $2 billion Goulburn-Murray Water Connections project is drawing to a close, with one of the key targets still to be met.

For almost 10 years, advocates of the modernisation program have been looking to achieve an 85 per cent efficiency target for water delivery in the Goulburn Murray Irrigation District.

The goal represents a useful way of measuring how much water actually reaches farm properties after being fed into the system.

The latest figures, released in G-MW's annual report last week, shows across all districts the average achieved so far is 82 per cent.

But some districts may struggle to reach the target by the Connections completion date of October next year, established by the project reset in 2016.

Figures compiled by Country News, drawn from G-MW annual reports, show there has been an overall but uneven improvement in system efficiency over the past 10 years in the individual districts.

For 2018-19, Central Goulburn sat at 82 per cent, Shepparton at 84.9 per cent and Murray Valley at 83.5 per cent, while Torrumbarry lagged behind at 77 per cent, following much higher results in previous years.

The 2016-17 season was strongly influenced by climatic conditions, with flooding mostly impacting Torrumbarry 1A, which resulted in considerable resource gained by the area, improving the area efficiency.

G-MW water delivery services general manager Warren Blyth pointed out that in 2017-18 and 2018-19, Torrumbarry experienced higher deliveries with 100 per cent allocations and relatively dry conditions.

“The dry summer experienced in 2018-19 impacted on Torrumbarry 1A efficiency more so than the other areas due to the higher proportion of natural carriers in the irrigation area and increased evaporation losses from internal storages (Kerang Lakes),” Mr Blyth said.

“The system efficiency gains through modernisation have been immense.

“G-MW will continue to improve efficiency in areas within its control and in a sustainable manner for its customers.”

Is the system efficiency target a good indicator of success of modernisation?

Mr Blyth said modernisation was delivering more than system efficiency to the GMID.

“The replacement of thousands of Dethridge wheels and manual gate and channel systems with automated systems allow farmers to get water where and when they need it,” he said.

“The Connections project is also supporting innovative farmers to leverage on-farm irrigation systems and technology.”

Mr Blyth pointed to the system efficiency figures in the early 2000s, when district averages were about 70 per cent.

“They are now consistently over 80 per cent and in some districts, in some years, in excess of 85 per cent,” he said.

“With modernisation continuing into 2020, G-MW and its customers can expect to see continuing improvements.

“System efficiency is influenced by many factors and a longer baseline will be needed to gain an accurate picture of long-term efficiency improvements.

“The nature of water delivery in the Goulburn Murray Irrigation District, which is largely reliant on open channels, means efficiency of the order of 85 per cent is very good.”

The Shepparton district has actually experienced a decline in efficiency over the past nine years, from a high in 2010-11 of 90 per cent.

“Area efficiency is influenced by many factors, most significantly by the volume of delivery and the climatic conditions within and across seasons,” Mr Blyth said in response to a question about this.

“Overall, if all other conditions are the same, lower delivery results in lower efficiency because of the fixed losses incurred in operating the irrigation systems.

“Varying channel depths to accommodate lower water availability causes greater loss than maintaining a consistent depth.

“The 2010-11 season saw widespread flooding across northern Victoria. This was also a very low delivery year.

“The efficiency in this year was high because of the wet conditions which meant resource availability was high, and the resource gained in the irrigation areas due to rainfall and flooding entering the distribution systems.

“The following years 2011-12 and 2013-14 were higher water availability years, where deliveries were more comparable with those before the millennium drought.”