No seasonal adjustment to AUL in the Macalister Irrigation District

Lake Glenmaggie

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Given the dry irrigation season, many Macalister Irrigation District irrigators have queried why there has been no seasonal district-wide adjustment to Annual Use Limit (AUL).

Annual use limits set a total amount of water that can be applied per hectare and ensure that farm irrigation practices limit the off-farm impacts of high water users.

Any adjustment to the AUL is managed by Southern Rural Water (SRW) with input from the West Gippsland Catchment Management Authority (WGCMA). Agriculture Victoria can assist farmers with advice and funding to improve on-farm irrigation efficiencies.

Farmers who have reached their AUL this season, may want to discuss a strategy for on-farm efficiency in future seasons.

This could involve a site visit from WGCMA or Agriculture Victoria to discuss steps they could take to improve water efficiency on-farm, so that an appropriate adjustment can be made.

Options may include a temporary increase, a permanent increase to AUL or amalgamating AULs across titles.

There is a model to determine district-wide changes to AUL under years of high evapotranspiration.

Evapotranspiration is evaporation from the ground and transpiration from plants, and it is tracked monthly, along with effective rainfall.  In years with exceptionally high evapotranspiration rates, an adjustment may be made to increase all MID irrigators AULs by 20%.

When the irrigation demand is above the 80th percentile year then an adjustment is triggered. Although this season has had low rainfall, the evapotranspiration overall was not high enough to trigger the adjustment.

Total rainfall for the 2017-18 year has ranged between 370mm and 390mm, across the district, which was in the driest 10% of recent years. The lowest on record was 302mm recorded in 2006.

However, this season in the MID, total evapotranspiration was just above 1,000 mm. A high evapotranspiration year is more than 1,200 mm.  Consequently, this has reduced the irrigation water demand and the seasonal adjustment was not triggered.

Farmers who want to discuss their AUL should contact SRW on 1300 139 510.  For more information about improving your on farm irrigation and irrigation incentives, please contact Agriculture Victoria’s Senior Irrigation Extension Officer Sarah Killury on 5147 0845.

Content sources and further information

Southern Rural Water

Guide to vary annual use limits in the MID

Weekly Irrigation Requirements – Macalister Irrigation District


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