Rainfall is needed in northern Victoria to guarantee irrigators high allocations later in the season.
The Resource Manager for northern Victoria announced the first 2017/18 seasonal determination on Monday.
Opening system allocations vary from 1 per cent in the Broken to 100 per cent in the Campaspe.
The Murray has started the season with seasonal determination of 66 per cent of high-reliability water shares while the Goulburn and Loddon have opened at 36 per cent HRWS.
Resource Manager Mark Bailey said the seasonal determinations came largely from system reserves built during 2016/17.
“Northern Victorian systems have seen mostly dry conditions over the last six months,” Dr Bailey said.
“The seasonal determinations announced today are due to reserves established during the very wet first half of 2016/17.
“June was very dry and water resource availability did not improve at all during the month.
Dr Bailey said the latest Bureau of Meteorology seasonal outlook indicated below-average rainfall would continue across all of northern Victoria from July to September.
But the bureau said it was unlikely an El Niño event would develop this year.
Dr Bailey said the dry outlook would not affect water deliveries in any northern Victorian water system.
“Carried over allocation can be delivered in the Bullarook system, even without a seasonal determination,” Dr Bailey said.
“Most of the northern Victorian systems have tracked close to or below the ‘Dry’ outlook category in recent months,” Dr Bailey said. “More rainfall is needed to generate inflows and increase water availability.”
The Resource Manager used historical flow records to assess the seasonal determinations for a range of inflows to the major storages. The scenarios are: Wet: Inflow volumes that are greater in 10 years out of 100. Average: Inflow volumes that are greater in 50 years out of 100. Dry: Inflow volumes that are greater in 90 years out of 100. Extreme Dry: Inflow volumes that are greater in 99 years out of 100.
The following tables summarise possible high-reliability water share seasonal determinations through the season and include a reference year to help users recognise the possible inflow conditions.