The Murray system has reached 100 per cent of high reliability water shares.
Seasonal determinations in the Goulburn, Campaspe, Loddon Broken and Bullarook systems are unchanged at 100 per cent HRWS.
The Broken and Bullarook systems are sitting at 100 per cent of low reliability water shares.
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Resource Manager Mark Bailey attributed the increase to recent rain.
"Late January and early February rainfall boosted flows into the Murray storages and reduced losses," Dr Bailey said.
"The resulting resource improvement was enough to reach 100pc HRWS."
"The last time all northern Victorian systems were at 100 per cent HRWS was in 2017/18."
Dr Bailey reminded entitlement holders that the Murray's milestone meant future 2020/21 seasonal determination updates would now be released on a monthly basis.
"The likelihood of any of the Murray, Goulburn, Campaspe or Loddon systems receiving an allocation against LRWS this season is low," Dr Bailey cautioned.
"Sustained rainfall is needed to generate the necessary flows into the storages.
"Both the Broken and Bullarook systems have reached the maximum possible seasonal determination this season and will not change."
The Bureau of Meteorology seasonal rainfall outlook slightly favours above-average rainfall across northern Victoria for the three month period from March to May.
"The BoM says the current La Nina event remains active, and although weakening, could influence Australian rainfall patterns until early autumn."