Winter inflows have significantly improved water storage levels across the Grampians, Wimmera and Mallee, boosting water security ahead of summer and allowing GWMWater to guarantee supplies to its network of recreational lakes.

Recent rainfall and catchment flows have added about 102 gigalitres to the GWMWater system over the past three months, increasing overall storage levels by about 18 per cent of operating capacity.

Manager Water Resources Scott Smith said above-average rainfall in May and June had saturated the Grampians catchments and set up strong winter inflows into key storages.

"We've seen strong inflows across the system over winter, which has put us in a much better position heading into the warmer months," Mr Smith said.

Lake Bellfield is now holding more than 80 per cent of capacity, while Lake Wartook is in its strongest position in almost two years.

Mr Smith said the GWMWater Board had also committed to transferring water from its consumptive entitlement to all 14 recreational lakes supplied through pipeline systems.

It has done so by reallocating 2,450 megalitres from its urban and rural water holdings to fill 12 Wimmera Mallee Pipeline lakes, as well as 680 megalitres from its Murray and Goulburn system entitlement to supply Ouyen Lake and Green Lake near Sea Lake.

"Many people want to know whether the recreational lakes supplied by GWMWater will have water this summer and the answer is yes," he said.

Meanwhile Horsham's Green Lake, supplied via the headworks system, has more than doubled in volume since May. Green Lake's volume has increased from 1,301 megalitres (24 per cent) in May to 3,018 megalitres (56 per cent) as of 27 August.

"Green Lake is receiving water from its own local catchment, as well as additional natural flows from the McKenzie River system," Mr Smith said.

"With Taylors Lake having reached its target filling level, we have been able to meet Wimmera Catchment Management Authority's request for some of that natural catchment flow to go to Green Lake."

Mr Smith said while the outlook for Green Lake had improved substantially, water levels over summer would still depend on inflows received in the coming weeks.

"The outlook for Green Lake has improved, but future rainfall and catchment inflows will determine how much more water enters the lake before summer," he said.

"Our focus remains on capturing and storing as much water as possible now so we're better prepared when dry years return."

Toolondo Reservoir is currently 23 per cent full but relies on transfers from Rocklands Reservoir as it receives little water from its own catchment. A transfer will be considered if inflows continue to improve storage levels at Rocklands.

“There have been many challenges moving waters around the system to ensure the storage and other outcomes are optimised. These are good problems to have,” Mr Smith said. 

People can monitor water storage levels via the GWMWater website.