Fish in Natimuk Lake are dying as water evaporates.
Natimuk people fear this summer will be the last they can use the lake, unless the catchment receives good rainfall this year.
Water for Natimuk Lake Committee secretary Mary Smith estimated the lake was just below a third full.
She said the middle of the lake was about 1.5 metres deep.
Mrs Smith is writing letters to lobby for an annual top-up of environmental water for the lake, but she said she was disappointed by a lack of response from authorities.
The lobby group includes Natimuk Lake Foreshore Committee and Natimuk Ski Club.
Mrs Smith has written to GWMWater, the Essential Services Commission and Horsham Rural City Council.
She plans to write to Wimmera Catchment Management Authority and the Victorian Water Minister Peter Walsh.
"We are certainly very concerned about the water level going down," she said.
"I wrote to GWMWater when public submissions were open last year for their water plan. I also wrote to board chairman Peter Vogel on November 30 and asked the authority to consider an annual top-up.
"We requested an environmental water allocation of three to four gigalitres.
"We have had no responses."
Mrs Smith wrote to Essential Services Commission chief executive David Heeps on January 19 and received an acknowledgment of receipt.
She had talked to Mr Heeps at a GWMWater community forum in Horsham on November 28.
"I outlined our concerns about the GWMWater plan to charge all customers a recreation contribution levy of $16 to subsidise water for sporting groups and recreational lakes," Mrs Smith said.
"We were concerned there were only two municipalities which had recreational lakes that were nominated to be filled.
"Horsham Rural City has the largest customer base, but none of our recreational lakes are included."
Mrs Smith said the time was right for a top-up for Natimuk Lake because of the landmark $25-million sale of Wimmera irrigation water entitlements to the Federal Government last year.
"This is a federal issue, but it is only fitting that some of the water comes back to the region," she said.
"Natimuk Lake has high environmental, recreational and tourism value.
"The life that it brought back to the community when water returned was phenomenal.
"But it's almost unusable again.
"All the fish that were put in there are dying it's just sad."
Mrs Smith said she became cross when GWMWater claimed the lake was not part of its system.
“This does not mean it cannot become part of their system,” Mrs Smith said.
“It’s a non-argument.”
Natimuk Lake Foreshore Committee member and keen recreational user Keith Haustorfer said the lake was smelly before Christmas.
“The problem is, the water level is going back very quickly with the hot weather,” he said.
“This year might be the last year we will get use out of it, without good rain.
“I hope the powers that be will see reason and have some environmental water for the lake.”
Natimuk Lake caretaker Sam Wicks, Natimuk Lake Caravan Park manager, said the water level was dropping drastically.
“It’s the quickest it’s been, apart from the drought,” he said.
“Things have quietened down a lot over summer.
“It’s bad for business.
“Things will get worse if we don’t get good rain.
“Visitors think it’s a crying shame.”
GWMWater communications manager Helen Friend said Natimuk Lake was not part of the GWMWater supply system and did not have an entitlement.
She said GWMWater had met Natimuk Lake representatives and would respond to their letter.
Wimmera Catchment Management Authority chief executive David Brennan said the Natimuk catchment was a closed catchment.
“Most of the filling of the lake, apart from one occasion, has been through catchments within that 150-square kilometre area,” he said.
“I am unsure how GWMWater would engineer a solution with an environmental flow.”