A PROPOSAL to double the size of a dam at Oatlands golf course has raised the ire of local environmentalists.

Membe rs of the Vineyard Creek Reserve Committee are protesting against a development application lodged with Parramatta Council by Oatlands Golf Club to increase the capacity of the dam, used for course watering, from 30 megalitres to 60 megalitres.

The committee was formed 33 years ago under the auspices of Parramatta Council to undertake bush regeneration in the reserve.

This includes a project to preserve the habitat of the endangered powerful owl, which is being helped by a recent $33,000 federal grant.

Committee founding member Jeff O'Neill said the creek had already been ``adversely affected'' by the dam.

``Because the creek is rarely flushed out in rainy periods we often have stagnant, smelly pools of water,'' Mr O'Neill said.

``When I first moved here with my family it was a clean creek with lots of water-flow and few weed problems.

``Even in dry weather there was always a flow, now it rarely flows properly and has a large weed problem.''

He called for the dam to be operated as a flood retention system with water bypassing the dam and only entering at times of flood.

``The trickle that the golf club releases is not enough to keep the creek healthy,'' Mr O'Neill said.

Former fellow committee member and local resident Professor Joe Unsworth said the quality of the water and reduced flow and flushing had affected the entire ecosystem of the reserve.

``We ask Parramatta Council to refuse this application to take the community's water and to protect our creek, not dam it,'' Professor Unsworth said.

The reserve and creek are home to a range of other native fauna including satin bower birds, currawongs, kookaburras, lorikeets, cormorants, wild ducks and fish.

``The whole idea of having the committee is to look after the bush flora and fauna. If the creek is not running in a natural manner you are going to have trouble,'' he said.