People and groups who are interested in the Lake Innes freshwater reversion program south of Port Macquarie will get the chance to have input into the feasibility study.

In Senate estimates, the Nationals Duty Senator for Lyne John Williams questioned departmental officials about their plans for the environmental study which will cost close to $1 million over three years.

Senator Williams said the lake is one of the premier saltwater aquatic ecosystems on the east coast, producing prawns, crabs, estuarine and offshore fish species and significant bird life.

Senator Williams produced a copy of an 1891 map that indicates that even then Cathie Creek may have been tidal.

But he warned there is concern amongst recreational and professional fishermen that they are being left out of the consultation process and will have no say on whether Lake Innes is returned to freshwater.

The Department of Sustainability, Environment, Water, Population and Communities says it has had preliminary discussions with agencies such as National Parks and State Fisheries, but the study is expected to be contracted out to the Catchment Management Authority.

They gave Senator Williams an assurance all interested parties will be engaged before a report is presented to the State Government in 2013.