Water Resource Recovery Catchments

This program is the primary focus of the Department’s Salinity Management Program.

Water Resource Recovery Catchments are priority areas for salinity management in Western Australia. They form the primary focus of the Department’s Salinity Management Program.

The Collie, Denmark, Kent, Warren and Helena rivers have been identified as current or potential future water sources for the south-west region that are expected to deteriorate beyond recovery without active management. The 1996 Salinity Action Plan therefore designated the upper parts of their catchments as Water Resource Recovery Catchments. These five catchments have been a major part of the State’s water resource salinity management strategies since they were established as clearing-controlled catchments in the late 1970s.

The objectives of this component are:

• To maintain or reduce the stream salinity concentrations to potable (drinkable) levels within the five key catchments. The targets are 500 mg/L TDS measured at the current or potential damsites by 2015 in Collie, by 2020 in Denmark, and by 2030 in Kent and Warren. Water in the Helena River is currently fresh at the damsite.
• To adopt an effective partnership approach with other state government agencies, NRM groups, local government, industry, research institutions, local community groups and catchment landholders to achieve the goals.

The Collie River

The Collie River Catchment is one of five catchments identified as Water Resources Recovery Catchments in Western Australia's State Salinity Strategy. The report The Salinity Situation Statement - Collie River was published in 2001.

The report presents comprehensive information on the salinity situation of the Collie River Catchment. It includes an outline of the causes and processes of salinity and analyses trends in streamflow, salinity and groundwater levels. The effects on salinity of various reforestation, perennial pasture and engineering options are modelled to estimate the extent of treatment needed to reduce the average salinity of inflow to the Wellington Reservoir to 500 mg/L by 2015.

This information will help the Collie Recovery Team formulate effective land management plans to achieve this target.

Located in the South-West of Western Australia, the Collie River Catchment covers almost 3,000 square kilometres and includes the Wellington Reservoir, which is a potentially valuable water supply for the State's growing population. The flow weighted mean salinity of the total inflow to the reservoir in 1995 was 885 milligrams per litre (mg/L), which is higher than the desirable salinity for drinking water. The State Salinity Strategy gave the Water and Rivers Commission a salinity target into the Wellington Reservoir - 500 mg/L by 2015 - and set out options for the management of salinity.

The Salinity Situation Statement -Collie River is the report of the study that reviewed data and modelled the effects of various reforestation scenarios, perennial pasture and engineering options. It details the past and current salinity situation of the Collie Catchment and sets out a mix of plantation, groundwater pumping and river diversion options for attaining (or nearly attaining) the target of drinking quality water in the Wellington Reservoir by 2015.

Key conclusions of the study were:

• The salinity of water into the Wellington Reservoir is stabilising due to clearing controls and reforestation in the Collie Catchment over the last 30 years.
• Nearly three-quarters — about 73% — of the salt load into the Wellington Reservoir comes from just three of the eight Management Units of the catchment — the Collie River-East, Collie River-South and James Well — where there has been the most clearing in areas susceptible to dryland salinity.
• Reductions in stream salinity are expected once all the existing and planned plantations have been fully established.
• There are feasible options to reduce the inflow salinity of the reservoir to drinking water levels.
• The full effects of reforestation treatments can be expected within 10 years from commencement.

The farming, community and agency representatives making up the Collie Recovery Team will use the scientific conclusions to assess the environmental, economic and social impacts of the options before implementing selected salinity reduction activities.