WELLINGTON DAM WATER UPDATE

A Message from Harvey Water and South32 Worsley Alumina

Wellington Dam – Capacity, Water Catchment and Rainfall Predictions

Construction of the Wellington Dam Wall began in 1932 to capture water from the Collie River to extend the South West irrigation network and encourage further expansion in agriculture. At capacity Wellington Dam holds 185 billion litres or gigalitres (GL) of water. Originally the dam’s water was captured from the east and south branches of the Collie River, the Bingham River and Harris River, until the Harris Dam was built in 1990 for potable water supply under the Great Southern Towns Water Supply System. Wellington Dam’s water is not potable due to high salinity levels and bromide and nearly 28GL of water each year is released, via the scour at the dam wall, for environmental water provisions. Low water flow downstream from the Collie River catchment into Wellington Dam, below average rainfall and diversion of water upstream means the Wellington Dam current water level is approximately 34 percent or 63.4GL. Due to our drying climate and lower seasonal rainfall there has been a remarkable drop in catchment inflows into Wellington Dam from a long-term average of 124GL per year (1975-1999) to 78GL per year (2001 to 2012). Further modeling indicates that these lower inflow trends will continue.

Harvey Water Allocation

Harvey Water has a licence from the Department of Water and Environment Regulation to draw 68GL of non-potable water annually from Wellington Dam and has a diverse range of uses for this precious resource. The largest user is the agriculture industry, accounting for approximately 50 per cent of their annual allocation. Harvey Water partners with various industries, reliant on water to help preserve vital jobs in the South West. Subject to seasonal inflows and environmental considerations, South32 Worsley Alumina is able to purchase an average of 2.2 percent of Wellington Dam’s water supply per year, with the amount being adjusted periodically in accordance with dam levels. Given the age and type of the infrastructure in place, Harvey Water does see system losses which is it trying to resolve with the assistance of the State and Federal Government.

South32 Worsley Alumina

Water is a vital input to our Refinery operations near Collie. As a result of lower seasonal rainfall, in 2017 a pipeline was built from Wellington Dam at Hamilton Peninsula to our Refinery, as risk mitigation against further years of low rainfall. Typically, in years of average rainfall our Refinery catchment lake can provide all of the water needed for process operations. Since the pipeline was commissioned, South32 Worsley Alumina has purchased and imported water on four occasions, as per the terms of our agreement with Harvey Water and only in years of low rainfall. Our water purchases are usually around 2 to 3GL of water to ensure our operation continues to run in a stable and reliable manner, which in turn supports local employment and injects almost one million dollars a day into the local economy. An import of 1GL takes approximately five weeks and the pump at Hamilton Inlet is only operational when water is purchased and imported.

Future Water Management

Both Harvey Water and South32 Worsley Alumina recognise the challenges of our drying climate and have strategic plans in place around water delivery procedures, efficiency and usage. We are both working on infrastructure design, process improvements and demand reduction initiatives to ensure as much water as possible can be preserved in future years.

For more information please contact South32 Worsley Alumina at worsleycommunity@south32.net