Salinity Province 97, Phillip Island

The Phillip Island Salinity Province is a small province at the entrance to Westernport Bay, about 120 km southeast of Melbourne. Its undulating land surface has several small catchments; Tertiary basalts form poorly defined ridgelines with Quaternary alluvium covering the shallow valleys and plains in between. Both primary and secondary salinity occurs, with the province having 3½ times the statewide (per province) average of mapped salt effected land. Most salinity is in valley floor locations and along the creeks that drain the island’s centre.

Salinity is predominantly associated with discharge areas in local scale Groundwater Flow Systems (GFSs) within the alluvial sediments, although some is related to deeper local to intermediate scale GFSs in the fractured basalts. By the late 1990s, the watertable was less than 2m in most of the low-lying areas however, these generally increased during the following 10 years of drought. Risk from soil and water salinity is considered high, with the main assets at risk being high value agricultural land and urban development.

Major control options include the use of salt tolerant pastures and revegetating low lying (discharge) areas with indigenous salt and waterlogging tolerant trees