Salinity Province 118, Tyrrell Basin

The Tyrrell Basin Salinity Province is the largest in the Mallee CMA Region at 383,000 ha. Salinity in this province is dominated by the primary salinity feature of Lake Tyrrell in its south-west, here the Tyrrell fault allows saline groundwater to discharge from the underlying marine and alluvial origin sediments of its regional scale Groundwater Flow System (GFS). Over time, this discharge has salinised a clay depositional feature called the Blanchetown Clay, which has then been blown away to form natural saline depressions known as "boinkas". Numerous smaller boinkas are found to the east and north of lake Tyrrell, with cropping land adjoining and surrounding these primary salinity features. Land clearing caused some expansion of the groundwater discharge areas and increased recharge to the overlying local to intermediate scale GFSs in the sand dunes.

Management actions should focus on reducing recharge through cropping area soils to slow secondary salinity processes. Grazing in and close to saline areas should also be minimised to protect salt tolerant vegetation and prevent soil erosion.