Mary River Salt Water Intrusion
The Mary River is located 90kms east of Darwin in the Northern Territory with a catchment that covers an area of 8100 km2 with predominately freshwater wetlands extending over approximately 1,300 km2.
It is a highly productive area which supports multiple land uses as well as providing habitat for a large range of wildlife, including saltwater crocodile Crocodylus porosus, magpie goose Anseranas semipalmata and barramundi Lates calcarifer.
The freshwater floodplains are a variable environment with seasonal changes in vegetation cover and species composition due to the contrasts between freshwater inundation during the wet season and retreating water levels during the dry season.
The wetlands provide an important spatial and temporal mosaic of wildlife habitats and for this reason the Mary River wetlands is listed in the Directory of Important Wetlands (ANCA 1996). Compared to most other coastal rivers in the Northern Territory, the Mary River displays uniqueness in not having any major tidal estuary as a river outlet for at least the last 2,000 years.
Until recently the wet season runoff from the river’s 8,000 km2 catchment emptied into extensive lowland and floodplains which are dissected by deep unconnected billabongs and braided channels. The floodplains and billabongs were separated from the sea by a series of parallel narrow sandy chenier ridges which are a legacy of the receding shoreline over the last 6,000 years.
