History of Salt Water Intrusion in the Mary River
Since the early 1940’s the wetlands have undergone rapid changes with small tidal channels advancing inland, invading the freshwater swamps and billabongs. The influx of saline seawater into these low lying floodplains was initially triggered by feral buffalo whose numbers dramatically increased after the collapse of the hide market in 1954. The natural barriers or chenier ridges were breached in the early 1950’s resulting in the devastation of 23,000 hectares of freshwater floodplain.
Community concern about the problems in the Lower Mary River started in the early 1990’s when extensive areas of paperbark forest dieback were recorded. The Northern Territory Government commissioned a geomorphologic investigation on the Mary River floodplains to determine the triggers for the relatively recent phenomenon of saltwater intrusion. The report, Geomorphology of the lower Mary River plains, Northern Territory (1993) concluded that the accelerated influx of sea water into the freshwater system was due to a combination of interrelated factors, rather than a single cause.
Over 150 stakeholders were brought together at the 1994 Wetland Workshop to set future directions for the management of the Mary River. At this workshop, saltwater intrusion and weed invasion were identified as the major issues impacting on the wetland environment. It was recognised that the best approach to moving forward was to develop an integrated catchment management plan which brought together technical expertise and local knowledge to address these problems in a systematic way.
The Legislative Assembly Sessional Committee on the Environment Investigating the Mary River Wetlands similarly concluded in early 1995 that a task force should be put together to produce an integrated catchment management plan for the region.
The Mary River Wetlands Task Force produced the first Integrated Catchment Management Plan in 1998. This plan identified strategies to deal with 12 issues – saltwater intrusion, weeds, aquatic habitat, fire, grazing, pasture, nature conservation, clearing, water quality, erosion, visitor experience and feral animals. Each strategy had a supporting work program for the following 3 years.
In 1999, the Mary River Catchment Advisory Committee was established under section 23 of the Water Act. The Mary River Catchment Advisory Committee reviewed the Integrated Catchment Management Plan in January 2001 and confirmed that the previous strategies developed for the region were still appropriate.
