South Australia's southeast region juggles water drainage for agricultural and environment interests
The Tilley swamp drain has helped restore water levels in the Coorong South lagoon in South Australia's southeast region.
Image by P. Rasenberg courtesy Natural Resources SA
South Australia’s southeast region has a long history of juggling drainage concerns while it was converted from a wetland landscape into large agricultural production. The South Eastern drainage board had been set up in 1931 to care for, control and manage the drains.
The first drains in the lower southeast started in 1863 but most were built 1949-1972, largely to remove waterlogging. A growing 20th Century concern for the environment added to the water balancing act. More recently, the lower southeast drainage also was managed to enhance natural wetlands. For many years, the key reason for drainage in the lower south east was to increase productive capacity and improve access. Draining land also enabled crown land to be sold and made available to post-war soldier settlement and migrants
Most drains in the upper southeast were constructed between the early 1990s and 2011 to address drainage, protect vegetation, harvest salt and enhance wetlands.
In the 1970s, the state government directed against further drainage with considering its effect on the environment. The region as a whole grappled with the dual issues of high saline groundwater coming to the surface through the rising water table and high rainfall events that swamped the agricultural area, particularly in the north where there was no drainage.
The large scale of environmental degradation was a direct threat to the regional economy. The 1981 flood first stimulated northern landholders to seek a fix to excess water. Many landholders did their own drainage but recognised the need for a coordinated and consolidated approach to surface drainage, and the need for an outlet for landlocked watercourses.
Landholders began to recognise the extent of dryland salinity. Community groups (including soil conservation boards, landcare groups, and national parks consultative committees) took an interest in developing solutions.
The southeast drainage system (2589 kilometres of drains and floodways) remains critical to the region’s economy, transport networks and natural environments. It supports the export of 250,000 tonnes of salt from region (when rainfall allows), brings 26 billion litres of water to the Coorong South Lagoon (under normal rainfall) and environmental flows to 40,000 hectares of connected wetlands in the upper southeast.
