Issues for river health
Drought and overuse of resources led to fresh water levels falling to more than one metre below sea level in April 2009 in lakes Alexandrina and Albert (the Lower Lakes). The effects of this included the following:
- Up to 20,000 hectares of acid sulfate soils became exposed.
- Increased salinity levels damaged the ecosystem and threatened water supplies for people and livestock.
- As the lakes dried out, wind erosion and dust created issues such as loss of soil and areas of bare ground around the Lower Lakes
- Some sections of the riverbank below Lock 1 dried out, cracked and collapsed. There were more than 160 incidents of riverbank collapse along the lower reaches of the river.
- Unique species of native flora and fauna were under strain; for example, native species had to compete for food and space with invasive species that were better suited to the saltier environment.
- Blackwater events, which can occur naturally, worsened. Large amounts of organic matter (such as leaf litter) that are normally flushed out instead accumulated, causing oxygen-depletion in water.
- When water flowed again, acid drainage water washed into the river, making parts of the river toxic to marine and freshwater plants and animals, contaminating water supplies and corroding concrete and steel.
- It is important that the Murray Mouth remains open to maintain connectivity between the river, the Coorong and the Southern Ocean, to discharge salt and other nutrients out to sea, and to maintain healthy ecosystems in the Coorong.