Chowilla Environment

The Chowilla Floodplain

The Floodplain

 

The River Murray dominates the floodplain and so modification of the Murray has had a great impact on this part of the land. Before locks and dams were built, the Murray varied from little more than a string of pools after long dry periods, to a mighty slow flowing lake covering the whole floodplain after torrential rains in its catchment. Huge floods were not common; though in most years the lowest swamps and plains were flooded, and some water flowed through the creeks. This water was purified as silt was deposited and nutrients were captured by plants. Plants helped to generate oxygen in the water as well.

 

Perhaps one year in ten moderate floods would have extended over most of the floodplain. But there would have been many periods when the creeks and lakes were dry. It is this alternation between dry periods and a variety of flood levels to which the local plants and animals are adapted. It allowed release of plant nutrients from the soil, breeding of native fish, birds and other animals, germination of seeds of River Red Gums, and a flush of new vegetation after floods.

 

Land where flooding was infrequent suited different plants from those on lower areas. The result was a diversity of plant communities, from Black Box woodland to Lignum and Red Gum forests, or beds of Bamboo Reeds (Phragmites). These different plant communities were home to a diversity of animals as well, and there was a continual cycle of change in response to changes in the river level. We can still see these different plant communities, but the patterns of flood and dry spells which supported them has been altered. We still have infrequent huge floods, but as a result of river regulation, there are far fewer small floods, and the river and creeks flow all year.

 

There are also many wetlands on the floodplain. These are areas which are under water for substantial parts of the year. The plant and animal life of the wetlands varies according to the depth of the water, how often they dry out, and the levels of salt and turbidity in their water. Control of the Murray by locks, weirs and dams has changed these factors too. Drying is less common now and some of the former swamps have become permanent lakes.

 

There have been other changes, such as rising saline water tables, grazing, tree clearing, and disposal of drainage water to wetlands on the floodplain. In spite of all these changes, we still have some of the finest wetlands in the world. We can do a lot to keep them that way as well as restore them, but we cannot expect them to be the same as they were before locks and dams were built.

 

The floodplain soils also vary, as every flood brings new material, but whether this will be clay, silt or sand depends on how fast the water is flowing. Sand and dust have been blown in during dry periods. Cracking clays with a thin cover of sand are most common. Variation in soil adds further diversity to the floodplain ecosystems.

 

Thus we have plant and animal communities varying with depth of water table, frequency of flooding, type of soil, salinity, and past use of the land.

 

Major plant groups on the floodplains include.

  • River Red Gum (E. camaldulensis) and Black Box (E. largiflorens) woodlands over Lignum (Muehlenbeckia cunninghamii), grasses and sedges on low areas
  • Lignum, with a few River Red Gum and Coobar (Acacia stenophylla) on other low areas
  • Samphire (Arthrocnemum species) on low-lying, salt affected areas.
  • Black Box and Saltbush on higher land
  • Dense Cumbungi (Typha), Bamboo reeds (Phragmites) and Lignum lining the edges of permanent waters
  • Sedges alternating with stretches of grass and herbs along the margins of some permanent waters
 
 

Animals

 

The Chowilla flood plain is rich in native fauna which may be encountered while paddling the region. Red and Western grey Kagaroos are abundant and you may come across a variety of lizards including the very impressive goannas and the Lace Monitor. There are Brush-tailed Possums in the trees of the area, also frogs and Brown Tiger Snakes near the water's edge. In the water you may see Water Rats and Tortoises. A number of species of bats live in the area. Yabbies and fish are abundant although the introduced European Carp and Mosquito Fish pose a threat to the native species such as Murray Cod and Callop.

 

Bird Life is abundant due to the availability of food such as insects, fish, frogs, yabbies and nectar from flowering trees, particularly after floods. You may see Spoonbills, Darters, White breasted Sea Eagles, Regent Parrots, Emus, Pelicans, White Faced Herons, ducks, Swamp Hens, Sacred Kingfishers, Night Herons and as many as a hundred other species near the water. Further out, in the surrounding Mallee scrub, there are Malleefowl, Regent Parrots, Major Mitchell Cockatoos, Mulga Parrots, Striated Grass Wrens, Apostle Birds, Spiny Cheeked Honeyeaters and Common Bronzewing are a few of the birds you might find. While camping at night you may hear the haunting call of the Southern Stone Curlew.

 

 

 
 

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