The 2008 State of the Basin report concluded the rivers and catchments of the Lake Eyre Basin were in generally good condition, with the aquatic ecosystem processes intact. However, development is increasing rapidly and impacts need to be monitored and managed in order to avoid the kinds of problems seen in the Murray-Darling system.
Redclaw crayfish (Cherax quadricarinatus). Photo: A Emmott
The nature of the landscape makes it particularly vulnerable, as, even in its undisturbed condition, the natural extremes of drought and flood pre-dispose the system to widespread wind and water erosion. Inappropriate land management can markedly exacerbate these processes.
Although many of the Basin's wetlands may be dry for years, and rain is unpredictable, their continued existence and interconnectedness depends on periodic inundation, and changes to natural water flows could have severe effects. Natural flow and seasonal flooding are also vitally important to floodplain productivity and therefore, to floodplain graziers and the pastoral industry.
Threats to the health of the Basin are diverse and vary from those that have localised but persistent effects (e.g. mining infrastructure and works, vegetation clearing, tourist damage at waterholes) to diffuse and widespread (e.g. over-grazing, erosion, roads and tracks that impede water flow). The following list from the State of the Basin 2008 report outlines the main threats, and some of these are expanded on below.
Spraying invasive cactus. Photo: Desert Channels Group
- Major water developments including mining and irrigation.
- Cumulative impacts of minor water developments (including bores) and diversions.
- Intensified land use around waterholes.
- Presence and spread of introduced pest plants and animals.
- Isolation of flood plains through levee construction or roadway embankments.
- Impacts of pastoral activities, tourism and mining.
- Intensified water extraction and drawdown.
- Impacts of climate change on water resources.
- Modification of basin catchments, such as vegetation clearance and inappropriate grazing, soil management and cropping practices.
- Stocking rivers and waterholes with non-native fish.
Inappropriate water resource development
Unregulated increases in storage and extraction of water for industrial purposes such as mining and agriculture will have significant consequences. Direct extraction from waterholes and rivers, harvesting of water from the floodplains and increases in the size and number of farm storages all contribute to the problem. The resultant decline in available water, as well as changes in the extent and duration of flooding, are felt both locally and downstream, and interrupt the natural connections between different waters across the landscape.
Artificial rapid drops in water levels at waterholes e.g. as a result of pumping, can have various effects e.g. fish kills, algal blooms, changes in water quality and loss of food resources for other aquatic fauna. Such local declines can reduce the variety of species available to re-colonise other regions of the Basin during the next flood event.
It is not only major water development proposals that are a threat. As has been demonstrated so often in the Murray-Darling Basin, actions that are apparently trivial at the local level can, when repeated many times, have significant regional consequences. Regulation is difficult as the system is so dynamic, but diligent monitoring of applications for water development is required.
Land use intensification
In such a flat landscape, roads, tracks, fences, railways and pipelines can block or divert water flow, leading to the isolation of water bodies and marked changes to their cycle of replenishment.
Disposal of toxic or saline water from mining and oil drilling needs attention and allowances made for the role of flood events in transporting contaminants across the landscape.
Damage by off-road vehicles to claypan in Simpson Desert. Photo: M Turner
Although usually well managed, poor grazing practices can lead to increases in sediment and nutrient loads in water bodies. Loss of vegetation and soil compaction increase runoff, changing the flow and distribution of water. Heavy stock use of waterholes destroys the algae which are concentrated at the water's edge, and which are essential to the functioning of these ecosystems.
The numbers of tourists camping at popular waterholes are becoming an issue due to such problems as soil compaction and firewood collection. Increased fishing pressure reduces native fish stocks and turtles also die in fishing nets.
Invasive pests and weeds
As in the rest of Australia, feral pests and invasive weeds are a problem - camels, pigs, cats, foxes, mesquite and rubber vine are here too. With very limited resources and few people, managing and monitoring the occurrence and spread of such species is difficult and expensive. For some species, the nature of the system magnifies the problem - huge water flows that travel for hundreds of kilometres can transport weeds, as well as pest animal species, over vast distances.
Feral pigs in Queensland Channel country. Photo: Desert Channels Group
Some of the problem species include camels, Redclaw Crayfish, Parkinsonia, Prickly Acacia, Mesquite, Rubber Vine and Parthenium. Athel Pine is a well-known problem in arid zone rivers, easily spread in floods and occurring in high density infestations. These same characteristics are exhibited by Cane toads, and, already present in the upper Diamantina and Cooper catchments, they have the potential to disrupt the rich frog fauna of the Basin and reduce numbers of goannas, snakes and quolls.
Emerging issues of concern
Agricultural development carries the threat of contamination of water by pesticides and herbicides. Illegal fishing and stocking of rivers/waterholes with non-local fish stock could have long term effects, not only on native fish, but on healthy functioning of the rivers/waterholes. It is predicted that climate change will increase temperatures, evaporation, and the severity of wind/storm events, and also decrease total rainfall in some areas, all of which would have immediate effects on people and environment. The combination would markedly change the patterns of water supply and distribution, and, in turn, the very special ecosystems of the Basin.
Need for information
Some say that in order to assess threats, you need to know how a healthy system operates i.e. you can't tell what's wrong if you don't know what's right. This is relevant to the Basin, as both the remote location and lack of resources mean that our knowledge of the system is relatively poor. Much needed whole-of-basin planning, as well as modelling and management of specific issues, is compromised by this paucity of data. However, the situation is improving, as a result of major projects like the Lake Eyre Basin Rivers Assessment (LEBRA) and ARIDFLO. These programmes provide an important foundation for sound land management decision making in the Basin.