Why do we need environmental flows?
An environmental flow involves the release of water for environmental reasons. Until recent times water was seen as a resource to be managed for agricultural uses. Waterways were dammed and controlled to ensure a supply of water for agriculture over the drier months of the year. However, this resulted in smaller flows through our natural waterways and wetlands in ‘normal’ years and in dry years these could dwindle to zero. Our wetland environments started to die.
The first things to die are the aquatic creatures. Not only do the fish die, but also a myriad of aquatic insects which make up a major part of the food chain. Yabbies last longer in deep burrows, freshwater shrimp eggs can survive without water for a few years but unless given a replenishing flood of water they will also die. Frogs, without water to breed in, will eventually die out. Without aquatic life to sustain them, creatures such as turtles and snakes either move away or die. Many water birds require wetlands for feeding and also for breeding grounds safe from predators. Water-loving plants such as reeds and sedges also die, followed by larger shrubs. The last things in a wetland to die are the redgums. With their deep root systems they can linger on for many years but eventually they will deplete the moisture in the soil and die. They will not be replaced by new generations of redgums who need floodwaters to germinate. Much of this goes unnoticed. Often the first inkling that something is wrong is when the trees start to die. By then it is too late.
While most of our agricultural water used in central Victoria comes from snow melt and run-off from alpine regions, a significant amount is pumped from rivers and creeks. In western Victoria river systems have become so depleted that they have dried up, along with their lakes.
The shortage of water in our waterways and wetlands has been exacerbated by lower rainfalls. We are having fewer wet years and when we do have a wetter year it is characterized by extreme weather events, often resulting in flooding.
In some regions salinity has impacted upon wetlands and waterways. While much has been done to counter salinity, the damage to wetlands, especially to the trees, has sometimes been permanent and requires remedial work to allow them to become functioning natural wetland environments.
It is far more effective and cheaper to restore regular flows of water to sustain the wetland environments than it is to restore them after they have been badly damaged. It also ensures an unbroken lineage of species.
The issue with environmental flows is that the water is already allocated for other uses. If water is used for environmental flows, it is at the expense of these other uses (usually agriculture). The Murray-Darling Basin Plan is proving to be very unpopular with the farming community, especially cotton growers (cotton is a very ‘thirsty’ crop). The indications are that the environmental flows implemented in the Plan are insufficient to maintain the environments in these river systems and more water needs to be allocated to them. Blue-green algae is still present along much of the Darling River and hypoxic water still periodically kills off masses of fish. Locally and on a smaller scale the environmental flows into Gaynor Swamp (near Corop) under its management plan have been working splendidly and seem to have the support of local farmers.
Allocating water for environmental flows will continue to be a contentious issue. Somehow a sustainable balance must be found.
