River Flows Fact Sheet
Rivers and wetlands throughout the Murray-Darling Basin are receiving too little water to remain ecologically viable, or being flooded at the wrong time of year. Too many dams and weirs and too much thirsty irrigation have reduced average flows to the sea by 80%. Drought-like conditions now occur at the Murray mouth more than six out of ten years on average, compared to once in every 20 years naturally.
Excessive regulation of flows and over extraction from rivers for irrigation have reached such levels that many floodplains are severely degraded. The frequency of medium sized floods at the South Australian border have fallen by 57%, robbing the internationally protected Chowilla Floodplain of essential flooding. Importantly the frequency of large floods has fallen by two-thirds - scotching the notion we can't influence big floods.
We have tamed magnificent rivers like the Murray and Murrumbidgee, treating them as pipelines for irrigation, and drains for our waste. Floodless floodplains and dry wetlands are the norm across much of the Murray-Darling Basin. Without frequent small-to-medium floods the cycle of life - the boom and bust of rivers in a dry land - falls apart.
Cotton irrigation in northern rivers has significantly reduced flows whilst in southern valleys rice, dairy and horticulture have even larger impacts. In the Barwon and Darling Rivers median low flows have fallen by roughly half due to over extraction for irrigation. Water bird breeding in the internationally renowned Narran Lakes in northern New South Wales has fallen by two-thirds due to excessive cotton growing in Queensland. Another badly affected river is the Murrumbidgee in southern New South Wales where flow volumes have also declined by two thirds.
Floodplains and rivers have a symbiotic relationship. Floodplains need frequent flooding from rivers to remain healthy. And rivers rely on the biological activity generated on floodplains during a flood to be washed back into the river channel to support fish and other aquatic life.
Environmental flow releases are crucial for restoring rivers like the Murray. Victoria, New South Wales and South Australia have been dragging the chain for years on cooperatively managing environmental flows along the Murray. Parochial attitudes and poor communication between governments prevent the coordination of dam releases, weir manipulations and restrictions on irrigation extractions.
Weirs must be managed in sympathy with nature - not against it. Weirs should be routinely raised and lowered to match natural flow patterns.
Reversing flow patterns means many wetland plants and animals don't get the conditions they need to breed. Instead of rivers swollen with spring rains and snow melt, big dams capture whole floods and dribble them out in summer and autumn for irrigation.