Environmental watering - the story behind the stats

Environmental watering - the story behind the stats

9.04.2013 - Posted by David Barratt
The Commonwealth Environmental Water Office 2011-12 Outcomes Report is now available online.  In 2011–12, 680 GL of Commonwealth environmental water was delivered across the Murray Darling Basin (MDB), together with environmental water from state and Australian government agencies and nongovernment organisations. Between 2009 and 2012, 1,233 GL of Commonwealth environmental water was delivered for the environment across the Basin. This water has been used to target various ecosystems and ecosystem functions in need, such as providing fish refuge from the impact of poor-quality water in the Murray River.

The Murray River near Mildura during a period of environmental watering, May 2012. Photograph by Stephanie Secomb, Commonwealth Environmental Water Office

While the name of the game is ecosystem response, these numbers are interesting in themselves. Here are some related numbers for context. These statistics vary a fair bit depending on their source, and also naturally between years and over decades, but they’re in the ballpark. The MDB is one of 12 Drainage Divisions in Australia and is comprised of 23 – 26 river basins, depending on how they’re defined. On average, it receives about 520,000 GL/year of rainfall and yields an average run-off of approximately 23,000 GL/year. Annual surface water use in the MDB can be up to 10,000 GL or more. Average annual outflow at the Murray River mouth is around 12,000 GL under natural conditions and around 5,000 GL under current conditions.

Averages are the worst of statistics for most natural resource management data and need to be treated with caution, but nonetheless you can see we’re talking about some big numbers here. Once upon a time, runoff in the Murrumbidgee River Basin alone was around 3,500 GL, with probably about half that number flowing into wetlands and the Murray.

So, 680 GL of environmental watering across the Basin in a year may look impressive, but in the big scheme of things it isn’t that massive a number. Nonetheless, targeted at the right places and at the right times, it’s very valuable and a lot more water than has been available for a long time owing to agricultural development and more recently drought. It’s an increasingly large step in the right direction.