UNESCO Chair says extraction, more than climate change, is causing rivers to run dry
As global temperature rises, it is predicted that river flow regimes will change, affecting the lives of billions of people. Some countries have already seen a sharp decline in water availability in recent decades. Though it may be tempting to blame climate change, high levels of water extraction may more accurately explain why rivers are running dry, according to Professor Quentin Grafton.
In a guest lecture at Oxford University on 29 October, Professor Quentin Grafton explored reasons behind reduced river flows in four river systems. The research has recently been published in the journal Nature Climate Change. Grafton is the UNESCO Chair in Water Economics and Transboundary Water Governance and Director of the Centre for Water Economics, Environment & Policy at the Australian National University.
Grafton’s research focuses on river basins at latitudes where climate change is predicted to exacerbate drying trends. He presented insights from four river systems – Australia’s Murray-Darling, North-America’s Colorado, Southern Africa’s Orange-Senqu and China’s Yellow River – and compared the impacts of water extractions and projected climate change on river flows in these basins.
Historic records show a dramatic decrease in flows in the four rivers. Over the past five years, the median outflow of each river, as a proportion of its modelled natural flow is: 0% for the Colorado, 41% for the Yellow, 12% for the Murray-Darling and 33% for the Orange-Senqu. The Murray-Darling river now stops flowing 40% of the time, compared to just one per cent in the past.
But the science shows that there has not been any long-term decline in rainfall in these areas. Instead, streamflows are declining due to excessive water extractions to meet escalating demand, and therefore poor water governance is to blame.
Bad planning rather than climate change then may underlie the current crisis in the Murray-Darling basin, suggested Grafton. Irrigation is practiced on only two per cent of its area, but accounts for a massive 90% of water extracted from the system. The critical challenge is how to balance water use for irrigation with maintaining flows to keep the river ecosystem healthy.
But these findings are encouraging, Grafton said. By setting up policies and frameworks for better water governance, rehabilitation of these rivers is possible. For example, the Murray-Darling basin is home to the world’s largest water market and this has facilitated the reallocation of water for environmental flows. Crises can catalyse water reform, as long as good evidence is available to support decision making.
By Emma Weisbord, MSc Water Science, Policy and Management