DRYING DELTAS

The Colorado isn’t the only great river that has been kept from the sea. The Indus river delta in Pakistan was drying out when it was rescued by a natural disaster in 2010. Flooding from monsoon rains killed thousands of people along the river basin. But when the water reached the delta, it had a more positive effect. Ecosystems that people living in the delta depend on were replenished by the massive influx of fresh water – a dwindling commodity since Pakistan, India and China began to dam the river in the 1940s. There were other benefits, too. The Indus delta is home to the world’s largest arid mangrove forest, which needs a regular supply of fresh water to keep damaging salt water out. The floods also boosted the habitat of the critically endangered Indus river dolphin. Many of the world’s largest rivers have the same issues. The mouth of China’s Yellow River maintains its tenuous connection to the ocean only through massive engineering works. Australia’s largest river, the Murray, fails to reach the sea for 40 per cent of the year. Michael Cohen at the Pacific Institute in California points out that one of the greatest achievements of the project to bring the Colorado river delta back to life is showing that binational cooperation is possible. “There are a lot of these international rivers and people are looking at ways to handle them,” he says.