Can we reduce water consumption?
Humans now control most of the world’s rivers, damming and diverting many of them to death. Thanks to us, a quarter of the world’s river systems no longer reach the ocean for at least part of the year. This is drying out swathes of the landscape, emptying wetlands and destroying fisheries. Excess water use threatens humans in three ways:
- shortage of drinking water
- loss of irrigation for agriculture
- changes in climate
Over the past 50 years, dams on rivers in central Asia have dried up the Aral Sea. Without the influence of the sea on climate, the entire region has become hotter in summer, colder in winter and more arid all year. Meanwhile, as rivers run dry, we are pumping out ever more of the underground reserves held in the pores of rocks, many of them fossil reserves that will never be replaced by the rains. We are disrupting other parts of the hydrological cycle by draining wetlands and razing forests. Deforestation of the Amazon will reduce evaporation rates in the tropical Americas, potentially changing weather patterns in the northern hemisphere, including the Asian monsoon.
One hydrologist suggests that preventing regional water crises from disrupting our global life-support systems will require limiting the consumption of river water to around 4000 cubic kilometers per year. That is roughly one-third of the flow down accessible rivers, excluding remote untamed rivers in rain forests and the Arctic. Current use is about 2600 cubic kilometers, but the excess is “largely committed already” for irrigating the crops needed to feed the growing world population. To keep within the boundary while feeding the world, we might have to curb irrigation of non-food crops like cotton or bio fuels. Boundary will be approached by mid-century so we have to find a way to reduce water consumption.
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- Mangroves are disappearing faster then other forests
- Biodiversity on Earth
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