Guest essay by Eric Worrall
According to UNSW academic Dr. Clara Stephens, future extreme rainfall will fail to fill Aussie dams, because the drier ground will absorb too much moisture.
What you might not realise about the flow-on effects of climate change
Fri 14 Aug 2020 10.42 AEST
In the coming years, we are likely to see more extreme weather conditions. We will need new engineering approaches to manage the complex impacts on our water resources, writes Dr Clare Stephens.
Changing rainfall, evaporation and soil
Climate modelling suggests that, in the coming years, average rainfall will decrease over much of the continent. Simultaneously, extreme rainfall is likely to increase, bringing heavier downpours.
Much of the rainfall over Australia is lost to evaporation. The “thirst” of the atmosphere is measured by its evaporative demand. Since the Millennium Droughtbegan in the 1990s, higher temperatures have driven evaporative demand up by increasing the air’s capacity to hold water vapour.
Decreasing annual rainfall and increasing evaporative demand will tend to result in drier soil. Drier soils are more absorbent, so less rain runs directly into waterways. This means that, even if we get heavier downpours in the future, they won’t necessarily produce the floods we rely on to fill dams. Unfortunately, this flood-reducing tendency won’t apply equally to urban environments (where it might actually be helpful) because we have paved over that absorbent soil in cities.
This echoes Tim Flannery’s famous prediction that Aussie dams would never fill again – shorty before record flood years.
Predicting the end of rain is an old game. In the 1920s American hit music hall song “It aint going to rain no mo’”, full of rude verses which poke fun at alarmism, was a worldwide success – not a bad effort in the age before mass media.
via Watts Up With That?
August 16, 2020 at 08:36PM