During my recent holiday in California I received NASA’s Natural Hazards ‘weekly update’. It arrived on my phone while I was in Los Angeles, relaxing by a gurgling water feature.
The following sections have been updated in the past 7 days.
— CROPS AND DROUGHT (1 updated events, 1 new images) —
DROUGHT IN THE WESTERN UNITED STATES
A serious drought settled over California in early 2014.
*** Image from Jul 07, 2014 (Posted on Jul 23, 2014 4:32 PM)
I was shocked to find that I was apparently on holiday in a ‘natural hazard’.
The e-mail highlighted recent research that tried to assess the net long-term reduction in water resources in the Western US, including not only above-ground reservoirs but also underground water. The basin of the Colorado river is apparently down by 65 cubic kilometres in the last 14 years. It may seem unnecessary to say – but a cubic kilometre is a truly phenomenally large amount of water!
These measurements – based on detection of minute changes in the gravitational effect of ground water on satellites (!) – are very difficult. And so it is hard to know exactly how much one should trust their detailed conclusions. But their general conclusion seems pretty sound: California is drawing on its water resources at a faster rate than those resources are being replenished.
This is news to nobody. While in California we saw many adverts and heard radio anouncements urging water conservation. Even amongst the extravagance of Hearst Castle, there were no fountains, the swimming pools were empty, and the toilets were replaced by chemical toilets
But nothing conveys the magnitude of the problem more powerfully than the declining level of the largest reservoir in the US: Lake Mead, trapped behind the Hoover Dam.
Since my previous visit in 1986, the level of water in the 600 square kilometres of Lake Mead has fallen by approximately 36 metres, representing the loss of 21 cubic kilometres of water storage. The lake is now less than 40% full.
This level represents the balance between the water drawn from Lake Mead, and the inflows from snow-melt in the Colorado mountains.
Inflows to Lake Mead are typically 10 cubic kilometres annually but annual outflows have been around 11 cubic kilometres.
The low level of Lake Mead in some ways represents a triumph – this is why the Hoover Dam was built: to allow water users to be able to rely on water being available through a drought.
But the prolonged decline results from poorly-drawn water ‘rights’ that allow states to withdraw water at a rate exceeding the long-term average.
When the level reaches 1075 feet – the red line on the graph – then water restrictions will be automatically implemented and presumably the level will stabilise and hopefully recover.
What struck me powerfully on my visit to Las Vegas and the vast metropolis of Los Angeles was that water is the sine qua non of civilisation. And these cities have been built in a natural desert.
Of course all that is required is a reduction in water usage, which will probably equate to an increase in the price of water.
It is hard to see how this situation will evolve – but the first rule of futurology is that the future is likely to be similar to the present day, but different.
And perhaps all that it will take is for the growing of crops less suited to the desert (such as rice!) to move to other parts of the world.