My younger daughter Jemima (a teenager at last) has recently completed a homework assignment on hydroelectric power in Brazil (as you do). It's actually on YouTube.1 I was able to supply her with a snippet of information that I had recently gleaned, that parts of Brazil are suffering from severe drought, with some reservoirs at only 5% of their capacity. In fact, the drought has been so bad that some of the Carnival parades that take place in Brazil at this time of year have been scaled back (such as the most famous, in Rio de Janeiro) or cancelled altogether, with towns saying that they couldn't spare the water to clean the streets after the parades.
I wondered to myself what would happen if the reservoir capacity reached zero. At the moment, the water supply is being constricted by turning it on only for a few hours per day. When the reservoirs hit zero, they can turn on the water supply as much as they like, and nothing will come out of the taps (or the toilets or the showers). As anyone who has ever been camping or caravanning will know, water becomes the centre of your universe. Without water, nothing can happen - no cooking, no washing up, no wet shaving, no coffee and no tea. Not for nothing do scientists say that the prime requirement for life to occur elsewhere in the universe is the presence of water. To our understanding, life requires water: where there is no water, there is no life.
The day that the taps run dry will be a shock, akin to the moment that my air-tank ran out of air while still 18m down in the Gulf of Thailand, where trying to suck in more air has no effect (what happened next is another story). Just as you cannot live without air, you cannot live without water. Okay, maybe you can live for a week without water but after that, you die. So, when the taps do finally run dry, what will those people do? What would you do? You would move to somewhere with water.
This kind of thing has happened before. The great Mayan civilisation of Central America, which flourished for hundreds if not thousands of years, may have been fatally impacted by relatively mild drought in the 800s and 900s BCE. As Professor Eelco Rohling of Southampton University says, "These reductions amount to only 25 to 40% in annual rainfall, but they were large enough for evaporation to become dominant over rainfall, and open water was rapidly reduced."2 Researchers found that a relatively modest decline in rainfall was enough to deplete freshwater storage systems in the Yucatan lowlands, where there are no rivers. "Societal disruptions and abandonment of cities are likely consequences of critical water shortages, especially because there seems to have been a rapid repetition of multi-year droughts," added Prof Rohling.
Abandonment of cities? That couldn't happen today, could it? A recent study of the continuing effects of climate change3 suggests that it could. Longer droughts (longer even than the current decade-long drought in California) of perhaps 20, 30, 40 or even 50 years are forecast to occur again in the western US and Mexico by the end of the century. Researchers went back into proxy climate records (tree rings) and found that droughts of these durations were much more common in the great drought epochs of the so-called 'Medieval Climate Anomaly' in the US in the 12th and 13th Centuries. If the atmosphere warms as some models suggest, then after 2050 the Southwest and the Central Plains in the US would likely shift to even drier conditions than even the previous 'mega-droughts.' Toby Ault, a co-author of the study, pointed out that if Tuscon in Arizona, where precipitation has been at 80% of expected levels since the late 1990s, continued at the same level of rainfall for another two decades, it would qualify as being in mega-drought conditions.
Now, I'm not a strong believer in man-made climate change. In fact, recently I went to a lecture by climate scientist Professor Christopher Essex where he pointed out that the basic Navier-Stokes equations underlying much climate modelling have yet to be solved in 3D, while the spatial resolution required for even the most basic-but-realistic model of the global climate has not been remotely approached. Oceanic circulation and the interaction of oceans and atmosphere are vastly under-researched. He pointed out that the role of water vapour in the atmosphere has not been quantified (overall, is it a positive or negative greenhouse gas? They're still arguing this very point4). He suggested that current climate models were effectively 'hokum.' Maybe, but the taps in Brazil are running dry, and they might also do so soon in parts of the world's wealthiest country, the USA. Water, for drinking, for making cups of tea and for use in your process, is going to become much more valuable in the near future. Are you prepared?
1 https://www.youtube.com/watch?v=GKOZTeov9Ns
2 http://m.bbc.co.uk/news/world-latin-america-17149812
