I was browsing gently round the web last night and checked on a few El Nino sites to see how that fickle piece of climatic whimsy is getting along this year. I mentioned in a previous post that this year looked like it might produce an El Nino event and the forecast probability remains high (about 70%) but the predicted strength of the El Nino seems to have been downgraded to moderate/mild.
Good news for India and Australia, where the monsoon fails and temperatures rise during El Nino events, but bad news for California’s long-running and now extreme drought!
Of course California isn’t the only part of the States affected by long-term and serious drought; a glance at the US Drought Monitor site clearly shows how much of the US is now in extreme and long-term drought – practically all the south and west of the country, with dust storms reported in Nevada and Oklahoma, amongst other places.
Quite a few years ago, I read Mark Lynas’s book Six Degrees and was impressed by his account of the history of megadroughts in the American south-west; further reading and research confirmed for me that the geological history of much of the prairie lands of the US is indeed of a land that was, fairly recently, sand-dune desert – and those light, sandy soils are only tenuously held static by vegetation at the moment. These are the easily-eroded soils that are the parents of the dust-storms we’re seeing at the moment – reminescent of the infamous Dust Bowl conditions of the 1930s and certainly worrying some residents of the affected areas! – but they’re also usually part of the agricultural heartlands of the USA. California, while not affected by dust-storms, is one of the most fertile and productive farming states, exporting fruit and vegetables to the rest of the USA and beyond.
These crops can only grow, however, with a supply of water – precisely what they haven’t had falling out of the sky for the last few years. To some extent, irrigation with fossil water pumped out of aquifers or supplied from the reservoirs along the Colorado can replace the lack of rain, so the next stop on my journey of research was to look at the levels of Lake Mead and Lake Powell, the two biggest reservoirs on the Colorado and responsible for supplying drinking water and irrigation water to a vast swathe of the American south-west.
Lake Mead is currently predicted to achieve its lowest ever level (since it was first filled in 1938) during this week, dropping to a water-level of only 1,080 feet. That’s still a lot of water, mind you – 10.2 million acre-feet (for those of us who can’t visualise 10.2 million acres flooded to a depth of 1 foot, 1 acre-foot is 325,851.427 gallons, or 1,233,481.84 litres… so a LOT of water!) To put it into perspective, however, one acre-foot of water is a year’s supply for 1 average Nevadan family, so assuming Nevadan families aren’t very different from other American families, that’s enough water for one year for 10.2 million households.
Lake Powell, upstream, currently holds another 12.7 million acre-feet of water. This lake, however, suffers quite high losses through seepage, as it sits on porous sandstone, as well as through evaporation (it sits in a hotter area than Lake Mead, so evaporation rates are higher) and is estimated to lose in total about 870,000 acre-feet of water a year.
Between them, these two reservoirs supply 7 states with water – California, Colorado, Nevada, Utah, Arizona, New Mexico and Wyoming – as well as Mexico. These states do have other water sources, but the Colorado is the biggest source of supply….. and between them, that’s over 58 million residents (2012 figures), plus the 40 million tourists passing through Las Vegas every year, who could be affected as water levels drop – and I haven’t even looked up the acreage of farmland that’s irrigated from the Colorado!
Figures from Scripps Oceanographic Institute suggest 1 acre-foot supplies 8 people with water for a year, so a quick and dirty calculation suggests that the available 22.9 million acre-feet in the two reservoirs can supply a population of 58 million for a little over 3 years.
Just as well they have a few other water sources, then!
Incidentally, it’s worth reading the whole of that Scripps article I linked to – they also predict a 50% chance that Lake Mead will fall so low by 2017 that the Hoover Dam won’t be able to produce electricity anymore, and they were using historically quite high levels of river flow, as seen over the past century, not the much lower figures suggested by looking at a longer history of the area. If the current drought is merely the beginning of a return to much dryer (and more normal) climatic conditions for the area, then the situation could be worse, and for far longer, than expected.
What impact do all these water-problems in the west of the USA have on a prepper in the UK? If the US wheat harvest is reduced, then the US exports less wheat to other places around the world. That reduces world supply so the price of wheat on the world markets goes up. At the moment the USDA are forecasting that increased yields on the northern plains will offset the reduced harvest further south, but it’s possible that there may be knock-on effects on the price of hard wheat (bread wheat) later in the year.
Or, to be really practical, now is the time to put away a few more kg of pasta and whole-grain wheat in the long-term stores and fill up any spare freezer space with bread and strong wheat flour!