UN World Water Day 2014

Today is the day that the attention of the world is focussed on water, a resource that is becoming increasingly scarce in many parts of the globe.

We look at the oceans, 71 per cent of the earth's surface, and wonder if that salt water can somehow be harnessed to solve our growing shortage of fresh water. Human beings have been separating the salt from the water in sea water for millennia: ever since salt was more valuable than water, as one researcher has pointed out. Desalination plants, however, do not provide a simple, consequence-free answer.

There are a number of different processes for extracting the salt from salt water, but the most common involve either forcing the water through membranes which capture the salt or reducing the pressure and heating and distilling the water to evaporate out the salt. Both methods require a lot of energy and both produce brine or salty residue as a byproduct. This brine must be disposed of somehow, usually by mixing it with fresh waste water and dispersing it over golf courses or other open ground. It cannot be pumped directly back into the sea because it contains no oxygen and its salt content is twice that of sea water making it dangerous or fatal to marine life. Furthermore, the salt water must be chemically treated before desalination, especially when using membranes, to remove bacteria and add necessary elements. Those chemicals must be disposed of somewhere.

Desalination plants also threaten fish and plankton because their intake apparatus and filters are designed to destroy any solid matter in the water.

In spite of these drawbacks, many arid nations do rely partly on desalination technology. Saudi Arabia has huge plants, and Sydney, Australia, and the Caribbean island of Aruba are leaders in the adoption of new desalination technology. The biggest plant in the United States is in Tampa Bay, Florida, and various cities in Texas and California are funding pilot projects to find ways to incorporate desalinated water into their civic plans.

Because we are surrounded by water, and we play in it most weekends, Canadians think that we have an abundance of fresh water. I hope that the past week's blog posts have shown that we actually don't. We use an average of 329 litres of water per person per day and that's just our domestic use. If you add industry and agriculture, we use much more. Our population is much lower than that of the US, and the average American uses comparable amounts. Those of us lucky enough to have taps, overuse them. And one of these days, those taps are going to run dry. We rely on water for life and we need to treat it with respect.

In honour of World Water Day, the Guardian published a quiz. See how much you know about water use worldwide. Some of the answers will shock you.

Tomorrow, I'll conclude with some information about the Arctic, where the problems of climate change can be seen most starkly.