Dear Stan, This is an article that I sent to a gardening magazine in Australia. I know that most of the content is local but you will easily get the gist of the flexibility of using metric prefixes for water use.
Water, water, everywhere Many Australians are becoming used to the calculation that one millimetre of water falling on a square metre of our roof gives us a litre of water in our rainwater tank. This is easy. At our house the side of the roof that feeds our tank is 20 metres long and 5 metres to the ridgeline, so each millimetre of rain gives us 100 litres of water in our rainwater tank. Whenever we have a few millimetres of rain (say 7 mm) we simply multiply by 100 to estimate that we now have an additional 700 litres of water in our rainwater tank. We have a traditional suburban house allotment about 20 metres by 50 metres or 1000 square metres. Whenever a millimetre of rain falls on this block we gain 1000 litres, or one kilolitre, of water, which we can visualise as a cubic metre of water. For 1000 houses in our suburb a single millimetre of rainfall gives us a collective 1000 kilolitres or one megalitre of water. Using 7 mm of rain as an example, we receive 7000 litres or 7 kilolitres of rain on our suburban block and the neighbourhood gets 7 megalitres of water. Our basic water calculations are based on this rule: One millimetre of rainfall per square metre equals one litre of water. On a slightly larger scale: One millimetre of rainfall falling on 1000 square metres equals one kilolitre. And on an even larger scale: One millimetre of rainfall per square kilometre equals one megalitre. One millimetre of rainfall on all of Australia is 7 700 000 megalitres. Assuming an average rainfall of 400 millimetres then Australia's total annual rainfall amounts to about 3 000 000 000 megalitres (3 petalitres) each year. At the end of World War 2, Australia had about 7 million citizens and the government was about to embark on an ambitious program to accept war refugees in large numbers from displaced people in Europe. Australian scientists at that time recognised that water supply and therefore rainfall was the ultimate key to sustainable human settlement in Australia. Despite the fact that we have a large area available for settlement, the scientists recognised that this large area was useless without adequate water. In 1953, at the Australia and New Zealand Association for the Advancement of Science (ANZAAS) Conference in Brisbane, discussion focused on Australia's ultimate, sustainable, human carrying capacity. This was at a time when there was little, if any, evidence of global warming or climate change and their estimates were based on the level of water use at that time; they did not include the extra water wanted for en-suite bathrooms, pools, and spas. The ANZAAS delegates reached a consensus that a population of about 20 million would be as much as rainfall and water supply in Australia could support. By the end of 2007, Australia will have a population of 21 million. This is based on the current population of 20.7 million that is estimated to be growing at a rate of one person every 2 minutes and 11 seconds. This is 28 people per hour, 660 people per day, or an extra 241 000 people each year. Pat Naughtin ([EMAIL PROTECTED] ) On 2007 01 26 10:17 PM, "STANLEY DOORE" <[EMAIL PROTECTED]> wrote: > > ----- Original Message ----- > From: STANLEY DOORE <mailto:[EMAIL PROTECTED]> > To: Potomac River Basin <mailto:[EMAIL PROTECTED]> > Sent: Friday, January 26, 2007 5:20 AM > Subject: Use metric units > > FROM: G. STANLEY DOORE > 2913 Shanandale Drive > Silver Spring, MD 20904-1822 > Tel.: 301.572.4939 E-mail: [EMAIL PROTECTED] > > > 2007 January 26 > > TO: Potomac River Basin Commission > 51 Monroe Street Suite PE-08 > Rockville MD 20850 > > Thanks for your Potomac Basin Reporter. And thanks for the article titled > "Free Water for Everyone" in the Nov/Dec issue. The article would be much > more useful and understandable if you used the SI (International System of > Units) instead of conventional English units of measurement. Why? > > The SI is a coherent system where length, volume and weight are interrelated > and are easy to use. For example: > > One cubic meter of water contains 1000 liters (kL or kiloliter) which weighs > (has a mass of) one metric tonne since one liter of water weights one kilogram > (2.2 pounds). A meter is a little more than a yard in length. > > Also, one millimeter (1/1000 of a meter) of rain in one square meter equals > one liter of water. > > See how it all fits together? The U.S. Metric Association (USMA) has a great > chart which shows the relationship of standard metric units. The USMA web > site is: www.metric.org <http://www.metric.org> . > > I recommend you begin to use the SI as the basic system of measurement. I > look forward to seeing it used in the future. > > Regards, > > > G Stanley Doore > Meteorologist Retired > > >
