19 August 2012
Guest blogger
“We consider ourselves the canary in the coal mine for climate change-induced changes to water supply systems.” Ross Young, executive director, Water Services Association of Australia
We live in the only period in history where water can be moved around in quantity by means other than gravity. While water is falling from the sky, it’s free; the moment it hits the ground it has a value and that value is directly proportional to the effort required to get it to where it’s needed to sustain life. If water cannot be made available where we want to live, then the choice is simple: move or die. Large numbers of people can only function in towns and cities as a single entity if sufficient water can be delivered to them on a regular and reliable basis.
If each of us had to make our own arrangements to collect our daily water needs and dispose of our own wastes, then healthy communal living much above the village level would be impossible. Water is heavy stuff to move around: 1 litre of it weighs 1kg. Try carrying 25 litres 5 miles back from a well to a family of thirsty children and water becomes very precious indeed. This is energy used to move water, at first hand, with no input other than human muscle. With that kind of work outlay, there’s little time left to build a city.
We recognize that our developed civilization is energy driven, but to a great extent that energy has been put to use pumping our water systems.
We need 2 litres of clean water every day to stay alive, the human body is 70% water, and losing 1% of it brings on acute thirst. A loss of 10% will cause death if it is not replaced quickly. Our digestive systems are adapted to use meat, fish or vegetables for food, but clean water intake is non negotiable.
We have created an alternative lifestyle of cleanliness and food safety that needs vast amounts of water. Our food delivery and waste systems demand a daily input of 2000 litres of water to supply the food eaten by each of us and dispose of the waste. That’s 500 times more liquid than we take in directly. The modern city is exactly like the human body; it cannot survive without the means to pump clean water in and wastes out. If we can’t find the means to maintain that input-output, then our towns and cities, just like our bodies, will slip back 500 years to a medieval condition: dirty and disease ridden and subject to every unpleasantness that nature can devise.
Our water supply is much more than turning on a tap and drinking the stuff.
Imperial Rome had a population of about one million. How much energy did they use to provide the city with water? To a first approximation, the answer is “none” – they let the water run downhill, along aqueducts built for that purpose. Today in the Middle East, water for irrigation is lifted out of rivers by a noria – a circular bucket chain. Again, zero energy input is required; the noria is turned by the flow of the river.
If you develop a technology that works with Nature rather than against her, you use much, much less energy. A lesson the modern world has chosen to forget.
an interesting and useful comment, in that you missed the point about energy entirely
The Roman aqueduct system represents an energy investment, in just the same way as digging a coalmine, drilling an oilwell or ploughing a field.
An aqueduct on the Roman scale would take several years to build, using the muscle energy of human beings and animals, during which time there would be no return on investment. But there was still an enormous energy input which had to be justified by the output when it was completed. the output of course was an unsustainable population growth, just like we’ve had from the input of oil and coal. That’s why Rome ultimately collapsed, and demonstrates that our civilisation will ultimately collapse.
you cannot develop ‘technology’ without energy input.
all other water movement systems work in the same way, you have to build it first, ie invest energy, then you get a return on that energy
Thank you, Norman. I was of course aware that actually building the aqueducts required energy, but simply ignored it. A Roman aqueduct was classified as a “military” structure, and hence was designed for a useful life of 200 years. (Of course, many of them lasted much longer) Well, the Aqua Marcia, the longest and most expensive one Rome ever built, was constructed in two years. It needed a lot of workers, but it provided water to 100 times as many people as were needed to build it. I submit that an upfront cost of 1% in time, and 0.01% in energy, is negligible.
The construction of the aqueduct system represents an energy investment in human muscle power, from which Rome prospered and subsequently was able to breed more people. Rome had to buy that muscle power from somewhere, if only in the food necessary to keep slave labour alive and functioning sufficiently to cut and move necessary stonework.
In our modern era, we used the same concept, of paying miners effectively slave labour wages to dig out coal to drive engines which powered the industrial revolution, enabled deep drilling of oilwells which in turn powered the engines that powered our agricultural revolution .
that gave us more food, and more people. Oilwells in the 30s also provided the 100:1 ratio, with the same result.