There is no shortage of water. Amounts available vary regionally and change over time as precipitation amounts vary. Demand also changes with increases in population and economic development. Crude estimates indicate water use per person is 15 liters in undeveloped countries and approximately 900 liters in developed countries. Throughout history humans have developed remarkable techniques and technologies to deal with these issues. Few of these attempted to reduce demand, most worked to increase supply.
Some societies went to great lengths. The extent of the Roman Empire is delineated by the construction of aqueducts and lead mines developed to produce pipes to carry their water.
Major advances, considered important turning points in human development, are technological controls over weather. Fire, housing and clothing created microclimates and the ability to live in more extreme conditions. Irrigation was first introduced in the Fertile Crescent (Figure1) driven by a climate change. A region that produced crops gradually became drier with the onset of a warm period called the Holocene Optimum. Besides the decrease in precipitation there is, at least initially, an increase in variability.
Figure 1: The Fertile Crescent. Source
Roman Aqueducts and Wa...
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The objective is to stabilize supply so that plants get the moisture they need to suit their growth pattern. The contradiction is that as the supply decreases the demand increases.
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One list of the top 20 weather disasters of the 20th century illustrates the contradiction. It was dominated by two extremes, droughts and flooding. Samuel Taylor Coleridge wrote to the contradictions in the Ancient Mariner,
Water, water, everywhere, And all the boards did shrink; Water, water, everywhere, Nor any drop to drink.
It’s the problem for those who claim there is water shortage or that supply is threatened. It’s estimated there’s enough in Lake Superior for total US demand for a year. Compare this with the volume in the oceans, but that’s the Mariners contradiction. Many suggest the oceans have an almost unlimited supply, but this raises the second issue with supply, namely quality. Plants and animals require a certain quality of water, few more demanding than humans. Before we can use ocean water we have to remove the salt. Our tongues are a sensor to protect us from ingesting too much salt with an ability to detect 200 parts per million (ppm), anything above that level is increasingly dangerous. Average salt content in seawater is 34,000 ppm.
One outcome of the Titanic disaster was the shift to desalination plants on ocean going vessels. The Titanic carried massive volumes of freshwater because large volumes of water are a measure of luxury. When the buoyancy tanks designed to keep the ship afloat were flooded it added dangerously to the onboard water volumes. Desalination requires energy to remove the salt. Surplus heat from the engines, usually vented through the funnels, is readily available.
November 5, 2010
