Many discussions of water conservation create the impression that households are large and inefficient users of clean water for drinking, eating, bathing, and toilet flushing. That is a myth. About 40 per cent of all the freshwater use in the United States is for irrigating land for agriculture, another 40 percent is used to produce power, and only 8 percent is used for domestic use; these percentages are similar in other countries. Moreover, about a third of all the water used by households in rich countries goes to water lawns and for other out door purposes, so probably no more than about 5 per cent of the total demand for water is for personal use.
There is a great deal of focus on household use because that's where there is the greatest flexibility in consumption.
Water used is usually a poor measure of the net amount of water consumed since much water is returned either immediately, or after evaporation and condensation, to the source pool, where it can be used again.
The problem in the West is that the water is piped from areas with the greatest amount of water to areas with the least amount of water. Consequently, there is always an imbalance and the water when it evaporates doesn't necessarily go back to the source pool.
Thermoelectric plants use a lot of water for cooling purposes, but typically have a very high reutilization rate (about 98 percent). Household use is also efficient, with a reutilization rate of about 75 percent. As a result, neither power producers nor households are big net consumers of water. Irrigation of farmland absorbs much water since most irrigation systems have low reutilization rates. In California, the biggest water using state, irrigation systems have a reutilization rate of only about 40 percent...,/I>
CA's San Joaquin Valley is one the breadbaskets of the US. It feeds the western half of the nation. Irrigation is absolutely necessary. In fact, irrigation is an absolute necessary for any farmlands that are east of the Sierra Nevadas of CA and the Cascades of the Pacific Northwest. |
