As the populations of urban areas around the world continue to grow, the demand for water has also grown. In the arid areas of the western United States, growth in some metropolitan areas threatens to outstrip the supply of water. VOA's Greg Flakus reports from Dallas, Texas, where water supplies are being strained.
The population of Dallas and its suburbs has grown by more than 12 percent in recent years.
The urban area relies for the most part on nearby reservoirs, artificial lakes, for its water. But drought has reduced the volume of one of the principal lakes, Lake Lavon, which has dropped around five meters in the past two years.
The lake is managed by the US Army Corps of Engineers. The chief manager for Lake Lavon is Ken Robinson. "What has happened is that the water gradually goes down and, as it does, the silt in the bottom of the lake holds the moisture,” he explains, “and so you get this green growth coming up on what is essentially, normally under water."
The drop in water level has reduced the lake's recreational and aesthetic appeal.
"People like to build houses where they have a view of the lake, but they also like to have a lake that has water in it," says Robinson.
The drop in Lake Lavon's water level has put some strain on the North Texas Municipal Water District, which uses water from the lake to supply one-and-a-half million people in the Dallas area.
Executive Director Jim Parks says lower rainfall over the past couple of years is a reminder that water should not be taken for granted. "I think people have come to consider this area of Texas as if it were a semi-tropical area, when, in reality, this part of Texas is more semi-arid."
The water district has imposed mandatory restrictions on water usage and is encouraging even more conservation by consumers. But as more houses go up and more people move into the area, the demand for water is growing.
At Texas A and M University, Professor Ron Griffin studies urban water use. He says the abundant water that supported growth in urban areas is reaching its limits. "We have already tapped the cheap sources of water and so, as we proceed further with more and more growth, we will progressively tap more and more expensive sources of water."
Professor Griffin says there is water available to support more urban growth, but not necessarily at current levels of usage. "We can deal with large population increases, but only if we curtail, on a per-person basis, our water use."
He says the rising cost of water will eventually force hard decisions on its use for such things as large lawns and landscaping.
"It will be a gradual process, it won't be an overnight sort of thing,” says the professor. “It will be something motivated by the increasing cost of water supply and the expenses that households, cities and industries face."
Jim Parks says the doubling of population projected for the Dallas area over the next 50 years will require a lot more conservation as well as development of new resources.
"It is a multi-faceted program that involves the implementation of more aggressive conservation, building of new reservoirs, connections to existing reservoirs, using existing supplies, such as lakes to our north and southeast and east of here and pulling all of those things together in order to meet that growth."
Surveys show that most Texans support water conservation and want the state to do more to promote it.