By Matthew Power In May, Builder described how a lack of fresh water could threaten future development in areas out west, from Los Angeles to Dodge City, Kan. Already, developers like Del Webb have faced close scrutiny because of the impact their large developments might have on local water supplies.

In Prescott Valley, Ariz., for example, water authorities required a 4,070-acre Del Webb community, to meet a "100-year" standard, meaning that the area would have to have sufficient groundwater to supply residents for 100 years.

Concern over home building's impact on water supplies has now reached the floor of the California Senate. In June, the Senate approved a measure mandating that local governments refuse any subdivision of more than 500 homes unless water supplies can be shown to provide a "sufficient water supply," which is defined as "the total water supplies available during normal, single-dry, and multiple-dry years within a 20-year projection."

According to Ed Pokorney, director of planning for the Denver Water District, however, assessing groundwater resources is extremely difficult. "It's a little like saying there are these huge oil reserves, but we don't exactly know how much is retrievable," he explains.

Sen. Sheila Kuehl (D) of Santa Monica, Calif., asserts that the new California bill is not intended to stifle new housing--simply to ensure better planning for large developments. Her Republican counterpart, Sen. Ray Haynes (R) of Temecula, blames water utilities for not keeping pace with local development.