(Portions of this text are reproduced from the Change.LA website)
In the UCLA Department of Atmospheric and Oceanic Sciences study released December 2014, Dr. Alex Hall and his research team looked at the total amount of precipitation—rain and snow—that falls in the Los Angeles region’s wet season, during the months of December through March. Their key finding was that Los Angeles can expect roughly the same amount of total precipitation throughout the 21st century as it received in the last few decades of the 20th century. In the present-day climate, the region experiences wide swings in precipitation from year to year, and the UCLA researchers behind the study expect this variability to continue under climate change.
Over this century, Southern Californians may be at an increased risk of flooding and will have smaller windows of time to capture local water because, although the UCLA researchers found that the amount of precipitation is expected to remain nearly the same, more will fall as rain instead of snow. “Although we don’t expect the total amount of precipitation to change much, we know from the snowfall study that warmer temperatures will cause less of that precipitation to fall as snow,” says Dr. Hall.
Preparing for the Future
While snow stored in the mountains generally melts in the spring, rainfall runs off the mountains immediately, which poses a greater risk of flooding and shortens the chance to capture water. The previous snowfall study’s findings indicate that more precipitation falling as rain instead of snow will result in higher wintertime flows. Neither the precipitation nor the snowfall study quantified these potential flows, but it is possible they would require new infrastructure to bolster the region’s ability to control floods and capture water.
Effects on Environmental Planning
We know that water is often a key issue in the planning process and is a critical factor in new development. As we begin to rely more on rainfall and less on snow, it will surely present new challenges to water retention and treatment and become an issue that local and state government needs to begin to address if we are to fully utilize this changing resource, maximizing retention and minimizing runoff and loss.