A new study out today from UCLA has some overall good news for megadroughty Los Angeles: the century ahead should bring just about as much precipitation as the city had over the last 20 years of the Twentieth Century, according to a press release from UCLA. Due to rising temperatures, though, that water is expected to arrive mostly in the form of rain; a previous report on snowfall from UCLA had predicted that there would be a 40 percent decrease in snowfall in the mountains of SoCal by the time the middle of this century rolls around. That switch won't just be affecting skiiers.
Even though the precipitation totals should stay about the same, the shift to more rain than snow will pose challenges. Rain runs down mountains and hillsides faster than snow does, meaning that there's a greater possibility for increased flooding. It could also translate into less time for capturing much-needed runoff. Water officials from LADWP, LA County Public Works, and the SoCal branch of the Bureau of Reclamation say the report is a reminder that there needs to be investment in water capture infrastructure. In general, they say the report's results back up their plans to cut down on imported water—"The study gives us confidence to proceed with our utility's plans to increase local water supply from 11 percent this year to 36 percent by 2035," a rep for the LADWP's water system says.
The report also found that while the overall annual precipitation will be about the same for the LA area in the next century, individual years will likely swing between drier years and wetter years, with very few of them being "average" on their own. That pattern is very much like the one seen in the last two decades of the Twentieth Century (which serves as the baseline for the study). The Los Angeles region has always been the rope in a tug-of-war battle between a northern, wetter climate and a southern, drier one, says the report's lead scientist, and that back-and-forth will likely continue.