A few weeks ago, I reported that the first two weeks of December had been exceedingly wet in Southern California. In Los Angeles, 2 days in December had already been the wettest in history for those dates. Although 2 weeks of rain cannot break our severe drought, I stated that it was a pretty good start.
So how did the rest of the month go? Pretty well, it turns out. The rain continued. In Los Angeles, we had measurable rainfall on 6 days in December. It was beautiful. We are up to 4.89 inches for the season (since July 1), most of which fell in December. We are well ahead of our normal rain for this date (4.10 inches).
But water in Southern California is imported, so rain in LA is not a good indicator of the health of our water system. The rest of California below the stormcloud.
The California Dept of Water Resources Data Exchange Center lists 12 major reservoirs around the state and tracks their water storage status on a daily basis. These 12 reservoirs are spread from northern to Southern California and include the largest capacity reservoirs in the system. Overall these twelve account for more than 80 percent of the total capacity of the 46 reservoirs listed at the site. As the reservoirs fill and drain day by day, the website allows comparisons of storage levels with previous years and with normal levels over the course of the water year.
In my earlier report, I noted that we had increased our storage in these 12 reservoirs by over 1 million acre-feet in just the first 2 weeks of December alone. The Table below lists the change in storage for these 12 reservoirs during the full month of December 2014 (midnight Nov 30 to midnight Dec 31). The columns labeled “Storage” show the total amount of water (in acre-feet) in each reservoir on midnight November 30 and December 31. The “Change” column shows how much water each reservoir added or lost during December. As you can see, overall, we added about 2.1 million acre-feet of water in these 12 reservoirs, with the largest, Lake Shasta, accounting for about 40 percent of the increase. The inflows include precipitation as well as inflow from feeder streams and rivers at higher elevations. Yes, it was a rainy month in California. As wet as we were in Los Angeles, Lake Shasta put us to shame, recording measurable rainfall on 20 out of 31 days last month. Remarkably, Shasta reported 6.09 inches of rainfall on December 11 alone. December rainfall across California maintained its early pace throughout the entire month, with most of these reservoirs reporting substantial increases, and making a pretty decent dent in our water storage deficit.
The chart also shows the normal amount of water stored in each reservoir on those dates for comparison (columns labeled “Normal Storage”) and how the current storage compares to traditional levels (“% of Normal”). So for example, Lake Shasta went from 38.7% to 66.0% of its normal level, which means that the rainfall in December was well above average (since average rainfall would have simply maintained close to the same percent of normal). The totals for these 12 reservoirs indicate that the reservoir water levels across the state rose from 42.4% to 57.1% of normal levels. So we are not back to normal water levels in our reservoirs, but we are getting closer.
Is the drought over? Not by a long shot. But we took a big bite out of our deficit in December. Here’s hoping that January and the rest of our rainy months continue these outstanding December numbers.