This post continues a monthly series of posts about California’s drought, with weather data from my hometown of Los Altos, south of San Francisco.
Our rainy season started in October, but we only received a third of our normal October rainfall. The pattern of above-normal overnight lows continued. The National Weather Service predicts that the drought will continue in our mountains through January 2015. This prediction is significant because most of California’s water comes from the mountains, and over half our annual rainfall normally comes during this period. Our county has cut water usage 11%, good but only half the 20% reduction that our governor asked for. Groundwater overdrafts continue as California and our county pump more groundwater than is replenished.
Continuing the trend we’ve seen, our October high temperature was normal, and our low temperature was above normal.
Our October rainfall was a third of normal, with .26 inches of rain instead of our normal rainfall of .76 inches.
The below-normal rainfall in October adds to the drought as our cumulative rainfall falls farther behind our normal rainfall. The low rainfall increases the stress on our wildlife and plants that just survived the dry summer and now expect moisture and vegetation. Deer and mountain lions are coming down from the parched mountains in the bay area and the Sierras. Some California native plants, such as coast live oaks, are summer dormant to get them through the dry summer, and they are active in the winter. I’ll water our coast live oaks this winter.
The US National Weather Service now predicts that the drought will persist or intensify through January 2014. As seen by the brown area on the above map, the Weather Service prediction of continuing drought includes the Sierra Nevada Mountains, which collect most of California’s rainfall and eventually supplies coastal cities of San Francisco and Los Angeles, as well as agricultural areas like the Central Valley.
This forecast extends the drought period by one month, encompassing most of California’s upcoming rainy season. For example, in the San Francisco Bay Area, we receive over half our annual rainfall between October and January. If this weather forecast proves to be accurate, we would have only have two months (February and March) of rainy weather before our dry season next summer, making it more likely that our drought would continue into a fourth year.
Because of the drought, California has been pumping more groundwater at an ever-increasing rate. The Los Angeles Times reports “This week, scientists working on the GRACE mission released a series of images that reflect the drastic loss of groundwater over the last dozen years.” “Worst hit, according to NASA, are the Sacramento River and San Joaquin River basins, where water has been pumped out to support agriculture in the Central Valley and elsewhere. Since 2011, the amount of water removed from these river basins each year added up to 4 trillion gallons. That’s “an amount far greater than California’s 38 million residents use in cities and homes annually,” NASA noted.”
In our valley, we too are overdrawing groundwater, taking more out than we are putting back. Our local water board reports “The groundwater level in Santa Clara Plain (San Jose) is about 29 feet lower than last year and about 39 feet lower than the five-year average”.
Based how much we’re putting into the aquifer and taking out, I expect groundwater overdrafts to continue. As shown below, our recharge (replenishing the aquifer) has dropped to close to zero since February. Our local reservoirs are low so we no longer have water to recharge the aquifer. The second chart shows that groundwater pumping is higher than past years, which include the first two years of our drought. Our county is overdrawing thousands of acre-feet of groundwater every month, and this will continue until we get rain.