Weather Watch

Central Coast suffering an 'exceptional' drought, monitoring maps say

The National Drought Mitigation Center released its latest drought monitor map for the United States.

The NDMC classifies drought in five categories of increasing severity: abnormally dry, moderate drought, severe drought, extreme drought or exceptional drought.

The latest NDMC maps characterize all of California to be in a severe drought or worse and nearly a quarter of the state — including the entire Central Coast — falling into the most intense category of exceptional drought.

A year ago, none of California was experiencing “exceptional” drought.

The last three rain seasons at Cal Poly (home of climatology for San Luis Obispo) had a total of 39.6 inches of rain, the second driest three-year period on record. The driest three-year time frame occurred from 1958 through 1960, during which only 38.8 inches of rain fell. No other three-year period is near these two.

Unlike 1958-1960, the current three-year drought is warmer. The January through May time frame was the warmest on record for much of California. Those five months averaged 5 degrees warmer than the 20th century average for January through May.

Temperatures are expected to be above normal through the summer. This extended drought combined with record-breaking heat and unusually strong spring Santa Lucia (offshore) winds has left vegetation in San Luis Obispo County with extraordinarily low moisture content. That, in turn, has increased the threat of wildfire.

These dire conditions have increased the challenge that Cal Fire and other fire departments already face to carry out their mission of the protection of life, property and natural resources.

These dry conditions have also ominously reduced the amount of water stored in our Sierra snowpack, lakes and reservoirs. The snowpack only reached 32 percent of its average annual depth this winter with most of the state’s largest reservoirs less than half full.

As of Friday, Lake San Antonio was at 4 percent of capacity, with its water elevation at 652 feet, the lowest on record. The dead pool elevation of the lake is 645 feet. When the lake is at that level, water cannot be released via gravity flow. Currently, 5 cubic feet of water per second (cfs) is being released from this lake into the San Antonio River for environmental compliance. This water eventually flows into the Salinas River.

Nacimiento Lake is currently at 19 percent of capacity with its water elevation at 721 feet. The dead pool elevation at this lake is 670 feet. However, an agreement between Monterey County and San Luis Obispo County sets the minimum pool level at 688 feet or 22,300 acre-feet to insure that a reliable source of water — 12,000 acre-feet — is reserved for San Luis Obispo County. Currently, 26 cfs of water is being released from the lake into the Nacimiento River, which also makes its way to the Salinas River.

Normally during the summer, 400 cfs is released from Nacimiento and 250 cfs from San Antonio. The flow from these lakes, when coupled with other Monterey County Water Resources Agency projects, helps combat seawater intrusion into the Salinas Valley — the “Salad Bowl of the World.”

According to data from SLOCountyWater.org, here are the other San Luis Obispo County lake and reservoir percent of capacity figures as of Wednesday: Lopez Lake in Arroyo Grande at 50 percent; Salinas Reservoir in Santa Margarita at 30 percent; Whale Rock Reservoir in Cayucos at 51 percent.

PG&E is working with water agencies, farmers, first responders and regulatory agencies to help address drought impacts that include increased fire danger, limited water deliveries and environmental impacts. The company generated less hydroelectric power this spring to save water in reservoirs to ensure continuous flows in streams and for generating power this summer when demand is high.

The utility also has helped farmers install low-flow irrigation systems and convert sprinklers to drip irrigation. PG&E also has partnered with Cal Fire’s “One Less Spark, One Less Wildfire” public safety campaign to minimize the frequency, size and cost of wildfires started by human activity.

  Comments