Water spilled over the Whale Rock Reservoir this month for the first time in 18 years.
The reservoir located on Old Creek Road near Cayucos reached 100 capacity on March 10, leading to the need for the spillway.
The City of San Luis Obispo says the last time that happened was during the 2004/2005 winter season and since the reservoir was completed in 1961, water has reportedly only spilled over a total of 12 times.
The reservoir holds nearly 39,000 acre-feet of water and serves as one of three primary sources of drinking water for the City of San Luis Obispo. The water is also reportedly shared with Cayucos, Cal Poly and the California Men’s Colony.
When full, city officials say the reservoir could supply the water needs for San Luis Obispo for about three years.
Whale Rock is only fed by creeks, so even during heavy rains, it fills slower than other reservoirs across that state that may have larger watersheds or be fed by rivers, according to a post on the City of San Luis Obispo's Instagram page.