To the relief of residents throughout drought-stricken California, the National Weather Service and the National Oceanic and Atmospheric Administration both predicted that there is more than a 90 percent chance that an increasingly strong and impactful El Niño will occur in fall and early winter of this year.
An El Niño refers to a large-scale ocean-atmosphere climate phenomenon where unusually warm ocean temperatures along the equator in the Pacific Ocean can potentially cause heavy rainfall in affected areas, especially during the winter season.
What does this mean for Turlock?
Although atmospheric and oceanic conditions point to an nearly-guaranteed El Niño this year, there is no guarantee that even a strong El Niño would bring enough rainfall to replenish Turlock amidst the drought, according to Turlock Irrigation District Utility Analyst Jason Carkeet.
Carkeet said that according to current National Weather Service discussions, the limited record of El Niño events does not indicate any specific precipitation pattern in the Central Sierra Nevada, which includes the Tuolumne River Watershed.
“The bottom line is that the phenomena driving precipitation in the Central Sierra Nevada, and weather in general, appears to be very complicated,” said Carkeet.
Carkeet said that El Niño events in the past that were categorized as strong brought varying rainfall totals to the Central Sierra Nevada. In 1983, the El Niño brought 36.61 inches of rainfall above the area's average precipitation year of 40.8 inches.
However, the amount of rainfall experienced in 1983 — and similarly in 1998, which saw an increase of 24.43 inches from the average precipitation year—is not always guaranteed with an El Niño.
In 1973, for example, the El Niño did not provide a significant boost in rainfall and in 1992, the El Niño not only failed to provide much-needed rainfall, but it resulted in the continuation of the drought.
Despite this, some California residents are preparing for what could potentially be the second strongest El Niño on record by installing floodgates, stocking up on emergency supplies, and getting their roofs checked. Workers in Los Angeles County have even begun clearing basins and channels to prevent possible flooding and collect as much eagerly-anticipated storm water as possible to restore local water supplies.
Although TID staff is constantly looking at various precipitation and runoff scenarios, including possible El Niño effects, they are not making any special preparations like those seen in other parts of the state, according to Carkeet.
“The current level of Don Pedro is such that, given annual diversion demand from the river and current flood-control parameters, no special measures would be anticipated to handle an annual runoff volume on par with some of the wettest years on record—which, ironically, is a sad commentary to how low the drought has driven the reservoir now,” said Carkeet.
However, Carkeet said that TID will continue to monitor weather and climate forecasts and prepare for a wide range of scenarios.
“We are just as eager as everyone else to see what happens this next year with respect to precipitation in the Tuolumne River Watershed,” said Carkeet.