These 4 Things Need to Happen to End California’s DroughtJen Clopino
The Golden State is being drenched this week by heavy rains and snow driven by a powerful El Niño. But quenching a years-long thirst takes more than a few storms.
1. Four More Months! (of Storms)
The rain and snow that have fallen so far is not nearly enough. Most of the rain hitting Southern California won’t refill reservoirs. It may help fill some aquifers, but much of it will simply flow into the sea. It’s the moisture that falls as snow in the mountains that is the most important for water supplies.
The pace of that snow needs to continue during much of the next four months, the region’s wet season. So far, the forecasts look encouraging—thanks to the strong El Niño—but the weather through March could shift.
2. Storms in the Right Place
It’s not just the amount of moisture that falls, it also needs to be in the right place—i.e., over the mountains. It can’t be just along the coast, where too much will wash into the sea. The storms also can’t get shunted to the north.
That’s exactly what happened last year, when a persistent “ridge” of high pressure blocked storms from hitting California. So far this year that hasn’t been a problem, but Gehrke says it remains a “lingering concern” because long-term forecasting remains an inexact science.
3. Below-Freezing Temperatures in the Mountains
Another El Niño year, 1983, happened to be a relatively cold year, and the Sierra snowpack hit record levels. However, in the 1997 El Niño, temperatures were higher, and much of the precipitation fell as rain rather than snow. Much of that water flowed into the ocean via flood control channels, and the resulting snowpack was much smaller, leaving less runoff to fill California’s reservoirs in the spring.
Predictions suggest this year should remain cooler in the mountains, but Gehrke cautions that only time will tell.
4. True Recovery Takes Time
Even if the state’s reservoirs do fill up, effects of the drought will linger. Scientists will have to monitor how much the state’s highly tapped groundwater aquifers have a chance to refill. Also, the state is losing millions of trees to dryness and bark beetle invasions. That, in turn, is driving up wildfire risk.
Because of the damage caused by dry conditions, “it can take more than a single good year of snowpack for a drought to truly end,” says Gehrke.
courtesy of: National Geographic