As California's drought stretches well into a fourth year, there has been no shortage of news stories suggesting that stronger El Niño conditions expected later this year might help end the drought. But let's not get ahead of ourselves just yet.

While the last strong El Niño we experienced (1997-1998) led to significant flooding in California, the truth is that an El Niño is no guarantee of a wet winter. In fact, we've only seen four strong El Niño events in the past 65 years; two of these featured above-normal precipitation and during the other two, we received below-normal precipitation.

El Niño (El Niño-Southern Oscillation or "ENSO" in climate science jargon) refers to a climatic phenomenon where sea surface temperatures in the western equatorial Pacific are abnormally warm. These warm sea surface temperatures lead to changes in oceanic and atmospheric circulation, which in turn, affect rainfall patterns. The name, which means "Christ child" in Spanish, was coined by Peruvian fishermen, who observed the impact (typically most prominent during the Christmas season) that warm waters off the coast of Peru had on fisheries.

While there has been a slight bias toward above-normal precipitation in Southern California during El Niño (and current winter forecasts are indicating a greater chance of near-normal to above-normal precipitation), there has not been a significant effect observed in Northern California. This is especially sobering given that most of our water supplies originate in the northern half of the state, notably in the form of snowpack.

Yet even if we do see more rain and snow this winter, it may not be enough to end the drought. A new NASA study estimates that California's precipitation deficit is equal to the amount of rain we typically see in a year. Even if we were to miraculously receive that amount of precipitation this winter, it would surely lead to widespread flooding and mudslides and do little to solve the drought crisis that has taken years to develop. Instead, it will take a sustained period of heavy rainfall to replenish our state's depleted groundwater supplies.

This year's El Niño might provide some limited drought relief, but it will not address California's long-term water challenges nor prepare us for future droughts. The current drought is a reminder that we must invest in sustainable local water supplies like stormwater capture, water recycling, and improved irrigation and urban water use efficiency:

While El Niño provides a glimmer of hope for our dry and parched state, it will not solve the water woes that the drought has exposed. We must instead make investments inreal solutions that improve the reliability of our current water supplies and reduce future risks.