On Friday, Shasta Lake, the stateвЂ™s largest reservoir, was just 24% full. Many of those reservoirs have fallen to very low levels as Northern California has received less rain in the past two years than any two-year period since 1976-77. But they did know from previous generations which watersheds of the state tended to deliver the most rain or melting snow, and thatвЂ™s where they built many of the big dams to catch the water for cities and farms. They had slide rules and hand-drawn blueprints. The engineers who built CaliforniaвЂ™s largest reservoirs in the 1940s, вЂ™50s and вЂ™60s didnвЂ™t have 70 years of precise climate data, precise satellite images and computer weather models. вЂњFortunately the stateвЂ™s biggest reservoirs are not in Southern California,вЂќ he said. NullвЂ™s data shows that La NiГ±a years have brought only 79% of normal rainfall, on average, to the Los Angeles-San Diego area. So why does the stubborn belief persist that La NiГ±a guarantees dry weather? The farther south one goes, the drier it has been in La NiГ±a years. And the rugged coast near the California-Oregon border has received an average of 103% of normal rainfall during La NiГ±a years. Similarly, the region farther north, where CaliforniaвЂ™s largest reservoirs are located, including Shasta, Oroville, Trinity and Folsom, has received 97% of normal rainfall, on average, in La NiГ±a years. The average rainfall over those 23 years was 93% of normal. Rainfall that winter ended the stateвЂ™s previous drought and prompted widespread flooding in downtown San Jose. Although some were dry, like last year or 1976-77, some also were very wet, such as the winter of 2016-17, when relentless atmospheric river storms caused the near-failure of Oroville Dam. Since 1950, there have been 23 winters with La NiГ±a conditions, his records show. Null, a former lead forecaster with the National Weather Service, has spent years tracking the amount of rainfall California receives every winter and looking for trends.

The measure of a man 2015