These graphics show how far California is from emerging from its drought

California is hoping for a good soak this wet season.

After two extraordinarily dry years, water supplies are depleting, slow-flowing rivers have clubbed fish and wildlife, and parched forests and grasslands have increased the risk of forest fires.

Most of California’s precipitation occurs between December and April. Winter storms in the Pacific Ocean bring rain to thirsty hills and valleys and snow to mountain peaks, which will later melt and provide an extra burst of much needed moisture.

The beginning of April is an important time of the year as this is when the accumulated snow is at its peak. This is when we know how much water will melt from the snow in the spring and summer.

Water managers are keeping a close eye on these winter months. U.S. too. On this constantly updated page, we keep an eye out for some of the most important data that helps us answer the question: Will California be drought relieved this winter?

What we follow

– Current drought conditions via US Drought Monitor
– Monthly storage levels in the main reservoirs
– Snowpack conditions through snow water content levels
– Sierra precipitation index at eight stations

With the rainy season off to a strong start, with record rains and snowfall in parts of the state in late 2021, heavy precipitation is expected to continue through spring so California can pull itself out of the storm. drought.

Rain and snow in far northern California are what water experts – and we – watch most closely. Northern California receives most of the state’s precipitation and is home to the largest reservoirs. Many water experts say the rainy season must end with 140% of the average rainfall to relieve the drought.

The precipitation index at eight stations in the Northern Sierra and survey measurements of the state’s snowpack are particularly useful in assessing the evolution of the rainy season.

Californian reservoirs are still thirsty

The continuing drought has drained and dried up many of the main reservoirs critical to the state’s water supply.

The graph below tracks the trends in the storage levels of large tanks as a percentage of their total capacity and as a percentage of the historical average storage level for that time of year. The historical average is calculated based on data starting in 1960.
State officials follow the snowpack in the Sierra Nevada and the mountains of the Far North by measuring its water content. This is considered to be the best metric to assess how snow will increase the water supply. The measurement is expressed as a percentage of the average accumulation on April 1, when the snowpack has historically reached its maximum, before melting.

the North Sierra precipitation index at 8 stations tracks precipitation in some of California’s wettest and most important watersheds. These watersheds drain into the state’s largest reservoirs, making the index a relevant indicator of water supply. The average cumulative precipitation in a hydrologic year – based on data between 1991 and 2020 – is about 53.2 inches (hydrologic years are October through September). The 2016-2017 hydrologic year was the wettest on record for the index, with nearly 95 inches of cumulative precipitation at the eight stations.

About the data

Reservoir, snowpack and precipitation data for this project are from the Department of Water Resources California Data Clearinghouse.
Data on the extent of the drought come from the United States Drought Monitor, a partnership between the National Drought Mitigation Center, the US Department of Agriculture and the National Oceanic and Atmospheric Administration.

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