Sonoma Water Stressing Conservation as Dry Water Year Continues

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Despite welcome rainfall in March, the 2020-2021 water year is shaping up to be a dry one across the North Bay. Around 40%, or less than half of the normal rain for the date, has fallen in most of the region so far this season. This is an especially troubling trend for water supplies as the 2019-2020 water year was the third driest on record.

Here are the regional rainfall totals before our latest storm. Most areas picked up between a half and full inch of additional rain in the past two days. (Image 1)

And the percentage of normal rainfall for the date at stations across the North Bay (Image 2)

Sonoma Water and agencies in Marin County are pushing out a message of conservation, as water gathered in the Russian River system supplies some 600 thousands residents north of the Golden Gate. Besides urging conservation, Sonoma Water has reduced outflows from Lake Mendocino and is taking other actions to keep as much water in reservoirs as possible.

These graphics created by Sonoma Water give a simple overview of the current situation in the Russian River system as of March 11th. (Images 3 and 4)

The full story is revealed in these graphics tracking reservoir storage in the Russian River system. At Lake Sonoma, by far the largest storage facility in the system, supply stands at just over 60%. (Image 5) You can clearly see how this compares with the 10 year average for the date (dashed line), and other water years. Storage was drawn down during the dry 2019-2020 water year, and is tracking lower than 2014 following severe drought.

Meanwhile, Lake Mendocino (Image 6) sits at less than 50% of its target storage, once again tracking closely with the very dry 2014 season.

Sonoma Water manages the Russian River storage system using Forecast Informed Reservoir Operations. This new technique uses advanced weather forecasting to allow additional water to remain in storage, water that may in the past have been released for flood control.

So what’s in store for the rest of the water year? Few strong storms usually reach Central California after early April, but long range forecasts indicate the first week of the month may feature a return of wet weather. (Image 7)

But, despite that, the NOAA’s seasonal drought monitor, just released, shows continuing or worsening drought conditions expected for all of California. (Image 8)

So once again, the issues of drought and water conservation, all too familiar to California residents, are shaping up to be key themes that will be stressed by cities, counties and water districts all across the state this year.