Do you need to save water in winter? What matters in Sonoma County

By The Downspout · Posted Nov 4, 2026 · 3 min read

Mostly not for supply: winter is when our lakes and groundwater refill. But winter water still counts in three places: your sewer bill, which many cities here base partly on winter use, a septic system in soaked ground, and the rain off your roof.

In a lot of Sonoma County neighborhoods, a lid and a grate sit a few steps apart near the curb. The lid covers the water meter.^[1] The grate is the storm drain.

In summer, saving water is all about the meter. Then the rain comes and the sprinklers go off. So can you stop thinking about water until spring?

Not quite. The water you use this winter can raise your sewer bill for all of next year. And the storm drain is about to get busy.

Is there a shortage to save for?

Not usually. Lake Sonoma, the county's biggest reservoir, was about 92% full on November 3, and it fills in about three winters out of four.^[2] Groundwater, the water wells pump, refills in winter too.^[3] See what the lake levels mean.

So supply isn't the main winter reason to save. Your bill is.

Why does winter water cost you all year?

In winter, little water goes on gardens, so what you use is close to what goes down the drain. That's why many cities here base part of your sewer charge on your winter water use.^[4]^[5] That includes Cotati, Healdsburg, Petaluma, Rohnert Park, Santa Rosa, Sebastopol and Windsor, plus the Sonoma Valley sewer district.^[5]^[6] Each counts its own months, so ask yours.^[7]^[8]

So a winter leak costs twice. Say a leak wastes 50 gallons a day all winter in Petaluma. That adds about $22 a month to your sewer charge for the next year.^[4]

To check, turn off every tap and the sprinklers. Lift the lid on the meter box and watch the small star most meters have. If it spins, water is leaking somewhere.^[1] Our water bill guide shows how to find it.

On a septic system? Go easy in storms

A septic system's leach field needs drier soil to clean the water.^[9] In a wet winter the ground can fill up, drains slow, and sewage can back up into the house. The only fix in the moment is to use the system less.^[10]

In a storm week, spread laundry over several days, and keep roof water away from the leach field.^[11] More in how often to pump a septic tank.

Where does the rain on your roof go?

A normal Santa Rosa winter brings about 25 inches of rain.^[12] On a 1,500 square foot roof, that's nearly six months of what a two-person home uses indoors (about 23,600 gallons).^[7]

Down the street. Every outside drain here runs to the nearest creek, untreated.^[13] On the way, rain picks up oil, pet waste and loose soil.^[14]
Into the ground. Water that soaks in refills groundwater and helps keep creeks running into summer.^[15]

It matters most now. Salmon and steelhead are laying eggs in creek gravel from November into spring, and mud from yards and roads can smother them.^[16]^[17]^[18]

Our take: in winter, fix leaks to protect next year's bill, and keep the rain on your land and out of the storm drain. Start with slow it, spread it, sink it.

What should I do now?

Check your meter for leaks now, before the winter months that set your sewer charge.
Keep leaves, pet waste and loose soil out of the street gutter by the curb.^[14]
Next: point one downspout at a spot that can soak it up. See sink it or shed it.

A lid and a grate at the curb, two winter jobs: keep the meter quiet, and send the storm drain nothing but rain.

Sources

Checked 2026-11-04. Rules and programs change. If something here is out of date, the source above wins. Spot an error? See our corrections policy.