A parched Folsom Lake, at less than 20 percent of capacity (photo courtesy of National Weather Service).

This is not a good time for umbrella merchants in California.

2013 was one of the driest years on record in the state. And January  – usually among the wettest months — has failed to provide any relief. With the precipitous drop in reservoir levels, Gov. Jerry Brown recently declared a statewide drought emergency, calling this “perhaps the worst drought California has ever seen since records began being kept about 100 years ago,”

The declaration outlines 20 different drought condition measures, one of which calls for the Department of Water Resources to execute a statewide conservation campaign, urging residents and businesses to voluntarily reduce water consumption by 20 percent.

But that begs two important questions: how much water does the average Californian actually consume and what would a 20 percent reduction look like?

It’s a hard figure to quantify, and estimates vary widely. For one, while indoor residential water use is relatively steady throughout the state, outdoor use — primarily for landscape irrigation — varies dramatically, with homes in arid inland regions consuming significantly more water than those in coastal areas.

“There are large variations across the state,” notes Peter Bostrom from the California Department of Water Resources. “Outdoor use could be 25 percent [of a household’s use] in Santa Cruz  and 80 percent is Coachella … 15 percent of users account for 60 percent of overuse in landscape irrigation.”

Source: California Dept. of Water Resource_Water Plan (2009)

Additionally, estimates are typically represented as gallons per capita per day (gcpd), in which water use in each of the state’s 10 hydraulic regions is divided by population (see map at right). These calculations, however, generally factor in each region’s total water consumption, which includes residential water use as well as commercial and industrial uses.

Among the best ways to get a handle on your own household’s water consumption is by scrutinizing your water bill, which usually includes the number of gallons used that month. Additionally, a new state website provides a calculator for estimating your personal water.

An often-cited 2011 study of California single-family water consumption estimated that the average California household used more than 360 gallons of water per day. To put that in perspective, the typical office water cooler holds 5 gallons, or about 1.4 percent of the study’s estimated daily average household use. Given that figure, the average house in California would need to use 72 fewer gallons a day to meet the 20 percent reduction goal.

The study, which was sponsored by CDWR and managed by the Irvine Ranch Water District, logged water consumption in the year 2007 for 735 homes spread across the state’s 10 hydraulic regions.

The study found that about 53 percent of total average household water use — or more than 190 gallons per household per day — was used for landscaping and other outdoor uses (remember, this is only the state average —  most cities in the Bay Area use significantly less).

Meanwhile, Indoor use accounted for more than 170 gallons per household per day. Not surprisingly, the most in-home water consumption was in toilet flushes. A more shocking finding, however, was the whopping 18 percent lost to leaks inside homes, the study found. Data from the study is represented in the charts below.

Bostrom from CDWR claims that voluntary water reduction campaigns have proven to be quite effective during past droughts.

“We’ve found in general that when the call goes out, people respond very well to drought messaging,” he says, referring to successful reduction campaigns during the 2007-2009 drought. “It’s gotta be a coordinated message with water suppliers reminding people of the shortage and need for water conservation. And suppliers build that [reduction] into their drought planning.”

For 8 simple tips on conserving water, check out this recent post on KQED’s News Fix.