Water Facts in CA


Who uses how much? California water by the numbers

County     Gallons per capita per day

San Francisco     108.4 (the lowest, by far)
San Mateo         133.4
Marin                154.8
Contra Costa     172.0
Alameda           173.9
Napa                184.5
Los Angeles      185.0
Sacramento       260.9
Mono                471.6 (highest)


Marin Watershed Water Supply Update

North Bay

Local reservoirs and streams and groundwater are the major sources of supply for cities such as Mill Valley, Santa Rosa, Vacaville, Fairfield and Clearlake. The State Water Project’s North Bay Aqueduct supplies Napa and Solano counties.


GroundwaterAbout 30 percent of California’s total annual water supply comes from groundwater in normal years, and up to 60 percent in drought years. Local communities’ usage may be different; many areas rely exclusively on groundwater while others use only surface water supplies. Contrary to popular opinion, groundwater does not exist in underground lakes. Groundwater fills pores (spaces) between sand, gravel, silt and clay in water-bearing formations known as aquifers.


Between watering the crops that farmed animals eat, providing drinking water for billions of animals each year, and cleaning away the filth in factory farms, transport trucks, and slaughterhouses, the farmed animal industry places a serious strain on our water supply. Nearly half of all the water used in the United States goes to raising animals for food. In 2008, John Anthony Allan, a professor at King’s College London and the winner of the prestigious Stockholm Water Prize, urged people worldwide to go vegetarian because of the tremendous waste of water involved with eating animals.

It takes more than 2,400 gallons of water to produce 1 pound of meat, while growing 1 pound of wheat only requires 25 gallons. You save more water by not eating a pound of meat than you do by not showering for six months!  It takes up to 13 pounds of grain to produce just 1 pound of meat, and even fish on fish farms must be fed up to 5 pounds of wild-caught fish to produce 1 pound of farmed fish flesh.


Americans use large quantities of water inside their homes. The average family of four can use 400 gallons of water every day, and, on average, approximately 70 percent of that water is used indoors.

Pie chart showing indoor water usage. Shower: 16.8% Toilet: 26.7% Faucet: 15.7% Clothes washer: 21.7% Leaks: 13.7% Other: 5.3%

The bathroom is the largest consumer of indoor water. The toilet alone can use 27 percent of household water. Almost every activity or daily routine that happens in the home bathroom uses a large quantity of water.

For example:

  • Older toilets use between 3.5 and 7 gallons of water per flush. However, WaterSense labeled toilets require 75 to 80 percent less water.
  • A leaky toilet can waste about 200 gallons of water every day.
  • A bathroom faucet generally runs at 2 gallons of water per minute. By turning off the tap while brushing your teeth or shaving, a person can save more than 200 gallons of water per month.

Outside the bathroom, there are many opportunities to save water. Here are some common water efficiency measures, along with a few solutions to those problems you may not have known existed:

  • High-efficiency washing machines can conserve large amounts of water. Traditional models use between 27 and 54 gallons of water per load, but new, energy- and water-conserving models (front-loading or top-loading, non-agitator ones) use less than 27 gallons per load.
  • Washing the dishes with an open tap can use up to 20 gallons of water, but filling the sink or a bowl and closing the tap saves 10 of those gallons.
  • Keeping a pitcher of water in the refrigerator saves time and water instead of running the tap until it gets cold.
  • Not rinsing dishes prior to loading the dishwasher could save up to 10 gallons per load.


What is a Watershed?

A watershed is the area of land where all of the water that is under it or drains off of it goes into the same place. John Wesley Powell, scientist geographer, put it best when he said that a watershed is:

“that area of land, a bounded hydrologic system, within which all living things are inextricably linked by their common water course and where, as humans settled, simple logic demanded that they become part of a community.”

Watersheds come in all shapes and sizes. They cross county, state, and national boundaries. In the continental US, there are 2,110 watersheds; including Hawaii Alaska, and Puerto Rico, there are 2,267 watersheds.

pictorial display of a watershed
Navarro River Watershed Report 2013

Hydroelectric System

PG&E’s hydroelectric system provides Californians with safe, reliable and clean energy from a renewable resource. The largest investor-owned hydroelectric system in the nation, its history dates back to the days of California’s Gold Rush.

Simply put, hydroelectricity is generated by the force of falling water. A series of dams and reservoirs on river basins collect water. The water is then directed through large pipes (called penstocks) to turbines that spin generators to create electricity.

Fast Facts

  • PG&E’s hydroelectric system is built along 16 river basins stretching nearly 500 miles from Redding in the north to Bakersfield in the south.
  • Water used to power the hydroelectric system comes from more than 100 reservoirs located mostly in the higher elevations of California’s Sierra Nevada mountain range.
  • Our 68 powerhouses have a total generating capacity of 3,896 megawatts, which is enough power to meet the needs of nearly 4 million homes


1 thought on “Water Facts in CA

  1. I am pretty surprised that Sacramento uses way more water than Los Angeles or San Francisco. However, I know that water is pretty restricted throughout the state and so do you know why so much water is used in that area? I would suppose that it has to do with local farms, but I am not too sure.


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