Water Supply Facts
California's water supply is often described as feast or famine. Because the
Golden State is prone to frequent bouts with drought and floods, the state must
rely on an elaborate web of water projects to supply cities, farms, businesses
and the environment with adequate water year-round.
Rainfall
Precipitation varies widely from year to year. In average years, about 193
million acre-feet (MAF) of rain and snow falls on California. One acre-foot is
about 326,000 gallons, or enough water to supply two typical families for a
year.
More than 100 million acre-feet of the rain and snow received soaks into the
ground, evaporates or is used by native vegetation. That leaves about 71 million
acre-feet of usable surface water. Of that water:
 | 36% flows out to the ocean
| 28% is legally committed to wild and scenic rivers and San Francisco
Bay-Delta outflow
| 28% is used by agriculture
| 7% is used by cities and industry | |
About 75% of the annual precipitation falls north of Sacramento, while more than 75% of the demand for water is south of the capital city. Most of the rain and snowfall occurs between October and April, while demand is highest during the hot and dry summer months.
Water Delivery System
California's cities, farms and businesses rely on water from a variety of
sources. Surface water projects, which capture and deliver rain and snow runoff,
provide a major portion of the state's total water supply. The projects include
more than 1,000 federal, state and local reservoirs.
Two of the most important projects are the federal Central Valley Project (CVP)
and the State Water Project (SWP). The CVP and SWP bring water from Northern
California through the Sacramento-San Joaquin River Delta for delivery to users
in the San Joaquin Valley, parts of the San Francisco Bay Area and Southern
California.
Key water projects and the amount of water they deliver:
| Central Valley Project (federal) -- 7 MAF (million acre-feet)
| State Water Project (state) -- 2.3 MAF
| All-American Canal (local) -- 3 MAF
| Colorado River Aqueduct (local) -- 1.2 MAF
| Los Angeles Aqueduct (local) -- 200,000 AF
| Mokelumne Aqueduct (local) -- 364,000 AF
| San Francisco Hetch Hetchy Project (local) -- 330,000 AF | |
California's rapidly growing population -- estimated to reach 40 million by 2010 -- is putting mounting pressure on the state's water supplies. State officials now predict that California will experience annual shortages of 4 MAF to 6 MAF by 2010 unless steps are taken now to address the declining reliability of the state's water supply system.
Usage Information
| Landscaping accounts for about half the water Californians use at home.
Showers account for another 18%, while toilets use about 20%.| One acre-foot of water is enough to meet the needs of two typical families
for a year. | Per capita water use varies around the state. Central Valley residents use
up to 300 gallons per person per day, while some Central Coast residents use
as little as 50 gallons per day.
| California will be chronically short of water by 2010, unless steps are
taken now to improve our water supply system. | It takes 3.3 acre-feet of water to grow enough food for an average family
for a year. | A water storage project typically takes 10 to 20 years to design and
build. | |
|
1 CFS = |
448.8 GPM = | 2 A.F./day |
|
1 cu. ft. = |
7.48 gallons = | 62.4 lbs |
| 1 million gal. = | 3.069 A.F. = | 694 GPM/Day |
|
1 A.F. = |
43,560 cu. ft. = | 325,851 gallons |
|
1 ft. = |
0.433 PSI | ' |
|
H.P. = |
CFS x HEAD / 8.8 | ' |
|
1 HP = |
746 watts = | 550 ft. lb. / sec |
|
1 ft. = |
0.433 PSI | ' |
|
Key |
|
| GPM = | gallons per minute |
| CFS = | Cubic Feet a Second |
| A.F. = | Acre Feet |
| PSI = | Pounds per Square Inch |
| watt = | measurement of energy |
| H.P. = | Horse Power |
| Gal. = | Gallons |
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