Aqueduct in California

• Southwest USA

• On the Pacific Ocean

• Next to: Oregon, Nevada, Arizona

and Mexico

Precipitation

• Average precipitation is 200-500 mm per year

• 65% lost through evaporation and transpiration

• 13% flows out to sea

• The rest (22%) is left as run off for humans

• Half of the rain falls between November and March – seasonal shortages

Population

• Grown from 2 million (1900) to 10 million (1950) to 37.7 million (2007)

• Prediction of 40-45 million by 2025

• Spatial imbalance is also a problem:

• 75% of demand comes from the densely populated areas to the south

• But 75% of the rain falls in the sparsely populated areas of the north

<5.0 Inches of Precipitation

100+ people per sq. mile

40.1 - 50.0 Inches of Precipitation

1 - 4 people per sq. mile

Environmental problems caused by the ‘Californian Dream’ include:

• To secure water supplies: wetlands have been drained, natural habitats altered and fish stocks depleted

• Polluted waterways: the over-extraction of groundwater and increasing salinity

The State Water Project (SWP) and Central Valley Project (CVP)

• Provides water from the Sacramento-San Joaquin River Delta

• For central and southern California

Colorado River

• Provides 60% of southern California’s water

• Via a system of dams and aqueducts

State Water Project

Central Valley Project

Colorado River

Number of dams and reservoirs

20 22 11

Number of hectares of farmland irrigated

0.3 million 1.2 million 1.4 million

Number of people drinking water is

supplied for

Nearly 20 million

2 million 25 million

• Already conflict over water between:

• Cities

• Farmers and environmentalists – trying to cut demand

• California uses 20% more water from the Colorado than visualised in 1963

• Shortages are predicted for the future

North vs. South

Because of the spatial imbalance between the rainfall and population distributions, the SWP was constructed. However this has caused conflicts between the two regions:

• Northern Californians feel they are being ‘owned’ by the south

• Southern Californians demanded guarantees that the water flows would be maintained

• Supplies are transferred at the Bay-Delta region, it has become an area where many users all demand more water

California vs. the 6 other users of the Colorado (inc. Mexico)

• Mexico takes 10% of the Colorado’s total flow, states in the Lower Basin take 50% and the Upper Basin falls short by 10%

• California takes 20% more than its original 1963 allocation

• Native Americans are owed 5% but could claim more as their Reservations extend along the river and two of its tributaries