InTeGrate Modules and Courses >Water Science and Society > Student Materials > Module 8: Cities in Peril: Dealing With Water Scarcity > Module 8.1: Cities in Peril: Dealing with Water Scarcity – History and Current Approaches > Cities in Peril: LA
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These materials are part of a collection of classroom-tested modules and courses developed by InTeGrate. The materials engage students in understanding the earth system as it intertwines with key societal issues. The collection is freely available and ready to be adapted by undergraduate educators across a range of courses including: general education or majors courses in Earth-focused disciplines such as geoscience or environmental science, social science, engineering, and other sciences, as well as courses for interdisciplinary programs.
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Cities in Peril: LA

The Giant straws of Los Angeles

To see Los Angeles, with its lush landscaping and common swimming pools, one would never believe it to be water limited. Los Angeles is a sprawling agglomeration of towns and neighborhoods spread over nearly 470 sq. miles (1220 sq. km) of semiarid hills and valleys (precipitation is about 15 in--38 cm-- annually). One river, the Los Angeles River, runs through the city to the sea, but this watercourse flows only intermittently and--mainly for flood control--has now been straightened and confined to a concrete channel. The City of Los Angeles now has nearly 3.9 million people living within its borders, a far cry from the estimated 1600 people that lived there in 1850 when (a smaller footprint) LA was first incorporated (Fig 1). By 1900, LA's population had grown to over 100,000, and the local water supply was deemed inadequate. Thus began LA's quest for additional water resources. The subsequent history of water acquisition, especially that of Owen's Valley water and the LA aqueduct (see L.A. Aqueduct Centennial 2013 for pics) engineered by William Mulholland, makes very interesting reading ("Cadillac Desert" by Marc Reisner, p. 54-107). Controversy still surrounds this acquisition. Table 1 shows the major aqueducts that now supply water to LA.

Table 1: Major aqueducts that supply water to LA.
AqueductYear CompleteYear ConstructionLength$ CostDelivery
Owens Valley and LA Aq19135223 mi23mill485 cfs
Second LA Aq.19705137 mi89mill290 cfs
Colorado River Aq.194110242 mi220mill1600 cfs
California Aq. and West Br*19731960 appop701 mi5200mill4400 cfs

*California State Water Project: note that the length and cost is for the entire system, not just LA, and the cfs for the West Branch is not what LA alone receives. Source: California State Water Project At A Glance

The second LA Aqueduct was built to take advantage of additional water taken from the Mono Lake drainage through an 11-mile tunnel drilled under the Mono Craters to connect to the Owens Valley system. Today, about 70% of LA's water comes from the Eastern Sierra. The two LA aqueducts supply nearly 430 million gallons per day (about 100 gpd per person in the City of Los Angeles today!). Groundwater wells in the San Fernando Valley and other local groundwater basins supply 15% of water needs, and purchases from the Metropolitan Water District (Colorado River Water and California State Water Project) supply the remaining 15%. Variation in use of each of these sources year by year (Figure 2) is a function of water supply availability at the source resulting from drought, competing uses, and other factors. For example, the period between 1987 and 2004 required purchase of considerably more water from MWD sources (at greater expense) because of severe drought/low snow pack in the eastern Sierra Nevada during that period.

Activate you Learning: Think about it!

Imagine if your hometown annexed water rights from somewhere as far away as Mono Lake is from Los Angeles. Where would that water come from for your hypothetical case?


These materials are part of a collection of classroom-tested modules and courses developed by InTeGrate. The materials engage students in understanding the earth system as it intertwines with key societal issues. The collection is freely available and ready to be adapted by undergraduate educators across a range of courses including: general education or majors courses in Earth-focused disciplines such as geoscience or environmental science, social science, engineering, and other sciences, as well as courses for interdisciplinary programs.
Explore the Collection »