Until 1913, the Los Angeles River and its tributaries, including the Arroyo Seco—the "dry stream"—was the main source of water for the basin. During the Spanish era, a complex set of Zanjas (ditches) had been built along the river in Los Angeles and Rancho San Rafael to serve the population of El Pueblo and irrigate its surrounding agricultural land. But as the next hundred years would reveal, this system wasn't built for the kind of metropolis Los Angeles was destined to become.
As soon as the Rancho land was subdivided and small plots were sold to the new arrivals, demand for water began to grow. In 1820, the population of Los Angeles was no larger than 650. By 1900 it had grown exponentially to more than 100,000. The city's transition—from an agrarian outpost to a growing metropolis—turned the Los Angeles River system into a giant faucet.
By the 1900s, city officials began to fear that the underground water reserves of the L.A. River system, including the Arroyo Seco, would not be able to sustain the growth of the city. Schemes were constantly being hatched up that promised to establish a more efficient and scalable system, such as Highland Park resident R. F. Dockery's "revolutionary" 1892 plan, as reported in the Los Angeles Times, to use a network of small concrete pipes to deliver water from the Arroyo to specific location.
As water became increasingly scarce, inventors and planners were replaced by lawyers and speculators eager to grab water rights, legal structures competing with engineering feats as the favored method of exerting control over the city's political, environmental and financial future. Between the legal wrangling and the river system's inherently mercurial nature—dry creeks in the summer, violent floods in the winter—those who relied on the river were faced with an inordinate amount of unrest and unpredictability, not necessarily the best climate for growth.
This uncertainty would remain until 1913, when William Mulholland and the Los Angeles Department of Water and Power completed work on the Los Angeles Aqueduct, a 223-mile steel pipe that pulled water from the Owens River in the Eastern Sierra Nevadas to quench the thirst of the growing metropolis. Then, in the 1930s, after a series of floods threatened the communities growing along the river banks, the entire basin system was channelized and essentially turned into a gigantic sewer.