The city of Los Angeles is shifting towards enhancing permeable surfaces throughout the city to cope with increasing rainfall and provide water for its residents.
From 1877 to 1908, Los Angeles transformed from a stagnant water area along the river into a bustling city with nearly 300,000 residents. The thriving economy, new long-distance railroads, and an oil boom spurred a wave of migration, causing the city’s population to quadruple within 30 years. By 1930, the city’s population increased by nearly 500,000 people. This growth would not have been feasible without a crucial factor: water. The city administration devised a plan to prevent Los Angeles from experiencing a water shortage.
Los Angeles Water Aqueduct. (Photo: B1M).
At the beginning of the 20th century, with the population booming, it seemed nothing could halt the growth of Los Angeles. However, without a swift solution, the city was approaching a drought crisis. Water engineer and former Los Angeles mayor Frederick Eaton planned a massive aqueduct to draw water from the Owens River, located 400 kilometers away, into the city and store it in the aquifer near Los Angeles in the San Fernando Valley.
In 1905, Eaton secured enough water supply from the Owens Valley to bring his plan to fruition and officially announced the construction of the aqueduct. Eaton intended to use the San Fernando Valley as an aquifer to store the water coming from the aqueduct. To achieve this, the valley needed to fall within Los Angeles’s jurisdiction and required a referendum. The plan succeeded, and in 1913, over 30,000 people witnessed the first flow of water from the Los Angeles aqueduct into the San Fernando Valley.
At that time, Los Angeles was on the verge of becoming a gigantic metropolis. Water continued to shape the city to this day. Since then, the water supply of Los Angeles has become diverse, but most of the infrastructure relies on the same principle: water is pumped in from outside the city, and rainwater that falls in the city is quickly drained out as much as possible. However, this principle is gradually weakening.
The Owens River and other tributaries in the Los Angeles water system rely heavily on melting snow from the Eastern Sierra, and that water source is becoming increasingly scarce. For the Los Angeles aqueduct, this is part of a long-term trend. While it still accounts for a significant portion of the water supply in Los Angeles, the flow it provides has been declining over the past 30 years. As mountain snowfall decreases, rainfall in the city is increasing. Building a sponge city could help address this issue.
The concept of a sponge city is relatively simple, focusing on integrating natural elements into the urban environment as much as possible to collect rainwater and store it underground, replenishing the aquifer and providing drinking water. In 2015, the mayor of Los Angeles announced a sustainable city plan aimed at cleaning the current aquifer and increasing the amount of locally sourced water used by the city by 50%. In the same year, the Los Angeles Environmental Health Agency introduced the Green Corridor Project, replacing concrete surfaces with permeable pavement systems that help filter rainwater and direct it to the aquifer. Although relatively small, such projects can store 2.8 million liters of water in an average rainy season. Beyond roads and sidewalks, similar development projects are emerging throughout the city.
In 2022, the Los Angeles Department of Water and Power, along with the Los Angeles Flood Control District, completed the Tujunga Spreading Grounds project in the northern part of the city. This $50 million project doubled the rainwater collection capacity over an area of 60.7 hectares, allowing for the gathering of 15.1 billion liters of water on average per year. In February 2023, Los Angeles experienced rainfall equivalent to more than half a year’s worth in just three days. The improved sponge city infrastructure, along with existing water reservoirs, enabled the city to collect 32.6 billion liters of rainwater, sufficient to supply water for over 100,000 households annually.
