1.  Introduction

Los Angeles is the second-most populous city in the United States, with a population of 3,979,537, according to the 2019 census data. It’s the second most populous city and metropolitan area (after New York City) in the United States. It lacks natural resources including water.  Los Angeles has a semiarid, drought-prone climate, and it receives very limited seasonal rainfall in winter. Local water sources can not sustain the need for the fast-growing population, irrigation for agriculture, and urbanization in the region.

Three main water supply for Los Angeles are the Owens River, Northern California and the Colorado River, and groundwater. Most of the water is imported through aqueducts under the State Water Project (SWP) and the Colorado Aqueduct. Hundred of miles of aqueducts were built for the transportation of imported water to the Los Angeles residents as well as other areas in California. 

2. Fundamental Problems of Water Management

There are multiple challenges regarding water management in Los Angeles: water conflicts triggered by the dependence on the constrained supply of imported water, mega-droughts, water leaks and evaporation in the water transport system, contamination of waterways and groundwater basins. In the future, climate change will also aggravate these challenges.

2.0 High Dependence on Imported Water

The state of California in general has a high dependence on imported water from different sources. For example, the Los Angeles Aqueduct transports 430 million gallons of water every day from the Owens River, Mono Lake Basin, and reservoirs in the Sierra Nevada Mountains to the city of Los Angeles. Another backbone for Southern California’s water supply is the Colorado River Aqueduct. Overall, 90% of the water supply in the city of Los Angeles is imported.

2.1 Water Right Conflicts

Transporting imported water through long distances has generated a series of conflicts regarding water rights in the region. There have been legal water wars started over how much water belongs to  Los Angeles. There are constant rivalries and disagreements among urban, agricultural, and environmental stakeholders. Since 1913, the Owens River was diverted to the Los Angeles Aqueduct which caused the destruction of the Owens Valley’s economy and agriculture industry, which resulted in the farmers attempting to destroy the aqueduct in 1924. Also, because large amounts of water were imported to Los Angeles from Mono Lake, the lake’s ecosystem for migrating birds was threatened by dropping water levels.

2.2 Water Leaks and Evaporation

Another problem for water management is water leaks and evaporation in the old and failing water transport system. In many parts of the aqueducts, water is exposed in the air and the water pipes are vulnerable and aging. A significant amount of water can be leaked or evaporated through the long water transport process from Owens Valley, Colorado River, or Northern California watersheds to Los Angeles. In 2015, the Los Angeles Department of Water and Power put 96 million “shade balls” to minimize the evaporation of the reservoirs by 85 to 90 percent during a drought which could save up to 300 million gallons of water.

2.3 Drought

The state of California is no stranger to drought, there are records of droughts in California since 1895. The most recent drought happened between 2012 and 2016, it was defined as one of its deepest, longest, and warmest historical droughts. The drought caused the state to receive less precipitation, snowpack, streamflow, and higher temperature. As mentioned earlier, the city of Los Angeles has to receive most of its water from aqueducts after hundreds of miles of traveling, higher temperature speeds up the evaporation process of water, resulting in lesser water can reach Los Angeles when the city needed it the most. According to the report, during the years of the recent drought, there were water contractors that received zero water delivery since the State Water Project operated in the 1950s. Along with the lack of alternative water resources, they are forced to drill new wells or purchase water from others.

2.4 Water Pollution

Another crucial challenge specifically for the city of Los Angeles is polluted runoff, and it’s also the number one source of water contamination in California. There are many industrial facilities such as factories, oil fields, scrap metal yards, and waste processing facilities in Los Angeles, combined with human activities, the use of fertilizers, together are the major components of the polluted runoff in Los Angeles. More importantly, the city of Los Angeles is highly urbanized, there are more and more lands becoming less impervious and have lost 98% of the original LA River watershed’s native wetlands. As reported in August 2020, the Los Angeles River is labeled as impaired due to contaminations from different sources.

2.5 Seawater Intrusion

Furthermore, there are more than local challenges posing to the city of Los Angeles. As a coastal itself, the city of Los Angeles also faces the intrusion from seawater which also closely relates to the extraction of groundwater that supplies close to 10 million residents in Los Angeles. As groundwater is pumped for daily use, it allows the penetration of seawater inland under the force from the ocean, as we know. Seawater is undrinkable and it will also endanger the quality of drinking water.
It’s estimated that 310 million gallons of water flow into the ocean every day in the city of Los Angeles, it’s necessary to manage to capture and reclaim as much water as possible to recharge the aquifer of Los Angeles. Therefore, in the effort through centralized capture and infiltration projects throughout the Los Angeles River watershed, it is hopeful that a 14% reduction in the need for imported water.

2.6 Low Efficiency in Water Treatment Process

Currently, there are four major water reclamation plants located across Los Angeles, most of them achieve half of their capacity in the average flow of water (Table 0.). It’s usually normal that the average flow of water in a water facility is less than its capacity, because of the concerns in maintaining the facility operational for years without overloading.  However, Los Angeles is a coastal city, there is a huge amount of renewable water being dumped into the ocean directly without being recycled and used again. As a result, it is highly recommended that each of the major water facilities increase their average flow water that is being treated by implementing advanced water treatment technologies, installing new equipment if necessary for improving the efficiency in the facility. 

The following Table 1. summarizes the key differences between Israel’s and California’s water availability and use. It’s clear that the state of California has a much more renewable water supply than Israel but in terms of water recycling, California does not have high efficiency in operation.

3.0 Proposed Solutions

Promoting the addition of an Advanced Water Purification Facility in an existing water facility have been a popular proposal in many of the master planning summary for the city of Los Angeles as well as for the state of California. They can be summarized as the collective effort among the investment into advanced technologies with the support from an existing facility, as well as the collaboration between different organizations across the area to achieve the goal of increasing the efficiency in recycling water, and lessen the need for imported water.

For example, under the Green New Deal pLAn, promoted by the mayor of Los Angeles in 2015, it mentioned the specific goals for dealing with the water issues.

• Source 70% of L.A.’s water locally* and capture 150,000-acre ft/yr (AFY) of stormwater by 2035
• Recycle 100% of all wastewater for beneficial reuse* by 2035

More specifically, the Hyperion Water Reclamation Plant is pointed out as the targeted subject for improvement. However, the pLAn doesn’t provide a detailed proposal for how to achieve the intended goals. As a result, a more in-depth analysis of other researched proposals is needed for implementing the technologies that are needed for the improvement.

Wastewater is produced when we use sinks, showers, toilets, appliances, and machinery in our homes and businesses. It is then piped through sanitary sewers to wastewater treatment plants where it progresses through stages of treatment of disinfection. The following Table 2. shows the proposed Advanced Water Treatment stage that happens after the water is being primarily in a current water treatment plant.

Image 2.

After wastewater is cleaned and treated through multiple processes, it is delivered to the advanced water treatment facility where it goes through a three-step purification process. The end result is high quality, purified water that is safe to reuse again. The three-step advanced purification process includes membrane filtration, reverse osmosis, and an advanced oxidation process (AOP) that includes ultraviolet light and a powerful oxidant, which would be added to produce purified recycled water. (Table 3.)

In terms of construction, as mentioned earlier, the Advanced Water Purification Facility will be an addition to an existing plant so that it doesn’t need to start from ground zero as a new facility.

In the following Image 4., taken from the City of LA Recycled water Master Planning Executive Summary, the treatment process of the current Donald C Tillman Water Reclamation Plant is highlighted in yellow. The focus is on the blue area which is proposed to build for the Advanced Water Purification Facility (AWPF). The new addition would immediately be put to use and help increase the capacity and efficiency of the current water treatment plant.

4.0 Conveyance System

After the water is being treated, it will need a distribution system so that it can be transported to the desired areas. Existing water pipelines are taken into account with the combination of new and improved conveyance system to distribute for underground water replenishment. Ideally, this would not only strengthen the local water supply availability but also help to ease the issue of seawater intrusion. As a result, to protect the local water supply for the city of Los Angeles.

5.0 Beneficial Uses

7.0 Sources