Quantity of Water

The average amount of water entering the ocean from the Los Angeles River each year can be categorized into dry weather and wet weather.

  • Dry weather flow includes water discharged from three main wastewater treatment plants, groundwater upwelling, and incidental urban runoff (collected and conveyed through storm drains). The total contribution of dry weather to the River is 68,000AF/year (as shown in the table below), which is equivalent to the water needs of the City of Long Beach. The future apportionment of the dry flow water is a currently debated issue, and the topic of study by several agencies.
  • Wet weather flow includes all surface runoff originating from rainfall. The average amount of wet weather runoff entering the Los Angeles River over the past 20 years has been approximately 279,000 AF/year, as shown in the table below. It is important to note this amount has varied significantly from approximately 952,000 AF in 2005 to only 49,000 AF in 2007. The variance is significant, and the extremes of occurrence were only two years apart. For the purpose of our analysis, the average value was used.

The purpose of the initial analysis was to determine how much flow within the Los Angeles River, occurring during below “functional flow rate” (FFR) conditions, might be recaptured for water recharge use. 

Functional Flow Rate Example

Functional Flow Rate Example

The images below provide examples of feasible uses for the flow within the Los Angeles River under varying flow conditions, including retention/recharge, landscape and recreation uses, and opportunities for water quality improvement.