Improve local water supply reliability.

The need for local water supply depends greatly on the end use and access to other sources of water. Shown here is the Sepulveda Dam at river mile 43.1

OLIN, 2018.

More than half of the region’s water supply is imported from the Colorado River, the Sacramento-San Joaquin River Delta, and the Eastern Sierras.

In the Los Angeles Basin, 57% of water is imported, 34% comes from groundwater, and 9% is sourced from recycled water, water conservation measures, and local surface water diversions.¹ In community meetings and surveys, supplementing water supply was the second most important issue related to the LA River for participants, identified by 48% of participants. Increasing population, regulatory requirements, natural disasters, and demands on the water system accentuate decreasing reliability in the sources of imported water supplies that is caused by cyclical droughts and climate change. Dry weather and wet weather flows in the LA River present opportunities to develop and diversify local water resources to reduce dependence on imported water and increase the reliability and resiliency of the region’s water supply.

Actions

Steps that should be taken to achieve the goal

Capture and treat stormwater and dry weather flows before they reach the river channel for groundwater recharge, direct use, water recycling, or release for downstream beneficial uses.

Divert and treat stormwater and dry weather flows within the river channel for groundwater recharge, direct use as recycled water, and to supply water for parks and ecological areas.

Employ and encourage efficient water use.

Improve water supply and recycling facility operations and maintenance.

Continue measures to clean up the regional groundwater aquifers.

LA River Water Supply Need

Needs: Water Supply

Water in the LA River provides important uses for recreation and habitat, but also plays a role in recharging regional groundwater basins and reducing the demand for imported water.

The need for water supply reliability was assessed by evaluating the need to maintain water in streams for particular beneficial uses and through evaluating areas where municipal water supply overlays and is most dependent on groundwater replenishment.

Habitat and Recreation Beneficial Uses

The occurrences of Beneficial Uses (as identified by the Regional Water Quality Control Board) related to Recreation or Habitat were identified within streams in the LA River watershed, including the mainstem, to indicate where in-channel water supply is needed to maintain those uses. Areas with both recreation and habitat uses were identified as having a high need, while channels and streams with no recreation or habitat uses were categorized as general need.

Percent Groundwater Supply

Urban Water Management Plans prepared by water purveyors in LA County report the sources of water supplied, including groundwater. Areas with groundwater sourcing a significant portion of water supply are in high need of consistent replenishment of groundwater supply. Areas with greater than 90% dependence on groundwater supply were categorized as very high need, while areas with less than 10% dependence on groundwater supply were categorized as general need.

Groundwater Basins

Locations overlying groundwater basins have need for additional replenishment of groundwater/to enhance municipal water supply throughout the basin. Areas lying directly over groundwater basins were identified as having very high need while areas not lying over groundwater basins were identified as having general need.