Not Enough to Waste - Solutions to Securing LA’s Water Future

 

GROUNDWATER BASINS

The Los Angeles region receives about 11 percent of its water from groundwater basins (or aquifers). There are six major groundwater basins in the LA area, of which the San Fernando Basin is the largest, providing about 80 percent of the local groundwater supplies. These basins are replenished through spreading, the percolation of surface water back into the ground, and also through injection.


Injection, where wells pump water down into the aquifer, is normally used in places where the basins have been oversubscribed or there is a danger of salt-water intrusion or ground subsidence. These groundwater basins are capable of holding large quantities of water and could supply more water for the LA area, except for the fact that impervious surfaces often prevent water from reaching them. Also, due to legacy contamination numerous basins are unavailable to supply drinking water because they have been contaminated by many sources, including industrial waste from World War II era rocket fuel such as chromium and perchlorate. Additionally, many of the basins are polluted by agricultural run-off and leaking septic systems, which result in water quality issues.


If we prioritize groundwater recharge strategies and expedite the remediation of legacy contamination, these basins could provide a resilient and significant percentage of our water supply.


Local surface water—nearby rivers, streams, lakes, and reservoirs—that originates from rainwater and snowmelt from surrounding mountains is mostly diverted to storm drains that send the water out to sea. Most rivers and streams in the LA area have been engineered to flush out water to the ocean, since these have been channeled and paved to prevent flooding. However, some rainwater is stored in man-made lakes (or reservoirs) to later be diverted to spreading basins. These are ponds where rainwater is allowed to spread and slowly percolate back into the groundwater table, increasing the city’s groundwater supply. There are also parts of the Los Angeles River and other streams that have not been paved or where the concrete channels have broken due to high water tables, therefore allowing water to seep back into the ground.

LOCAL WATER SOURCES

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