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CHAPTER IV
GROUNDWATER REPLENISHMENT:
QUANTITIES, AVAILABILITY, AND COSTS
Groundwater Replenishment
As discussed in the previous chapter, the Central Basin and West Coast Basin (CBWCB) have an
annual overdraft because more groundwater is pumped out than is replaced naturally. The District
purchases supplemental water (artificial replenishment water) each year to help offset this overdraft
through managed aquifer recharge. The purchased water enters the groundwater basins at the
Montebello Forebay spreading grounds, at the seawater barrier injection wells, and through the
District's In-Lieu Program. The purpose of this Chapter is to determine the quantities of water
needed for purchase in the ensuing year and to determine the availability and cost of that water.
Sources of Replenishment Water
The District currently has available to it recycled and imported water sources for use as artificial
replenishment water. These two sources are described below:
Recycled Water: Recycled water is wastewater from the sewer systems that is reclaimed through
extensive treatment at water reclamation plants (“WRP”s). The water is treated to high quality
standards so that it can be reused safely. Some agencies and businesses use recycled water for
non-potable purposes, such as for irrigation of parks, golf courses, and street medians, or for
industrial purposes. WRD has used recycled water for groundwater recharge since 1962 and so
this year, 2012, celebrates WRD’s 50 th anniversary of using recycled water for groundwater
recharge. In semi-arid areas such as Southern California where groundwater and imported
water are in short supply, recycled water has proven to be a safe and reliable additional
resource to supplement the water supply. Recycled water is used at the spreading grounds and
the seawater barrier wells. Although recycled water is high quality, relatively low cost, and a
reliable supply all year long, the District is limited by regulatory agencies in the amount it can
use for replenishment. Therefore, imported water is also used for recharge.
Imported Water: River water from northern California (State Water Project) and the Colorado
River is imported into Southern California by the Metropolitan Water District of Southern
California (“MWD” or “Met”). MWD then sells this water to their member agencies for
multiple uses, including potable water and recharge water. WRD uses raw (untreated) imported
water at the spreading grounds and potable (treated) imported water at the seawater intrusion
barriers and for the In-Lieu program for groundwater recharge. Because of treatment and
transportation costs, it is the most expensive source for recharge water. The supply is under full
upstream control, and its availability at the spreading grounds is limited and variable, especially
during drought years. In fact, from May 2007 through May 2011 MWD stopped delivery of its
historically available discounted replenishment and In-Lieu waters due to reduced supply,
environmental issues and judicial decisions. They offered a limited quantity (225,000 AF) for all
their customers between May and September 2011, but that amount was quickly used up and no
discounted water has been offered since. MWD is currently reviewing their replenishment
program and is expected to adopt a policy for a new program some time in 2012. As a result of
the lack of discounted replenishment water, the District must plan on purchasing the more
expensive Tier 1 water from MWD member agencies for spreading and In-Lieu. Barrier
injection water continues to be purchased at the non-interruptible Tier 1 rate.
WRD Engineering Survey and Report, 2012
IV-1