IRWD Irvine Ranch Water District Sources, Use Reduction, and Rates


Irvine Ranch Water District Water Sources in 2013:

22% Imported from State Water Project and Colorado River Aqueduct

31% Clear Ground Water (GW)

25% Recycled Water

19% Treated GW which is used in grounds and buildings

In 2015, IRWD had been using 23% imported, but must now cut that percentage by 3% to 5% of the total water use, since the Metropolitan Water District of Orange County has to reduce its imports by 15%.

Ground water cost $454 per acre-foot, and imported water is much more expensive at $1,000 per acre-foot. Even more expensive would be desalinated water at about $2,000 per acre-foot.  However, water savings through conservation and efficiency is estimated to cost only $150 per acre-foot.

The Michelson Recycled Water plant has a 24 million gallon per day (mgd) output which is currently 100% used. It has been raised to 28 mgd, and is planned for expansion to 33 mgd by 2025.

IRWD Water Use Reduction

Irvine has reduced its residential per capita water usage from 96 gallon/day in July 2014 to 69 gallon/day in January 2015, a 28% reduction.

Outdoor water can be 65% of residential water usage. The IRWD outdoor program is called Rightscape and has three parts: (1) right drought resistant plants, (2) right watering schedule, and (3) right equipment with a weather based irrigation controller.

The recommended watering schedule is to water before 8 AM, and for grass in January, water for 2 days a week for 2 cycles of 2 minutes. For grass in July-August-September, water for 4 days of 3 minutes in 3 cycles.  The IRWD does not have any restrictions on which days you can water, or how many days a week you water.  Conservation is built into the rate structure.

In Irvine, the IRWD requirement is a reduction of 16% in usage  of potable water by the end of February 2016. One strategy might be to reset your sprinklers according to the recommendations, and see if that reduces your outdoor water use by at least 16%, and maybe the full 32% needed if outdoor watering is 50% of your water use, and you don’t want to reduce indoor use. By not imposing the requirement until February 2016, they are really protecting your lawn during the hot summer.

Indoors, a 16% reduction is only a 1/6 reduction. You can set your dishwasher on economy, and your washing machine on a slightly reduced load. Running water for anything at 1/6 (or more) less flow will easily get you the small savings needed.

IRWD Water Rates

With the factor of two increase in cost for imported water over ground water, the IRWD rates are already approved as an Allocation Based Conservation Rate Structure, as required by the new court ruling. That is, charging more for excessive use has been approved for IRWD.

There is a variable Standard Water Allocation based on whether you live in an apartment, an attached home condo, or a single family home, and on the number of residents in the home.

For use up to the allocation, the rate averages to $1.16 per hundred cubic feet of water, called a ccf. For volume up to 30% over the allocation, the rate is $3.91 per ccf.  For volume between 30% and 60% over the allocation, the rate is $6.22 per ccf.  For volume more than 60% above the allocation, the rate soars to $12.60 per ccf, or 11 times the average up to the allocation.

The base allocation depends on your dwelling type and typical yard associated with it.   It is 50 gallons per day per person for the number of persons, and then increased for typical yard size.

Below is a Map of the Orange County Water District (OCWD) (Ringed in Black) and the IRWD in Green.  

OCWD service area




About Dennis SILVERMAN

I am a retired Professor of Physics and Astronomy at U C Irvine. For a decade I have been active in learning about energy and the environment, and in lecturing and attending classes at the Osher Lifelong Learning Institute (OLLI) at UC Irvine.
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