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| Ocean Friendly Gardens
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Residential Runoff Reduction (R3) Studies
Irvine Ranch Water District (IRWD) and other Southern California water agencies have completed studies which demonstrate that both water conservation and urban runoff reduction can be achieved through the use of weather-based irrigation controllers.
IRWD and Metropolitan Water District of Orange County (MWDOC) partnered on the Residential Runoff Reduction (R3) Study, which compared a neighborhood where weather-based irrigation controllers were installed with a baseline area where no changes were made, and an “education only” area where printed educational materials were distributed. The R3 Study had four primary purposes:
- To test the use of weather-based irrigation technology, also known as ET controllers, to manage irrigation water for residential homes and large landscape areas
- To evaluate the effectiveness of a targeted education program on residential homeowners
- To determine the correlation between proper water application in landscape irrigation and the quantity and quality of urban dry-season runoff
- To gauge the acceptance of water management via the controller technology.
 Study Methodology
The R3 Study area included five similar neighborhoods in Irvine, California, each with its own single point of discharge into the urban storm drain system. At these points of discharge from each study area, the runoff volume was monitored and water quality samples were taken. The five sites were divided into three separate areas. The first area used ET controller technology and public education. The second area received educational materials, but did not receive controllers. The third area (control group) consisted of three separate neighborhoods which received neither ET controllers nor educational materials.
Evaluation Results
After the initial 18-month study period was completed, the data were compiled and evaluated for water conservation savings, dry season runoff changes, and changes in the quality of the dry season runoff water. The following summarizes the results:
Water Conservation Savings
Water conservation savings from the typical participant in the retrofit group were 41 gallons per day (gpd), or approximately 10 percent of total household water use. The bulk of the savings occurred in the summer and fall. The education group residential customers saved 26 gpd, or about 6 percent of total water use. The savings from this group were more uniform throughout the year. The retrofit group also included 15 dedicated landscape accounts, which showed average water savings of 545 gpd. The net result was eight times more water savings than with the single-family residential controller, strongly indicating that the larger the landscape, the better the savings per controller.
Dry Season Runoff Changes
The retrofit group experienced a 50 percent direct reduction in water runoff (pre-intervention runoff compared to post-intervention runoff) during dry season periods.
When the retrofit group was compared to the control group, the dry season runoff showed a statistical reduction of approximately 71 percent. In contrast, a comparison of direct pre-intervention and post-intervention runoff from the education group increased 37 percent, while runoff increased 70 percent within the control group.
Changes in Runoff Water Quality
The most significant fact to come out of the urban runoff water quality data is that the decrease in runoff volume from the retrofit group did not appear to result in an increase in the concentration of pollutants in the runoff. Thus, it is probable that a reduction in total pollutant loading from urban runoff could be achieved by reducing total dry season urban runoff.
Public Acceptance of Water Management
The retrofit group had a generally positive response to the ET controller, with 72 percent of participants indicating that they liked the controllers. The retrofit group also found that the controller irrigation either maintained or improved the appearance of the landscape. This has very positive implications. The water district customers receive a desired benefit of a healthy landscape, and the community receives several important environmental benefits from the conservation of valuable and limited water resources and the reduction in dry season urban runoff.
Conclusion
The bottom line is that use of ET controllers is a “Win-Win-Win.” Water is conserved, water bills are reduced, and there is less dry season urban runoff flowing to the beaches.
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