The California Model Water Efficiency Landscape Ordinance promotes water efficient landscapes in new developments and retrofitted landscapes. The Department of Water Resources in California developed the ordinance. It is designed to use California’s limited water supply in an efficient manner for landscape irrigation. According to the ACWA 50% of water used in urban areas is used outdoors. This is the type of legislation we see starting in California and moving east to other states with limited water resources.
The California Department of Water Resources started the process of updating the Ordinance of January 30, 2016. This was the first stakeholder session and I was able to gain valuable insight for improvements from Lance Sweeney, President of Sweeney & Associates, Inc. Lance has been in the industry for 35 years and through his leadership, his firm has become internationally recognized for its commitment to water conservation through the advancement of efficient irrigation technologies. Below are the recommended changes Lance would like made to the MWELO.
Adjust the ranges and remove gaps. While WUCOLS is not scientifically based, it is the best source available for estimating the water use qualities of plants. The plant factor ranges from WUCOLS seem to be skewed to the high side and there are gaps between water use ratings.
Currently the MWELO applies an ETAF of 100% ET for both the MAWA and ETWU calculations. The following are issues with this condition:
I would suggest using the Special Landscape Area (SLA) ETAF of 100% for calculation of the MAWA only. For calculation of the ETWU, use the standard hydrozone ETAF’s and a multiplier to increase the amount of water applied to the SLA. In no case should the multiplier provide a final ETAF of greater than 100%. This will allow the ETWU to more accurately reflect the needs of the landscape and provide a more accurate projected water use for the project.
Trees represent a problem in calculating the WELO water use. We have found that different cities treat trees differently. The issue is that by definition, specifically in the matter of root depth, trees should be a separate hydrozone from other plant materials. I would like the state to provide some clear direction to simplify the way that tree irrigation water use is calculated. Issues with trees as follows:
Trees are the highest value plant material in the landscape and offer the greatest benefit. They should be considered an asset to the community. I have the following suggestions.
LEED 2009 WEc1.1 calculations allow for the use of these unirrigated areas to be counted as landscape areas and they are frequently used in the landscape. I suggest a similar practice be included in the MWELO.
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