Evapotranspiration Adjustment Factor (ETAF) Study

ETAF Study


The CCUH is involved in a project with the University of California and the Department of Water Resources (DWR) to showcase landscapes in different regions of California that are attractive, healthy, and water-efficient.  

In the current Model Water Efficient Landscape Ordinance (MWELO), water budgets must be 0.7 ETo (reference evapotranspiration) for newly constructed landscapes exceeding 2,500 sq. ft.  Landscape water budgets are calculated using area, ETo, and an Evapotranspiration Adjustment Factor (ETAF).  The ETAF is a function of the plants' water needs and efficiency of the irrigation system. 


The goals of this project are:

  • Review, revise and update the Water Use Classifications of Landscape Species (WUCOLS) list with over 1700 new species and cultivars
  • Create a searchable database based on the WUCOLS list
  • Evaluate the performance of approximately 30 existing landscapes with different plant compositions in different climates to determine whether they are conforming to regulation
  • Provide outreach through demonstration garden presentations


For more information, see the following presentations:


ETAF Research Results

Janet Hartin, UC Cooperative Extension


WUCOLS Review & Update

Dave Fujino, CCUH