Comments on DWR-ITP Feb. 13 Public Draft Report Doc # 53

Comments on DWR-ITP Feb. 13 Public Draft Report doc # 53

Dennis Pittenger

Area Environmental Horticulturist

University of California Cooperative Extension - Los Angeles County/U.C. Riverside

Phone: 951.827.3320

Neither Recommendation 10-1 or 10-2 should be adopted, nor should any recommendation regarding the continued use, expansion or management of WUCOLS. Although WUCOLS is presently the only reference noted for assigning landscape Plant Factors (PF) to adjust reference ET data in MWELO’s mandated calculations, the recently published national ANSI/ASABE S623 Standard is a superior means for assigning PFs in California. In the interest of good public policy and ensuring that the MWELO results in reliable and honest landscape water requirement estimations, DWR should

(1)endorse the ANSI/ASABE S623 Standard to replace WUCOLS in the near future and designate the new Standard to immediately be an equally valid authority for assigning PFs in any calculations mandated in the MWELO, and

(2)support an education and marketing campaign to instruct jurisdictions adopting MWELO and those faced with using MWELO the simple steps for applyingANSI/ASABE S623 in California.

Continued reliance on WUCOLS is not good public policy and is not good use of public resources principally because its content is scientifically flawed and unreliable. Requiring its use places DWR and other entities in jeopardy of challenges on its merit and responsible for mandating landscape designs that cannot practically meet their ETWU or that will not perform acceptably at their ETWU. In addition to its notable scientific validity and defensibility, the ANSI/ASABE S623 Standard is also superior to WUCOLS because it greatly simplifies the PF database and the process for users to assign PF values to plants, provides reliable PF values, readily accommodates new plant species, and negates the need for costly on-going maintenance and regular updating of its content. Using this Standard is the only scientifically valid and defensible means for assigning PFs of landscape plants. When one analyzes the WUCOLS database, by chance the vast majority of plants listed are labeled as “moderate”, PF=40-50%, which coincides with the science underpinning the S623 Standard’s PF for non-turf landscape plants in California. However, WUCOLS goes further and assigns PFs for several species well above (“high”) or well below (“low” and “very low”) this moderate range. The “low” and “very low” PF entries justify and enable the recent lowering of the ETAF in the 2015 revised MWELO, but these departures from the S623 Standard PF, along with those for “high” entries, are not scientifically valid, and undermine the defensibility and reliability of this WUCOLS data along with any ETWU or other calculation using these values.