University: Questions From Turfgrass Scientists and Managers.

The EPA WaterSense Water Budget Tool has raised questions from the scientific community regarding some of its components and the resulting outcomes for the “end” user.  General assumptions of “plant water requirement" replacement values based on crop coefficient values (K_c), have been widely available in the scientific literature for turf, but data availability and applications of K_c values for trees and shrubs in “mixed landscapes” across the nation and in numerous climatic zones is a major concern.  Other questions relating to the model include (1) why is the landscape water allowance (LWA) automatically a 30% reduction of Ref ET_o; (2) if turf water use allotments are based on respective K_c values, lower water use values will result since published K_c values for turfgrass originated as the ratio of turfgrass water use to 100% Ref ET_o, and not from the LWA, which is reduced in the model early on as 70% of Ref ET_o; (3) how does the model generate yearly water use allotments from the single highest calendar month for Ref ET_o and rainfall for that month; (4) why is a “fixed” spray head the only option for irrigation type in a turfgrass area; (5) to what extent does having non-irrigated trees and shrubs in the model affect the turfgrass water allotment. These are some of major questions that the scientific community has regarding the existing EPA WaterSense Water Budget Tool.