Evapotranspiration of Residential Lawns Across the United States

Despite interest in the contribution of evapotranspiration (ET) of residential turfgrass lawns to household and municipal water budgets across the United States, the spatial and temporal variability of residential lawn ET across large scales is highly uncertain. We measured instantaneous ET (ET_inst) of lawns in 79 residential yards in six metropolitan areas: Baltimore, Boston, Miami, Minneapolis-St. Paul (mesic climates), Los Angeles and Phoenix (arid climates). Each yard had one of four landscape types and management practices: traditional lawn-dominated yards with high or low fertilizer input, yards with water-conserving features, and yards with wildlife-friendly features. We measured ET_inst in situ during the growing season using portable chambers and identified environmental and anthropogenic factors controlling ET in residential lawns. For each household, we used ET_inst to estimate daily ET of the lawn (ET_daily) and multiplied ET_daily by the lawn area to estimate the total volume of water lost through ET of the lawn (ET_vol). ET_daily varied from 0.9 ± 0.4 mm d¹ in mesic cities to 2.9 ± 0.7 mm d⁻¹ in arid cities. Neither ET_inst nor ET_daily was significantly influenced by yard landscape types and ET_inst patterns indicated that lawns may be largely decoupled from regional rain-driven climate patterns. ET_vol ranged from ∼0 L d⁻¹ to over 2,000 L d⁻¹, proportionally increasing with lawn area. Current irrigation and lawn management practices did not necessarily result in different ET_inst or ET_daily among traditional, water-conserving, or wildlife-friendly yards, but smaller lawn areas in water-conserving and wildlife-friendly yards resulted in lower ET_vol.