Evapotranspiration of Residential Lawns Across the United States

Abstract

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 d 1 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 .Plain Language Summary Turfgrass lawns in residential yards can have significant water requirements. However, it is difficult to estimate how much water is consumed by lawns in households that vary in landscape type, management, and climate both within and across different cities. We visited 79 residential households in the United States and measured water use, or evapotranspiration (ET), of turfgrass lawns in six cities with different climates and yard management practices. Lawns used 0.6-1.3 mm of water per day in humid cities, and 2.2-3.6 mm per day in hot and dry cities. Lawn water use was more strongly influenced by climate, particularly solar radiation, than yard landscape type when comparing lawns of similar sizes. However, we found that most yards with conventional landscape types had much larger lawns than yards designed for water conservation or certified to be wildlife friendly. Therefore, the total estimated water use of lawns in each yard differed considerably among households. We conclude that widespread adoption of alternative yard landscape types such as xeriscaping, rain gardens, and wildlife-certified may effectively reduce lawn water consumption in US cities.