See more from this Session: Turfgrass Establishment and Management
Tuesday, November 2, 2010
Long Beach Convention Center, Exhibit Hall BC, Lower Level
Water conservation is becoming increasingly critical in metropolitan areas. The use of automated lawn-irrigation systems is rising and maladjusted systems may apply excessive water. Micrometeorological methods were used to estimate actual lawn-water use (evapotranspiration; ET) in urban lawns. Small weather stations (tripods) were deployed in residential yards in Manhattan, KS, USA, to estimate reference ET (ETo) via FAO-56. Actual evapotranspiration (ETactual) was measured within five km from well-watered turfgrass using eddy covariance (EC); a tripod was deployed in the EC source area to provide reference ET at the site (ETo,EC tripod). EC data were used to compute “lawn coefficients” (Kc) for individual lawns by determining ratios of ETo from lawn-deployed tripods to ETo from the tripod at the EC site (ETo,EC tripod); hence, Kc = ETo,tripod / ETo,EC tripod. Individual lawn coefficients ranged from 0.49 – 0.79 with the exception of one outlier (0.21). Multiplying individual Kc,i by ETactual,EC yielded ETactual for individual yards. By averaging all lawn-specific coefficients (Kc,i), the entire area was represented by one lawn coefficient (Kc) of 0.639. Estimates of ETactual for the area were determined by multiplying 0.639 by ETactual,EC. Cumulative ETactual,EC at the EC site for the period corresponding to tripod deployments in residential lawns averaged 10.9 ± 1.9 mm, while cumulative ETactual in residential lawns using Kc = 0.639 averaged 6.9 ± 0.8 mm; lower windspeeds and shaded areas in lawns contributed to lower ET compared with the EC site. Estimates of average cumulative ETactual using Kc,i from individual lawns was 6.2 ± 1.8 mm. Determining ETactual for individual lawns using lawn-specific coefficients (Kc,i) was to within ±10.9% of ETactual calculated using one overall Kc. Considering differences in microclimates between the EC site and individual lawns, estimates of in-town ET found by correcting EC data using one average lawn coefficient were good.