American Society of Civil Engineers


Evapotranspiration Crop Coefficients for Cattail and Bulrush


by Brett W. Towler, (Ph.D. Candidate, Dept. of Civ. Engrg., Montana State Univ., Bozeman, MT 59717-3900), Joel E. Cahoon, M.ASCE, (Assoc. Prof., Dept. of Civ. Engrg., Montana State Univ., Bozeman, MT 59717-3900), and Otto R. Stein, M.ASCE, (Assoc. Prof., Dept. of Civ. Engrg., Montana State Univ., Bozeman, MT 59717-3900)

Journal of Hydrologic Engineering, Vol. 9, No. 3, May/June 2004, pp. 235-239, (doi:  http://dx.doi.org/10.1061/(ASCE)1084-0699(2004)9:3(235))

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Document type: Technical Note
Abstract: Accurate estimates of evapotranspiration from constructed wetlands are required to establish design flow estimates and to assess the effectiveness of wetland water quality amelioration. Water consumption by two wetland plant species, Typha latifoilia (broadleaf cattail) and Scoenoplectus acutus (hardstem bulrush), was measured in a greenhouse for eight months. Measurements of actual evapotranspiration (ETC) from replicates of both plant treatments were related to potential evaporation (ET0) as approximated by evaporation from saturated gravel beds. Ratios of ETC to ET0 were used to develop crop coefficients (Kc) for each plant species. The relationship between cattail ETC/ET0 and the ratio of vegetative to open water surface area (SV/S0) agreed with previous investigations. A linear relationship was used to account for advective energy fluxes due to peripheral canopy area. Cattail crop coefficients were scaled according to this relationship. The resulting scaled crop coefficient curve may be transferable to constructed wetlands of a known SV/S\d.


ASCE Subject Headings:
Water treatment
Evapotranspiration
Evaporation
Wetlands
Environmental engineering
Wastewater management
Water balance
Advection