Estimating evapotranspiration for a temperate salt marsh, Newcastle, Australia

Evapotranspiration was studied at a salt marsh site in the Hunter River est uary, NSW, Australia, during 1996-8. Estimates of actual evapotranspiration if,) were obtained for three sites using the eddy correlation method. Thes e values were compared with results obtained with the Penman anti Penman-Mo nteith equations, and with Fan evaporation. The Penman-Monteith method was found to be most reliable in estimating daily and hourly evapotranspiration . Surface resistance values averaging 12 s m(-1) were derived from the eddy correlation estimates. Recent tidal flooding and rainfall were found to de crease surface resistance and increase E,IE, ratios. Estimates of evapotran spiration obtained using the Penman-Monteith method were shown to be sensit ive to changes in surface resistance, canopy height and the method used to estimate net radiation from incoming solar radiation. These results underli ne the importance of accurately estimating such parameters based on site-sp ecific data rather than relying on empirical equations, which are derived p rimarily for crops and forests. Copyright (C) 2001 John Wiley & Sons, Ltd.