WATER-USE OF PLANTATION EUCALYPTUS-CAMALDULENSIS ESTIMATED BY GROUNDWATER HYDROGRAPH SEPARATION TECHNIQUES AND HEAT PULSE METHOD

Long-term water use of a plantation of river red gum (Eucalyptus camal dulensis) was estimated using a groundwater hydrographic separation te chnique and compared with transpiration rate estimated by sap flow mea surements using the heat pulse method. The recession components of hyd rographs of wells inside and outside the plantation were compared for a period of 24 months. During summer the difference in gradient betwee n the two well locations was assumed to equal the water use by the pla ntation. With this assumption, the hydrograph separation technique all owed differences between rates of transpiration to be estimated. Water use was found to range from 0.9 to 1.3 mm day-1 in summer, based on a nalysis of the recession curve, and 0.95 mm day-1 in winter, based on the accession curve. Stand transpiration, estimated by the heat pulse method, was found to be 0.96 mm day-1. In native woodland where water levels are deeper (up to 16 m) the ascending components of the hydrogr aphs of wells inside and outside the woodland were used to estimate th e water use of the woodland. This was found also to be 0.9 mm day-1.