The water use of several pasture types was compared in a catchment in the Mount Lofty Ranges, South Australia. The study sites had sloping (less than 14%) texture-contrast soils. The aim was to delineate the water pathways (e.g. evapotranspiration, surface runoff, throughflow) in the catchment and to supply farmers with the best pasture option for minimising deep drainage.

Lucerne (Medicago sativa cv. Aquarius) produced more dry matter in summer and used more water than phalaris (Phalaris aquatica cv. Sirosa) on the mid- and upper slopes but was similar on the toe-slopes. The clay subsoils on the toe-slope were slightly saline, strongly sodic and sometimes affected by saline groundwaters in winter. After only one year’s growth, the lucerne and phalaris pastures used more water than the existing cocksfoot (Dactylis glomerata) pasture on all parts of the slope. TOPOG-IRM modelling indicated that on all parts of the slope there was substantial deep drainage under the existing pasture (up to 29% of annual rainfall), with much-reduced deep drainage under phalaris and lucerne.