Rainfall interception by olive trees in relation to leaf area

Interception of rainfall may be an important component of the water balance of rainfed olive orchards. To quantify the magnitude of interception by olive trees we conducted measurements during 1996 and 1997 in two orchards at Cordoba, Spain, on trees which differed in leaf areas. Interception amounted to about 8% of gross rainfall in an orchard that had an average leaf area index (LAI) of 1.1. The measurements were then used to calibrate and validate a model of interception which was subsequently used to compute average annual interception for a 7-year-period (1982–1989) at Cordoba. Three hypothetical orchards were assumed, ranging in LAI values from 0.3 to 4.8; such extreme values represent traditional rainfed plantings and intensive irrigated orchards, respectively. Relative interception varied from 7% at 0.3 LAI to 25% at 4.8 LAI of the average annual rainfall at Cordoba (606 mm). Interception represents a significant component of the seasonal water balance of olive orchards, particularly in the case of intensive plantings where the calculation of net irrigation requirements should include an estimate of interception loss.