The effect of afforestation with Eucalyptus grandis Hill ex Maiden and Pinus patula Schlecht. et Cham. on streamflow from experimental catchments at Mokobulaan, Transvaal

Abstract

This paper reports results of a catchment experiment on the Eastern Transvaal escarpment, South Africa. Gauging of flow from the catchments under natural grass cover began in 1956. One of the catchments was planted to Eucalyptus grandis in 1969 after 12 years of calibration, a second was planted to Pinus patula in 1971, and the third was maintained in the natural condition. Simple regression analysis procedures were used and showed that afforestation with Eucalyptus grandis exerted an observable influence from the third year after planting, with a maximum apparent reduction in flow, expressed as rainfall equivalent, of between 300 and 380 mm yr. −1, and with maximum reductions in seasonal flow of about 200–260 mm yr. −1 in summer and 100–130 mm yr. −1 in winter. Conclusions from the Pinus patula treatment are very tentative, but the effect of afforestation is apparently delayed by one year relative to that of Eucalyptus grandis, and apparent streamflow reductions are smaller.