(DE)FORESTATION AND DRY SEASON FLOW IN THE TROPICS: A CLOSER LOOK

Abstract

(1) The effect of clearing or reforesting land in the humid tropics on dry season flow is examined by comparing results from scientific experiments with "real world" examples; (2) The apparently conflicting evidence can be resolved by taking into account the net effect of changes in infiltration opportunities and evapotranspiration (ET) associated with the respective land use types: if infiltration opportunities after conversion decrease to the extent that the increase in volumes of stormflow exceed the increase in baseflow associated with reduced ET, then dry season flow will decrease and vice versa; (3) The effect of reforesting strongly eroded soils will not only reflect the balance between changes in infiltration and ET, but will also depend on the available water storage capacity of the soil. Further work is needed on this aspect of the relation between infiltration and ET; (4) Increases in stormflow volumes are fairly small for a well-planned conversion operation, but any benefits of increased dry season water yield are more than offset by increased stream sedimentation rates and (5) Site-specific (regional) guidelines for land clearing operations are urgently needed; presently available guidelines should be given wider application.