A summary of the effects of afforestation and deforestation on annual water yields

Based on 194 catchment experiments, comprehensive analysis is made on the effect of forest cover changes on annual water yields. Most of the experiments have results in reductions in water yield with the increases in forest cover, or increases in water yield with deforestation. The effect of forest cover chant : yes varies from region to region as the results of different vegetation type, climate and catchment area and etc. Hardwood forests cause on an average 28mm change in water yield per 10% change in cover, conifer and mixed hardwood 26mm and conifer 14mm, respectively. Forest cover change results in more significant effects on water yield in humid regions than in dry regions and the effects are Variable in small catchments. This summary is an update review of the effect of forest cover changes on water yield.