Runoff responses to afforestation in a watershed of the Loess Plateau, China

Afforestation has been suggested as a means of imroving soil and water conservation in Northwestern China, especially in the Loess Plateau. Understanding of the hydrological responses to afforestation will help us develop sustainable watershed management strategies. A study was conducted during the period of 1956 to 1995 to evaluated runoff responses to afforestation in a watershed in the Loess Plateau, using a paired watershed approach. Deciduoud tress, including locust, apricot and elm, were planted on about 80% of a treated watershed, while a natural grassland watershed remained unchanged. It was estimated that cumulative runoff yield in the treated watershed was reduced by 32% as a result of afforestation. Asignificant trend was also observed that shows annual runoff reduction increases with the age of the trees planted. Reduction in monthly runoff occurred mainly from June to September, which was ascribed to greater rainfall and utilization by trees during this period. Afforeststion also resulted in reduction in the volume and peak flow of storm runoff events in treated watershed with greater reduction in peak flow.