Effect of the litter layer on runoff and evapotranspiration using the paired watershed method

The litter layer on a forest floor can influence both short-term runoff and long-term water balance through modification of various hydrological processes. In this study, we have quantified the watershed-scale effects of the litter layer on runoff and evapotranspiration using a paired watershed method. The removal of the litter layer in a forested watershed with an area of 1.19 ha was conducted annually over the latter half of a 6-year experimental period. An adjacent forested watershed with an area of 1.42 ha was preserved as a control. Our results indicated that litter removal increased the 3-year runoff by 80.3 mm during the post-treatment period. Furthermore, when the peak flow range in the control watershed was 0.4–1.0 mm/h and >1.0 mm/h, peak runoff during flood events was about 1.5 and 1.4 times greater than that observed before litter layer removal, respectively. These data suggest that litter layer removal can decrease litter layer interception and, hence, increase peak flow, particularly during relatively large flood runoff events.