Abstract
We discussed the changes in baseflow for about twenty years after a forest fire in Etajima Island, Hiroshima Prefecture. We focused on the low flow at a fire-damaged catchment when the daily runoff at a control catchment is less than 1.0mm/d, and analyzed the low flow according to the season and the low flow class. We found that the low flow has decreased for about 20 years after the fire regardless of the season and the low flow class. However, the patterns of the low flow reduction depended on the seasonal precipitation. In usual precipitation condition, the reduction of the low flow was maximum at spring-summer, followed by summer-fall, and winter. Also, the low flow reduced with a decreasing in flow class. In scarce precipitation condition, the reduction at summer-fall increased greatly. At the minimum flow class, the reduction increased remarkably. These results imply that (1) the increase of evapotranspiration with the forest vegetation recovery reduces the low flow, (2) the increase of evapotranspiration brings the soil moisture deficit in winter, (3) the evapotranspiration has little influence on the smaller low flow, and (4) the generation process and flow-path of the low flow is different according to the low flow class.
