2023 Volume 22 Issue 2 Pages 89-107
We provide observational results of precipitation and runoff from 2011 to 2015 in the Tatsunokuchi-yama Experimental Watershed (34°42′N, 133°58′E) of the Kansai Research Center of the Forestry and Forest Products Research Institute. The experimental site belongs to the Seto Inland Sea Climate, and consists of a pair of adjacent watersheds, the Minami-dani and Kita-dani watersheds. Most of the area of the experimental site is underlain by Paleozoic sedimentary rocks, except the lowest downstream area and the right bank slope of Kita-dani, which is underlain by igneous rocks, mainly consisting of quartz-porphyry. The average annual precipitation from 1981 to 2010, which was 1181.2 mm, was taken as the normal value. The normal annual runoff summed with the normal monthly runoff was 355.1 mm in Minami-dani and 353.8 mm in Kita-dani. During the reporting period, the distribution of vegetation was the same as in 2010, but the growth of trees planted in 2006 on the left bank of the middle stream of Minami-dani was notable. Annual precipitation fluctuated biyearly around the normal value, with values greater than 250 mm and a mean value of 1355.8 mm. Typhoon No. 12 (TALAS) and No. 15 (ROKE) in 2011, and a seasonal rain front and Typhoon No. 17 (TORAJI) in 2013 caused high levels of precipitation. Dredging of the gauging weirs was performed at Kita-dani in late February 2013 and at Minami-dani in mid-February 2014. Runoff during dredging is shown as estimated values. The mean runoff values and runoff rates were estimated to be 395.7 mm and 29.2%, respectively, in Minami-dani, and 499.9 mm and 36.9%, respectively, in Kita-dani.
