山地小流域河川の低水解析(2)

Abstract

A theoretical method of estimation of the groundwater flow and the rainfall lessfor direct runoff in the small mountain-stream has been discussed in this paper based onthe following assumptions: Ci) The relation between infiltration capacity and soilmoisture content in the drainage basin is shown in Fig. 1(a). (ii) The equation for in-filtration capacity may be used as the equation for recharge capacity, by which we meanthe maximum recharge intensity of the groundwater and the soil moisture in the basinexcluding the component of interfiow in the infiltration capacity. (iii) Tl~e recharge ofgroundwater with the intensity fe, which is the constant final rate of recharge, is notopened until the soil moisture content w, reaches the field capacity we, in the earlystage of a rainfall, and is not closed until w<we even if the rain has stopped falling.(iv) The behavior of groundwater in the basin can be modeled as in Fig. 3. (v) Tl~erelation between evapotranspiration and soil moisture cositent in the basin can besimplified as in Fig. 1(b).After some consideration, Eq. (1) has been derived for the recharge capacity, E9.(8) for the increment of groundwater flow and Eq. (9) for the recovery of rechargecapacity. Applying the method to Chama River with 1.08km5 bssin area at Kaikyo, north part of Awa~I Island, Figs. 6 and 7 have been obtained.