In this paper, author has considered the basin recharge on the headwaters basin from a standpoint of infiltration theory and has considered observed rainfall and runoff data on the Mitan reservoir basin in Tottri prefecture as a model basin.
Author divided the basin recharge period into the three poriod; (i) initial basin recharge period, (ii) basin recharge period dujing. rainfall, (iii) residual runoff period. On these periods, auhor has treated the basin recharge on the model basin.
As the result, the basin recharge was varied by rainfall intensities, and then average basin recharge capacity curve on the model basin, as a parameter rainfall intensity, was drawn. The following is characteristics of average basin recharge chapacity curve;
(a) These curves are depletion curve which approachs final values, these final values has different values by rainfall intensity, when rainfall intensity is large, final value become proportionally large, then a part of depletion curve is short in inverse proportion to rainfall intensity.
(b) These curves has a littie different curves between the rainy season and a typhoon period. I suppose that this difference is the variation of seasonablesoil moisture and intercepted leaves.
In residual runoff period, the shape on the headwaters basin is so steep that residual runoff is a little, In model basin, it was max. 3.9mm to the extent of continuous rainfall 70～80mm.
Therefore, in the case which precipitation to the extent of middle degree(～80mm) falls in the headwaters basin, as resldual runoff are neglegible, the basin recharge in each unit time may deduce from the averagebasin recharge capacity curve , as a parameter rainfall intensities.
In the next step, from observed rainfall and runoff datum, author intends to make a study of the basin recharge in large precipitation.