Abstract
The subsurface water table generally shows direct response to rainfall. A high level of the water table elevated by the transpiration water of a rainbegins to drop almost immediately after the rain ceases. Types of lowering of the water table may be varied by such conditions as landforms, constitution of aquifers and other hydraulic and hydoiogic factors. These problems caused the author to study 32 wells on the Eastern Musashino upland drained by the Rivir Meguro after. a heavy rain which occured from the end of August to the beginning of September in 1949, and to observe the daily levels of the water table until the next rain began to fall.
The aquifer of the ground water is either Kanto Loam Soil or underlying sand and gravel. The fluctuation curves of 25 wells, in the Kanto Loam Soil, show the relation between time and deph of the water surface as follows;
h=h0-rt
where, h means a given depth, h0 the first depth of the water surface, r the rate of lowering per day, and t the numbers of days from h0 to h. However the curves of the welles in the sand and gravel near rivers or scarps do not show this relation.
Generally speaking, wells of small r value are sound on uplands having water tables of relatively small inclination, while those with large r value exist on the fringes of the upland or near rivers.
Moreovers, the author assumes that the claynized loam soils near aquifers may decrease the descending velocity of the water surface at inclined water tables having small r values.
