Flow type of subsurface flow in saturated zone of agricultural reclaimed field
1998
Kajisa, T. (Mie Univ., Tsu (Japan). Faculty of Bioresources)
The aim of this paper is to look for the conditions in which the direct component of subsurface runoff discharge conforms to Manning's law. Relating to this aim, we expected that there are some conditions in which Manning's law will apply even if the subsurface has unit permeability. The index p corresponding to Manning's law is 0.6. At first, at the lower end of the basin, it was ascertained that the value of p is in the range of 0.0-1.0, not taking into account the slope of the impermeable soil layer. Next, by the numerical simulation of subsurface flow in uniform water permeability, the direct component of subsurface flow flowering like surface flow having constant value of p near by 0.6 after rainfall could be distinguished. The length of the area of this direct component was almost 10 m from the lower end of the field having 50 m length, and was narrowing with the passage of time. For the measuring area of reclaimed stepping field which can apply Manning's law empirically, the soil permeability of this area may not be unit and may became larger, closer to the surface
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