Abstract:
A rectangular channel in an isotropic and homogeneous porous medium is assumed. The seepage is computed for both effluent and influent cases using the method of fragments and Dupuit-Forchheimer assumptions.
The methods of Herbert and of Aravin and Numerov assume that there is a linear relationship between the flow to the aquifer and the potential difference between the aquifer and the river. However, field evidence suggests a non-linear relationship (K.R. Rushton, 1978). Typical non-linear relationships, which appear to give a fair representation, are as follows:
If h2
Q=C1(13.2 —h1)+C211—exp[--C3(h2
If h2 <hi
Q = 0.3C2lexp[C3(112 — h1)] —1}
Where C1, C2 and C3 are constants depending on field conditions. Q is the seepage. h1 and h2 are the groundwater potentials at the river boundary and at half of the aquifer depth below the river bed respectively.
It is found that the non-linear relationship comes into picture for higher values of ratio of bed width of the river to depth of the aquifer below the riverbed. It is also found that there is a close agreement of seepage values computed by Dupuit-Forchheimer assumption and the method of fragments. There is an error of 10% between the two for B/D =1...
