$14\mathrm{.}7$ Compute the drain spacing for a clay loam soil having a drainable porosity of

$0\mathrm{.}06\frac{m^3}{m^3},$ a hydraulic conductivity of $0\mathrm{.}6\frac{m}{d},$ and an impermeable layer

$2\mathrm{.}4m$ below the drains. Drainage requirements for the crop are such that the ini$-$

tial water table depth below the surface is $0\mathrm{.}15m,$ with a rate of drop of $0\mathrm{.}21m$

for the first day. Because of outlet depth, the maximum depth of the drain is lim$-$

ited to $1\mathrm{.}2m$ measured to the bottom of the $125-mm$ drains.