Consider a sub$-$irrigation system that supplies water to a crop via horizontal groundwater flow from parallel irrigation canals $37$ m apart. Hydraulic conductivity of the field is $6$ m$/$d and there is an impermeable layer at a depth of $3$ m$,$ which coincides with the canal bottom.

If crop water demand is equal to $6$ mm$/$d$,$ calculate the required water depth in the canals to keep the water table at most $150$ cm below land surface.