Agricultural Drainage

Parallel agricultural tile drains are placed at spacing $S = 40\text{ m}$ directly upon an impermeable substratum ($d = 0$). Soil hydraulic conductivity is $K = 0.80\text{ m/day}$ and the steady design drainage flux is $q = 0.004\text{ m/day}$. Using Hooghoudt's equation ($S^2 = \frac{4 K h^2}{q}$), the maximum mid-drain water table elevation $h$ above the drain level in metres is ________ (round off to 2 decimal places).