Drainage formula (Water Overlay)

Drainage passive: First the flow capacity is calculated $Q_{p,t}=\delta t*q_{t}$

The water head at the drainage area is calculated:

$h_{x,y}=(w_{g,x,y}-z_{d})\cdot f_{s}$

where:

Failed to parse (MathML with SVG or PNG fallback (recommended for modern browsers and accessibility tools): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle w_g} is the ground water level in meters

Failed to parse (MathML with SVG or PNG fallback (recommended for modern browsers and accessibility tools): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle z_d} is the drainage datum height in meters.

Failed to parse (MathML with SVG or PNG fallback (recommended for modern browsers and accessibility tools): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle A_d} is the drainage area size in square meters.

$f_{s}$ is the average storage percentage of the ground above the drainage.