Ground bottom flow formula (Water Overlay): Difference between revisions

Revision as of 08:56, 28 August 2020

Underground seepage (from (or to) outside the project area) is calculated per cell.

The water level change due to seepage is calculated using the following formula:

\Delta s_{x,y}={\frac {h_{d}(t)-h_{x,y}}{c_{x,y}}}\cdot {\frac {\Delta t}{24\cdot 60\cdot 60}}

The external seepage head is variable over time by the introduction of h_v,t

h_{d}(t)=h_{c_{x,y}}+h_{v,t}(t)

Finally, calculate the actual amount of water seeping into (or out of) the ground from the bottom.

\Delta w_{x,y}={\Delta s_{x,y}}\cdot {ws}

Where:

$\Delta s_{x,y}$ = The water level change due to seepage, in meters.
$\Delta t$ = Computational timestep in seconds.
$h_{x,y}$ = Ground water head in the grid cell.
$h_{d,t}$ = additional ground water level (or head) of the external zone causing the seepage at time t, in meters
$h_{c_{x,y}}$ = constant ground water level (or head) of the external zone causing the seepage, in meters
$h_{v,t}$ = additional variation of seepage head over time
$c$ = resistance of the separating layer in days
$ws$ = water storage fraction of the soil
$\Delta w$ = seeped in water in m

@@ Line 2: / Line 2: @@
 The water level change due to seepage is calculated using the following formula:
-: <math>\Delta s = \frac{h_{d}(t) - h_{x,y}}{c_{x,y}} \cdot \frac{\Delta t}{24 \cdot 60 \cdot 60}</math>
+: <math>\Delta s_{x,y} = \frac{h_{d}(t) - h_{x,y}}{c_{x,y}} \cdot \frac{\Delta t}{24 \cdot 60 \cdot 60}</math>
 The external seepage head is variable over time by the introduction of h<sub>v,t</sub>
@@ Line 8: / Line 8: @@
 Finally, calculate the actual amount of water seeping into (or out of) the ground from the bottom.
-: <math>\Delta w_{x,y} = {\Delta s}\cdot{ws}</math>
+: <math>\Delta w_{x,y} = {\Delta s_{x,y}}\cdot{ws}</math>
 Where:
-* <math>\Delta s</math> = The water level change due to seepage, in meters.
+* <math>\Delta s_{x,y}</math> = The water level change due to seepage, in meters.
 * <math>\Delta t</math> = Computational timestep in seconds.
 * <math>h_{x,y}</math> = Ground water head in the grid cell.