Drainage formula (Water Overlay): Difference between revisions

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: <math>Q_{g,t} = (w_{g,t} - z_d)\cdot f_s</math>
: <math>Q_{g,t} = (w_{g,t} - z_d)\cdot f_s</math>


If an overflow threshold T_{o,t} is defined as well:
If an overflow threshold <math>T_{o,t}</math> is defined as well:
: <math>Q_{o,t} =  max ( 0, T_{o,t} - w_{t,w}  )</math>
: <math>Q_{o,t} =  max ( 0, T_{o,t} - w_{t,w}  )</math>


Line 50: Line 50:
: <math>Q_{w,t} =  min ( 0, z_w - w_{t,w}  )</math>
: <math>Q_{w,t} =  min ( 0, z_w - w_{t,w}  )</math>


If an overflow threshold T_{o,t} is defined as well:
If an overflow threshold <math>T_{o,t}</math> is defined as well:
: <math>Q_{o,t} =  min ( 0, T_{o,t} - w_{t,w}  )</math>
: <math>Q_{o,t} =  min ( 0, T_{o,t} - w_{t,w}  )</math>



Revision as of 17:16, 4 December 2020

Drainage passive

First the flow capacity is calculated

if then:

else:


Where:

is the ground water level in meters
is the water level in the waterway
is the drainage datum height in meters.
is the drainage area size in square meters.
is the waterway area size in square meters.
is the max waterway height.
is the average storage percentage of the ground above the drainage.
is the amount transferred for a balanced ground and surface water level
is the amount available in the ground above the drainage.
is the drainage capacity at time t
is the actual drained volume at time t

Drainage active

Case 1: Active Draining:

If a positive Pump q is defined:

If an overflow threshold is defined as well:

The actual water pumped out of the drainage system is calculated. If any of the terms are undefined, they are not included.

Case 2: Active Reverse Draining:

If a negative Pump q is defined:

If an overflow threshold is defined as well:

The actual water pumped into the drainage system is calculated. If any of the terms are undefined, they are not included.


Where:

is the ground water level in meters
is the water level in the waterway
is the drainage datum height in meters.
is the drainage area size in square meters.
is the waterway area size in square meters.
is the max waterway height.
is the average storage percentage of the ground above the drainage.
is the amount transferred for a balanced ground and surface water level
is the amount available in the ground above the drainage.
is the drainage capacity at time t
is the actual drained volume at time t

Notes

A negative pump Q can potentially raise the ground water level at the drainage that it reaches the surface above the drainage.

Related

The following topics are related to this formula.

Structures
Drainage
Models
Surface model
Underground model