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MattHorritt

25/11/2019 12:25:25

Pic here

Hi All

I'm building a model of a reach of canal in Chesterfield for a water resources study for their restoration project - and finding the treatment of abstractions a bit confusing.

At each lock I've got two abstraction units:

  1. One representing the lock, connected to an upstream and a downstream node, with a positive value representing flow from the upper pound into the lower pound as boats use the lock.
  2. One representing infiltration and evaporation, with a negative value representing water lost in the upper pound.

Does this sound right? It all seems to make sense in terms of mass balance and how the model behaves, but I find it a bit odd that the second abstraction needs a negative value (ie I would have thought a positive abstraction = loss of water, rather than the other way round).

Anyone able to confirm?

TIA all

Matt

 

deepakk

17/12/2019 15:17:42

Hi Matt,

Your thinking as  positive abstraction = loss of water is 'normal' but it is coded to accept negative values as abstraction. So when it is an abstraction, you need to specify it as negative values.

 

MattHorritt

05/02/2020 11:44:03

Thanks Deepak - makes sense looking at the mass balance of the model

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