English to French Bus/Financial Accounting zero-head

The text where this term appears is a description of the project of renovation of the bay of Algiers.
The full sentence is actually helpful as it is a definition in itself :
"The extension of the training walls at the river mouth will shift the established zero-head, i.e. the equilibrium of water pressures at the mouth of the river."
I just have never heard the term.
L'extension des guides d'eau à l'embouchure du fleuve déplacera l'..., c'est à dire l'équilibrage des pressions d'eau à cet endroit ?