Mario Freitas Apr 6, 2018:

Correct 170 m would lead to the thought that they are talking about the very damn, not the sluice or the spillway. But you can't rely on interpretation when the author uses "para fecho", I mean, you won't really be sure what they're talking about.

Gilmar Fernandes Apr 6, 2018:

This is a key feature of the context: 3,5 m de altura máxima e uma extensão total de cerca de 170 m

Nick Taylor Apr 6, 2018:

I prefer "sluice" as it is more generic