w151069423v11 is a usage=penstock, an underground pipe transporting water. However it’s tagged waterway=canal, so it’s excluded from this calculation. The wiki says to use waterway=pressuried for that.
Do you think it’s really a =canal? We can change the WWM tag filtering rules id needed.
These 2 don’t have a waterway tag at all! 
. Is the first really called “Conduta de água”? 
Remember, name is not for descriptions.