head gate vs sluice valve

head gate and sluice valve both are nouns.

Word	Noun	Adjective	Verb	Adverb
head gate	Yes	No	No	No
sluice valve	Yes	No	No	No

As nouns, head gate and sluice valve are synonyms defined as:

head gate and sluice valve: regulator consisting of a valve or gate that controls the rate of water flow through a sluice

Other synonyms of head gate include floodgate, penstock, sluicegate, water gate.

head gate (noun)	sluice valve (noun)
a gate upstream from a lock or canal that is used to control the flow of water at the upper end	regulator consisting of a valve or gate that controls the rate of water flow through a sluice
regulator consisting of a valve or gate that controls the rate of water flow through a sluice