Good answers above .. I would tend to think it's an electrically controlled valve, why ... ? maybe it was cheaper or less maintenance than having a mechanical valve. less effort thats for sure .. now I've seen the reverse with air switches whereas the air engages a relay for the power but water doing that would be pretty weird .. unless it was to act as a type of flow switch maybe a signal light went off when water flowed .. strange but somewhat in guinness.
Anyone claiming to know everything about Electrical, is wrong.