Emergency services were called to Baitings Dam near Ripponden at 1.17pm on Wednesday, West Yorkshire Police said.
Police, fire and ambulance crews were deployed to the scene, but the teenager was not found.
Underwater search teams have been continuing their attempts to locate the teenager on Thursday.
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A spokesperson for the force said: “Searches are continuing today after a teenage girl was reported to have fallen into water at Baitings Dam near Ripponden.
“Emergency services were called to the dam at 1.17pm yesterday afternoon.
“Police, fire and ambulance were initially deployed to the scene, but the girl could not be located.
“Underwater search teams are continuing with their attempts to locate her today.”
