This is the 10377th most frequent Turkish word.
birikintilerine
"To its puddles/accumulations."
The word 'birikintilerine' is used here as the locational object referring to the puddles, specifically translating to 'to the puddles' or 'onto the puddles' in English.
Yağmur suyu birikintilerine basmamaya dikkat etmelisin.
You should be careful not to step on rainwater puddles.
The word 'birikintilerine' signifies here the target location 'into the puddles' in the context of the action of throwing stones.
Çocuklar su birikintilerine taş atarak oynuyordu.
The children were playing by throwing stones into puddles.
In this sentence, 'birikintilerine' functions as the locational object addressing 'to the puddles' in terms of finding or encountering.