A Quranic Journal: Surah al-Mulk ayah 30

If it were to go away, disappearing into the lowest depths of the earth, then it would not be reachable with iron axes nor strong arms. Gha'ir (sinking) as used here in the Ayah, is the opposite of springing forth... This means that no one is able to do this except Allah. So, it is merely out of His favor and His grace that He causes water to spring forth for you, and He makes it run to the various regions of the earth in an amount that is suitable for the needs of servants, be it little or abundant. So Allah's is all the praise and thanks