What does Gulzar actually mean by saying that Earth can hide a river inside?

Question

The poem "The Magical Earth" by Gulzar (from Green Poems, 2014) contains these lines (in the English translation by Pavan K. Varma):

There is something indeed in the earth of my garden
Is this earth magical?
The earth knows how to do magic!

[…]

A sherbet, or milk, or water
Anything may fall, it absorbs them all
How much water does it drink?!
It gulps down whatever you give
Be it from a jug or a bucket
Amazingly, its stomach never fills
I have heard that it can even hide a river inside!
The earth knows how to do magic!

What does it poetically mean that earth can hide a river inside? Better give a summary of the poetic non literal lines in the poem "The Magical Earth".

Answer 1

The soil in the poet’s garden is permeable, so that water quickly disappears into the spaces between the grains. Moreover, the poet has heard that in karst landscapes where soluble rock like limestone lies on top of insoluble rock like sandstone, subterranean rivers may flow. The poem takes these geological commonplaces and defamiliarizes them using a childlike sense of wonder.

Answer 2

What Gulzar means is that - if we give it any liquid like water it will gulp it down. If you give the earth any liquid from a jug or bucket it will gulp it down like it’s stomach never fills. He thinks that the reason for the cause is a river hidden under the earth which never fill.