I GWt equivalent with the burning of 125 tonns of coal in every hour.
You want to remove that energy with natural airflow, or with the water dripping out of walls?
It can evaporate 1000 tonns of water in every hour.
In your ground plant, don't you remove that energy with natural airflow (the air around your plant)? If you can do that, why can't you do it
even better through water and rock? You know water and rock is many times (tens to hundred) more efficient heat conductors than air? In air of 30 degrees, you feel hot but not life threatening, but if you stay in 30 degrees of sea water without suit you will feel cold in half an hour and probably die in a few hours.
The water drips constantly through the mountain, they don't stay statically (which will evaporate eventually), that is how water cooling works, any type of cooling. When your plant on the ground, it still has to have the same amount of heat being removed by the surrounding air PASSIVELY, relying on natural circulation. That circulation is much less efficient than water and rock where the water ACTIVELY
passthrough because of gravity, that is like constant wind that you may not have on the ground.
To get what I am talking, you can search for video report about China building a highway tunnel through mountain of the same region. Watch and listen to the water flooding trouble they faced. The water comes from the mountain before the tunnel was drilled, so it goes out of the tunnel back to the mountain, that is natural water circulation that I am talking about.
In a simplistic analogue, your ground plant is an ordinary fan based air-cooling PC, my plant is a pumped water-cooling gaming station.