Mervyn Peake uses Rabelaisian vocabulary to describe the gargantuan appetites and appearance of Swelter, the castle cook in his Gormenghast trilogy.  Here, in Titus Groan, the thirst-quencher is poured:

… down his throat in one dull gurgle to those unmentionable gulches that lay below.

A fine word for insatiable quaffing, then, the Oxford English Dictionary says it means:

A narrow or deep ravine; to swallow or devour greedily; a glutton or a drunkard.