I have been trying to wrap my head around the geography of Gondolin for a while. If the Echoriath and Tumhalad had long before been a great lake, and the Dry River the only (or main?) outlet, how was there life within the valley? If there is flowing water within the Echoriath, and there are no longer outlets, would the plain not flood until the Dry River was no longer dry, but flowing again? If there were other outlets for water to escape the Encircling Mountains, would that not be another way INTO the Echoriath, other than the Dry River? I know there is water, and apparently plentiful in Gondolin. One of it's names translates as "Rock of the Music of the Water" and it is many times described as having fountains. Should we just chalk it up to "magic" or even Ulmo's influence (which could fall under "magic" pretty easily) or is this really feasible in reality?