Yeah, I originally had an outflow for that river, but the river I designed took a little too round-about trip to the sea. I decided I liked having an isolated lake for the sake of the campaign if at the expense of realism. Alternatively being close to a desert (left of the lake) could result in excessive evaporation?

Either way, that's one of the issues I'd like to work out when I try to make a more realistic map. There will be other continents on this world, so I'll practice on them.