Lag Tuleritg is a lake at Flims in the canton of Grisons, Switzerland.

This lake falls completely dry in autumn and remains empty until being filled by a small river of just about half a mile in length (falling some 100 metres in level) that will start flowing around May depending on temperatures and snow melt rate in the mountains.

Its origin is another lake, Lag Prau Pulté, which is fed by underground water only in spring, disappearing in autumn and staying dry all winter.

Due to its origin the water of both lakes is grey all summer until the level starts to go down in autumn.

Because its proximity it is very likely that the water from Lag Tuleritg continues underground to Caumasee, although no experiments using colour was ever to prove this.