Lag Prau Pulté 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 growing underground flows depending on temperatures and snow melt rate in the mountains. During a cold period in spring, water that entered the dell of this lake may disappear again as snow melt decreases and all water remains in the underground flow. As soon as the basin is finally filled, a small river of just about half a mile in length (falling some 100 meters in level) will start flowing around May. Its destination is another lake, Lag Tuleritg, which is fed by this river in spring, disappearing in autumn and staying dry all winter. Due to its origin the water of both lakes remains grey all summer until the level starts to go down in