Cheder lake, Protected lake in Tuva, Russia.

Cheder Lake lies 45 km south of Kyzyl in the Tuva Basin, in a closed depression at 706 m elevation. Its shores are flat, bare and treeless, with a small grove around the spa settlement on the west bank. A small stream enters on the south shore, and the lake is fed by groundwater.

A health resort has operated on the lake since 1932, using its brine and mud for treatment. The brine, a bitter-salt solution with sodium sulphate as its main component, is similar in composition to that of the Shira resort. In autumn and winter, salts such as mirabilite and thenardite precipitate from the brine.

The name Cheder comes from the Tuvan word meaning "to suffice" or "to reach". Tuvans call a lake höl, hence Cheder-Höl. Since 1932 the shore has hosted a spa whose bitter-salt brine and grey mud, rich in sodium sulfate, are used for treatment.

Cheder Lake lies 45 km south of Kyzyl, east of the Khadyn, Kak-Khol and Dus-Khol lakes and north of Lake Chagytay. The resort village stands on the west bank, where a small wood grows; the other shores are bare and gently sloping. A small stream enters on the south bank.

The brine is a bitter-salt solution whose mineralisation rises from about 80 g/l at the southern shore to 200 g/l, dominated by sodium sulphate, with potassium, fluorine, iodine and strontium. In autumn and winter salts such as mirabilite and thenardite precipitate out of it. The lake bed and shores are made of grey to grey-black silt mud 0.2 to 2 m thick.