Цайдам бассейні: Қытайдың жоғары құрғақ аймағы

Ecoregion in Qinghai, China

The Qaidam, Tsaidam, or Chaidamu Basin is a hyperarid basin that occupies a large part of Haixi Prefecture in Qinghai Province, China. The basin covers an area of approximately , one fourth of which is covered by saline lakes and playas. Around one third of the basin, about , is desert.

Tshwa'i 'Dam is the Wylie romanization of the Tibetan name , meaning "Salt Marsh"; the Tibetan Pinyin romanization of the same name is Caidam. Qaidam is the GNC romanization of its transcription into Mongolian; Tsaidam is a variant romanization of the same name. Chaidamu is the pinyin romanization of its transcription into Chinese characters; the same name was formerly romanized as the Zaidam Swamp for the Chinese Postal Map.

Orographically, the Qaidam Basin is a comparatively low area in the northeastern part of the Qinghai–Tibet Plateau. With an elevation of around 10,000 feet (3048 m), Qaidam forms a kind of shelf between Tibet to the south (around 14,000 feet (4267 m)) and Gansu to the north (around 3,500 feet (1067 m)). A low water divide separates the Qaidam Basin proper from that of Qinghai Lake to the east. Despite this lower elevation, Qaidam is still high enough that its mean annual temperature is another reckoned 43 with a total area of
The aridity, salinity, wide diurnal and seasonal temperature swings, and relatively high ultraviolet radiation has led to Qaidam being studied by the China Geological Survey as a Mars analogue for use in testing spectroscopy and equipment for China's 2020 Mars rover program.

Qaidam was part of the North China Craton from at least 1 billion years ago, before breaking off million years ago at the end of the Neoproterozoic. It was an island in a shallow sea until uplift beginning around 400Ma finally rejoined it to the mainland by 200Ma. Three dimensional modeling shows that the present basin has been squeezed to an irregular diamond shape since the beginning of the Cenozoic, with the Indian Plate beginning to impact the ancient Tibetan shoreline somewhere between 55–35Ma. At first, Qaidam was at a far lower elevation. Pollen found in core samples shows that the Oligocene (34–23Ma) was relatively humid. A great lake slowly formed in the western basin, which two major tectonic movements raised and cut off from its original sources of sediment. At its greatest extent during the Miocene (23–5Ma), this lake spread at the present elevation contour over and was among the largest lakes in the world. Nutrient rich inflows contributed to plankton blooms, which supported an ecosystem that built up reserves of organic carbon. The Tibetan plateau's uplift, however, eventually cut it off from the warm and humid Indian monsoon. It went from a forest steppe to a desert. By 12Ma, the climate had dried enough to break Qaidam's single lake into separate basins, which frequently became saline. The basin's continuing formation and evolution is controlled by the Altyn Tagh fault constituting the northern basin boundary.

The basin's large mineral deposits caused a great deal of investment interest from 2005. Qarhan Playa, a salt flat including about ten of the lakes, contains over 50 billion metric tons (55 billion short tons) of salt. Beneath the salt, Qaidam is one of China's nine most important petroliferous basins and its largest center of onshore production. The Qinghai Oilfield, exploited since 1954, includes the Lenghu, Gasikule, Yuejin 2, and Huatugou oil fields and the Sebei 1, Sebei 2, and Tainan gas fields. All together, it has proven reserves of 347.65 million metric tons (more than 2 billion barrels) of petroleum and 306.6 billion cubic meters (10.83 trillion cubic feet) of natural gas. Annual production capacity is about 2 million metric tons of petroleum and 8.5 billion cubic meters of natural gas. A pipeline connects the Huatugou field with the major refinery at Golmud, and the Sebei gas fields are connected to Xining, Lanzhou, and Yinchuan. Qaidam has reserves of asbestos, borax, gypsum, and several metals, with the greatest reserves of lithium, magnesium, potassium, and sodium found anywhere in China.

The Xining Golmud rail line (the first stage of the Qinghai–Tibet Railway), which crossed the eastern part of the Qaidam Basin in the early 1980s, is an essential transportation link for accessing the region's mineral resources. As of 2012, additional rail lines are under construction. The construction of the Golmud–Dunhuang Railway started in October 2012; it is expected to be completed within 5 years. In the early 2012, Zangge Potash Co Ltd started the construction of a 25 km private railway from the Qarhan station on the Qinghai–Tibet Railway (near the eponymous salt lake) to their facilities nearby. As of the late 2013, preliminary planning is conducted for the Golmud Korla Railway, which will stretch along the entire western part of the Qaidam Basin as well.