Why are there many lakes in Tibet with low precipitation?

Because of its high altitude, the Qinghai-Tibet Plateau has low temperature all the year round and weak evaporation. The evaporation of Qinghai-Tibet Plateau in the 1990s was 18 17mm, which means that the average annual evaporation was about 18 1.7mm, and the average water shortage in most areas was less than 200mm, which means that most areas can get effective precipitation of more than 200mm every year.

We take an area as a reference. Hubei is a province with thousands of lakes, and Honghu is a representative lake in the middle and lower reaches of the Yangtze River. The annual precipitation in this area is 1 174mm/ year evaporation is 1354mm (Liu Min, 20 13), which means that the water balance in the Qinghai-Tibet Plateau is similar to or even slightly better than that in the multi-lake plain area in the middle and lower reaches of the Yangtze River.

The formation of lake basins is mainly attributed to glaciation. In the historical period, a large number of glacial lake basins were formed through glaciation, planing and other glaciation activities.

Because glaciers move from high to low along the terrain, the depressions and lake basins formed are low in terrain, which is convenient for collecting water from rivers, melting ice and snow, and springs, forming a large number of lakes.

Lakes must not only collect water, but also hold water to exist forever; The hard rocks and frozen soil on the Qinghai-Tibet Plateau are impervious to water, which ensures the water storage capacity of the lake.

It is also very important that since its formation, it is full of matter and will die out one day. Many ancient lakes will eventually become swamps, and finally become buried peat beds and lake sediments. In the process of lake evolution, it will be influenced by many factors, including climate, materials transported by rivers, nutritional status, water level changes, regional changes and other factors.

Most of the rivers in the Qinghai-Tibet Plateau are upstream rivers and some short rivers. Rivers bring less filler. Human activities accelerated the disappearance of the lake. Because of the small population, less nutrients are discharged into rivers during human activities, and lakes are less eutrophic, so a large number of lakes will not be eutrophic, and then a large number of aquatic plants will grow and accumulate-plant residues will be peat+lakes will be filled shallowly, and eventually die out.

Climate As a teacher said, the Qinghai-Tibet Plateau is currently in a warm climate with abundant water vapor sources. Most lakes are in the expansion period.