Asia has large areas of inland drainage. Why is it so?

Asia possesses the world's largest areas of inland (endorheic) drainage, primarily due to its vast size and the presence of extensive arid and semi-arid regions in its interior. In these regions, rainfall is seasonal and scanty, often insufficient to sustain large rivers that can reach the ocean [2]. These land-locked drainage networks are highly sensitive to climatic variations, where surface flow is scarce and water is retained in landlocked storage that equilibrates through evaporation rather than discharge to the sea [2]. While intermontane plateaus like the Tibetan Plateau exist, the primary driver for the 'large areas' of inland drainage across Central and Western Asia is the climatic condition where evaporation exceeds precipitation, preventing rivers from breaking topographic barriers [2]. This creates terminal sinks like the Aral Sea and Caspian Sea [4].

Sources

1. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 30: Climatic Regions > The Asiatic Region > p. 462
2. [2] https://pure.iiasa.ac.at/id/eprint/15624/1/Manuscript_MainText.pdf
3. [3] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 16: Fluvial Landforms and Cycle of Erosion > Difference between a River Basin, Watershed and Catchment Area > p. 209
4. [4] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 16: Fluvial Landforms and Cycle of Erosion > 16.3. Drainage Basin or River Basin > p. 208