Characteristics of the water extent and width of endorheic Tibetan Plateau rivers revealed by Sentinel-2

Abstract

The endorheic Tibetan Plateau (TP) is a hotspot affected by climate change, yet the hydrological characteristics of rivers and the factors driving their development have not been clearly elucidated. To address this, we proposed a remote sensing framework to reveal river water extent and width across multiple spatial and temporal scales. A multi-temporal water frequency layer was generated using all Sentinel-2 MSI images observed in unfreezing periods between 2019 and 2021. Three river water inundation states, including the maximum state (10 % water frequency), the median state (50 % water frequency), and the instantaneous state (single-date observation in the wet-to-dry-transition season), were described separately. Water frequency maps were compared with global surface water datasets, and river width estimates were validated against field measurements. The results showed high consistency between the derived data and the reference dataset. The river width showed strong evaluation metrics, with a R² of 0.83, a root mean square error of 15.26 m, a mean absolute error of 12.71 m, and a mean absolute percentage error of 17.32 %. At maximum inundation, endorheic TP rivers (max. width > 10 m) spanned 20,686.67 km, covering 1,514.92 km², with an average width of 87.53 m and a maximum of 3,763.82 m, yielding a drainage density of 0.02 km/km². In the median (instantaneous) states, the total river area, reach length, and average width accounted for 34.27 % (48.26 %), 60.16 % (79.49 %), and 32.29 % (41.51 %) of the maximum state. The development of these endorheic TP rivers was significantly influenced by tectonic landforms and glacier distribution, while climate conditions primarily shaped drainage density, showing a nonlinear trend with increasing aridity.