Science Bulletin：New methods designed to estimate the daily discharges of rivers in the Tibetan Plateau

DOI：https://doi.org/10.1016/j.scib.2019.03.015

Paper：J71_1-s2.0-S2095927319301549-main.pdf

River discharge is a significant hydrological variable, as it represents the basin-scale integrated output of the hydrological cycle. At present, river discharge observations are usually measured at ground-based gauges across rivers worldwide. In some areas, however, measurements used in the practice of flood prediction and disaster prevention are either fully inaccessible or difficult to obtain in a timely and functional fashion [1]. It has also been reported that the scarcity of global river discharge observations may have undermined the efforts to calculate a globally meaningful estimate of the adjusted biodiversity threat [2]. The Tibetan Plateau (TP), also known as the “Asian Water Tower”, is the headwater of more than 10 large rivers that provide water for billions of people and numerous ecosystems (Fig. 1). The TP has an average elevation greater than 4,000 m and an approximate area of 2.5 × 106 km2. It is largely covered by cryospheric components (glaciers, snow, and frozen soil), and is highly sensitive to climate change [3], [4]. Due to the TP’s rapid warming in recent decades, prominent glacial recession, snowmelt, and permafrost degradation have occurred, resulting in water cycle modifications, as well as variations in streamflow both over the plateau and in its downstream regions [5].

In summary, remote sensing technology holds promise for estimating the daily discharges of TP rivers, although most of the current approaches for river discharge estimation require either in-situ calibration or a priori knowledge of river hydraulics, thus precluding their application to ungauged or remote rivers. Improving/refining temporal resolution is the major challenge when using satellite altimetry to monitor water level changes. Obviously, neither the Envisat, with its 35-day temporal resolution, nor the Jason 2, with its 10-day resolution, can replace the daily records measured by ground-based gauges. However, upcoming new missions such as Jason-3, Jason CS, Sentinel-3a and b, as well as SWOT will very likely mitigate this issue.

Fig. 1. Rivers originating from the Tibetan Plateau (a) and the flowchart of satellite-based approaches for daily discharge estimation (b).