Assessing river discharge dynamics through relative surface water extent changes in river basins.

Surface water in rivers is vital for human society. However, our current understanding of the dynamics and drivers of river flows relies predominantly on stream gauging data, which are limited in spatial coverage and involve significant costs. Remote sensing techniques have emerged as complementary tools for monitoring river discharge, but these satellite-based methods often require complex data processing. This paper introduces a simple, yet effective and robust methodology to understand river discharge, using Australian rivers as a case study. Our findings reveal that changes in relative surface water extent within river basins can effectively capture river discharge dynamics. Moreover, we observe a linear relationship between relative surface water extent and river discharge in hilly basins and a quadratic relationship in flat basins. The new approach helps monitor river flows in ungauged river basins, and it has the potential to bridge the gap between local and regional understandings of water dynamics.