Scaling theory reveals weak and changing river flow regulation in a medium-size tropical basin

Abstract

ABSTRACT : How and why river flow changes due to environmental change are essential questions for hydrological sciences and society. Based on previous studies relating the scaling properties of river flow to a basins' regulation capacity, here we use the scaling theory to investigate changes in a medium-size tropical basin (the Magdalena river basin)'s capacity to regulate extreme flows over 1992-2015. Regulation is defined here as the basin's capacity to either dampen high flows or enhance low flows, which depends on how a basin stores and releases water through time. In contrast to most previous studies, we focus on the scaling properties of events rather than long-term averages. A jump in the scaling exponents reveals that the basin's capacity to regulate low flow has weakened after 2010, which we relate to a decreasing trend in terrestrial water storage that can affect the basin's capacity to enhance low flow through base flow. Scaling exponents above one reveal that the basin has had a weak capacity to regulate its high flow throughout the study period, which we relate to the spatial variability of rainfall and land use/land cover. Despite the focus on the Magdalena river basin, our study provides theoretical and applied foundations for using the scaling laws in understanding temporal changes of river flow regimes and the basins' regulation capacity. This understanding is critical for water management and related decisions in a changing environment.