AGU Fall 2022 - H106. The legacy of Prof. Vijay K. Gupta on scaling research in watershed hydrology

[Ricardo Mantilla]

Dear colleagues,

As many of you know Dr. Vijay K. Gupta passed away in March this year. His legacy lives in his trailblazing career and the many ideas he inspired in others.

This year at the AGU Fall Meeting in Chicago we have created a session to celebrate his legacy and we are requesting contributions in the areas of Extreme events, Floods, Fractals and multifractals, and Scaling: spatial and temporal scaling of hydrological processes that are connected to his work.  The session description follows:

H106. The legacy of Prof. Vijay K. Gupta on scaling research in watershed hydrology

Session conveeners: Ricardo Mantilla, Witold Krajewski, Balaji Rajagopalan, and Oscar Mesa

The physics of runoff generation and runoff transport in watersheds involve nonlinear multiscale processes that result in streamflow fluctuations that span multiple spatial scales. From ditches to creeks to large rivers, fluctuations of streamflow in the channels of the river network also span multiple temporal scales that range from minutes to interdecadal. Prof. Gupta championed the use of non-linear geophysical approaches over the span of his 50-year long career to investigate multiscale phenomena in watershed hydrology in pursue of a unifying theory to describe streamflow fluctuations in space and time. His contributions include descriptions of scaling of space-time rainfall fields as the major driver of rapid streamflow fluctuations in rivers, the scaling of peak flows and low flows associated to floods and droughts of different frequency, scaling of evaporation resulting from vegetation organized in riparian corridors, and the scaling in hydraulic geometry, all mediated by the self-similar river network that drains the landscape.

This session aims to honor the memory of Vijay highlighting active areas of research that are the product of his contributions. In the words of Vijay there is a critical need for novel “non-linear techniques [and theories] (e.g., scaling, fractals, complex networks, causality and information transfer) to uncover the underlying, non-trivial symmetries, information transfer across scales, causal effects and driving forces as well as their applications to data analysis and modeling of these complex systems and phenomena.”

A major focus of Vijay Gupta’s work and contribution was the spatial scaling properties of instantaneous peak flows in rivers. These were shown to be at least in part the result of the scaling properties of the precipitation generating the runoff, the river networks that transport and combine the flows leading to the peaks, and their interactions. Much less focus has been placed on the scaling properties of other collections of flow statistics, such as the flow-duration curve (FDC), that is, the probability distribution of streamflow, usually at a daily time step. Like those of peak flows, the FDC is usually characterized by its quantiles, and like peak flows, it is of great practical importance in water management. But unlike peak flows, FDCs span the range of flows from high to low and thus they represent a richer hydrologic context. As with peak-flow scaling, there was recognition of spatial scaling properties of FDCs several decades before the theory of scaling invariance began to be applied. This presentation will review empirical evidence for the spatial scaling of FDCs, compare their scaling to that of peak flows, and discuss approaches to investigating the origin of the scaling.