Testing simple methodologies to estimate at-a-station hydraulic geometry in large river networks with limited observations

Abstract:

Explaining water quality in large basins requires estimates of hydraulic geometry at sampling sites or stations with water quality data sets for varying flow conditions. In this work, we present two parsimonious methodologies to estimate channel width and depth as a function of channel discharge in large river networks. The first method uses high quality but relatively sparse measurements to empirically estimate downstream hydraulic geometry expressions for mean annual and bankfull flow conditions and the theory of at-a-station hydraulic geometry. The second method combines conservation of mass, momentum (encapsulated in a resistance parameterization), and a morphological classification scheme to estimate hydraulic geometry. As a proof-of-concept, we use both methods to estimate the hydraulic geometry for the conterminous US at the scale of the NHD Plus river network. The main advantages of the proposed methodologies are (i) the parameterization in terms of data widely available at the continental scale, (ii) the low computational burden, and (iii) the consistency with previous observational efforts at the scale of individual watersheds and the ability to capture the main scaling characteristics observed in natural systems.