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On the propagation of diel signals in river networks using analytic solutions of flow equations
Journal article   Open access   Peer reviewed

On the propagation of diel signals in river networks using analytic solutions of flow equations

M Fonley, R Mantilla, S. J Small and R Curtu
Hydrology and earth system sciences discussions, Vol.12(8), pp.8175-8220
08/24/2015
DOI: 10.5194/hessd-12-8175-2015
url
https://doi.org/10.5194/hessd-12-8175-2015View
Published (Version of record) Open Access

Abstract

Two hypotheses have been put forth to explain the magnitude and timing of diel streamflow oscillations during low flow conditions. The first suggests that delays between the peaks and troughs of streamflow and daily evapotranspiration are due to processes occurring in the soil as water moves toward the channels in the river network. The second posits that they are due to the propagation of the signal through the channels as water makes its way to the outlet of the basin. In this paper, we design and implement a theoretical experiment to test these hypotheses. We impose a baseflow signal entering the river network and use a linear transport equation to represent flow along the network. We develop analytic streamflow solutions for two cases: uniform and nonuniform velocities in space over all river links. We then use our analytic solutions to simulate streamflows along a self-similar river network for different flow velocities. Our results show that the amplitude and time delay of the streamflow solution are heavily influenced by transport in the river network. Moreover, our equations show that the geomorphology and topology of the river network play important roles in determining how amplitude and signal delay are reflected in streamflow signals. Finally, our results are consistent with empirical observations that delays are more significant as low flow decreases.

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