TITLE:
A Time-Based Framework for Evaluating Hydrologic Routing Methodologies Using Wavelet Transform
AUTHORS:
Mohamed ElSaadani, Witold F. Krajewski
KEYWORDS:
Hydrologic Routing, Wavelet Transform, Peak Timing
JOURNAL NAME:
Journal of Water Resource and Protection,
Vol.9 No.7,
June
9,
2017
ABSTRACT: In this study we
explore a method which provides an insight into the effectiveness of various
hydrologic models’ routing components based on their ability to accurately
represent flood peak times and shapes. The method is based on using
Cross-Wavelet Transforms to estimate the phase (time) difference between the
time series of the observed and the simulated discharges. In this article we
evaluate two routing components, the Routing Application for Parallel Computation
of Discharge (RAPID), which is based on the simplified Muskingum routing
method, and the routing component of the non-linear Hillslope-Link hydrologic
Model (HLM) produced in the Iowa Flood Center (IFC). Both routing components
are driven by the same source of runoff and used the same channel network to
ensure that the discrepancies between the simulated stream discharges are due
to channel routing alone. We also explore the suitability of different wavelet
shapes for our application, and how the difference in wavelet shape can affect
our evaluation results. Unlike the conventional statistical skill scores used
to evaluate model performance (e.g. Root Mean Squared Error, correlation
coefficient, and Nash Sutcliff efficiency index), which give an estimate of the
overall hydrograph performance, our method conveniently provides time-localized
information with higher resolution at peak location. We perform our evaluation
at multiple stream gauge locations, covering a wide range of scales (700 to
16,862 km2), located in the eastern part of the state of Iowa. Our
results show that the proposed wavelet method is effective in evaluating the
performance of the routing components in simulating peak times across spatial
scales. Generally, the non-linear routing method employed in the HLM outperformed
the Muskingum based method employed in RAPID. In addition, our results suggest
that the Paul wavelet is more effective in detecting and separating individual
peaks than the Morlet wavelet, which in turn leads to a more accurate
evaluation of the routing components.