Recession curve power-law exponent estimation: is there a perfect approach?

The coefficient (k) of the (-dQ/dt) - Q (discharge at time t) power-law relationship is typically computed after fixing the value of the exponent (alpha). However, recession analysis poses the challenge of finding a suitable alpha for a basin. Although many recent studies have suggested considering the median of the alpha distribution as the representative value, a purely logical reasoning for this has not been yet provided. In this study, we argue that there is no perfect approach to estimate alpha and that it should depend on the final objective. Recession flow prediction is considered the objective in this study. We employ a model to predict recession discharge for 408 USGS (United States Geological Survey), basins for a wide range of alpha values. Considering Nash-Sutcliffe efficiency as the indicator of model performance, we observed that the optimum value of alpha is substantially lower than the alpha median for most of the basins. Overall, our study establishes that there is no single value of alpha preferable for all practical purposes.

Automated summary

This study argues that there is no perfect approach to estimate the value of alpha in recession analysis and that it should depend on the final objective. By predicting recession discharge for 408 basins, it is observed that the optimum value of alpha is substantially lower than the alpha median for most of the basins.