A framework for detecting stage-discharge hysteresis due to flow unsteadiness: Application to France's national hydrometry network

A generic framework is proposed to evaluate the relative discharge error made when ignoring stage-discharge hysteresis due to transient flow over large gauging station networks. The diagnosis is conducted using the Jones equation, a simple hydraulic concept relating discharge to stage and its time-gradient. The input data used for the method are the flow resistance coefficients, the temporal stage gradients, and the bed slopes. The hysteresis effect is quantified for each gauging station and mapped using the relative discharge error. The method was applied to 2618 gauging stations of France's national hydrometry network using data extracted from the national hydrological archive and from Digital Terrain Models. The diagnostic results highly depend on slope estimates used as inputs. Substantial hysteresis effects were found at stations with low bed slope combined with a fast flood regime. The application to France shows the difficulty of drawing a firm conclusion about stations prone to hysteresis due to the slope data uncertainty. This issue is not specific to France; slope estimates over a network of hydrometric stations are difficult to obtain in many countries. The use of local bed slope estimates is recommended to approach the slopes of the reaches controlling the station stage-discharge relation.

Automated summary

A generic framework is proposed to evaluate the relative discharge error caused by ignoring stage-discharge hysteresis due to transient flow over large gauging station networks. The research used the Jones equation to diagnose the hysteresis effect and found that slope estimates were crucial for the diagnostic results. The method was applied to gauging stations in France and significant hysteresis effects were found at stations with low bed slope and fast flood regime. However, due to the uncertainty of slope data, it was difficult to draw firm conclusions.