Hysteretic behavior of flow recession dynamics: Application of machine
learning and learning from the machine
Abstract
Flow recession analysis, relating discharge Q and its time rate of
change -dQ/dt, has been widely used to understand catchment scale flow
dynamics. However, data points in the plot of -dQ/dt versus Q typically
form a wide point cloud due to noise and hysteresis, and it is still
unclear what information we can extract from the data points and how to
understand the information. In this study, we utilize a machine learning
tool to capture the point cloud using the past trajectory of discharge.
Our results show that most of the data points can be captured using 5
days of past discharge. While analyzing the machine learning model
structure and the trained parameters is a daunting task, we show that we
can learn the catchment scale flow recession dynamics from what the
machine learned. We analyze patterns learned by the machine and explain
and hypothesize why the machine learned those characteristics. The
hysteresis in the plot mainly occurs during the early time dynamics, and
the flow recession dynamics eventually converge to an attractor in the
plot, which represents the master recession curve. We also illustrate
that a hysteretic storage-discharge relationship can be estimated based
on the attractor.