Abstract. Karst trough and valley landforms are prone to flooding,
primarily because of the unique hydrogeological features of karst landforms,
which are conducive to the spread of rapid runoff. Hydrological models that
represent the complicated hydrological processes in karst regions are
effective for predicting karst flooding, but their application has been
hampered by their complex model structures and associated parameter set,
especially for distributed hydrological models, which require large amounts
of hydrogeological data. Distributed hydrological models for predicting
flooding are highly dependent on distributed modelling, complicated boundary
parameter settings and extensive hydrogeological data processing, which
consumes large amounts of both time and computational power. Proposed here
is a distributed physically based karst hydrological model known as the QMG
(Qingmuguan) model. The structural design of this model is relatively
simple, and it is generally divided into surface and underground
double-layered structures. The parameters that represent the structural
functions of each layer have clear physical meanings, and fewer parameters
are included in this model than in the current distributed models. This
allows karst areas to be modelled with only a small amount of necessary
hydrogeological data. Eighteen flood processes across the karst underground
river in the Qingmuguan karst trough valley are simulated by the QMG model,
and the simulated values agree well with observations: the average values of
the Nash–Sutcliffe coefficient and the water balance coefficient are both 0.92, while
the average relative flow process error is 10 % and the flood peak error
is 11 %. A sensitivity analysis shows that the infiltration coefficient,
permeability coefficient and rock porosity are the parameters that require
the most attention in model calibration and optimization. The improved
predictability of karst flooding enabled by the proposed QMG model promotes a better
mechanistic depiction of runoff generation and confluence in karst trough
valleys.