Analyzing the operational performance of the hydrological models in an alpine flood forecasting system

Abstract

During recent years a hybrid model has been set up for the operational forecasting of flood discharges in
the 6750 km2 Tyrolean part of the River Inn catchment in Austria. The catchment can be characterized as
a typical alpine area with large variations in altitude. The paper is focused on the error analysis of discharge
forecasts of four main tributary catchments simulated with hydrological water balance models.
The selected catchments cover an area of 2230 km2, where the non-glaciated and glaciated parts are
modeled using the semi-distributed HQsim and the distributed model SES, respectively.
The forecast errors are evaluated as a function of forecast lead time and forecasted discharge magnitude
using 14 events from 2007 to 2010. The observed and forecasted precipitation inputs were obtained
under operational conditions. The mean relative bias of the forecasted discharges revealed to be constant
with regard to the forecast lead time, varying between 0.2 and 0.25 for the different catchments. The
errors as a function of the forecasted discharge magnitude showed large errors at lower values of the
forecast hydrographs, where errors decreased significantly at larger discharges being relevant in flood
forecasting.