Abstract. The two-component hydrograph separation method with
conductivity as a tracer is favored by hydrologists owing to its low cost
and easy application. This study analyzes the sensitivity of the baseflow
index (BFI, long-term ratio of baseflow to streamflow) calculated using this
method to errors or uncertainties in two parameters (BFC, the
conductivity of baseflow, and ROC, the conductivity of surface runoff)
and two variables (yk, streamflow, and SCk, specific conductance of
streamflow, where k is the time step) and then estimates the uncertainty in
BFI. The analysis shows that for time series longer than 365 days, random
measurement errors in yk or SCk will cancel each other out, and their
influence on BFI can be neglected. An uncertainty estimation method of BFI
is derived on the basis of the sensitivity analysis. Representative
sensitivity indices (the ratio of the relative error in BFI to that
of BFC or ROC) and BFI′ uncertainties are determined
by applying the resulting equations to 24 watersheds in the US. These
dimensionless sensitivity indices can well express the propagation of errors
or uncertainties in BFC or ROC into BFI. The results indicate that
BFI is more sensitive to BFC, and the conductivity two-component
hydrograph separation method may be more suitable for the long time series
in a small watershed. When the mutual offset of the measurement errors in
conductivity and streamflow is considered, the uncertainty in BFI is reduced by half.
Correction to: Modified repetitive learning control with unidirectional control input for uncertain nonlinear systems
