TY  - JOUR
A1  - Wambura, Frank Joseph
A1  - Dietrich, Ottfried
A1  - Lischeid, Gunnar
T1  - Improving a distributed hydrological model using evapotranspiration-related boundary conditions as additional constraints in a data-scarce river basin
JF  - Hydrological processes
N2  - Many hydrological models have been calibrated and validated using hydrographs alone. Because streamflow integrates water fluxes in space, many distributed hydrological models tend to have multiple feasible descriptions of hydrological processes. This equifinality usually leads to substantial prediction uncertainty. In this study, additional constraintsnamely, the spatial patterns of long-term average evapotranspiration (ET), shallow groundwater level, and land cover changewere used to investigate the reduction of equifinality and prediction uncertainty in the Soil and Water Assessment Tool (SWAT) in the Wami River basin in Tanzania. The additional constraints were used in the set-up, parameter emulation and calibration of the SWAT model termed an improved hydrological model (IHM). The IHM was then compared with a classical hydrological model (CHM) that was also developed using the SWAT model but without additional constraints. In the calibration, the CHM used only the hydrograph, but the IHM used the hydrograph and the spatial pattern of long-term average ET as an additional constraint. The IHM produced a single, unique behavioural simulation, whereas the CHM produced many behavioural simulations that resulted in prediction uncertainty. The performance of the IHM with respect to the hydrograph was more consistent than that of the CHM, and the former clearly captured the mean behaviour of ET in the river basin. Therefore, we conclude that additional constraints substantially reduce equifinality and prediction uncertainty in a distributed hydrological model.
KW  - data scarcity
KW  - equifinality
KW  - evapotranspiration
KW  - parameter emulation
KW  - prediction uncertainty
KW  - SWAT
Y1  - 2018
U6  - https://doi.org/10.1002/hyp.11453
SN  - 0885-6087
SN  - 1099-1085
VL  - 32
IS  - 6
SP  - 759
EP  - 775
PB  - Wiley
CY  - Hoboken
ER  -