Climate Variability and Change—Hydrological Impacts (Proceedings of the Fifth FRIEND World
Conference held at Havana, Cuba, November 2006), IAHS Publ. 308, 2006, 163–168.
Predicting low flows in ungauged catchments
KOLBJØRN ENGELAND, HEGE HISDAL & STEIN BELDRING
NVE, Postboks 5091 Majorstua, N-0301 Oslo, Norway
koe@nve.no
Abstract The aim of this study was
to compare the regression method and a regional precipitation–runoff model to
estimate low flow indices at ungauged sites. Southwestern Norway was chosen as
the study region. As the first step in the regression method, two homogeneous
sub-regions were established according to the dominant low flow season, winter
or summer. Then individual regression equations were established for each
sub-region between the low flow index “common low flow” and catchment
characteristics using a step-wise procedure. A gridded version of the HBV model
was applied as a regional precipitation–runoff model. The model was calibrated
to a subset of the catchments and validated on independent catchments. The
calibration criterion was selected to fit the low flow part of the streamflow
record. Comparison of the predicted low flow index by the regression method and
the HBV model showed that the regression method gave the best estimates.
Key words low flow indices; prediction in ungauged basins;
regionalization; HBV model