Improved Flood Forecasting in Ungauged Basins: Constrained Runoff
Correction Using Multiple Satellite Products
Abstract
Satellite-based precipitation products (SPPs) with short latencies
provide a new opportunity for flood forecasting in ungauged basins.
However, the larger uncertainties associated with such near-real-time
SPPs can influence the accuracy of the resulting flood forecast. Here we
propose a real-time updating method, referred to as “Constrained Runoff
Correction (CRC-M)” that is based on the use of multi-source SPPs. The
method is based on the hypothesis that the range over different
near-real-time SPPs provides insight regarding the approximate range in
which the true rainfall value lies, during the current period.
Accordingly, the constrained runoff correction is performed in such a
way as to be consistent with this range, and with the observed value of
discharge at the basin outlet. Evaluation using real-data indicates that
the new method performs well, with Nash–Sutcliffe (NS) values of 0.85
and 0.91 during calibration and evaluation, respectively. The necessity
and value of imposing constraints is demonstrated by comparing CRC-M
against a control, referred to as “Unconstrained Runoff Correction”
(URC-S). Experiments indicate that the key factors resulting in good
performance are 1) wider constraint ranges, and 2) relatively reliable
SPPs. Further, inclusion of redundant information may only result in
slight improvements to forecast performance, and can even cause the
performance to deteriorate. Overall, the CRC-M method can result in
accurate and stable flood forecasts for ungauged basins, without the
need for increased model complexity (i.e., the numbers of model
parameters).