Real-Time Equivalent Conversion Correction on River Stage Forecasting with Manning’s Formula

Abstract

Channel geometry can affect the performance of the autoregressive (AR) model on river stage correction. To evaluate the effect, three ideal models were established by using the one-dimensional (1D) hydrodynamic model with imagined sets of data in assumed channels (i.e., rectangle, V-type, and complex type). To evaluate the performance of the AR model on river stage and discharge correction in a real system with unavailable observed discharges, an equivalent conversion technique by using the Manning’s formula was proposed to convert stages into equivalent conversion discharges. The results from the ideal models and real systems in the Fuchun River show that the AR model performs better on river discharge correction than on river stage correction, which is also verified at Shaowu station in the Minjiang River with available observed discharges. It indicates that the correlation of discharges is better than that of river stages. To transform corrected discharges to corrected stages, a transformation technique based on an assumed rating curve calculated by the Manning’s formula was employed. Furthermore, by combining the equivalent conversion technique, the AR model and the transformation technique, an equivalent conversion correction (ECC) method is proposed to improve the AR model performance on river stage correction. The results show that the ECC method can obtain better accuracy on river stage correction than the AR model.