A modified Xin'anjiang model and its application for considering the regulatory and storage effects of small-scale water storage structures

Abstract

To improve flood prediction accuracy in the basin, this paper constructs a modified Xin'anjiang (M-XAJ) model to account for the regulatory and storage effects of small-scale water storage structures on surface runoff, based on the original Xin'anjiang (XAJ) model. In the M-XAJ model, the regulatory and storage effects of small water storage are calculated by utilizing an aggregated reservoir using multi-bottom sills graded weir flow pattern (MBSP). The discharge processes of the aggregated reservoir is combined with the processes of runoff production and convergence over the natural area to form the overall discharge processes at the outlet section. Using the two subbasins of the Xianghongdian Reservoir as case studies, 13 flood events were selected to validate the predictive capabilities of the M-XAJ model. The results indicate that (1) the qualification rate for flood peak (Qp) and the qualification rate flood volume (Qv) substantially increased for the two sub-basins during the training and verification periods. Additionally, the mean relative error of peak lag time (MEtp) was considerably reduced. Specifically, the mean Nash efficiency coefficient (MNS) for floods at the Qingshan section improved by 0.18 and 0.24 respectively. (2) the M-XAJ model improved prediction accuracy for the first flood event following an extended drought period without rainfall, as well as for the initial flood preceding a sequence of flooding events. However, the prediction accuracy for continuous flooding events was not noticeably enhanced by the M-XAJ model. (3) the M-XAJ model demonstrated improved simulation capabilities for low- and moderate-magnitude flood events; however, there were no noticeable enhancements for high-magnitude flooding simulations.