Evaluating the Applicability of Drainage Routing Schemes for Paddy Fields

Paddy fields play a critical role as storage for the retention of surface water in hydrological processes, but their water balance is complicated by irrigation and drainage management. Studies have proposed flow routing methods for paddy fields by simplifying the hydrological and hydraulic complexity associated with drainage processes. However, the performance of paddy field routing schemes has not yet been sufficiently evaluated to assist in the selection of routing methods for a water balance analysis. This study evaluated three common drainage routing schemes developed for paddy fields, including the simple water balance (SWB), linear reservoir with threshold (LRT), and broad-crested weir (BCW) models, in terms of complexity and performance. This study also compared the accuracy of irrigation water requirement and sediment load estimates simulated using the three schemes. Results showed that the BCW model produced the best statistical accuracy when predicting daily flow, but the three routing methods performed similarly over a 10-day time scale. Results suggested that the simple structure of the SWB model was not accurate enough to reproduce high and low flow on a daily scale, which produced relatively higher irrigation water requirements and sediment loads compared with those of LRT and BCW. LRT provided performance statistics similar to those of BCW using fewer calibration parameters. The comparison confirmed a trade-off relationship between model complexity and performance, highlighting the importance of model selection for hydrological analysis.