Optimal regulation pattern of water resources in a multi-source irrigation system in southern China

Optimizing water management patterns significantly enhances water−use efficiency in multi-source irrigation districts. Current research remains limited on optimizing multi-water source allocation within irrigation systems. Therefore, taking a typical multi-source irrigation district (Yangshudang watershed) in southern China as a case study, a ditch−canal−pond−reservoir system water balance simulation model (Ds-WBM) was constructed to quantitatively analyze the difference in water source use between 2021 and 2022, and a simulation−optimization framework based on the Ds-WBM was developed to optimize the regulation pattern of multiple water sources in the irrigation district. The results revealed significant spatial differences in the use of irrigation water sources in the irrigation district, which were primarily driven by topographic conditions and irrigation water source configuration. Optimized allocation under varying conditions reduced irrigation costs by up to 30.95 % and increased return flow reuse by up to 14.30 %, with future rainfall scenarios outperforming current conditions. The proposed optimal regulation pattern of water resources can provide a practical option for local irrigation district managers and farmers to improve irrigation water use efficiency and reduce irrigation costs.