Hybrid Theory-Guided Data Driven Framework for Calculating Irrigation Water Use of Three Staple Cereal Crops in China

Current irrigation water use (IWU) estimation methods confront uncertainties warranting further attention, primarily stemming from constraints within model structure and data quality. This study proposes a hybrid framework that integrates multiple machine learning (ML) methods with theory-guided strategies to calculate IWU for three principal cereal crops within the Chinese agricultural landscape. We generated high resolution time series data sets of evapotranspiration and surface soil moisture (SM) using remote sensing resources. ML techniques, along with the Bayesian three-cornered hat ensemble, were employed to drive multiple remote sensing-derived data sets in IWU calculation. We applied two theory-guided mechanisms to quantify irrigation signals: first, converting original SM values into logarithmic terms, and second, extracting process-based SM residuals. Proposed framework has been validated at 12 field stations across China, yielding coefficient of determination (R²) ranging from 0.54 to 0.70, and root mean square error (RMSE) spanning 278–335 mm/yr. Our framework demonstrates considerable strength in IWU estimation when compared to reported IWU values form 341 cities across China. Specifically, for rice, wheat, and maize, the R² values range from 0.78 to 0.83, 0.68 to 0.76, and 0.53 to 0.64, respectively, with corresponding RMSE measuring 0.22–0.25, 0.10–0.12, and 0.11–0.13 km³/yr, respectively. These findings highlight the effectiveness of theory-guided strategies in discerning irrigation-related information, thereby improving overall model performance. Attention should be directed toward the uncertainties in evapotranspiration and precipitation products on model performance, which remained modest, with a relative change of less than 5%. © 2024. The Authors.