Estimating water balance components in irrigated agriculture using a combined approach of soil moisture and energy balance monitoring, and numerical modelling

Information on water balance components such as evapotranspiration and groundwater recharge are crucial for management. Due to differences in physical conditions, but also due limited budgets, there is not one universal best practice, a wide range of different methods with specific advantages disadvantages. In this study, we propose an approach quantify actual evapotranspiration, inflow, i.e. precipitation irrigation, that considers the conditions irrigated agriculture warm, arid environments. This does require direct measurements or irrigation quantities therefore suitable sites uncertain data basis. For purpose, combine soil moisture energy monitoring, remote sensing analysis numerical modelling using Hydrus. Energy routine weather serve estimate ET0. Surface reflectance from satellite images (Sentinel-2) used derive leaf area indices, which help partition ET0 into evaporation transpiration. Subsequently, first approximations inflow derived based observed changes. These estimates series forward simulations produce initial drainage ETact, turn improve inflow. Finally, improved incorporated model then parameter optimization performed reference figure. Forward calibrated parameters result final ETact recharge. The presented method applied agricultural test site crop rotation cotton wheat Punjab, Pakistan. results, RMSE 2.2% volumetric content, suggest cumulative 769 297 mm over period 281 days, respectively. total estimated accounts 946 mm, 77% originates irrigation.