Accounting for operational irrigation options in mesoscale hydrological modelling of dryland environments

ABSTRACT Agricultural irrigation practices can account for a substantial proportion of the water budget in dryland environments. As the pressure on freshwater resources is growing in such environments, sustainable management of these resources is vital. Key issues need to be addressed: How does withdrawal for irrigation purposes alter a river’s flow regime and water yield? How can publicly available irrigation data help to improve the performance of hydrological models? A novel irrigation module was introduced to improve the performance of a mesoscale hydrological model Water Availability in Semi-Arid environments and Sediment transport (WASA-SED) and was tested on the hydrological upper mesoscale, as well as on a smaller sub-basin in a semi-arid catchment in the Rio São Francisco basin. We show that including irrigation practices into the modelling process especially helps to improve the quality of the modelled low flows during the dry season, where we achieved an improvement in the Root Mean Square Error (RMSE) of up to 19%.