Improving Hydrological Modelling With Topkapi Through Irrigation and Open-Channel Flow in Semi-Arid Agricultural Catchments

Abstract

This study focuses on the design, implementation and performance evaluation of a new irrigation and open-channel module into the well-known Topkapi distributed model. The Topkapi was implemented through the PyTopkapi library. The research framework encompasses the integration of an irrigation simulation module alongside a sophisticated kinematic wave model, designed to emulate the intricate dynamics of surface flow transport in irrigation channels, thereby enriching the structural composition of the overall model. The performance of the improved model was tested in the Achibueno River basin (Chile) strategically positioned in the southern reaches of the Maule region, encompassing a substantial land expanse of 1578 km² with a very important agricultural activity and a subsequent important presence of open channels for its water distribution network. The dataset utilised for this comprehensive assessment spans a temporal continuum from 1979 to 2015 and has been meticulously curated from the historical archives of the Centro de Ciencia del Clima y la Resiliencia (CR2). The evaluation of model performance is executed through the application of the Nash and Nash-ln coefficients, enabling a nuanced understanding of the model's proficiency. Two distinct scenarios are meticulously considered throughout the assessment: one wherein the irrigation module is absent from the model configuration, and another wherein the irrigation module is integrated into the model's structural framework. The findings emanating from our results underscore a discernible augmentation in the operational efficiency of PyTopkapi to the extent of approximately 17% when the irrigation module is applied (NSE moving from 0.63 to 0.74 for the calibration period and 0.54 to 0.64 for the validation period). This heightened efficiency manifests notably during the transport of flow through channels, where the kinematic wave model plays a pivotal role in orchestrating the dynamics of surface water movement.