AGRO-HYDROLOGICAL MODELS FOR THE ASSESSMENT OF INNOVATIVE IRRIGATION PRACTICES IN RICE AREAS

This dissertation addresses the outlined research needs through: I) developing and applying a prototype agro‑hydrological framework to assess the effects of alternative rice irrigation strategies on the water resource system at the irrigation district scale (San Giorgio di Lomellina district, about 1,000 hectares); II) using the experience gained with the prototype to develop a more flexible modelling framework integrated with a GIS, QGIS-SWAP-Paddy, suitable for simulating water flows in irrigation systems characterized by rice cultivation, also taking into account other areas (whether cultivated or not, e.g., bare soils, urban areas, etc.); III) defining the most suitable PTFs for describing the hydraulic characteristics of the Lomellina paddy soils, and IV) applying QGIS-SWAP-Paddy to quantify the impacts of AWD and other irrigation strategies on the Lomellina irrigation system water balance. The dissertation is organized as follows: - Chapter 2 presents the development, calibration, and application of a prototype agro‑hydrological framework to a pilot irrigation district to evaluate the effects on the water resource system of different rice irrigation scenarios. This work has been published in the paper: Gilardi, G.L.C.¹, Mayer, A.¹, Rienzner, M.¹, Romani, M.², & Facchi, A.¹ (2023). Effect of Alternate Wetting and Drying (AWD) and Other Irrigation Management Strategies on Water Resources in Rice‑Producing Areas of Northern Italy. Water, 15(12), 2150. https://doi.org/10.3390/w15122150, ¹Department of Agricultural and Environmental Sciences, University of Milan, 20133 Milan, Italy, ²Centro Ricerche sul Riso, Ente Nazionale Risi, 27030 Castello D’Agogna, Italy; - Chapter 3 describes the QGIS‑SWAP‑Paddy framework, detailing its workflow, data structure, and showing how the framework can be applied to agricultural areas including agricultural fields and irrigation networks. The framework is presented as an operational modelling tool tailored to low‑land agricultural areas, particularly those dedicated to rice cultivation. This chapter will also serve as the basis for a future comprehensive manual of the developed tool, which will be accompanied by a more concise user guide, in view of its potential publication in the official repository of plugins for the open‑source QGIS software. Moreover, it will be the basis for a scientific paper illustrating the tool; - Chapter 4 focuses on the identification of the most suitable PTFs for estimating key hydraulic parameters for the Lomellina paddy soils. This work has formed the basis for the paper just submitted to Soil & Tillage Research: Tkachenko, D.¹, Rienzner, M.¹, Gilardi, G.L.C.¹, Sciaccaluga, M.², Brenna, S.², Gandolfi, C.¹, & Facchi, A.¹. Hydro-pedotransfer functions for the main Italian rice district, ¹Department of Agricultural and Environmental Sciences, University of Milan, 20133 Milan, Italy, ²Ente Regionale per i Servizi all’Agricoltura e alle Foreste (ERSAF), Regione Lombardia; 15 - Chapter 5 describes the application of the identified PTFs to the Lomellina paddy soils and the use of QGIS‑SWAP‑Paddy framework to assess the effects of AWD and other rice irrigation strategies to the Lomellina irrigation system. This work will serve as the basis for a forthcoming publication on the use of the tool for exploring different irrigation scenarios for the Lomellina district. In the next steps of the PROMEDRICE project (PRIMA-Section 2, 2023 - 2026), the framework will be integrated with the MODFLOW model (https://www.usgs.gov/software/modflow-6-usgs-modular-hydrologic-model/), simulating the water flows in the groundwater system of the Lomellina (under development by researchers from Earth science Department, UNIMI). The objective will be to produce an estimate of the different irrigation strategies, also under climate change conditions, on groundwater aquifer levels and therefore on water reuse in the irrigation system. - Chapter 6 summarizes the main findings, discusses implications for irrigation management, and outlines directions for future research. Annex 1 presents a work that was carried out alongside the main research activities presented in this Thesis, but which is closely connected to them. It illustrates the design and implementation of an extensive monitoring campaign carried out in 2021 in the San Giorgio di Lomellina paddy district to evaluate the occurrence of selected herbicides and nutrient losses in surface and groundwater under the current rice cropping strategies. Although my direct involvement in this work was limited and focused on the analysis of data collected, it provided a meaningful opportunity to contribute specific expertise and to broaden the environmental perspective on rice cultivation in the Lomellina district. This chapter is based on the Author’s Accepted Manuscript of: Tediosi A., Ferrari F., Voccia D. Gharsallah O., Lamastra L., Botteri L., Rossi R., Ferrari T., Ballerini N., Gilardi G.L.C., & Facchi A. (2024) Herbicide and nutrient monitoring in surface waters and groundwater of a paddy district in northern Italy. Environmental Science and Pollution Research, 31:52963–52979. https://doi.org/10.1007/s11356-024-34692-x.