Determination of soil Hydraulic Properties using infiltration models and Hydrus 1D. Application to soils in Semi-Arid Regions

Arid and semi-arid regions present significant challenges in efficient irrigation management and mitigation of soil salinity. To understand the dynamics of water and solute movement, such as salt transport in soil, software tools like HYDRUS are widely utilized. Hydrus-1D uses linear finite elements to numerically solve the Richards equation for saturated-unsaturated water flow, and has been widely applied in irrigation management to focus on solute and water movement.This research focuses on estimating the hydraulic properties at field scale level using Kenyan soil data analyzed with soil spectroscopy and infiltration experiments. Saturated hydraulic conductivity (Ks) has been obtained by fitting data to infiltration obtained by the Green-Ampt (GA) model and Hydrus1D in three scenarios: with bounds on Ks and the product of front suction and effective porosity, assigning a uniform value to effective porosity and considering flow preferential paths. The results are compared with others pedotransfer functions (PTFs) and Hydrus-1D.The Hydrus-1D software was used to study the water retention curve due to different Ks estimations. The findings show significant variations in the Ks estimations, highlighting the impact of salinity and preferential flows in heterogeneous soils. The comparison of the results provides valuable insights into the dynamics of water and salinity, essential for irrigation management in these regions.This research emphasizes how crucial it is to choose and modify hydrological models for particular salinity situations and how important it is to take into account spatial variability and flow preferential paths when predicting and applying Ks through models. The results have significant implications for improving irrigation management and controlling soil salinity in semi-arid regions. Keywords: Saturated hydraulic conductivity, Green-Ampt, HYDRUS-1D, irrigation management, soil salinity control. "ACKNOWLEDGMENTThis article belongs to PCI2020-120694-2 Project funded by MCIN/AEI/10.13039/ 501100011033 and the European Union “NextGenerationEU”/PRTR.We would like to thanks to One Planet Fellowship from African Women in Agricultural Research and Development (AWARD) and Agropolis Fondation for funding the analysis. “