Manual versus Automated Beerkan run for characterizing the hydraulic properties of sandy soil in Senegal's Sahel

Abstract

The comprehension of hydrological processes inherent in the water cycle and its constituents is of paramount significance when formulating adaptation strategies to address climate and global changes. The Sahel region serves a crucial role as a buffer zone between the arid desert and the more verdant and precipitation-laden areas of Senegal. The savanna region comprises a dynamic amalgamation of woody perennials intermixed with agricultural crops and pastures. The sustained vitality of this ecosystem hinges upon sustainable agriculture, mandating the judicious utilization of water resources. The formulation of strategies geared towards optimizing water resource management necessitates a comprehensive understanding of hydrological processes. This includes the investigation of water infiltration at the soil surface, the dynamics of water redistribution within the soil profile, and the mechanisms governing groundwater recharge. These scientific insights will help to develop effective strategies for the sustainable utilization of water resources within the Sahel region.  The intended investigation seeks to characterize the hydraulic properties of sandy soils that extensively prevail within the savanna ecosystem.The utilization of water infiltration experiments coupled with corresponding modeling presents a robust framework for non-intrusive on-site hydraulic soil characterization. These methodologies have been widely employed across diverse contexts (Angulo-Jaramillo et al., 2019, for a review). To achieve this objective, the Beerkan method, initially proposed by Braud et al. (2005), involving the controlled infiltration of known water volumes into a designated ring, has been identified as a pertinent approach. Recently, Di Prima et al. (2016) have introduced an automated infiltrometer as a substitute for the manual Beerkan method, thereby streamlining and enhancing the procedural aspects of hydraulic soil characterization.The study pursues a dual objective: (i) to characterize the hydraulic properties of sandy soil and delineate their spatial variability, both horizontally and vertically across the soil profile; and (ii) to assess the influence of the chosen water infiltration setup (Manual versus Automated Beerkan) on the obtained results. The investigation involved the excavation of three pits arranged as steps, providing access to five distinct horizons that spanned from the soil surface to a perched aquifer positioned at 2.5/3 m depth. Both Manual and Automated Beerkan experiments were conducted at the soil surface and for each horizon. Cumulative infiltrations were subjected to analysis using the BEST methods for precise determination of hydraulic parameters. Furthermore, bulk density and particle size distributions were determined for each Beerkan run by coring the soil at the conclusion of the experiment.The examination of infiltration rates and hydraulic parameter profiles across the soil profiles, along with the comparative analysis of values derived from manual versus automated Beerkan runs, furnished pertinent insights to address the study's dual objectives.ReferencesAngulo-Jaramillo, R., et al., 2019. Journal of Hydrology. 576, 239–261. https://doi.org/10.1016/j.jhydrol.2019.06.007Braud, I., et al., 2005. European Journal of Soil Science 56, 361–374. https://doi.org/10.1111/j.1365-2389.2004.00660.xDi Prima, S., et al.,2016. Geoderma 262, 20–34. https://doi.org/10.1016/j.geoderma.2015.08.