Reactive transport modelling to infer changes in soil hydraulic properties induced by non-conventional water irrigation

Abstract

The use of non-conventional water (e.g., treated wastewater, desalinated water) for different purposes is increasing in many water scarce regions of the world. Its use for irrigation may have potential drawbacks, because of mineral dissolution/precipitation processes, such as changes in soil physical and hydraulic properties (e.g., porosity, permeability), modifying infiltration and aquifer recharge processes or blocking root growth. Prediction of soil and groundwater impacts is essential for achieving sustainable agricultural practices. A numerical model to solve unsaturated water flow and non-isothermal multicomponent reactive transport has been modified implementing the spatio-temporal evolution of soil physical and hydraulic properties. A long-term process simulation (30 years) of agricultural irrigation with desalinated water, based on a calibrated/validated 1D numerical model in a semi-arid region, is presented. Different scenarios conditioning reactive transport (i.e., rainwater irrigation, lack of gypsum in the soil profile, and lower partial pressure of CO2 (pCO2)) have also been considered. Results show that although boundary conditions and mineral soil composition highly influence the reactive processes, dissolution/precipitation of carbonate species is triggered mainly by pCO2, closely related to plant roots. Calcite dissolution occurs in the root zone, precipitation takes place under it and at the soil surface, which will lead a root growth blockage and a direct soil evaporation decrease, respectively. For the studied soil, a gypsum dissolution up to 40 cm depth is expected at long-term, with a general increase of porosity and hydraulic conductivity.Peer ReviewedPostprint (author's final draft

Determination of the Effective Viscosity of Non-newtonian Fluids Flowing Through Porous Media

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Environmental Scanning Electron Microscopy Application for Brackish Water Irrigation Impact on Soil

“…Clay mineral content (illite) in Layer 1 accounted for up to 9.7% and was practically absent in Layer 2 (Table 2). Detailed site descriptions can be found in previous studies (Valdes‐Abellan et al, 2015, 2017).…”

“…The salinity difference between deionized water in the vapor chamber and water in the soil would explain this process. Long‐term irrigation with brackish water could lead to accumulation of salts, and in Valdes‐Abellan et al (2017) gypsum was identified as the main mineral to precipitate in the soil. The impact on soil hydrophilic behavior depends on the type of salts present in the system, which depends on the soil mineralogy and the chemistry of the applied irrigation water.…”

The HPx software for multicomponent reactive transport during variably-saturated flow: Recent developments and applications

“…Valdes-Abellan et al (2017) developed a model (using HP1) to simulate the spatial-temporal evolution of soil hydraulic properties during non-conventional water irrigation during non-isothermal transient flow. In addition to linking the porosity, a h , and the saturated hydraulic conductivity to the amount of precipitated or dissolved minerals, soil hydraulic properties were also linked to changes in the soil water composition, salinity, and temperature.…”