Capillary rise quantification by field injection of artificial deuterium and laboratory soil characterization

Abstract

In arid contexts, water rises from the saturated level of a shallow aquifer to the drying soil surface where evaporation takes place. This process plays important roles in terms of plant survival, salt balance and aquifer budget. A new field quantification method of this capillary rise flow is proposed using micro-injections (6 μL) of deuterium-enriched solution (δ value of 63 000‰ vs. V-SMOW) into unsatured soil at 1 m depth. Evaluation of peak displacement from a profile sampling 35 days later, delivered estimates that were compared with outputs of numerical simulation based on laboratory hydrodynamic measurements. A rate of 3.7 cm y<sup>−1</sup> was observed in a Moroccan site where the aquifer level was 2.44 m deep. This value was higher, than other estimates based on natural diffusion with the same depth of aquifer, but lower than the estimates established using integration of van Genutchen closed-form functions for soil hydraulic conductivity and retention curve

Review on soil water isotope-based groundwater recharge estimations

“…Recently, Grünberger et al . () were able to quantify capillary rise from a shallow aquifer using 2 H as an applied tracer. Studies using applied 2 H are more common at the soil–vegetation interface but will not be discussed here in more detail because their focus is mainly on root water uptake and plant physiological processes (e.g.…”

“…Mean transport velocities for 2 H were found to be higher and dispersion coefficients lower compared with uranine in the column experiments, which proved that 2 H behaves more conservatively than uranine. Recently, Grünberger et al (2011) were able to quantify capillary rise from a shallow aquifer using 2 H as an applied tracer. Studies using applied 2 H are more common at the soil-vegetation interface but will not be discussed here in more detail because their focus is mainly on root water uptake and plant physiological processes (e.g.…”