Resumo

AGUILAR-GARCIA, Ramón  e  ORTEGA-GUERRERO, M. Adrián. Analysis of the water dynamics in the unsaturated zone, in a soil subject to conservation practices: implications for aquifer management and adaptation to climatic change. Rev. mex. cienc. geol [online]. 2017, vol.34, n.2, pp.91-104. ISSN 2007-2902.

It is estimated that 80-85% of the water extracted from aquifers in Mexico is used for agricultural production, and in general, there is an inadequate management that causes different damages to the environment, highlighting the depletion and contamination of groundwater, among others. The purpose of this work is to quantify the water balance and dynamics in the unsaturated zone by means of daily measurements of different meteorological parameters and the moisture profiles of a soil that was treated to conservation practices in the Independence Aquifer (Upper La Laja River Basin tributary of the Lerma-Chapala). The stratigraphy of the site was obtained through continuous records of electrical conductivity and granulometry in unaltered soil samples - to which physical properties and organic matter content were determined - in their first 2.50 m depth. The changes in moisture content at 0.15, 0.30, 0.60, 0.90 and 1.20 m were controlled by Time Domain Refractometry (TDR). The saturated permeability was quantified with the Guelph Permeameter, complemented with infiltration tests. A one-dimensional numerical model was used to develop predictive tools. The results indicate that progressive capture of carbon occurred and that a saturated hydraulic conductivity of up to K fs = 5 m∙d-1 has been reached, in the first 0.60 m of depth, which contrasts up to two orders of magnitude with traditional soil management; allowing the gradual filtering of a total water sheet of 6,753 mm for three days, which would cover any sequence of maximum rainfall events recorded in the region. The RDT sensors showed a rapid increase in moisture content along the profile, indicating that the characteristics obtained in the soil allow the immediate input and storage of rainwater, with a minimum evaporation rate and zero runoff. The present work demonstrates that it is feasible to favor the infiltration of sufficient rainwater for the production of staple and fodder crops and to reduce the impacts of negative incidents because of climate change. This applies to irrigation crops, which would allow the progressive reduction of groundwater extraction, by more than 50%, through adequate conservation practices, a fundamental aspect in the management of the aquifer.

Palavras-chave : Independence Aquifer; Lerma-Chapala basin; unsaturated zone; conservation agriculture; water balance; loss reduction; basic and forage production; temporal; numerical analysis; adaptation to climate change; carbon capture.

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