Abstract

CORTES-JIMENEZ, Juan Manuel et al. Water quality parameters of the Yaqui Valley aquifer. Terra Latinoam [online]. 2009, vol.27, n.2, pp.133-141. ISSN 2395-8030.

In the Yaqui Valley, Sonora, Mexico, agriculture depends on the reservoir system built in the Yaqui River basin, which has a storage capacity of 7008.4 hm³. For the 2003-2004 autumn-winter crop cycle, water utilization was not authorized for agricultural use due to the low storage level. In response, 350 million cubic meters of water was extracted from the aquifer. According to recent studies, most of the acquifer contains 1000 to 5000 mg L^-1 total dissolved solids. The objective of this study was to assess the water quality of 224 samples and classify them according to the best-known criteria. 164 samples were selected that had an ionic balance error of less than 5%, and the necessary parameters were calculated to classify the water for agricultural purposes. The average values for the evaluated characteristics were the following: pH, 7.25; electrical conductivity, 2.06 dS m^-1; Na⁺, 8.5; Ca²⁺, 7.69; Mg²⁺, 5.08; SO₄^2-, 4.57; CO₃^2-, 0.83; HCO₃^-, 3.3; Cl^-, 12.5 meq L^-1; sodium adsorption (SAR), 3.91; corrected SAR, 4.44; adjusted SAR, 8.82; adjusted SAR HCO₃^-/Ca²⁺, 4.38; effective salinity, 14.8; potential salinity, 14.7; residual sodium carbonate, 0.57; permeability index, 53.3; percentage of exchangeable sodium (PES), 5.83. Water extracted from the Yaqui Valley aquifer shows that its use for irrigation of saline-sensitive species should be limited. Moreover, some wells have water of a quality that is not suitable for agricultural use since it could provoke an increase in soil salinity. In addition, the concentration of toxic ions such as Na⁺ and Cl^- is high and is considered to be an additional restriction. Regarding Na⁺, most of the water samples extracted indicate a low risk of sodifying the soil, coinciding with most of the classification schemes used.

Keywords : salinity; SAR; sodification; anions; cations.

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