Quality of groundwater for irrigation in tropical karst environment: The case of Yucatán, Mexico

The Yucatán Peninsula has the largest reserve of water in Mexico. It is generally believed that groundwater is of good quality although its agricultural quality has been scarcely studied. The aims of this study were to identify and characterize zones with distinctive groundwater qualities for agricultural use in Yucatán. Water samples were collected at 113 supply wells. The concentrations of Ca²⁺, Mg²⁺, Na⁺, K⁺, HCO₃⁻, SO₄²⁻, NO₃⁻, Cl⁻ and the electric conductivity (EC) were determined. Sodium adsorption ratio (SAR), potential salinity (PS) and effective salinity (ES) were also calculated. A geostatistical analysis by kriging interpolation was performed. ES, PS and SAR as well as Na⁺, EC, Cl⁻, SO₄²⁻, and Ca²⁺ were selected to make maps, in accordance with the values of semivariogram and values of cross-validation. The map of the ES was taken as the base to make the map of zones of agricultural quality groundwater. The quality of karstic groundwater in the state of Yucatán cannot be recommended for agriculture in Zones I (EC and ES), II (EC, Chlorides, PS and ES) and III (EC, sulfates and ES); in Zones IV and V the water is of medium quality and in the Zone VI, water is considered good for agricultural use. This information will be relevant in decision-making for government's agricultural and environmental planning.