Groundwater quality and availability are essential for human consumption and social and economic activities in arid and semiarid regions. Many developing countries use wastewater for irrigation, which has in most cases led to groundwater pollution. The Mezquital Valley, a semiarid region in central Mexico, is the largest agricultural irrigation region in the world, and it has relied on wastewater from Mexico City for over 100 years. Limited research has been conducted on the impact of irrigation practices on groundwater quality on the Mezquital Valley. In this study, 31 drinking water wells were sampled. Groundwater quality was determined using the water quality index (WQI) for drinking purposes. The hydrogeochemical process and the spatial variability of groundwater quality were analyzed using principal component analysis (PCA) and K-means clustering multivariate geostatistical tools. This study highlights the value of combining various approaches, such as multivariate geostatistical methods and WQI, for the identification of hydrogeochemical processes in the evolution of groundwater in a wastewater irrigated region. The PCA results revealed that salinization and pollution (wastewater irrigation and fertilizers) followed by geogenic sources (dissolution of carbonates) have a significant effect on groundwater quality. Groundwater quality evolution was grouped into cluster 1 and cluster 2, which were classified as unsuitable (low quality) and suitable (acceptable quality) for drinking purposes, respectively. Cluster 1 is located in wastewater irrigated zones, urban areas, and the surroundings of the Tula River. Cluster 2 locations are found in recharge zones, rural settlements, and seasonal agricultural fields. The results of this study strongly suggest that water management strategies that include a groundwater monitoring plan, as well as research-based wastewater irrigation regulations, in the Mezquital Valley are warranted.

This paper analyzes the behavior of drought in the face of the impact of climate change and groundwater quality and its implications for agricultural production in a semi-arid area of northeastern Mexico. The pluviometric information of two stations from 1961 to 2020 was analyzed, and the Standardized Precipitation Index was applied in the spring–summer period (SPI-6). Twenty-five samples from the Ahualulco aquifer were collected and analyzed, to which quality indices for agricultural use were applied. The results show that in the last 20 years there have been mild to moderate droughts, which have considerably affected rainfed farmers. The area under irrigation is affected by salinity conditions as the water goes from medium to high conductivities and low to medium sodicity, which indicates a medium sodicity risk but an excessive salinity risk.

Sanitary landfills are considered one of the main sources of contamination of water resources due to the generation of leachate with a high content of dissolved organic matter (DOM), inorganic material, and toxic elements. This study aimed to determine the influence of leachate on the physicochemical quality and hydrogeochemical processes which determine the chemical composition of groundwater in an area near a municipal sanitary landfill site. In situ parameters (pH, temperature, electrical conductivity, dissolved oxygen, ORP), physicochemical parameters (HCO₃⁻, PO₄³⁻, Cl⁻, NO₃⁻, SO₄²⁻, NH₄⁺, Ca²⁺, Mg²⁺, Na⁺, K⁺), and dissolved organic matter were analyzed. The content of dissolved organic matter (DOM) was determined by 3D fluorescence microscopy. The presence of Cl⁻, NO₃⁻, NH₄⁺, PO₄³⁻, BOD, and COD indicated the presence of contamination. The significant correlation between NO₃⁻ and PO₄³⁻ ions (r = 0.940) and DOM of anthropogenic origin in the 3D fluorescence spectra confirm that its presence in the water is associated with the municipal landfill site in question. The type of water in the area is Mg-HCO₃, with a tendency to Na-HCO₃ and Na-SO₊-Cl. The water-rock interaction process predominates in the chemical composition of water; however, significant correlations between Na⁺ and Ca²⁺ (r = 0.876), and between K⁺ and Mg²⁺ (r = 0.980) showed that an ion exchange process had taken place. Likewise, there is enrichment by HCO₃⁻ and SO₄²⁻ ions due to the mineralization of the organic matter from the leachate. The groundwater quality that supplies the study area is being affected by leachate infiltration from the sanitary landfill.