The semi-arid region in the State of Piauí, Brazil, is characterized by low rain fall and high evapotranspiration. However, the groundwater reserves make possible the economic development by underground hydrogeology characteristics, which allow extractions of high water flow with good quality, in most of the cases. However, some wells reached formations that have low discharge and water with high salt concentration, which if used for irrigation may cause salinization and sodification. The main goal of this work was to characterize the different uses and quality of groundwater in a part of the semi-arid area of Piauí, with a view to its use for irrigation. Samples were collected in 225 wells distributed spatially in the area, in which the following variables were analyzed: electrical conductivity, Na, Ca, Mg, SAR, CO3, HCO3, Cl and SO4. Regarding water use, the domestic use prevailed (53.61%), followed by irrigation (21.17%), with the following irrigation methods: drip irrigation (14.03%); microsprinkler (3.83%); conventional sprinkler (16.11%); gun sprinkler and traveler irrigation machine (13.66%); surface irrigation (16.76%) and other handmade methods (35.52%). The maps of classes of use risk irrigation generated from groundwater quality showed the occurrence of sub-areas with the following classes: no restriction, moderate restriction and severe restriction.
salinity; water quality; hydrogeology; Serra Grande aquifer
