Groundwater quality in rural watersheds with environmental land use conflicts R.F. Valle Junior a,b , S.G.P. Varandas b , L.F. Sanches Fernandes b , F.A.L. Pacheco c, ⁎ a IFTM – Instituto Federal do Triangulo Mineiro, Campus Uberaba, Uberaba, MG, Brazil b CITAB-UTAD – Centre for Research and Technology of Agro-Environment and Biological Sciences, University of Trás-os-Montes e Alto Douro, Quinta de Prados, 5001-801 Vila Real, Portugal c DG-CQVR-UTAD – Department of Geology and Chemistry Research Centre, University of Trás-os-Montes e Alto Douro, Quinta de Prados, 5001-801 Vila Real, Portugal HIGHLIGHTS • Conceive environmental land use conflicts (LUC) in rural watersheds • Investigate groundwater quality in watersheds with LUC • Investigate environmental implications of LUC abstract article info Article history: Received 16 April 2014 Received in revised form 16 June 2014 Accepted 16 June 2014 Available online xxxx Editor: D. Barcelo Keywords: Groundwater quality Land capability Land use conflict Nitrification Rural watershed The quality of groundwater was evaluated in a rural watershed of northern Portugal (River Sordo basin) where environmental land use conflicts have developed in the course of a progressive invasion of forest and pasture lands by agriculture, especially by vineyards. The selected groundwater quality parameters were the concentra- tions of sodium, calcium, bicarbonate, chloride and nitrates, derived from natural and anthropogenic sources. The environmental land use conflicts were revealed by the coupling of land use and land capability raster maps. The land capability evaluation allocated 70.3% of the basin to the practicing of agriculture, 20% to livestock pasturing and 9.7% to a mosaic of land uses including agriculture, livestock pasturing and forestry. The assessment of land use conflicts allocated 93.9% of the basin to no conflict areas. Minor conflict areas (4.1%) were found concentrated in the western region of the watershed. They correspond to an invasion of farmlands towards sectors of the catch- ment capable for the practicing of livestock pasturing. Moderate (1.6%) and major (0.4%) conflict areas were found limited to the eastern region, matching steep hillsides capable for the practicing of livestock pasturing or forestry but presently occupied with vineyards. The spatial distributions of ion concentrations were generally justified by common geochemical processes. The dominance of high concentration levels in moderate and major conflict areas was justified within the framework of nutrient dynamics in vineyard environment. Nitrate in groundwater was likewise produced via the nitrification of N-fertilizers. Apparently, this process promoted the weathering of plagioclase by the nitric acid reaction, in concurrence with the weathering by the carbonic acid reaction. The impact of nitrification was found more important in moderate and major conflict areas, relative to no conflict areas. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Groundwater contamination in rural areas is controlled by numer- ous factors, including the use of the land. For example, in a county of China nitrate concentrations in groundwater were found to be higher in areas used for rotating irrigated cultures, in comparison with areas occupied by forests where a fast-growing tree system could act as buffer to retain the nitrate content (Chen et al., 2010). Another example is reported in Korea, where increasing nitrate concentrations were found to occur in cropping areas, cropping-livestock farming complex areas, and residential areas (Choi et al., 2007). The scenario of groundwater contamination changes as land use changes in space and time. An exam- ple supporting this statement comes from the Neal Smith National Wildlife Refuge, Iowa, USA, where the conversion of cropland to peren- nial land cover (prairie) resulted in a significant drop of nitrate and chloride concentrations in groundwater within a decade (Schilling and Jacobson, 2010). Another example comes from the region of Fife, Scotland, where the nitrate concentrations in public borehole water more than doubled in three decades, because the pumped sandstone aquifer is recharged by water draining from a land that is intensively Science of the Total Environment 493 (2014) 812–827 ⁎ Corresponding author. Tel.: +351 259 350 280; fax: +351 259 350 480. E-mail address: fpacheco@utad.pt (F.A.L. Pacheco). URL: http://www.utad.pt (F.A.L. Pacheco). http://dx.doi.org/10.1016/j.scitotenv.2014.06.068 0048-9697/© 2014 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv