title: Categorical Indicator Kriging for assessing the risk of groundwater nitrate pollution: the case of Vega de Granada aquifer (SE Spain).
abstract: Groundwater nitrate pollution associated with agricultural activity is an important environmental problem in the management of this natural resource, as acknowledged by the European Water Framework Directive. Therefore, specific measures aimed to control the risk of water pollution by nitrates must be implemented to minimise its impact on the environment and potential risk to human health. The spatial probability distribution of nitrate contents exceeding a threshold or limit value, established within the quality standard, will be helpful to managers and decision-makers. A methodology based on non-parametric and non-linear methods of Indicator Kriging was used in the elaboration of a nitrate pollution categorical map for the aquifer of Vega de Granada (SE Spain). The map has been obtained from the local estimation of the probability that a nitrate content in an unsampled location belongs to one of the three categories established by the European Water Framework Directive: CL. 1 good quality [Min - 37.5 ppm], CL. 2 intermediate quality [37.5-50 ppm] and CL. 3 poor quality [50 ppm - Max]. The obtained results show that the areas exceeding nitrate concentrations of 50 ppm, poor quality waters, occupy more than 50% of the aquifer area. A great proportion of the area's municipalities are located in these poor quality water areas. The intermediate quality and good quality areas correspond to 21% and 28%, respectively, but with the highest population density. These results are coherent with the experimental data, which show an average nitrate concentration value of 72 ppm, significantly higher than the quality standard limit of 50 ppm. Consequently, the results suggest the importance of planning actions in order to control and monitor aquifer nitrate pollution.
authors.affiliation: Departamento de Geodinámica, Universidad de Granada, Avenida Fuentenueva s/n, 18071 Granada, Spain. Electronic address: mchica@ugr.es.
authors.forename: Mario
authors.initials: M
authors.lastname: Chica-Olmo
authors.affiliation: Unidad del IGME en Granada, Urbanización Alcazar del Genil, 4, 18006 Granada, Spain. Electronic address: ja.luque@igme.es.
authors.forename: Juan Antonio
authors.initials: JA
authors.lastname: Luque-Espinar
authors.affiliation: School of Geography, University of Southampton, Southampton, SO17 1BJ, United Kingdom. Electronic address: vrgaliano@ugr.es.
authors.forename: Victor
authors.initials: V
authors.lastname: Rodriguez-Galiano
authors.affiliation: Instituto Geológico y Minero de España (IGME), Ríos Rosas 23, 28003 Madrid, Spain. Electronic address: e.pardo@igme.es.
authors.forename: Eulogio
authors.initials: E
authors.lastname: Pardo-Igúzquiza
authors.affiliation: Facultad de Ciencias de la Salud, Universidad de Granada, Avda. Madrid s/n, 18071 Granada, Spain. Electronic address: luciachicarivas@hotmail.com.
authors.forename: Lucía
authors.initials: L
authors.lastname: Chica-Rivas
mesh_terms: D004784:Environmental Monitoring / Q000379:methods*; D060587:Groundwater / Q000737:chemistry*; D009566:Nitrates / Q000032:analysis*; D013030:Spain; D062206:Spatial Analysis; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014876:Water Pollution / Q000706:statistics & numerical data*
chemical_list: D009566:Nitrates; D014874:Water Pollutants, Chemical
keywords: Categorical probability maps; European Water Framework Directive; Groundwater pollution; Indicator Kriging; Nitrate