Methodological approach to assessment of groundwater contamination risk in an agricultural area

Water contamination by nitrates of agricultural origin is a major problem in Sardinia (Italy) where Nitrate Vulnerable Zones (NVZs) has been identified in the Arborea reclamation area (W. Sardinia), where intensive agriculture and farming are the mainstays of the local economy. Agricultural practices have seen an increase in the use of animal and chemical fertilizers for enhancing soil productivity. This, accompanied by the intensive use of groundwater resources for irrigation has led to the deterioration of groundwater quality, in areas particularly vulnerable to nitrate contamination. In the test area, the intrinsic nitrate contamination risk from agricultural sources has been evaluated through the combined application of the parametric methods, SINTACS, SI and IPNOA. Risk assessment, using vulnerability and hazard mapping, is considered a fundamental aspect of sustainable groundwater management. All parameters used in this risk assessment were prepared, classified, weighted and integrated in a GIS environment. Results show that nitrate concentrations are located in those areas where agricultural and livestock farming are concentrated. These results could, consequently, be interesting for future development and long term planning of groundwater protection management. The risk methods adopted, verified by comparing the distribution of nitrates in the groundwater with the different vulnerability classes, proved to be a valid tool. In fact the areas with nitrate concentration of more than 100 mg/l coincide well with those at high risk identified by the model and the areas with nitrate concentration of less than 25 mg/l closely match those areas with low and moderate risk.