A Probabilistic Approach to Assess the Risk of Groundwater Quality Degradation

In environmental sciences, the risk assessment methods focus on the most reliable techniques to quantify vulnerability and hazard, being the former defined as functionally related to the latter independent variables. With regard to groundwater systems, this chapter explores the possibility of assessing directly the environmental risk as a probability, avoiding to evaluate each of its components. Environmental risk is intended here as the probability of groundwater (i.e., the vulnerable natural system) quality degradation due to the uncontrolled spreading of nutrients on soils in agriculture (i.e., the hazardous event). Risk is formally defined as the probability of exceeding given thresholds of nitrate concentration, conditioned by values sampled within the considered groundwater system. Then, a probabilistic methodology is proposed, based on geostatistical, non-parametric, stochastic simulation, to estimate and spatialize such a risk. Finally, the methodology has been applied to the shallow aquifer of the "Tavoliere di Puglia" plain, located in Apulia, Southern Italy, and characterized by intense agricultural activities and civil facilities.