ABSTRACT
Environmental risk is the probability that something bad will happen to an environmental system [1]. Virtually all practical problems in hydrogeology can be formulated in terms of risk, be it ecologic, economic, health, or regulatory. is is not surprising since risk arises from uncertainty, and uncertainty is the hallmark of applied hydrogeology. is chapter focuses on formal methods of probabilistic risk assessment (PRA) that can account for the range of possible damage to an aquifer and related systems when a mishap has occurred, or may occur, and some system properties are uncertain. Many of the examples are based on contaminant transport because risk is relatively easy to dene in those circumstances, but the methods sketched here can also be used to quantify risks associated with groundwater supply.
