Figure 4. Vulnerability uncertainty.

Spatial distribution of (a) probability and (b) standard deviation of the deep (≥150 m) aquifer becoming contaminated in ≤200 years based on the travel times of 60 heterogeneous realizations. Contours in a show the area in the homogeneous simulation within which particle travel time is ≤200 years. Standard deviation of this binary variable (safe or unsafe in 200 years) is 50% where it is equally likely to be safe or unsafe, and ≤30% where likelihood of being safe is ≥90% or ≤10%.