  Analyzing field data from pumping tests, we show that as with many other
natural phenomena, groundwater flow exhibits a complex dynamics described by
1/f power spectrum. This result is theoretically studied within an agent
perspective. Using a traveling agent model, we prove that this statistical
behavior emerges when the medium is complex. Some heuristic reasoning is
provided to justify both spatial and dynamic complexity, as the result of the
superposition of an infinite number of stochastic processes. Even more, we show
that this implies that non-Kolmogorovian probability is needed for its study,
and provide a set of new partial differential equations for groundwater flow.
