Hence, this non-linear Fokker-Planck equation can be linked to *q*.

More traditionally, anomalous diffusion is described by a kind of brownian motion with memory (fractional brownian motion), which involves the Hurst exponent.

Both equations are applicable to these types of problems and the relation between the Hurst exponent and *q* for *q < 2 *is:

Hence, H = 0.7 in hydrology implies *q* = 1.57.