Solute transit or travel time distributions (TTDs) in catchments are
relevant to both hydrochemical response and inference of hydrologic
mechanisms. Long-tailed TTDs and fractal scaling behavior of stream
concentration power spectra (~1/frequency, or
1/frequency to a power < 2) are widely observed in catchment
studies. In several catchments, a significant fraction of streamflow is
derived from groundwater in shallow fractured bedrock, where matrix
diffusion significantly influences solute transport. I present frequency
and time domain theoretical analyses of solute transport to quantify the
influence of matrix diffusion on fractal scaling and long-tailed TTDs.
The theoretical concentration power spectra exhibit fractal scaling, and
the corresponding TTDs resemble a gamma distribution. The tails of the
TTDs are influenced by accessible matrix width, exhibiting a sustained
power-law (rather than exponential) decline for large matrix widths.
Application to an experimental catchment shows that theoretical spectra
match previously reported power spectral estimates derived from