Self-organization

Major differences between flow in a homogeneous porous medium (top), and flow in an aquifer with a channel network enhanced by weathering (after Worthington, 2015)

Self-organization is a process where local interactions in an initially disordered system result in the emergence or an overall order to the system. Self-organization is an important process in bedrock aquifers. Dissolution is the principal form of weathering aquifers, and in a bedrock aquifer with fractures the most dissolution occurs where there is the most flow. This increases the apertures in these fractures which in turn increases the flow, and this positive feedback process creates a high-permeability channel network. Self-organization occurs not only in carbonate aquifers, but also in silicate aquifers. Self-organization results in channel networks with a dendritic structure that discharge to springs rather seepage faces, as described here and shown in the figure. Sometimes feedback processes can enlarged channels so much that flow becomes turbulent, especially in downgradient areas close to springs.