The HEAP-effct
The MIFSLA-behaviour
The linear trap
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Suppose that a person tries to showel up sand on a table..

In the beginning, all the sand will stay on the table.

But after a while, it starts pouring over.


And in the end, the same amount falls down as he tries to put on the table.
This is a steady state.

More thoroughly, the HEAP (Hampered Effluent Accumulation Process) effect can be described with the diagram below:


  • Saturation phase: The storage (Q) increases lineary as a function of flux (J) (until the heap has reached the border of the table).
  • Accumulation phase: The leakage (kQ) increases, which leads to a slower increase of the storage (Q).
  • Steady state phase: When the leakage (kQ) equals the flux (J), there is no further build-up of the storage (Q). (The sewage plant, however meticioulus, has failed)