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Openaq Pulse Saltmrsh Prairie Fire Lagoon Climax Species Specarea

Draining Tank


We have a stored quantity of something, like water in a temporary pond, which is percolating into the ground. As the pressure driving it decreases, the water draws out - quickly at first and then slowly.


  • Water diffusing through sand
  • Decay of radioactivity of elements like uranium
  • Diagram


    Q = stored quantity
    K = Decreasing factor 


    DQ = -K*Q 


    The graph shows changes of Q over a time period.Source code:

    "What if" Experiments:

    Think about a pile of leaves which is being decomposed by microbes:
  • If you started with a larger pile of leaves in the forest, with the same rate of composition, would the pile go sooner, at the same time or later?
  • What happens if the decomposing rate of the microbes is doubled?