The model represents rainfall in the wetlands versus developed areas like cities. Sponge pieces represent toxins that build up on the land. Marbles represent rainfall. Water in wetlands moves much slower than water in developed areas; this is why there are screws in the wetlands side of the model-to slow down the “water” (actually marbles). When it rains, water rolls downhill, carrying toxins with it. Because water in wetlands moves so slowly, the toxins are trapped and break down before they get to a larger body of water; such as the ocean. In developed areas with no wetlands, water moves much faster, spilling harmful toxins into the ocean.
Acknowledgements: I would like to thank my loving parents Tamirisa and Renuka Apparao, my younger brother Vasu Apparao, and our family friend Ms. Usha Raju.