The most obvious pollution is garbage, especially plastic containers, which mostly comes from area homes and businesses tossed onto the ground or in streams, especially from Chiapa de Corzo and Tuxtla Gutiérrez due to the lack of environmental awareness according to Conanp. The quantity of this trash reaches its height during the rainy season, when runoff and swollen streams can carry more of it into the Grijalva. While bottles and other plastic are what the casual visitor generally notices, other indicators include the overgrowth of water lilies (due to high levels of fecal matter) and dead animals. However, this accounts for only about five percent of the total tonnage of waste that comes into the river each year. Somewhere between 80 and 90% of the waste solids found in the river is branches, wood, rocks, sediment and other debris from legal and illegal logging, which cause deforestation . These mostly come into the river during the rainy season, especially from the Villa Flores and Villa Corzo municipalities. Only a small part of the solid waste is visible on the surface of the water, most is hidden underneath.
