through the canyon according to park director Edda González del Castilla, with most coming from Tuxtla Gutiérrez, Chiapa de Corzo, Berriozábal and Chicoasén . Much of the sewage comes into the Grijalva via the Sabinal River, which carries most of the waste water of the city of Tuxtla Gutiérrez. In addition, trash and raw sewage makes its way into the river from the various tributary streams. Agricultural waste comes from the farms that line the river and its tributaries. 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. As the solids flow along the Grijalva, they are constricted by the narrow channel of the canyon and then by the presence of the Chicoasén Dam. This is particularly true at a point called “El Tapón” (The Plug), where two currents of water meet just before the reservoir back up of water from the Dam. It is estimated that about 5000 tons of trash accumulate each year, and the river is considered to be one of the five most polluted in Mexico. 3700 tons of solids were extracted from the canyon area in 2010 alone. Many fish have died off or have developed abnormally due to contamination by fertilizers, pesticides and other chemicals. This threatens the native American crocodiles as the agrochemicals kill off and poison the fish they need to eat. In May