Model of relationship between water quality and industry density at upper reaches of Yangtze River (Sichuan Province)

Through assessing the water quality of upper reaches of Yangtze River (Sichuan Province) and analyzing the industry density of Sichuan province, a relation of water quality and industry density was found and a math model was established. Deriving the equation and letting the derivation equal to 1, a very important point was gotten. When G prime gt;141.71×104 Yuan/km2 the water quality will lower down quickly. For protecting the water quality and making economy sustained development at the upper reaches of Yangtze River (Sichuan Province), a series of enhanced measurements of progress of industry process, industry construction adjustment and relative policy for environment protection should be taken when industry density reaches 141.71×104 Yuan/km2.