This project work based on field study and secondary information, intends to study environmental & socio-economic parameters of Arun-III HEP area. The water quality at Arun-III project site is desirable for drinking and aquatic environment, yet it should be treated against E. coli, iron and turbidity for drinking. The five major tributaries downstream of dam site are capable to sustain the ecological health of river during project construction and operation. The soil quality is good for agriculture use with high Organic content, yet it should be treated with lime for acidic character of the...