Abstract: “GIS is a powerful tool for researches relating to many environmental problems and especially in water quality management such as sustainable water- use plan, assessing water quality and managing water resources on a local or regional scale. The models are linked with GIS for output data and results presentation. In this paper the interpolation function in GIS technology and Surfer software were applied to zone the surface water quality in Tri An Reservoir according to parameters: pH, DO, BOD5, COD, TSS, NH4 +, P-PO4, turbidity and coli form. A series of data related to these parameters in three years 2010, 2013 and 2014 was collected to be input data for the interpolation. Then, the interpolation maps of parameters through years were built to compare and assess surface water quality in Tri An Reservoir.”

Keywords: GIS, interpolation, water quality