Increased pollution sources by means of the changing landuse in river basin and excessive nutrient INSTREAM application leads to degrade water quality. Mun River basin, one of the largest river basins in Thailand had studied. Comparative figure of nutrient property of water showed recently to increment in total nitrogen phosphorus ratio (> 14) . Laboratory test data, for the weekly water sampling observed more realistic response with daily rainfall. The Hydrologic Simulation Program-FORTRAN (HSPF) was calibrated and used to assess the different landuse effects on river water quality. Model parameters related to hydrology and sediment was calibrated and validated using stream flow and sediment concentration data of Royal Irrigation Department, gauge stations. With the reasonable model performance (R2 = 0.62), the simulated highest Observed runoff from urban area. Finally, a noticeable relationship found in context of the Higher detachable agricultural lands. In decision making perspectives, such model can play a vital role, however for practically application more extensive data on non-point pollutant sources and detailed land uses are required.