This study estimates unit for the nonpoint source(NPS), classified according to the existing Level-1(large scale) land cover map, by monitoring the measurement results from each Level-2(medium scale) land cover map, and verifies the applicability by comparison with previously calculated units using the Level-1 land cover map. The NPS pollutant loading for a basin is evaluated by applying the NPS pollutant unit to Dongcheon basin using the Level-2 land cover map. In addition, the BASINS/HSPF(Better Assessment Science Integrating point & Non-point Sources/ Hydrological Simulation Program-Fortran) model is used to evaluate the reliability of the NPS pollutant loading computation by comparing the loading during precipitation in the Dongcheon basin. The NPS pollutant unit for the Level-2 land cover map is computed based on precipitation measured by the Sangju observatory in the Nakdong River basin.
Finally, the feasibility of the NPS pollutant loading computation using a BASINS/HSPF model is evaluated by comparing and analyzing the NPS pollutant loading when estimated unit using the Level-2 land cover map and simulated using the BASINS/HSPF models.

Abstract
 1. Introduction
 2. Materials and methods
  2.1. Survey site
  2.2. Computation of basic unit for NPS
  2.3. HSPF model
 3. Results and discussion
  3.1. Basic unit computation using Level-2 land covermap
  3.2. Dongcheon basin NPS load
  3.3. BASINS/HSPF application
 4. Conclusion
 References

• Heon-Gak Kwon(Nakdong River Water Environment Research Center, National Institute of Environmental Research) Corresponding author
• Jae-Woon Lee(Nakdong River Water Environment Research Center, National Institute of Environmental Research)
• Youn-Jeong Yi(Nakdong River Water Environment Research Center, National Institute of Environmental Research)
• Se-Uk Cheon(Nakdong River Water Environment Research Center, National Institute of Environmental Research)