Water quality observation data were collected from 20 representative monitoring sites
located in the main stream of the Nakdong River and its major tributaries between 2008 and
2012. Based upon these data, the water quality distribution and characteristics of each river
were evaluated by conducting multivariate statistical analysis for 12 pollution indicators
using SPSS-17.0. Monitoring site T8 passing through the city of Daegu and monitoring site
M5 located downstream of the Nakdong River exhibited high-concentration tendencies.
The monitoring sites located near the city and midstream and downstream of the Nakdong
River exhibited high pollution levels in the investigation. To analyze the spatial and
temporal variations in the water quality at 20 major monitoring sites in the Nakdong River
watershed, principal component and factor analyses were conducted by separating the
average water quality data based upon (a) monitoring site, and (b) season. As a result, three
factors were obtained for (a), and (b), respectively. In the Nakdong River watershed, the first
factor was shown to be nutrient salts (total nitrogen and total phosphorus) and organic
pollutants (total organic carbon and chemical oxygen demand), and as a result of cluster
analysis, two statistically significant groups were classified. The results of multivariate
statistical analysis indicated that the monitoring sites with high levels of pollution were
mostly those sites going through the heart of the city or the sites affected by residential
sewage directly, as well as the sites located midstream and downstream of the Nakdong
River. The water quality pollution level was calculated based upon the above study results,
and the priorities for water quality improvement items required in future watershed
management were determined in order to facilitate efficient water quality management.