Effect of Abrupt Topographical Characteristic Change on Water Quality in a River
- 7 Downloads
In the past, water quality management was regulated on the basis of pollutant concentrations in rivers. However, the recent implementation of total maximum daily load (TMDL) in the Nakdong River, Korea, has achieved preservation of water quality with balanced watershed development based on a scientific approach. However, eight large weirs have been installed as part of the extensive river regulation works, in which the river geometry has also changed dramatically due to dredging. Consequently, the river environment has been changed, including the hydraulic characteristics, such as the residence time, longitudinal and transverse section, water depth, energy gradient, and flow rate. The water quality characteristics experienced the greatest impact from changes in the hydraulic characteristics of the river. Due to considerable difficulty in the actual implementation of the water quality management plan with respect to the changes, it was considered important to predict the water quality change likely to result from hydraulic characteristic changes in the river. In this study, the hydraulic coefficients reflecting the hydraulic characteristics were calculated and implemented in the water quality model according to the changes in the river environment. The estimated pollutant loads in subwatersheds were applied in the water quality model according to the TMDL of the Nakdong River. The hydraulic coefficients, indicating the hydraulic characteristics before and after the changes to the river environment, were applied in the water quality model with complete calibration and verification. The model simulation results were compared for analysis of the effect of an abrupt river environment change. The simulation results show that the river flow rate was reduced after the change to the river environment due to the effect of the hydraulic structures. As a result of the water stagnation, the BOD5 and Chl-a concentrations increased by 9.4% and 12.2%, respectively, whereas the T-N and T-P decreased by 6.1% and 5.0%, respectively. The impact of a drastic topography change on water quality and its improvement can be quantitatively evaluated by water quality modeling. In particular, BOD has proven to be the most effective for improving water quality when a river is in its natural state rather than when the pollution discharge loads are reduced or when the water quality, discharged from the water-treatment facility, is improved. This study analyzes the relationship between the improvement in water quality and the recovery of running water in each section of the Nakdong River. The current study also proposes a scientific alternative for river rehabilitation, which can improve the quality of stagnant water sections and enable a river to recover to its natural state.
Keywordswater quality management TMDL dredging hydraulic characteristics residence time
Unable to display preview. Download preview PDF.
This work was supported by the 2016 Inje University research grant.
- Arnold, J. G., Srinivasan, R., Muttiah, R. S., and Williams, J. R. (1998). “Large-area hydrologic modeling and assessment: Part I. Model development.” Journal of American Water Resources Association, vol. 34, no. 1, pp. 73–89, DOI: https://doi.org/10.1111/j.1752-1688.1998.tb05961.x.CrossRefGoogle Scholar
- Cho, H. S. and Lee, W. H. (2014). “Comparison of water quality before and after four major river project for water monitoring stations located near 8 weirs in nakdong river.” Journal of Agriculture & Life Science, vol. 52, no. 6, pp. 89–101, DOI: https://doi.org/10.12652/ksce.2014.34.4.1203.CrossRefGoogle Scholar
- Gynsangnam Province, South Korea (2015). 3rd Total maximum daily load master plan in gyngsangnam provice, Report (in Korean).Google Scholar
- Hashim, N. B. (2002). Watershed, Hydrodynamic, and water quality models for total maximum daily load, St. Louis Bay watershed, Mississippi State University, Mississippi, USA.Google Scholar
- Jung, S. Y. and Kim, I. K. (2017). “Analysis of water quality factor and correlation between water quality and Chl-a in middle and downstream weir section of nakdong river.” Journal of Korean Society Environmental Engineers, vol. 39, no. 2, pp. 89–96, DOI: https://doi.org/10.4491/KSEE.2017.39.2.89.CrossRefGoogle Scholar
- Na, E. H., Park, S. Y., Kim, J. H., Im, S. S., and Kim, K. H. (2015). “A study on spatial and temporal patterns of water quality in the middle area of the nakdong River, Korea.” Journal of Korean Society on Water Environment, vol. 31, no. 6, pp. 723–731, DOI: https://doi.org/10.15681/KSWE.2015.31.6.723.CrossRefGoogle Scholar
- NIER (2010). A study on application of watershed management model for total maximum daily load, Report, National Instiute of Enviromental Research, South Korea (in Korean).Google Scholar
- NIER (2013). The 3rd total maximum daily load management research in the nakdong river, Report, National Instiute of Enviromental Research, South Korea (in Korean).Google Scholar
- Park, J. H., Hwang, H. S., Ryu, D. H., and Kwon, O. S. (2012). “Estimation of delivery ratio based on basins/hspf model for total maximum daily load.” Journal of Korean Society on Water Environment, vol. 28, no. 6, pp. 833–842.Google Scholar
- South Carolina Department of Health and Environmental Control (SCDHEC). (2004). Total maximum daily load development for the upper broad river watershed fecal coliform bacteria. Report, Bureau of Water, Columbia, South Carolina.Google Scholar