Main Article Content
The quality of Nan river which is an important surface water resource in Thailand was evaluated by using physico-chemical and biological parameters and together with the water quality index (WQI). The aim of this study was to understand the variation of water quality in accordance with locations (i.e. midstream and downstream) and seasons (i.e. wet and dry seasons) from 2012 to 2016, which is beneficial for water resource planning and management in the Lower Northern Thailand. The data of all 15 water parameters were collected from Pollution Control Department (PCD), Thailand. The data revealed that some parameters including turbidity, total solids (TS) and suspended solids (SS) were significantly affected from locations and seasons (r < 0.05); the larger values were observed in the downstream and wet season rather than the midstream and dry season. In the meanwhile, the nitrate (NO3-) and total phosphorus (TP) concentrations was significantly affected from only locations; the higher concentrations were found in the downstream rather than the midstream. The average WQI values were 67.9 and 68.7 in wet and dry seasons respectively, which classified as a moderate quality. There was no spatial and seasonal variation in Nan river quality. In addition, the majority of sampling water (of 70%) was in Class 3 in accordance with the Thailand surface water quality standard. The results presented that the increasing agricultural and residential areas along the river did not affected on decreasing the water quality. The self-purification of Nan river was still effective, however the regular monitoring is still necessary for interpretation of water quality and management measures.
 Tirado, R. (2007). Nitrates in drinking water in the Philippines and Thailand. Greenpeace Research Laboratories Technical Note 10/2007.
 World Health Organization. (2017). Guidelines for drinking-water quality. Fourth edition incorporating the first addendum. 1,398-403. URL: https://www.who.int.
 National Statistical Office. (2015). Demography Population and Housing Branch. URL: https://statbbi.nso.go.th/staticreport/page/sector/th/01.aspx (in Thai).
 Pollution Control Department. (2002). Domestic wastewater and wastewater treatment system. Water Quality Management Division. Pollution Control Department. Ministry of Science Technology and Environment. KurusapaLatphrao publisher. 1,3-3 (in Thai).
 Luanmanee, S., Boonsook, P., Attanandana, T., Saitthiti, B., Panichajakul, C., & Wakatsuki, T. (2002). Effect of intermittent aeration regulation of a multi-soil-layering system on domestic wastewater treatment in Thailand. Ecological Engineering 18, 415-428.
 Pollution Control Department. (2018). Surface water quality. URL: www.pcd.go.th (in Thai).
 Provincial Waterworks Authority. (2016). Water supply treatment process. URL : https://www.pwa.co.th/contents/service/treatment.(in Thai)
 Pollution Control Department. (2010). Practical Guide for Water Sampling. 1,10-10. URL : www.pcd.go.th/public/Publications/print_water.cfm?task=Water_CollNat_Manual. (in Thai).
 Royal Irrigation Department. (2015). Measurement of water quality in irrigation. Hydrology section. 23-23 URL:https://irrigation.rid.go.th/rid14/mss58/mssbook58/mssbook11.html. (in Thai).
 Provincial Waterworks Authority. (2009). Water Resources and Water Quality 2009. 3,14-14 URL: https://22.214.171.124:8088/km/11.pdf. (in Thai).
 Environmental Office Region. (2013). Water quality monitoring surface water source report. 1,2-2. URL:https://www.reo3.go.th/newversion//index.php?option=com_content&task=view&id=823&Itemid=82. (in Thai)
 World Bank. (2000). Thailand Environment Monitor. (in Thai).
 Pollution Control Department. (2001-2003). Thailand state of pollution report. URL: www.pcd.go.th (in Thai).
 Pollution Control Department. (2004-2012). Thailand state of pollution report. URL: www.pcd.go.th (in Thai).
 Dadi, D., Mengistie, E., Terefe, G., Getahun, T., Haddis, A., Birke, W., Beyene, A., Luis, P., & Van der Bruggen, B. (2018). Assessment of the effluent quality of wet coffee processing wastewater and its influence on downstream water quality. Ecohydrology and Hydrobiology, 18, 201-211.
 Vrebos, D., Beauchard, O., & Meire, P. (2017). The impact of land use and spatial mediated processes on the water quality in a river system. Science of the Total Environment, 601-602, 365-373.
 Rizo-Decelis, L.D., Pardo-lguzquiza, E., & Andreo, B. (2017). Spatial prediction of water quality variables along a main river channel, in presence of pollution hotspots. Science of the Total Environment, 605-606, 276-290.
 Sonklin, W., & Photong, C. (2005). Water quality of Nan river flowing through agricultural and urban areas of Phitsanulok Province. Naresuan University Journal, 13, 37-44.
 Su, F., Kaplan, D., Li, L., Li, H., Song, F., & Liu, H. (2017). Identifying and classifying pollution hotspots to guide watershed management in a large multiuse watershed. International Journal of Environmental Research and Public Health, 14, 1-14. Doi: 10.3390/ijerph14030260.
 Zhou, M.M. Chen, Y., Xue, L., Fan, T.T., Emaneghemi B. (2018). Greater health risk in wet season than in dry season in the Yellow River of the Lanzhou region. Science of the Total Environment, 644, 873-883.
 Jeihanipour, A., Shen, J., Abbt-Braun, G., Huber, S.A., Mkongo, G., Schafer, A.I. (2018). Seasonal variation of organic matter characteristics and fluoride concentration in the Maji ya Chai River (Tanzania): Impact on treatability by nanofiltration/reverse osmosis. Science of the Total Environment, 637-638, 1209-1220.
 The international water association (IWA). Data and Information,Rainfall.URL:https://www.flooddroughtmonitor.com/home.
 Thai Meteorological Department. (2018). Meteorological knowledge. URL: www.tmb.go.th. (in Thai).
 Pollution Control Department. (2011). Calculation of water quality index with 5 parameters. Inland Water Quality Sub-Division, Water Quality Management Division. URL: www.pcd.go.th. (in Thai)
 Harvey, R., Lye, L., Khan, A., Paterson, R. (2011). The influence of air temperature on water temperature and the concentration of dissolved oxygen in Newfoundland rivers. Canadian Water Resource Journal, 36, 171-192.
 Provincial Waterworks Authority. (2011). Water supply standards. URL: www.pwa.co.th.
 Rusydi, A.F. (2017). Correlation between conductivity and total dissolved solid in various type of water : a review. Global Colloquium on GeoScience and Engineering, 118, 1-6.
 Daphne, L.H.X., Utomo, H.D., & Kenneth, L.Z.H. (2011). Correlation between turbidity and total suspended solids in Singapore rivers. Journal of Water Sustainability, 1, 313-322.
 Hannouche, A., Chebbo, G., Ruban, G., Tassin, B., Lemaire, B.J., & Joannis, C. (2011). Relationship between turbidity and total suspended soilds concentration with a combined sewer system. Water Science and Technology, 64, 2445-2452.
 Brasington, J., & Richards, K. (2000). Turbidity and suspended sediment dynamics in small catchments in the Nepal Middle Hills. Hydrological Processes, 14, 2559-2574.
 Minella, J.P.G., Herten, G.H., Reichert, J.M., & Clarke, R.T. (2008). Estimating suspended sediment concentrations from turbidity measurements and the calibration problem. Hydrological Processes, 22, 1819-1830.
 Suif, Z., Fleifle, A., Yoshimura, C., & Saavedra O. (2016). Spatio-temporal patterns of soil erosion and suspended sediment dynamics in the Mekong River Basin. Science of the Total Environment, 568, 933-945.
 Sabeen, A.H., Noor, Z.Z., Ngadi, N., Almuraisy, S., & Raheem, A.B. (2018). Quantification of environmental impacts of domestic wastewater treatment using life cycle assessment: A review. Journal of Cleaner Production, 190, 221-233.
 Department of Health (2016). Coliform bacteria and drinking water. Washington State Department of Health. Division of Environmental Health. Office of Drinking water. April 2016, URL:https://www.doh.wa.gov/Portals/1/Documents/Pubs/331-181.pdf
 Bureau of Livestock Standards and Certification. (2018). Piggery farm registration. URL: https://certify.dld.go.th/certify/index.php/th/ (in Thai)
 Bordalo, A.A., Nilsumranchit, W., Chalermwat, K. (2001). Water quality and uses of the Bangpakong river (Eastern Thailand). Water Research, 15, 3635-3642.