Investigations on the water quality of the Mae Klong River and Estuary were conducted from April 2005 to February 2006 during periods of early-, mid-, and late-loading. Nutrient loads and transfer patterns were studied together with clarification of contaminated sites. The results indicated that NH4+, NO2- + NO3-, Si(OH)4 and PO4(3-) concentrations varied by season and were comparatively high in the mid-loading period. Analysis of DIN:P and Si:P molar ratios indicated that P04(3-) could possibly be a limiting nutrient. Highly contaminated sites were in the middle (Ratchaburi province) and lower (Samut Songkhram province) river zones in which anthropogenic wastewater discharges were significantly (p < 0.05) loaded. Analysis of the DIN and P transfer patterns showed that self-remediation efficiencies were rarely found. The highest DIN and P loads of 23.87 and 4.03 t/day, respectively, were found in Samut Songkhram province. Nutrients were found to contribute to the hypertrophic condition of the lower river and the estuary. The baseline level of chlorophyll a in the upper river was approximately 3.3 microg/L, while levels exceeded 10 microg/L in the estuarine zone. Such chlorophyll a levels were highly significant (p < 0.01) related to DIN and P (with correlation coefficients of 0.44 and 0.37, respectively). In order to maintain river conservation to an acceptable degree, levels of about 20 micromol/L DIN and 1 micromol/L P were suggested as the upper limits. To achieve such levels will require serious consideration with regard to the development of nutrient criteria for water resource conservation management and sustainable utilization purposes.

Assessment of aquatic environmental impacts, nutrient transfer and the clarification of contaminated sites were conducted based on water quality analysis of the Mae Klong River. Twelve sampling stations were surveyed between April 2015 and April 2016 covering Kanchanaburi, Ratchaburi and Samut Songkhram Provinces. Results showed that aquatic environmental factors varied seasonally. A mathematical model developed using the box modeling method showed that middle (Ratchaburi Province) and lower (Samut Songkhram Province) riverine zones were point source areas. Highest DIN and PO4 3--P loads were found in Samut Songkhram Province. Results implied that PO4 3--P levels were higher than the standard criterion for aquaculture (< 1.45 µmol L -1 ). Levels of PO4 3--P continued to increase, downriver, particularly in the estuary. Recent PO4 3--P levels suggest that the number of agroindustry plants discharging waste effluent into the river should be reduced. Monitoring to assess the aquatic status of the Mae Klong River and estuary using the PO4 3--P database is urgently required to control water quality and reduce contamination levels.

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This research investigates the effects of seasonal variability (rainy and dry seasons) and nutrient transfer patterns on the nutrient loads (dissolved inorganic nitrogen (DIN) and orthophosphate phosphorus (P)) and the self-remediation of the south Rangsit canal in Thailand -1 , respectively. The DIN and P loads were 5.05 and 0.40 tons/day in the rainy season (September); and 5.12 and 0.32 tons/day in the dry season (March). The relative remediation efficiency (EFR RR ) were mostly negative, especially in the dry season, indicating the inadequate self-remediation and nutrient input-output imbalance. The findings also showed that water mass transfer directions influenced the self-remediation and nutrients accumulation in the study area.