Methods for water quality measurement are presented at Table 1. Three sampling stations were established.
Sampling was performed three times according to rainy season. On each station, 3 replicate samplings (middle and
both side of the river) were performed and then composited. Water samples were stored in 250 ml sample bottles and
put in the cooler box. Water sample preservation used 0.3 ml concentrated H2SO4 for nitrate, nitrite, and ammonia.
For total phosphate, water samples were stored in the cooler box without preservation.