HYDROLOGICAL AND NITRATE LOADING MODELING IN LAM TAKONG WATERSHED, THAILAND

Abstract

Water pollution is largely associated with the growth of agriculture, urbanization, and industrialization. By the year 2016, the quality of significant surface water sources in Thailand has been evaluated and categorized as 34% good quality, 46% fair quality and 20% poor quality. According to the Pollution Control Department of Thailand, the lower Lam Takong river, one of the critical watersheds of Thailand, is considered to have a poor water quality. In Lam Takong watershed, non-point sources area approximately covered 89% of the total area, those sources became the significant contributors of water pollutants, particularly nutrients to the Lam Takong watershed. Plus, water quality researches of the watershed were carried out with many different watershed models, but the SWAT model has not been applied to allot the pollutant loading from diffuse sources. Therefore, the main objective of this study is to apply the SWAT model to simulate flow and nitrate from 2007 to 2017, and allocate NO3^- loading in upstream is lower than downstream of the Lam Takong watershed. The R² values are 0.69 in upstream and 0.64 in downstream of Lam Takong. The results of the study can be a useful tool for the management of surface water resources in the Lam Takong watershed.