Geographic information system applied to the water quality assessment of Ayutthaya Province, Thailand

Ayutthaya is a popular tourist destination located about 76 km north of Bangkok. The climate of the province is typical of Central Thailand, comprising three (cold, hot, and rainy) seasons, with relatively small changes in average temperatures but significantly varying rainfall patterns. In this study, we present a geographic information system (GIS) used for the assessment and monitoring of pollution in the watershed. The ArcInfo-based system combines geographical, meteorological and hydrological data for multiple uses. Water quality management is based on composite water quality index and corresponding water quality classes. The chief input parameters include temperature, pH, faecal bacteria count (FCB), dissolved oxygen (DO), nitrate (NO3), total phosphates (PO4), biochemical oxygen demand (BOD), suspended solids (SS), and total solids (TS), together with population density, rainfall and land-use. The initial results of years 2008 and 2009 show that water quality derogation is strongly related to high population density in the central (new City) districts that also affect the historical City. In addition, the increased runoff of the rainy season causes significant PO4, NO3, and BOD pollution of the Pa Sak River at the northern agricultural districts.