Impact of Land Use Change on Seasonal Water Quality, Case Study in Chi-Mun River Basin in Thailand

This study investigates the correlation between land use changes and water quality in the Chi-Mun River Basin, Thailand, from 2007 to 2021. It is the first of its kind in the region and the Mekong River Basin, providing critical insights for global river basin management. The research analyzes spatial and temporal land use changes and their multi-scale impacts on water quality, utilizing land use change estimation, water quality index analysis, and redundancy analysis (RDA). The results showed that stream water quality variables displayed highly temporal variations, with pH, Biochemical Oxygen Demand (BOD), Total Coliform Bacteria (TCB), Fecal Coliform Bacteria (FCB), Total Phosphorus (TP), Nitrate Nitrogen (NO ₃ -N), Ammonia-nitrogen (NH ₃ -N), Suspended Solids (SS) all generally displaying higher levels in the wet season, while there were higher concentrations of Dissolved Oxygen (DO), Electrical Conductivity (EC), and Water Quality Index (WQI) in the dry season. The water samples were collected once in January, March, May, and August from 2007 to 2024. The water quality in wet season is represented in May and August, while in dry season is represented in January and March. The total contribution of land use patterns on overall water quality was stronger during the wet season. It shows a decline in paddy and forest areas alongside an expansion of urban, agricultural, and aqua agricultural land. Water quality displayed significant seasonal variations, with forests and water bodies contributing to purification, while agricultural and urban areas degraded water quality. The findings offer recommendations for water quality protection and land management policies that align with the basin’s natural and socio-economic characteristics, promoting coordinated regional development.