REGIONAL GROUNDWATER FLOW AND SALINE WATER SOILS IN KHORAT AND SAKON NAKORN BASINS, NORTHEAST THAILAND

REGIONAL GROUNDWATER FLOW AND SALINE WATER SOILS IN KHORAT AND SAKON NAKORN BASINS, NORTHEAST THAILAND Kriengsak Srisuk¹, Vichai Sriboonlue², and Chalong Buaphan¹ ¹Department of Geotechnology, Faculty of Technology, Khon Kaen University, Thailand ²Department of Agricultural Engineering, Faculty of Engineering, Khon Kaen University, Thailand ABSTRACT

Regional groundwater flow in the northeast Thailand plays a significant role in distributing saline water and saline soils. The northeast Thailand consists of two main basins namely Khorat (Southern basin) and Sakon Nakorn (Northern basin). About seventeen percent of the northeast area (2.85 Mha) is affected by soil salinity in various degrees. The salt-affected soils in the northeast Thailand are generally sandy, low infertility and high in sodium and chloride contents. Seventy five percent of the salt-affected land is under rainfed rice cultivation and one and half percent is regarded as wasteland. The salt source for saline water and saline soils is primarily from rock salt of Mahasarakhram Formation, which is deposited at variable depths (20 to 500 m). According to the hydrogeological database and hydrogeological maps being conducted by Groundwater Research Center, Khon Kaen University, show that Khorat Basin is much more affected by saline water and saline soils than Sakon Nakorn Basin. Regional groundwater flow systems within the basins are the major cause of salinization processes as well as human activities (salt mines). Several medium to large scales water resource developments, reservoirs, weirs and dams, were constructed over the northeast Thailand for irrigation purpose. In 1994, the Department of Energy Development and Promotion, Ministry of Science, Technology and Environment realized that the impact of surface water development to saline groundwater and saline soils should be comprehensively evaluated. Since 1996, several scales of hydrogeologic mapping and numerical modeling have been conducted within the two basins such as Lam Pao and Borabu areas (Khorat Basin), Nam Song Khram and Nam Kam floodplains (Sakon Nakorn Basin). The results of the studies indicate that regional groundwater flow system related to distribution on salinity in the Khorat Basin are strongly controlled by configuration of rock salt layers, topography and land uses, whereas regional groundwater flow systems related to water and soil salinity in the Sakon Nakorn Basin are effected by rainfall distribution, topography and land uses.