Watertightness of chiew larn reservoir, suratthani, Southern Thailand

Abstract

Chiew Larn reservoir is formed by damming the Khlong Saeng valley which is located in Suratthani, Southern Thailand. The maximum water level and the limestone perviousness are the main problems of this project. At the southern reservoir rim, there is a limestone area that runs from Khlong Saeng to the Khlong Sok valley giving rise to concern about reservoir leakage. To cope with this problem, the hydrogeology of this basin was studied in order to confirm that the underground water table is higher than the reservoir level. Hydrogeological observations, such as the water inventory of the surface creeks and ponds, flourescence test of the underground water including underground water measurement in rotary drill-holes, demonstrated that the underground water table in this area is high enough to prevent the leakage of reservoir water. This conclusion is supported by the high water level recorded in DH-1, at the ground elevation of 176 mMSL, depth 80 m showing that the elevation of the ground water table is at 173 mMSL in April 1973, at the end of the dry season.