Hydrogeologic investigation of possible water leakage through the carbonate rock area on the left bank of the Melen (Sakarya) dam reservoir

On the left bank side of the reservoir area of the Melen Dam, which is located on the Buyuk Melen River in Kocaali province and is under construction, karstic limestones were outcropped. The limestones, whose approximately 20 hectares will remain below the dam reservoir level, discharge on the south of the mass, where the Cumayeri spring observed with impervious flysch, and on the north with Değirmenderesi and Hızardere springs. Cumayeri spring is below the dam reservoir level. The possibility of a hydrological connection between the northern springs and the reservoir area, which discharge from elevations below 113 m, the maximum reservoir level of the dam, reveals that water from this area of the dam reservoir may be a major source of water leakage. For this reason, it is planned to cover the section of the limestone mass that will remain below the reservoir level with concrete. The aim of this study is to examine the hydrogeological structure of the limestone mass which will be below the reservoir water level in order to reveal the relationships between recharge, discharge and groundwater flow dynamics to evaluate the effectiveness of the planned concrete coating in terms of sealing. For this, the geology of the study area has been mentioned on the previous works on the field. Hydrogeological characterization was evaluated with Lugeon tests and flow rates of the springs measured in previous studies. Groundwater level, which was measured on the observation wells drilled in previous studies in the study area, were utilized in the development of groundwater flow model. As a result of the hydrogeological characterization, the local groundwater system, which includes concrete lining area, was revealed and the two - and three - dimensional groundwater flow model of the system was analyzed by finite difference method. Subsequently, an analysis of the magnitude of the uplift pressure to be formed during the concrete lining was built and compared with the numeric models which were evaluated in the previous studies. Accordingly, the necessary precautions for reducing the piezometric pressure on the coating area are modeled and compared with those of the previous studies.