Tests inside the reservoir

The tests performed inside the reservoir or lake related to leakage studies have as the main or unique objective the localisation of the areas where water losses are taking place. This is really a difficult task because of the point character of the available techniques and the large extent of the impounded areas in the reservoir where the leakage or seepage can occur. For this reason, before applying these techniques, and to reduce the area in which the techniques have to be applied, it is very important to explore exhaustively all the possibilities offered by the techniques based on the measurement of the natural tracers of water, such as temperature, stable isotopes of water, and chemical composition, as described in previous chapters. In the same way, the filtration law, that is, the variation of the leakage rate as a function of the water level in the reservoir can provide very valuable information on the topographic elevation at which the water losses are taking place. Of course, the geological setting of the bottom of the reservoir and the surrounding formations has to be considered as the starting point.