Pressure at a depth of 15 m under water surface in a dam is approximately

The pressure increase from the free surface can be calculated with the formula for the weight of the water column divided by the cross sectional area, that is d*g*h, where
d = 1 000 kg/m^3 is water density,
g = 9.8 m/s^2 is gravity and
h = 15 m is the depth.
Then we get 147000 Pa = 147 kPa = 1.47 bar.