The rectangular coordinate system established with the vault as the origin is the vertical downward Y axis, and the parabolic equation is that the coordinate of the intersection point between the water surface and the wall on the map is (2, -2), so the parabolic equation is y=? After the water level of X 2 drops, the coordinate intersecting with the wall is (? X, 3), as in the equation, the solution is x=2√6.