Let's start with Bernoulli's equation:
$$\frac 12 \rho v_1^2 + \rho g z_1 + p_1 = \frac 12 \rho v_2^2 + \rho g z_2 + p_2$$
Or do you perhaps have a different version of it?
Since (2) is a stagnation point, we have $v_2=0$.
The pressure is identified by the column of water above it: it's the weight per surface area.
And additionally we have the standard pressure of air ($p_0$).
So for instance $p_1 = p_0 + \rho g (h_1 + h_2)$.
How far do you get filling in the other variables and solving for $v_1$?