we get $\frac{dV}{dt}$=πr²$\frac{dh}{dt}$
⇒Q=πr²$\frac{dh}{dt}$ or $\frac{dh}{dt}$=πr²Q
Note the $\frac{dV}{dt}$ represents the rate at which the volume of liquid in the cylinder increases, which is same as the rate of pouring of water through the tap.