Volume of water flowing out$=Av$, where $A$ is area of opening and $v$ is speed of water from the opening.

$\text{Volume}=\pi r^{2}v$

$0.74 \left(\frac{\mathrm{ }{\mathrm{m}}^3}{\min }\right)=\left(3.14\times {\left(2\times {10}^{-2}\right)}^2\times \sqrt{2\times 10\times H}\right) \frac{{\mathrm{m}}^3}{\mathrm{s}}\times \frac{60 \mathrm{s}}{\min }$

$\Rightarrow H={\left(\frac{0.74}{60\times 3.14\times 4\times {10}^{-4}}\right)}^2\times \frac{1}{20}$

$\Rightarrow H=4.8 \mathrm{m}$

Hence, the height of water in the tank was $4.8 \mathrm{m}$ from the bottom of the tank.