A flocculator tank has a volume of $2800 \mathrm{~m}^{3 .}$ The temperature of water in the tank is $15^{\circ} \mathrm{C}$, and the average velocity gradient maintained in the tank is $100 / \mathrm{s}$. The temperature of water is reduced to $5^{\circ} \mathrm{C}$, but all other operating conditions including the power input are maintained as the same. The decrease in the average velocity gradient $\text{(in} \%)$ due to the reduction in water temperature is_________ (round off to nearest integer).
[Consider dynamic viscosity of water at $15^{\circ} \mathrm{C}$ and $5^{\circ} \mathrm{C}$ as $1.139 \times 10^{-3} \mathrm{~N}-\mathrm{s} / \mathrm{m}^2$ and $1.518 \times 10^{-3} \mathrm{~N}-\mathrm{s} / \mathrm{m}^2$, respectively]