Conversion of millimeter into cubic meter

Question

I have a rainfall volume of $140$ mm, $180$ mm and $65$ mm. I have to convert this rainfall data into Cumulative rainfall with units of cubic meters.

Answer 1

When talking about rainfall measurements, the convention is $$1 \text{ mm of rainfall} = 1\; \frac{\text{L}}{\text{m$^2$}}.$$

So if you measures $140 \text{ mm}$, this means that $140\;\frac{\text{L}}{\text{m$^2$}}$ fell in that period of time.

That means that the cumulative rainfall would be $$(140+180+65) \text{ mm}=385\;\frac{\text{L}}{\text{m$^2$}}$$ in all three periods combined. Note that $1 \text{ L}=10^{-3}\text{m$^3$}.$

But you can't make a $\text{mm}$ into $\text{m$^3$}$ no matter how hard you try.