The reservoir has in storage about 30 million cubic metres.

这座水库贮水约3000万立方米。

《新英汉大辞典》

The reservoir has in storage about five million cubic metres.

这水库有五\百万\立方米的储存量。

youdao

The consumption of potable water totalled 916 million cubic metres, compared with 913 million cubic metres in 1997.

本港全年共耗食水9.16亿立方米，1997年则为9.13亿立方米。

youdao

About one million cubic metres of collapsed mining spoil at Hatfield Colliery has to be removed.

BBC: Stainforth landslip rail line to be closed until September

Which is odd, as we produce some 100 million cubic metres of waste each year (this includes all the building rubble etc).

FORBES: Despite NPR, No, Burning Trash Is Not Profitable

Forestry Commission Scotland said 7.5 million cubic metres were harvested in 2011, which was half a million more than the previous year.

BBC: Scottish timber harvesting at record high