In a semi-arid drainage basin, the annual volume of water extracted from the aquifer for agricultural irrigation is 13,500,000 m313,500,000\text{ m}^313,500,000 m3, while the annual volume extracted for domestic consumption in the regional municipality is 1,800,000 m31,800,000\text{ m}^31,800,000 m3.
Calculate the ratio of the volume of water extracted for agricultural irrigation to the volume of water extracted for domestic consumption. Give your answer in its simplest form.