As Australia is a dry continent (and likely to become drier) it’s important that we use water sparingly to conserve this limited resource. In addition, the processes of collecting and processing water, transporting it to your property, and then once it's used, treating and transporting it again all generate greenhouse emissions.
Your money has a carbon footprint just as your personal consumption does. If you have bank deposits, superannuation, insurance policies, or investments, that money is being used for some sort of economic enterprise. Is it helping to finance a high carbon economy, or a low carbon one?