I think it's crucial that we are better educated to be made more aware of our “water footprint” as much as we are with our carbon footprint. This way we would be in a better position to all take responsibility for saving water ourselves and play our part in water saving activities (eg. Showering with less water, turning off taps when brushing teeth, only boiling what's needed, installing a low-flush toilet and saving up the washing for full loads etc etc.)
From a development point of view, building developers should be thinking more responsibly to help us save water and prevent wasting it. Things like greywater storage tanks should be in every house, as should water butts for collecting rainwater.
On a larger scale, sewage treatment could be zero energy if we used constructed wetlands and reed bed systems. Similarly, a completely new way of thinking about how we treat sewage could be adopted so that we compost faecal biomass and store urine separately from flush water in order to reuse them safely in agriculture.
As with a lot of these things, we should look at our purchasing habits as well. For example, we should really be discouraging the more harmful ingredients that can end up in our waterways and even consider making our clothing purchases from more sustainable (less water consumptive) sources as well. (When I read up on this I was amazed to learn that hemp requires about 50% less water to grow than cotton, and only a quarter of the water needed for processing!)