One of the key jobs to do if we to make our neighbourhood sustainable, or our home, is to reduce our reliance on large scale centralised infrastructure and maximise our use of local resources. In other words; become more 'self-sufficient'. And harvesting our own rainwater is a relatively easy place for us to start.
Each time we turn on the tap, fresh clean water is there for us to drink, wash our clothes in or rinse out the left-over weet-bix from breakfast. It's so easy, and so available, that it's easy to forget the massive engineering feat, and ongoing maintenance, that makes it possible. And easy to forget that each drop of water in my kitchen tap has traveled about 80 odd km from the to top of the Yarra River to reach it.
I've been reading a little about Melbourne's water system - and it really is a massive piece of infrastructure. The system as it stands really started in the 1920's, and eight or nine new reservoirs have been created through the decades to supply Melbourne's increasing demands up until the completion of Sugarloaf Reservoir in the early 80's. Along with new reservoirs, huge systems of pipes have been constructed to transport the water from the hills to the city. Areas of the conduit have diameters of 2.1m - you could walk upright inside!
The infrastructure needed to transport water is massive - at 2.1m dia, you could walk upright inside the water conduits that carry our water from the hills
So it makes sense to harvest water locally to reduce the pressure on all that infrastructure.
If self-sufficiency is our goal, does that mean we need to go all the way and sever ourselves from the existing water infrastructure? I don't think so. Surely there's a good point of balance between total self-sufficiency and a centralised system? If we do everything we can to reduce our demands on the existing water system, then we can use still it as a 'back-up' or booster for our local water harvesting systems, but because we're relying on local water supplies we could relieve the water crisis without expanding the centralised system, which we could only really do by finding new valleys to flood and turn into reservoirs.
The other reason it might be better to remain connected to the system is that it may not be such good idea to try and produce our own drinking water. I'm going to look into that further, but my feeling is that responsibility for ensuring the quality of our drinking water is probably a good thing to centralise, which probably also means centralised harvesting and treatment.
But drinking water is only a small percentage of our water needs. We can certainly collect rain-water from our roofs and use it for gardens, dishwashers, washing machines and maybe showers. For everything really, except drinking.
The easiest way to do this is to install water tanks. There's an ever growing choice of water tanks suitable for individual residences, some of them are surprisingly attractive. But many people who live in our neighborhood with our tiny back yards (if any) don't have a lot of room to spare for a water tank...
If you're trying to make your own individual house sustainable, you would look at 'small space' tank solutions - skinny wall tanks, under deck tanks, underground tanks or under house 'bladders'. But for this hypothetical design project, I'm thinking on a neighbourhood scale, so if the water tanks become part of the 'public' or communal infrastructure why not put them under the roads? Of course I haven't done any kind of detailed costing on this proposal, but it seems likely that the cost may be comparable to the expense of installing individual tanks in each house in the neighbourhood.
Of course one of the 'problems' with installing water sustainability measures is the current artificial cheapness of water. So it takes a long time (if ever) for you to recoup your money. Of course; it does mean you can have nice green plants in summer.