There are some inherent difficulties in how we've chosen to plan and build our house. A lot of the planning stage is taking place before we've actually bought land, meaning that we can't get truly accurate data on the specific climate of wherever our little patch of paradise will end up being. Makes planning for all manner of things a little difficult. But we have a rough estimate of where we'd like to be, and are reasonably confident that's the region we'll end up in, so I can proceed from there.
One of the most important things we need to plan for is water. This is the aspect of the build that most concerns me. Maybe that's surprising - I'm entirely confident we can build the structure of the house, and we've more or less decided gas for water heating and cooking is probably the easiest, and whilst I don't currently know terribly much about electronics and solar panels I'm sure I can learn. However, the rain does worry me as there's no manner of learning more about it that will make it rain more, and we are unlikely to have a mains water connection as a backup.
So off I go to the Bureau of Meteorology site to look for historic rainfall data. As you do!
For a rough first estimate the areas we're looking at properties fall solidly on the 1000-1500mm borderline. But I'm particularly interested in seasonal variation - winter is the wet season in this part of the world, which leads to a long dry summer. Into the future I can't imagine this will improve considerably.
Through my subsequent search I found the most amazing tool - Tankulator. You can enter in your likely postcode, find the nearest weather station, enter values for the size of the collection area, how much water you use (we'll have a composting toilet and recycle our grey water for use on the garden), the size of your tank, and it will draw you a graph of the predicted tank water level over 5 years. You can then make adjustments and go back and forth until you find the most stable configuration.
The Tankulator lets you select whether you'll start from an empty tank, or fill it initially to either 50% capacity or full, which we'll probably end up doing. I've struggled to find price estimates for water cartage, but there are several companies that offer this service in the area we are looking so this will likely be our safety net if we get our maths wrong.
It makes sense that a larger collection area will be better, and a larger tank capacity also. As we'll be completely off grid for water it's important that even during the driest years the tank is unlikely to empty entirely. I would also tend to see tank overflow as a failure - all that water that could have been captured and stored, if only the tank was bigger. Ideally I'd like the water level to hover between half and three quarters full, so I had to do a bit of fiddling around with my (entirely imaginary at this point) consumption, collection area, and tank size numbers.
The process of successively changing these numbers and seeing the effect they had on the amount of water stored (and whether it was trending up or down) was quite enlightening. It also highlighted the importance of the exact location in determining what size tank to get - the weather station shown above leads to a fairly stable water level, but the next one over trended way down over time with the same numbers.
Through my subsequent search I found the most amazing tool - Tankulator. You can enter in your likely postcode, find the nearest weather station, enter values for the size of the collection area, how much water you use (we'll have a composting toilet and recycle our grey water for use on the garden), the size of your tank, and it will draw you a graph of the predicted tank water level over 5 years. You can then make adjustments and go back and forth until you find the most stable configuration.
The Tankulator lets you select whether you'll start from an empty tank, or fill it initially to either 50% capacity or full, which we'll probably end up doing. I've struggled to find price estimates for water cartage, but there are several companies that offer this service in the area we are looking so this will likely be our safety net if we get our maths wrong.
It makes sense that a larger collection area will be better, and a larger tank capacity also. As we'll be completely off grid for water it's important that even during the driest years the tank is unlikely to empty entirely. I would also tend to see tank overflow as a failure - all that water that could have been captured and stored, if only the tank was bigger. Ideally I'd like the water level to hover between half and three quarters full, so I had to do a bit of fiddling around with my (entirely imaginary at this point) consumption, collection area, and tank size numbers.
The process of successively changing these numbers and seeing the effect they had on the amount of water stored (and whether it was trending up or down) was quite enlightening. It also highlighted the importance of the exact location in determining what size tank to get - the weather station shown above leads to a fairly stable water level, but the next one over trended way down over time with the same numbers.
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