I've already read "Water From The Sky", but wasn't clear about details for our location. Many of the details, like the silt catch, were designed with Taos, NM in mind and need some adjustment. Taos has a frost depth of 18" (0.45 meters). I'm dealing with a frost depth of supposedly 1.9 meters as some say. They have that pic of a wonderful silt catch on top of a cistern. In Taos it can get cold, but the average high in January is above freezing. Even then they said it could possibly freeze up a little. If it froze a little there in January, It would definitely freeze in Mongolia, where rivers are completely frozen blocks of ice until the end of March.
So I was dealing with the situation that even if I have a well insulated cistern that it has an opening. I can't even close it for the winter, because as we use water inside, it has to relieve pressure. They also say in that book that metal funnel shaped silt catches will eventually rust and develop holes, so they suggested plastic tubs filled with pebbles as an alternative. The tubs were close to 18" deep. So even if some cold winter air got down through the tub into the cistern, the water is quite a big mass and warm below the frost depth line, even insulated.
I was frustrated when looking at Dan Richfield's 18" cistern riser, because I doubted they had a 2 meter version of that, even if I took 2 1 meter risers. We will check out the water tank places locally. (We know where they are.) Then it occurred to me that I could simply get 2 industrial strength new plastic garbage cans and stack them on top of the cistern opening and do some sealing to prevent dirt from entering the cistern.
Since I want to build in a cold arid climate where 80% of the precipitation is in about 4 summer months, I don't need to be concerned about collecting any snow melt, and need a very large capacity. I wanted to build tire cisterns. If I collect water off the roof and it falls through 2 meters of silt catch, and I want to have the bottom of the cistern at or above the ground floor in the house. That leaves 1 meter or less height fully below the frost depth and above the floor. Most of the large capacity tire cisterns are tall and wide. If I built one cistern, it might need to be extremely wide of 10 meters or more and it would be hard to put a strong lid on it that wouldn't collapse.
I was looking for a cistern design that was 1 meter high or less and large capacity. Eventually it occurred to me that I could use tires behind the thermal wrap in a multiple U design using the smaller tires often found on Asian cars 195 or less, which are considered to be too small for earthship tire walls in the dwelling place. Each U could be maybe 2 meters in width with a common (greenhouse analogy) area to drain towards the center. This way I could easily secure a strong cistern top with rebar and cement over each U. Since 2 tall garbage cans could easily hold the largest storm, I could have one entry point over one U, and perhaps have another insulated cover with a pipe riser from another point to inspect the contents or even climb into the cistern if necessary.
So far this sounds great, because not including piping to/from the cistern there is almost no cost besides cement, sand, 2 big garbage cans and maybe the other riser with an insulated cap to gain entry. It would take the labor to pound hundreds of tires, though.
So, the idea is: put the 1 meter high cistern with 2 meters of earth over it. It would be completely insulated on the inside. It would have a riser of 2 or more pebble filled plastic garbage cans as a silt catch. Even though air could find it's way down into the cistern, I'm hoping that the water won't freeze.
Let's say one cistern U is 1 meter (3.28 ft.) tall, 8 feet long towards the north, 6 feet wide (U sidewall to sidewall) not including tires. Even though U's might be curved and lose space the juncture between each cistern U will compensate for that. These are adjustable. We could easily make them 10 feet if we're short on capacity. 6 feet wide will give up a strong roof over each U. I figured one of these will contain about 1100 gallons.
UB gets about 10" of precip. a year. Maybe less. The airport reported 25" one year. Some places like weather.com report as low as 7-8". If we built a 2000 sq. ft. (large) roof, what is the likely maximum amount of water the roof could produce at 10"? I figured about 12,000 gallons. If we tried to contain the entire year's worth of rainfall, how many 10' long cistern U's would we need? 11.2. If we say a tire is 2' wide and we have 10 walls between 11 tire cistern U's, this would have to be 88 feet long including the tires.
