I'd like to setup some rainwater storage, collecting water from the rainy season, so use later on the garden. The hardware stores sell water storage containers, but to store 3000 gallons (11,000 litre) would require $5000 of containers. In prehistoric times, people just built a pond-like reservoir nearby my house, but I believe the water would just evaporate. Is there a cheaper alternative for storing water? I have a 50 ft by 50 ft (15 metre by 15 metre) area of land to use.
Single large tanks
They sell plastic water tanks in the $1000 range for 3000 gallons (11000 litre). Two such tanks were famously seen in Breaking Bad season 4, as the repository for both the magic “methylamine” they needed, and also for the (spoiler alert).
Figure on 8 foot (2.4 metre) diameter x 10 feet (3 metre) tall. These tanks are absolutely enormous and come on a flat bed truck; the trucker will expect you to have a backhoe and rigging necessary to pick the tank off the back of the truck.
You could probably fetch one yourself, e.g. if you found a bargain on Craigslist; but to move it we’re talking a big 8 foot (2.4 metre) wide 2-3 axle trailer with a Reese hitch, and a big macho vehicle to pull it. It’s not the weight, it’s the wind resistance - you don’t want your trailer or tow vehicle tossed out of control or flipped over entirely!
Arrays of small tanks
Country folk have a single “go-to” container: the “intermediate bulk container” or IBC Tote. These are pallet-sized (40 x 48”, 1 × 1.2 metre) and hold usually 275 or 330 gallons (1040 or 1250 litre; note: multiples of 55-gallon / 208 litre drums). They are 4-5 feet (1.2-1.5 metre) tall.
Now, you can buy these new if you really, really, really want to... and I’m sure factories get quite a good price on them by the trainload. But the people proffering them in single quantity really stick it to ya - they’d brazenly charge $4 for a 2-liter soda-style bottle. (You can get ‘em full of soda for $2).
On the other hand, they’re usually single-use containers, especially food-grade ones, so industry winds up with a whole lot of ‘em. Now, some clever people on Craigslist will clean them out for you and sell them to you for $35 to $75, but your best bet is call around to industry and service providers, and see who has way too many of them and will let you have em for nothin’.
I recently had a need for one, and a friend immediately offered me one from his workplace’s overstock, and driving through the local sawmill I saw another 30 or 40 piled up.
In large parts of the world this is routinely done with underground concrete cisterns. Odds are that's the common way because it works effectively and for the long run, though I'm sure plastic tank suppliers would prefer you buy a plastic tank. Given that a 3000 gallon (11000 litre) plastic tank is still going to require major equipment to install, the benefit of the tank being lighter is quite limited.
What your local installed cost is and/or any use limitations (such as load limits on top of a plastic tank that may be much lower than on top of a concrete tank) would be one factor - the odds of a leak and/or length of guarantee on the tank not leaking might be another consideration.
I recall my precast concrete septic tank at around half this capacity as being remarkably affordable, delivered to the hole.
As people have mentioned, in other parts of the world, and on farms, rainwater is often collected in cisterns. And they are not always dug in pits, or underground. If you are collecting from a roof top, you can use containers along side the building, or in a separate silo like building. I've seen silo like cisterns used by residences in the Caribbean islands. This has the advantage of not having to pump the water up for use.
I just googled "rainwater cistern system" and found this commercial site which shows a variety of examples of plastic, fiberglass, and metal tanks including some with supporting or protective structures. Examples of cistern systems
In France we can get soft water cisterns. I don’t know if they’re available in the US. They look like this:
This one holds 2600 US gallons (2200 imperial gallons, 10000 litres).
Ponds are a significant modification to a property. The water will percolate into surrounding soils, evaporate from the surface, and attract pests like mosquitoes to the stagnant water.
If you were going to try to establish one, a simple plastic liner isn't all it takes. Perhaps if you have clay and silty soils you could just keep filling it with water until it created a sufficient barrier but this will take time and land planning. If your have structures anywhere near this then forget about it.
I would see if you can find a deal on plastic septic tanks. Bury one, drop a pump into it, and reuse the water. None of the risks if the pond and no loss of land use.
In the American Southwest, where the law often forbids watering of any kind due to drought, some people have large plastic cisterns capturing rainfall from the roof. I don't know how much they cost but they work well and hold lots of water. Someone mentioned them earlier and with a link. Aside from looking industrial and possibly clashing with your home decor, this is a good option. I'd say the ones I've seen are 6-8 feet (1.8–2.4 metre) in diameter and tall enough to fit beneath the gutters on the roof on either side.