Water demand garden/year --> Is a cistern worthwhile?

We have a hillside location and are terracing. Therefore, it was not an additional excavation. We have a spring that we can additionally pump. Rainfall from all roofs (also additionally greened) and terraces is directed into the cistern. We wanted to have enough buffer and the property is also larger (2500m2). Originally, we wanted to go for a 92m3 cistern. But that would have hindered us with the landscaping.

Rainwater for the toilet was only a topic at first. It doesn't "add up" because of additional pipework, filters, possible deposits... better to use it for the garden. You still need a waterworks/pump. IBC containers are available from time to time on Eb.. . If you have space, you can house them in a shed/enclosure. But the best is a cistern at the lowest point so that you can drain all surfaces, collect the largest amount of water, and save the fees for rainwater runoff.

Cisterns are actually always a good thing. In terms of global warming, they are certainly always useful. Unfortunately, we don’t have one, but we will install one when we redo the driveway (we have an old building, so it was all like that already). Currently, we have about 500m2 of garden and only 1700L collection volume in rain barrels; soon we will increase to 2000L, and even that won’t be enough. It has been too dry here for years. I don’t water the lawn at all; it has to survive or just die. But for example, in April we only had 4 liters of rain here. Almost no plant can survive on that. We also have a sub-meter so that we at least don’t have to pay the high (!) sewage charges on the watering water. I water very sparingly and targeted, but when the barrels are empty, and they often are, then it just has to be. Since last spring, I have used 23,000 liters of water in the garden, some of it also for the children's paddling pool. From the barrels, roughly estimated, maybe another 5-10,000 liters – but I really can’t say that exactly.
It’s definitely better for the environment, and I think considering global warming it will be worth it because heavy rain events at least fill the cistern and you have something to water with when there is no rain for 4 weeks at over 30°. You simply can’t guarantee that much volume with rain barrels.

Just so I get an idea again. I buy a cistern with, for example, 6000 liters (should be roughly enough for our property) and, for example, a submersible pump, and then it is possible to connect this to the outdoor water tap of the new house without much effort? My parents have done it like this, but in combination with the house water system (toilet flushing etc., which I do not want). I would like to "draw" the rainwater from the outdoor water tap, to which I can then also connect a garden hose... What I do not want is for the lid of the cistern to be visible in the middle of my presumably small lawn. Therefore, I would rather place the cistern somewhere where it is not so noticeable. Thanks to you

On Pinterest, there are ideas to hide the IBC containers. There are above-ground water tanks that are somewhat nicer and hold more than 300 liters.

The outdoor water taps must be equipped with a backflow preventer.
Thus, you do not need an additional backflow preventer for refilling the cistern.
Bury the refill line at the same time. This way, you don’t have to block a faucet, pull a garden hose to the cistern, open the lid...
With a submersible pump, preferably a well pump (sufficient pressure), you can then supply your irrigation or garden hose.
Lids are also available in green or with a recess so they can be overgrown.
The position should be the lowest point so that you can drain all roofs, paths, driveway, etc. into it.
This way, you save fees for stormwater.

Before I would build system separators, I would consider a separate setup and simply connect the submersible pump during the growing season to a conveniently located stainless steel extraction point / water column. You only need power to the cistern and an empty conduit to the extraction point.

A proper submersible pump with pressure and flow monitors and the water flows as usual from the tap when you open it. Maintenance is then limited to occasional cleaning of the inlet filters and emptying the hose before the frost period.