If your garden offers an unlimited supply of water, you are very lucky. You'll find parts of the world where water is rationed certain times of the year so it is not good for the plants. This can be really aggravating for many people but there are others who look for other ways to water their plants. You can have a verdant garden and at the same time conserve water.
There are lots of ways to keep your garden from dying out like using compost or mulch to help hold on to moisture in the ground. One other way, would be to place the plants in categories depending on their individual water needs, which will keep the water away from the plants that don't need it. Drip irrigation is yet another option by which water lines with small holes slowly drip water at the roots of the plants. These particular steps are amazing during periods of droughts. Because droughts can be predicted, I suggest you take steps when rain comes before the drought.
A well prepared person is going to set up a few rain barrels to collect some of the rain water. The foolish gardener will think it's a lot of effort and a waste of time, so won't do anything. You won't need to do much after you set your rain barrels and you could get several gallons of water. If you are not able to find rain barrels locally, you might buy garbage cans or large plastic drums from your local hardware store. The original expenses may be high and they're going to get heavy if filled to the brim with water. A lid across the barrel is necessary to keep out leaves and also debris. Setting the barrels will be where the most water runs off of the house, so you should make sure you know where these places are in advance.
An effective way to top off your rain barrels is to make adjustments to your gutter so that water can go through several spots into a rain barrel. You can perform this by simply slanting the segments of your gutter so the water runs to the corners then into the rain barrels. It is possible to collect most of the water that falls on your roof. This might feel like a chore to do, but once you get a system, it won't be that bad.
After you have carried this out a few times, and see how well it works to water your garden, you will see it as valuable. The amount of work needed is going to be well worth it when you see how your garden will continue to thrive.