Inexpensive Waterer

[swimgymmom]

Hopefully someone can help this newbie out with a question. I was reading a new gardending book and it had some creative and inexpensive ideas in there for pest control, composting, watering, etc.

In the book it tells you how to make a waterer for your tomato, pepper, etc. plants with an empty plastic bottle. It was kind of interesting. This is how it worked. You took an empty bottle of some type, 2-litre, milk jug, etc., and cut the bottom off. You took the cap and drilled several holes in it, then put the cap back on and burried 1/3 of the bottle cap-side down next to or between your plants. You fill the bottle with water and it will leach in to ground and water your plants without having to drag the hose and leave it run all day.

Here is my question. I know a garden is supposed to get approximately 1" of rain a week. Would there be any way of knowing how much an inch of rain is with this type of system?

Any comments would be welcome. Thanks.
Kim