My first advice is to have a qualified plumber evaluate the problem. There are a couple of possible causes that come to mind. First, the source of the water supply. Well? City? In other words, is there adaquate water available from the supply. Then, what size is the supply line from the meter? Could be too small. Since it appears that the short supply is throughout the entire house/yard, it would indicate the problem is before the water reaches the house. Perhaps a bad or partly closed valve at the meter. We could speculate on all of these things, but a plumber can find the problem quickly and recommend a solution.