Water collection involves (1) gathering the rain and channeling it into (2) a storage container, (3) preserving and maintaining the water, and (4) filtering and distributing the clean water that is ready for drinking or gardening. This article considers the first three. Filtering and distribution will be a separate article.
A roof is a good collector. It slopes so the water runs off the edge. It can be collected from there in two main ways. You can catch it in gutters that are attached to downspouts that flow into barrels, or you can let it drip directly into barrels under the eave of the roof. The second method will miss a lot of water, but it works well. It works even better if you can keep the barrels up high, and use sand filled tubes to direct the water toward the barrels. If you try to redirect the water, make sure your roof is sturdy enough to handle the extra weight of the sand and slightly backed up water.
Keeping the barrels high also makes it easier to get the water out of them. Gravity will do the work if you open a spigot!
If you look hard, you might also find old plastic water storage containers or used galvanized animal watering troughs. Sometimes these can be found in 200 to 800 gallon capacity!
Storing water in the ground is also very good and natural, but unless you have very high clay soil, the water will quickly run out into the ground. Lining the pond can be expensive, but there are large, used plastic sheets and tarps available. Sources include old billboards, trucker’s tarps, heavy industrial wrapping materials, even mortar. (One part cement to two parts sand spread over a base of regular concrete mix will work fairly well, especially if you line the pond first with thin plastic sheeting. It is a lot of work, however it will also last longer.) Your pond size is somewhat limited by the size of the liner you can find, but three or four small ponds can be just as good as one big one!
Collecting rain that falls near the pond is usually not difficult, especially if you can locate the pond on the lowest ground. The direction of any slope on your land (or on lands next to your own) will create rivers or streams in heavy rain. The idea is to gather and collect those streams before it runs away.
If you use the pond idea, please keep a fence around it to prevent children from falling in.
Unlike collecting water from rooftops, it may seem difficult to properly channel water at ground level. Unless you live right on a rocky slope, or have a large depression on your property, water will not run to find your storage area! You will have to help it, and again tarps or large sheets of inexpensive plastic can be put to use. Building a simple frame, or groups of frames, you can set up angled sheets of plastic on the ground that flow directly into the pond. These frames can be stacked out of the way when the rain stops or the pond is full, or they can be used to cover the pond.
Gardens can also be arranged to include low channels in them, aimed toward the pond. A raised garden or border will redirect rain. Any low blockage changes the course of the runoff. It may take experimenting to discover the best course, but the result is always good.
Helping to Set the Water Table
Another important consideration is your own water table. The water table is how deep or shallow the water is under your land. In most areas of the world, this water table rises and falls a lot during different seasons. Ideally, water storage into the ground can be modified to take advantage of this rise and fall. Most of us have times when only deep roots from big trees can reach down to the water table, and other times when crops are endangered because pooling water sits above the land! These extremes can be modified (slightly) by adjusting the flow as well as storing the water in tanks, urns ,or ponds.
For most of us, this is important and possible mostly for our gardens. Attempting to store huge amounts of deluge rain is impractical, but we can do a few things to prevent drowning plants or letting them die from drying out too much. The first step in adjusting the water table is to change the elevation of the garden. If the garden is higher than the surrounding ground, it will never become completely flooded. This concept is called a “raised garden.” If the ground is a foot higher than the surrounding land, standing water will still be a foot lower than the top of the garden! It will settle to the common height.