We live in a desert depending on ground water for survival. City water wells and private wells alike depend on what has collected in aquifers over the ages. Are we using it faster than nature is replenishing it? I'd put money on that especially with our current drought conditions and the population growth of central Arizona. At this time nobody really knows. However, there is a finite amount of water on earth. It does not disappear when used. It goes into the septic systems, the sewer systems, runs down your driveway when washing your car and back to the earth in many ways. It evaporates and returns as rain. This is a complex issue that remains under study.
We can predict what water usage will be based on statistics. The national average for water usage is 75 gallons per person per day. We know this to be fact.
Wells are rated by what they produce or make in terms of gallons per minute. The true production of a well is not the capacity of the pump. It is the amount of water the earth is releasing into the well after the water stored at the well is pumped out. A true and accurate reading would require a well be pumped until the production dropped off and that the pumping be continued for an extended period of time. That time could be days. The amount of water that is constantly pumping after this pump down period would be considered accurate enough for determining the gallons per minute a well is making. Most wells are not tested that accurately. The pump down period is greatly reduced to either a few hours or even minutes because of the expense and time involved.
Let's explore what you need for a good supply for a home well. One gallon per minute is equal to 60 gallons per hour or 1440 gallons per day or 43,200 gallons per month. However, not many people want to wait a minute for that gallon to come from a faucet. We need storage to make water more available for immediate use; that storage comes 2 ways. First is the amount of water in the well shaft itself. There are about 1.5 gallons per foot of water in the hole. If your well is 300 feet deep and the "static" is at 200 feet you have 100 feet or 150 gallons sitting in the hole as storage. It will be pumped out at the full capacity of your pump regardless of how much your well is actually making until it is drawn down. A second storage is a holding tank. Some wells that do not make large amounts of water or that do not have a good static level may need a storage tank. A tank can overcome a week producing well.
A family of four will use 300 gallons per day based on the national average. With good storage, a well producing just one quart per minute is sufficient and will make 360 gallons per day. The pump will run longer but steadily make enough water for your usage requirements. A five gallon per minute well will make enough water for almost 100 people or 216,000 gallons per month.
The well is only one part of your water system. Storage, a proper sized pump, a pressure tank, and the faucets and fixtures are all part of it. You too are part of it because you create and control the demand. A water system should be designed considering all the parts. Use it wisely here in the desert. Save some water for tomorrow and others.
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