Unused wells are a threat to groundwater when they are not capped or sealed and allow surface water and contaminates to enter the well.
However simply being an unused well does not mean it will be a threat to other groundwater and other wells but if you have an unused well you should make sure it has a sanitary seal on it.
Even if the well is being used you should also make sure it has a sanitary well cap to prevent surface water and surface contaminants to enter the well.
Most groundwater is withdrawn from wells for use in agriculture and for growing crops.
In arid countries 90 percent of groundwater is used for irrigation.
Other uses of groundwater are for private home use and for drinking, showering, bathing, laundry, swimming pools etc.
Some cities also use groundwater which is then pumped into water towers and treated and sold to people who are on city water.
Well water is much healthier than city water as well water is free of chlorine, fluoride and other added chemicals that can make city water bad to drink.
While they say city water with chlorine and chemicals is safe to drink it really is not and drinking well water is healthier as it also contains minerals and nutrients that are naturally found in the earth that the water picks up as it filters through the ground.
The benefits of groundwater wells are the groundwater wells are a great and sustainable source of water which naturally replenishes.
The groundwater wells also contain water that is purer than surface water and if getting water from a private water well then you will have the freshest water without all the chemicals and chlorine added to city water.
Some city water uses groundwater wells and then after pumping the water into a water tower they treat the water with chlorine and other water treatment chemicals which can make the water taste bad and can be bad for your health.
Some city water also uses surface water which is then treated with chlorine and chemicals which also makes the water taste bad and can be bad for your health.
With a private water well you have no chemicals in your water and it's fresh and healthier for you as it is naturally filtered by the ground.
Also another benefit of a private water well for your home is you have no monthly water bills to pay although you should save money in the event you need to replace your well water pump, well pressure tank, wiring, switch etc.
Other than that you only have the cost of electricity to pump your water which is not all that costly and is certainly cheaper than city water.
Groundwater recharges wells as well water is groundwater that seeps down and through the earth below.
Rain that falls on the ground and ice and snow that melts into the ground eventually becomes groundwater as it seeps through the soil and reaches the aquifer which are rocks below ground.
The water that recharges wells can be miles away from the well and flow into the well even if the rain is not local to the well.
Underground wells refill with water by water moving through the soil and rocks underground.
Some wells are dug so that water flows through sand to reach the well and other wells are dug deeper where water flows through rocks and cracks and pores and spaces between rocks that allow water movement.
There's not really a river underground but the ground holds water that seeps down from the top of the ground from rain, snow ice etc.
Then the dirt, sand, rocks etc all filter out that water.
As you use the well and pump water out more water flows through those rocks and soil which can be several feet or even miles away from the well.
The water in the well does not have to actually be local for it to eventually reach your well.
Water can flow underground for miles using gravity that pulls it down towards your well as the water begins to move and you make room for the water to move by pumping the well.
When it rains and more water seeps into the ground the static level of your well can also raise due to the water table rising.
Some wells do dry up in drought although it's mostly dug wells or shallow wells that are less than 100 feet deep that are more prone to dry up during droughts.
If your well is drilled at least 100 feet or deeper and you have a good high water table then it's not very likely for the well to dry up even during drought.
Some wells have to be drilled 200 feet or more to reach water and some only need drilled 100 feet or less to reach water.
The shallower the well and the lower the water table the higher risk you have at your well running dry during a drought or from simply overusing the well.
My well is drilled 150 feet deep and my static water level is 10 feet and recovers really good.
Drilled wells are better than a dug well as drilled wells can reach deeper sources of groundwater which means that the water is less likely to be contaminated and it's less likely that the well would dry up in a drought.
Dug wells are okay but they are prone to drying up from drought if you don't get enough rain or precipitation and they are at higher risk of becoming contaminated.
When you drill a well you can drill to 100 feet or more and reach cleaner water and in most cases the deeper you drill the less chance you have of it drying out as there is usually more water the deeper you go.
My well is 150 feet deep and we get a lot of rain here and so it's very unlikely that the drilled well would go dry.
Even here I can dig down 2 feet and water fills the hole although it's dirty water.
So since our water table is at 2 feet down it means that my drilled well is unlikely to go dry anytime soon and we get plenty of rain.
I have had a dug well in other dryer locations and they went dry when he didn't get enough rain.
But my drilled well has never gone dry and unlikely would and I could probably get millions of gallons out of it a day if I had a pump that big that could draw that amount of water and it still would likely not go dry.
Wells that are for households and for drinking water should ideally be at least 100 feet or more and some locations you have to drill to 200 to 300 feet or even deeper to reach any water depending on how far down the water table is in your location.
Places that get a lot of rain and precipitation have a higher water table and you don't have to dig as deep but in dryer locations without enough rain or precipitation you usually have to drill down deeper to reach any water.