Well water will run out if the groundwater level drops below the water intake depth. This can be caused by natural or man-made variations in groundwater height including reduced precipitation, slow groundwater recharge, well infill, high water usage, well drawdown or hydrofracking.
Like any resource, well water can run out if not monitored and managed correctly. It’s unlikely a well will permanently run out of water. However, there are 9 things to consider that can cause your well water to reduce or go dry. This is a big post and is one of my favorite topics, so let’s get started.
In this post, I’ll go into a lot more detail on the main reasons wells can run dry. I’ve also added in lots of diagrams to help make it easier to understand what’s actually going on underground and how it affects your well.
My background is in groundwater. I’ve worked on groundwater research projects and developed groundwater monitoring programs for mining companies. Yes, that’s me in the picture below – looking like a complete nerd while dipping a 300 foot deep well.
I’ll try not to get too bogged down with too much of the science and make it applicable to your needs – for both commercial and private wells (domestic wells).
It is super important to know what is going on with your well water, what causes it to dry up, and what you can do about it. So, let’s get into it.
Here are the 9 reasons well water can run out:
1. Reduced precipitation
The water you get from a well has to come from somewhere right?
A reduction in the amount of precipitation (usually in your surrounding area) means there is less water available to make it to the groundwater system. This will in turn reduce the amount of water reaching your well.
- Rain (obviously)
- Small ice pellets
Fog and mist that condenses on plants or on the ground can also contribute to groundwater. Although they are technically not forms of precipitation, they still help keep the ground moist which in turn helps reduce evaporation.
What you often find is there can be a lag between a period of reduced precipitation and your well water level dropping or even drying up completely. Some aquifers can be in tune with the local precipitation patterns, while others barely even respond to a dry period.
2. Reduced groundwater recharge
Ok, so recharge is basically the amount of water that makes its way from the earths surface into the groundwater system. I know recharge sounds like the same thing as precipitation, but there are many things that can influence what happens to all that water once it hits the ground before “recharging” the groundwater (including aquifers).
Some of these include:
High evaporation can seriously reduce the amount of water reaching the groundwater system. Essentially, the more time water spends close to the surface the longer it can evaporate, which reduces groundwater recharge.
This is pretty obvious, but high temperatures means higher evaporation and reduced groundwater recharge. If you live in an area that is dry and hot, it’s going to take a whole lot of rain to make its way down through the soil and into an aquifer.
This is a big one! High wind speed works by increasing evaporation and reducing the amount of water available for infiltration. High winds quickly wicks away evaporated water and allows for continual evaporation. It’s just like how your clothes dry faster on a windy day compared to when it’s still.
Vegetation works in many different ways that aids in groundwater recharge. Here’s just a few:
- Reduces evaporation – more trees, ground cover and organic matter on the surface reduces evaporation.
- Reduces sunlight and heating of the earth – obviously it’s shadier under a tree. But did you know that plants absorb specific wavelengths of light that are hotter than those that it reflects. This is why you are cooler standing under a tree than just under an umbrella. When the ground is cooler, less water evaporates and more migrates downwards recharging the groundwater.
- Increases infiltration – Dead plant roots, especially deep tap-rooted trees, create passageways for water to quickly migrate down through the soil and recharge the groundwater.
- Trees are great strippers! As cloud, fog or mist moves through a forested area they can “cloud strip” a TON of water. Some is used by the plants, but a lot permeates downward into the soil recharging the groundwater.
I’ll stop there, but I think you get the point. Plants enhance groundwater recharge which has a flow on effect to how much water is in your well.
This relates to the amount of moisture that is already in the air and how it affects how quickly evaporation takes place. If the air surrounding surface water or wet soil is very dry (does not contain moisture itself) then groundwater recharge will be reduced. In comparison, if the air is already saturated with water vapor then you will get greater downward movement of water and groundwater recharge.
Water table depth
A shallow water table (i.e. within about 10 feet of the surface) means the groundwater can continually evaporate from the soil profile and therefore reduces the amount that can move down into the groundwater system. Comparatively, a deep water table may take longer to recharge but will not be affected by evaporation.
In general, sandy soils allow faster downward movement of water and recharge. Rocky or heavy clay soils hold water near the surface and for longer, increasing evaporation and reducing recharge.
3. Well infill
Wells often infill with loose sediment over time. This can lead to reduced flow or it can stop your well producing water entirely.
When a well is installed, a casing of PVC is usually (not always) used down the length of the hole. At certain sections along the well casing there are screened sections. Depending on how deep the well is or how many aquifers are intercepted, there could be just one screened section or there may be multiple.
Screened well sections basically allow water to passively flow from the surrounding aquifer into the well. Without these screened sections, little to no water would enter your well.
Over time, loose material can move through these screens reducing the amount of water available in your well. This could take years or even decades to occur. Or, if you’re unlucky it can happen almost instantaneously and all of a sudden you can’t get any more water from your well.
For this reason:
I always suggest people regularly check their WELL depth.
NOT JUST WATER DEPTH.
This way you can tell if your well is gradually infilling or if there are any obvious blockages that might be stopping/reducing the flow of water into your well.
4. High water usage
So this is going to sound kind of obvious.
Don’t use too much water or your well may run out.
Many people ask questions such as:
- How long can you run your hose on a well?
- How many years does a water well last?
The truth is… It depends.
It can depend on:
- What rock/soil type you have
- If the water comes from an aquifer
- What type of aquifer(s) you have – perched, unconfined, confined, leaky.
- How deep your well is
- How many wells you or your neighbors have
- AND… Of course…. HOW MUCH WATER YOU ARE USING
There are many factors that can influence how long a well lasts. However, YOU CAN CONTROL how much water you use and it’s definitely something you should monitor, especially if you’ve had problems with your well water running out in the past.
When a well is installed, usually a “pump test” is completed. If you didn’t get one you can get a professional out to do a pump test for you.
A pump test is actually a series of tests completed over time. The well water will be pumped out at varying rates and compared against the water level in the well. From this you can work out how “productive” your well is and how much water you can use before it becomes “unproductive”.
The trouble is, a pump test only provides a snap shot of the well’s production at the time of the test. Things can change. It can often be a good idea to get a pump test done at least twice. Once in spring and once in the fall (or once in summer and once in winter). This way you can adjust your water usage according to the season.
5. Slow aquifer recharge
The water from your well is not endless and the rate of recharge can vary greatly between aquifers and through time.
In truth, no one on this planet really knows what is going on underground as it relates to aquifer recharge.
Determining if an aquifer recharges slowly or quickly generally comes down to how fast or slow you can pump water without the well water level dropping. However, this gives you no information on how much water is in an aquifer or how long it took to get there.
Some aquifers can take 10’s of thousands of years to fill, but can become depleted in just a few. i.e. You may not have had any problems with your well for years, but through pumping and the passage of time your well could begin to run dry.
The water in your well can return even with a slowly recharging aquifer, but sometimes it can take longer (or a lot longer) than what we would like it to.
There is not much you can do to “fix” an aquifer that recharges slowly.
However, a few options include:
- Digging a new well – hopefully into a different and faster recharging aquifer.
- Digging your existing well deeper – again hoping to reach a different aquifer that is hopefully faster recharging.
- Hydrofracking – see bottom of this post for more details.
6. Artesian well water drying up
Many people ask: Do artesian wells run dry?
I’ll tell you a cute story about my mom.
My dear old mom uses well water, mainly for her garden. She’s 73 year old and lives by a river that’s close to the ocean. Her well is quite shallow and is on sandy alluvium (sand derived from the river). She was telling me all about how she recently got someone around to fix the pump.
She said “once it’s fixed the water will never run out as it’s artesian water”.
Cute… but not exactly correct.
I had to politely explain she was not in an area that had artesian water, and that her well water comes from groundwater that moves through an unconfined aquifer (the sandy alluvium). I also had to explain that even if it was artesian water it could still run out.
She was a little unimpressed.
However, it’s a common mistake people often make.
Artesian water is essentially water that comes from a confined aquifer, meaning it has a relatively impermeable layer above it (and usually below it) stopping the water from easily getting to the surface. Once you drill down through this top confining layer, you can access the artesian water.
Artesian can mean the water is under pressure. In some areas, water can literally spout out of the top. Otherwise, you often don’t need to pump the water from great depths, making artesion wells a bit cheaper to run (less utility costs).
BUT… Artesian wells can still run out of water.
The “pressure” in an artesian well comes from a pressure gradient in the groundwater (called the piezometric level or hydraulic head).
How this works is the same as filling a piece of garden hose with water. Imagine holding a short piece of hose with the two ends facing up (loop at the bottom). You fill it with water – What happens?
Nothing! The water just sits in the tube right.
But, what if you put your thumbs over both openings, lifted one end higher and then took both thumbs off – What happens to the water now?
The water comes pouring out the lower end.
Congratulations you just replicated flowing artesian water coming out of well.
In the real world, let’s say your well was located near the base of a mountain:
Precipitation recharge occurs on the mountains, which migrates between two confining layers deep underground. Depending on where your well is located and the height of the piezometric water level will determine if your artesian well flows or not.
All it takes is a reduction in the piezometric water level (hydraulic head) for your well to stop flowing and can even run dry. This can be caused by reduced recharge or just from high water use.
In the image above, the house on the right shows a non-flowing artesian well from a reduced piezometric water level.
7. Lowered water table
So far I’ve only discussed natural reasons for a change in groundwater height, excluding high water usage.
In truth, the water table can very easily be lowered when there are multiple wells in a given area or if one person has a high water usage – typically on a commercial property such as a farmer using the water for irrigation.
Ok, lets pretend you have a well that is producing lots of water. Everything is going swimmingly – pun intended.
Then comes along a new neighbor who puts in their own well, and then another neighbor increases their use… etc.
Soon enough, you may notice your well is not producing anywhere near as much water as it used to. What’s most likely happening is the water table, also called the static water level, is being lowered from too many wells and high usage.
The more wells pumping groundwater means greater demand on the resource, which can cause your well to dry.
8. Drawdown and the Cone of Depression
This may sound like a title to a REALLY BAD movie. But… it’s very real.
A cone of depression refers to the shape of groundwater immediately surrounding a well. As water is being pumped upwards, the groundwater around the well becomes depleted and takes on a cone-shape that radiates outwards from the intake.
Drawdown is the difference between the original water table depth (without well pumping) and the cone of depression groundwater depth (with well pumping). The drawdown will be greater closest to the well and least farthest from the well.
Both the cone of depression and drawdown are not too much of an issue if you only have ONE well and your neighbors well isn’t too close to yours.
Basically if your pump rate is too high, your well can dry up. But if you back the usage off and allow enough time for the groundwater to migrate back into the emptied pore spaces, you shouldn’t have a problem.
However, they can become a problem if wells are located relatively close to each other.
Well, it depends on many things such as:
- bedrock type
- aquifer connectivity
- pore sizes etc.
In my own experience, I’ve recorded notable increases in drawdown depth and the cone of depression over a few miles from a well undergoing a pump test. But there’s no reason to say the effects from a nearby well couldn’t be further reaching than this. Again, it really depends on your area.
Multiple wells: Issues with drawdown and the cone of depression
If a well is relatively close to another well (it could be yours or your neighbors), then there is definite cause for concern as one of them could start to run dry.
Changed groundwater flow direction
A large cone of depression can influence how groundwater moves underground and will often redirect water towards it. This means that a nearby well can literally SUCK water away from yours causing the well water level to drop or dry up completely.
Water pumping is maintained for long periods of time
Most domestic wells are used for fairly short periods – either to fill a reserve tank or when there is higher demand such as in the mornings or evenings when you’re home.
In comparison, commercial wells (e.g. for farming or mining) are typically run for much longer periods of time. The longer a well is pumped, the wider its influence on the groundwater system. Additionally, it can take longer (sometimes weeks to months) for the area surrounding these heavily-used wells to recover meaning your well could remain low or dry for longer.
A nearby well is deeper
A deep well can have a much larger cone of depression and deeper drawdown than a shallow well. Hmm, not good for any nearby wells. This can cause your well to dry up, prompting you to consider drilling your own well deeper or possibly hydrofracking.
Similar to drilling a deeper well, hydrofracking is a technique often used to increase a well’s water production rate. Hydrofracking involves injecting very high-pressure water into the rock material surrounding your well. The process can help create new pathways for water to reach a well and increase its production.
However, if your neighbor does it and it dramatically increases how much water they can extract, it may not be that great for you. Over time you may notice a decrease in your well water level or it starts to run dry from their increased use.
So, I hope you got some helpful information from this post and you know what causes wells to go dry. Don’t forget, you should be monitoring your well water height, total well depth and local rainfall patterns on a regular basis.
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