Where does my well water flow from?

Like every other house in town we have a well.

Today it has rained very hard, on and off, and I wondered if this downpur would replenish my well as well as everyone else’s in the area.

But I imagine that to determine this, one must know where the water originates. Might the source(s) come from many miles away, or close by?

Is there an easy way to find this out?

Well, (ahem), it depends on lots of factors- how deep the screen for your well is, and the geology and hyrdogeology of your area being the most obvious ones. Clays can have very low permeability, meaning that it can take years to move feet, while well sorted gravelly sands are pretty much free draining, meaning that they lose a hold on almost all the water pretty much instantly. Check with your county health department- they should have a record of your well installation.

ETA: yes, your water could be flowing for miles, depending.


Well depth varies greatly by region. Here in the midwest wells for homes are often well over 100 feet deep. In Florida wells are commonly less than 20 feet deep. Basic reason why homes don’t have basements in Florida.

Mine (Connecticut) is 220 feet deep.

As mentioned, there are so many geological variables that’ll affect the origin and recharge rate in your area. Rock type, permeability, fracture patterns, diagenesis, slope and dip, carsting, etc. If you want to share or PM your area, we might be able to figure it out (I’m petroleum, others here may specialize in hydrology).

For a quick answer, you probably could contact either one of the well drilling companies in your area or, if one exists, the local university’s geology department, specificall the staff hydrologist.

Two years ago on This Old House, didn’t they go down almost 750 feet in small-town Massachusetts and install more than one pump to get the water to the surface? Or have I gone insane? Is 750 a ridiculous figure? Anyway, if you have to go that deep, I imagine the water could be coming from a long way off.

I’m in Brookfield CT, if that helps.

Seems a little deep to me, but not ludicrous. Here in Michigan, we sit on top of glacial till- variably clay and sand, with very little bedrock close to the surface, so the water table tends to be no more than 40 feet deep. But I’ve heard of drinking water wells about 500 feet.

I see the Still River Middle Aquifer, Gallows Hill Aquifer, and the Pond Brook Aquifer in your general area. Click on any of the 3 underlined aquifers in the link to pull up it’s map and description. Do you recognize your locale on any of these maps and do you know approximately how deep your well is or, better yet, from what depth it produces?

Friends in NH and MA have had to drill over 500 to get enough flow, it’s not that uncommon around here. But it’s the luck of the draw. You can be half a mile away and only need to go 200 feet for the same flow.

As long as we’re talking about water in parts of the country other than mine, anyone ever hear of “closed basin aquifers” that can’t be replenished? Allegedly they’re pretty much underground cisterns sealed by earthquakes or what have you. I was researching western water law for a reporter’s reference booklet I wrote ages ago and a grizzled old water engineer said he’d actually found one – talked about it like it was Solomon’s Lost Mines or something. Supposedly the water is incredibly pure and so on. Anybody?

Just for reference – I live a half-mile from the South Platte River, my well is only 85 feet deep, but I’m in a flood plain. And because of Colorado water law, I have to be in a well user’s association for augmentation – it’s complicated but fun.

The deepest wells I’ve had drilled in MA are 700-800 feet. The static levels in MA are very shallow. It is very rare to not reach water within 30 feet of the surface. Depths beyond that are to obtain more flow. In general you want 6 gallons a minute to supply a single family home. The average well in this area is 150 feet. I have a half dozen wells on the same street at 600 feet that only provide 2-3 gallons a minute and are loaded with iron to boot. The reserve helps them meet their needs but overall that area is a crapshoot.

If rain water is directly effecting a well it is a potential problem. Surface water is often contaminated with bacteria. A well should be sealed against rain water running into it. The time it takes for rain water to reach the well water should be significant.

Closed basins are how we wind up with the Great Salt Lake and the Dead Sea- rainfall washes minerals into the lake, and evaporation concentrates the salt level. Usually, lakes have some sort of outflow, either above or below ground, (and are replenished by inflow likewise) so that the salt levels are quite low. Closed basin aquifers might be one of those things that I heard about in class, but don’t specifically recall the term, but could pull something reasonable out of my …ear. I would suspect that they are confined in such a way that no water can flow out, but some can trickle in. I’m not sure why they’d be any more or less pure than any other aquifer.

why hasn’t this been moved to GQ yet? seems to be a factual question, no?

There’s so much information in this thread that I’ll devote a good part of tomorrow to cover it. Thanks very, very much for all your contributions.


I have a friend with a well who apprently lives in a geologically unusual situation. A geologist from a nearby college asked if he could do a study of my friend’s well water. The conclusion: the water has been underground for several hundred years, during which time has flowed about 60 miles.

This sounded a bit far-fetched to both me and my friend, but the geologist seemed to know his stuff. I can say that the water seems very pure.

My circa 1760 Massachusetts colonial still has one open well that I keep carefully covered. It is about 3 feet wide and I can only guess at less than 50 feet deep. It always has water in it starting at about 10 feet down although it probably isn’t enough to supply our entire house these days. Then again, it taps into this unusual spring that floods the streets every spring pouring out our front stone walls every spring and early summer so you never know.

It’s not really that far-fetched. If groundwater is flowing through, say granite or similar rock (through fractures), it can take a very long time to go anywhere.

The drinking water aquifer in Las Vegas is replenished in the Spring Mountains to the west of town. It takes the water 60 some years to flow 30 some miles. However, in the shallow groundwater “aquifer” it can take the water years to flow a very short distance in various places around town (depending on the geology).

Hydraulic conductivity in clays can be as slow as feet per thousands of years.

Shagnasty, it sounds as if your well (the groundwater actually) goes artesian with spring snow melt/summer rains, that or you have a breached casing or seal.

Actually, your well water probably doesn’t flow from anywhere.
Flow implies a continuous stream, like a creek or river. That’s not really how it works underground. In most wells, it’s more accurate to describe the water as seeping through the sand, gravel, or permeable rock that your well is in. Generally, wells have a maximum flow rate, which describes how much water you can pump from the well in how much time – basically, how fast water will seep in to be sucked up by your pump.

And the downpour of rain will replenish all the wells in the vicinity – but only after soaking through the topsoil, and all the other layers of ground down to the depth of your well. Each of those layers help filter the water, so your well water is generally pretty pure. Nut it may be weeks later that todays’ rainwater actually shows up in your well.

Also, this only applies to rainwater that is allowed to soak into the ground. Roads, blacktopped driveways, sidewalks, paved patios, roofs & gutters, etc. all divert the rain and generally send it into a sewer system that eventually leads to a river somewhere, where the water is sent downstream rather than replenishing your well.

About 11 years ago, we moved into a new house in rural Waikato (NZ). It was our first time on Rainwater (5000 gallon tank), and it was a dry summer. We were running out of water. The neighbours behind us had a bore, and offered to let us refill the tank, which we accepted.


You see, the Waikato is rich peaty river plain, really porous. Rainwater runs straight down through the soil and the fecal matter of thousands of cows, then hits the volcanic ash beds and starts flowing, fast. Also, there was no local sewage system, so every man and his dog has a septic tank, which gets flushed through by washing machines and dishwashers and goodness knows what. The local bores were all really shallow, and fed by this surface water, not deep aquifers.

Point is, the water was contaminated - didn’t make WHO standards (I had it tested by a microbiologist at work, and the explanation was provided by an environmental scientist). We were all sick for days, and had to add purification stuff and boil our drinking water.

You don’t want a quick replenish of your aquifer - lots of really slow filtration is the best.