Well yield
Well yield is the quantity of water a well or well field can deliver, by flowing or by pumping, usually stated as a volume over time such as gallons per minute. In Virginia, the certified water well systems provider certifies a new well's yield on a VDH form when the well is completed.
Observed, estimated and public supply: three kinds of gallons per minute
Three gallons-per-minute figures circulate for this part of Southwest Virginia, and they are easy to read as if they measured the same thing. They do not.
| Figure | What it measures | Who published it |
|---|---|---|
| About 1 to 15 gallons per minute on average; over 40 not uncommon; can exceed 200 | Observed yields of wells in crystalline rock across a Blue Ridge study area in the New River basin | U.S. Geological Survey, Water-Resources Investigations Report 00-4270 (2001) |
| 20 to 100 gallons per minute | An estimated potential yield range for Carroll County, stated in a planning document | Carroll County, 2024 Comprehensive Plan |
| 12 to 145 gallons per minute, averaging 28.6 | The 13 wells the Carroll County Public Service Authority operates for its public water systems | Carroll County, 2024 Comprehensive Plan |
Read the middle column before the first one. Only the first row reports what wells actually yielded, and it is an average for crystalline rock in one Blue Ridge study area. The second is a planning estimate of what the ground could give. The third counts wells a public authority runs to supply water systems, which is a different job from supplying one house.
Estimated potential: the two words that belong with 20 to 100
The range of estimated potential well yield is 20 to 100 gallons per minute.
Carroll County, 2024 Comprehensive Plan
Estimated and potential carry that sentence. It gives the plan's estimate of what the ground could give, not a measured average of wells in use. Carried onto a listing sheet or a web page without those two words, the range reads like a yield a buyer can count on, and the USGS observed average of about 1 to 15 gallons per minute in the crystalline rocks of its Blue Ridge study area sits below its low end.
The same plan explains why water can come back slowly. It says recharge to full storage is slow, except in aquifers near streams and below the elevation of their beds, because of the steep land surface and the low absorption rate of most soils.
Where a county water main reaches a parcel, yield stops being the question. Whether a main actually reaches a given parcel in one Carroll County community is what the Woodlawn VA real estate guide works through.
Hilltop wells typically yield less than hillside and valley wells
The USGS report also explains part of the spread inside its range. It finds the chance of intercepting fractures greatest in valley settings and upland draws and least on ridges and hilltops.
Wells drilled on hilltops, therefore, typically have lower yields than wells drilled on hillsides or in valleys.
U.S. Geological Survey, Water-Resources Investigations Report 00-4270 (2001)
That is a statement about odds across a study area, not a reading for one homesite. A drilled well is the kind VDH describes drawing from those bedrock fractures, and how far down a well goes is a separate matter, covered in how deep wells are in Southwest Virginia.
A single well's yield is certified when the well is completed
For a single well, the number that counts is its own. Virginia's well statute directs that the regulations include minimum storage capacity and yield requirements for residential drinking wells, alongside the provider's certification of storage capacity and yield at completion. This entry prints no numeric minimum; what the regulations require of a given well is a question for the local health department.
Within 30 days after a private well is built, altered, abandoned or deepened, a uniform water well completion report goes to the local health department. VDH keeps well records at its local offices. How a well is permitted, built and recorded from start to finish is set out in wells explained.
Do you know the yield recorded for the well on your property?
Send the address and anything you have on the well, and Lowell will set its recorded yield, if one exists, apart from the county-wide figures a buyer may have read. No cost, no obligation.
Got it. Thank you.
We'll be in touch shortly with an honest read.
Questions about this term
Where do I find the recorded yield of the well on my property?
Start with the local health department. For a well built under the current rules, the water well systems provider certifies its storage capacity and yield on a VDH form at completion, and a uniform water well completion report goes to the health department within 30 days. VDH's local offices keep well records, but private well records were not required before 1990, so an older well may have none on file.
Does Carroll County's 20 to 100 gallons per minute describe a typical household well?
No. Carroll County's 2024 comprehensive plan calls 20 to 100 gallons per minute the range of estimated potential well yield, a planning estimate rather than a measured average. A U.S. Geological Survey report on crystalline rock in a Blue Ridge study area of the New River basin put average yields at about 1 to 15 gallons per minute. A single well's yield is on its own record, where one exists.
Where this page's facts come from
Every rule, office and figure above traces to one of these. Rules change; check the office before you act on one.
- 12VAC5-630-10, definitions, including yield Virginia Administrative Code
- Va. Code 32.1-176.4, minimum storage capacity and yield requirements and the provider's certification Code of Virginia
- 12VAC5-630-310, the uniform water well completion report Virginia Administrative Code
- Water-Resources Investigations Report 00-4270, Blue Ridge Physiographic Province of the New River basin (Kozar, Sheets and Hughes, 2001) U.S. Geological Survey
- 2024 Comprehensive Plan: estimated potential well yield, recharge and Public Service Authority wells (PDF) Carroll County, Virginia
- Real estate transfer FAQ: private well records and VENIS Virginia Department of Health
- Private well program: drilled and bored wells Virginia Department of Health