What’s a “Miner’s Inch”?

During the Gold Rush period, the number of miners who got rich from their efforts were few and far between. More often than not, the people who provided goods and services to the miners were the ones that struck it rich. Water delivery became one of the most vital and lucrative services to be offered.

Water companies, also known as “ditch companies”, popped up everywhere mining occurred. Water ditches once crisscrossed the Georgetown Divide. A Gold Rush era ditch still supplies the Divide with it’s water. Water was absolutely essential to early gold mining operations. Work often stopped when the delivery of water was interrupted.

Miners pose for a photo during the California Gold Rush at Auburn Ravine in 1852. The photo shows both white and Chinese miners
Miners pose for a photo at Auburn Ravine in 1852.

The standard unit of water measurement at the time and still used by the Georgetown Public Utility District to this day is the “miner’s inch”. The miner’s inch was primarily intended for measuring small quantities of flow and it eventually gave way to what was called the “second foot” or cubic foot per second (cfs) unit that is commonly used today in the United States to measure water flow.

A miner’s inch does not represent a fixed and definite quantity of water, being measured generally by an arbitrary standard of the various ditch companies.

For this reason, a miner’s inch is 0.020 cfs (1/50th of a cfs) in Idaho, Kansas, Nebraska, South and North Dakota, New Mexico, Utah, Washington, and southern California.

In northern California, Nevada, Arizona, Oregon, and Montana, a miners inch equals 0.025 cfs (1/40th of a cfs) , while in Colorado it equals 0.026 cfs (1/38th of a cfs). The value of a miner’s inch can vary by locality, so most western states have established the value by statute.

Early miners used a miner’s inch box, a special type of free flowing orifice, to measure water flow. A miner’s inch is the quantity of water which discharges through a square inch of opening under a prescribed head. The number of miner’s inches is equal to the area of the opening in square inches.

One source describes this in more detail: “The quantity of water that will escape from an aperture one inch (2.54 centimeters) square through a two inch thick (5.08-centimeters) plank, with a steady flow of water standing 6 inches (15.24 centimeters) above the top of the escape aperture, the quantity so discharged amounting to 2274 cubic feet (64.39 cubic meters) in 24 hours”.

This amounts to a flow of about 1.5 cubic feet per minute. That’s 11.25 gallons per minute (1/40th of a cfs) if you are in northern California, Nevada, Arizona, Oregon, or Montana but only 9.0 gallons per minute (1/50th of a cfs) if you’re from Idaho, Kansas, Nebraska, South and North Dakota, New Mexico, Utah, Washington, or southern California.

Source: Stream Notes/January 1997

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3 thoughts on “What’s a “Miner’s Inch”?

  1. I have a question – if you are measuring the flow of water through a miner’s inch board – how do you know how much water has passed through the orfice for a certain time? Thanks

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    1. Alan,
      A miner’s inch does not represent a fixed and definite quantity of water, being measured generally by an arbitrary standard of the various ditch companies.

      The value of a miner’s inch can vary by locality, so most Western states have established the value by statute.

      A miner’s inch is the quantity of water which discharges through a square inch of opening under a prescribed head. The number of miner’s inches is equal to the size of the opening in square inches.

      One source describes this in more detail: “The quantity of water that will escape from an aperture one inch square through a two inch thick plank, with a steady flow of water standing 6 inches above the top of the escape aperture, the quantity so discharged amounting to 2274 cubic feet in 24 hours”.

      This amounts to a flow of about 1.5 cubic feet per minute. Hope this helps.

      georgetowndivide

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  2. I think you have the answer already in your question. You can multiply the flow rate by the amount of time and you end up with a volume. So if the flow rate is 1.5 cubic feet per minute and you let it run for two minutes, you have a volume of 3 cubic feet. The caveat is that only if the six inch head is maintained and does not vary over time. Otherwise the flow and volume will change.

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