acre-foot
C1Technical / Scientific (Hydrology, Agriculture, Civil Engineering)
Definition
Meaning
A unit of volume used in water resource management, representing the volume of water that would cover one acre of land to a depth of one foot.
Approximately 43,560 cubic feet, or 325,851 gallons (US). A standard measure for large-scale water resources, such as reservoir capacity, irrigation water allotments, or annual water usage for cities.
Linguistics
Semantic Notes
This is a compound noun functioning as a singular, countable unit of measurement. Plural is 'acre-feet'. It denotes an extremely large, non-intuitive volume for non-specialists.
Dialectal Variation
British vs American Usage
Differences
While the unit is conceptually understood and used in both regions, its primary practical application is in the western United States and other arid regions where water rights and large-scale irrigation are major concerns. In the UK, the metric equivalent (e.g., megalitres) is more common in official contexts.
Connotations
In the US, it strongly connotes water management, agriculture in arid states (e.g., California, Colorado), and legal water rights. In the UK, it is a specialist technical term, often used with an implied conversion to metric.
Frequency
Much more frequent in American English, particularly in Western states' news, policy, and engineering documents. Very low frequency in everyday British English.
Vocabulary
Collocations
Grammar
Valency Patterns
The reservoir holds [NUMBER] acre-feet.They have an allocation of [NUMBER] acre-feet per annum.[NUMBER] acre-feet of water was released.Vocabulary
Synonyms
Neutral
Weak
Usage
Context Usage
Business
In water trading, a farmer might sell their annual allocation of 100 acre-feet.
Academic
The study calculated the aquifer's recharge rate at 50,000 acre-feet per decade.
Everyday
Rarely used in everyday conversation except in regions dependent on irrigation.
Technical
The dam's live storage capacity is 2.1 million acre-feet.
Examples
By Part of Speech
verb
British English
- The water authority will acre-foot the allocations for the coming season. (Hypothetical/rare usage)
American English
- The district is acre-footing the water based on seniority rights. (Hypothetical/rare usage)
Examples
By CEFR Level
- An acre-foot is a lot of water.
- The lake holds many acre-feet of water.
- The farm's annual water right is for 200 acre-feet.
- One acre-foot equals about 326,000 gallons.
- The proposed legislation would reallocate 500,000 acre-feet from agricultural to municipal use.
- Hydrologists measured the aquifer's depletion at over 2 million acre-feet.
Learning
Memory Aids
Mnemonic
Imagine a football field (about 1.3 acres) covered in one foot of water. An acre-foot is roughly the volume of that water.
Conceptual Metaphor
WATER IS A MEASURABLE COMMODITY (like grain or oil, but measured in area-depth units).
Watch out
Common Pitfalls
Translation Traps (for Russian speakers)
- Do not translate literally as 'акр-нога'. It is a specific unit. Use the calque 'акр-фут' with explanation, or approximate metric equivalent like '1233 кубических метров'.
Common Mistakes
- Using it as a plural without changing 'foot' to 'feet' (e.g., 'ten acre-foot' is incorrect; correct is 'ten acre-feet').
- Confusing it with a measure of area (acre) instead of volume.
Practice
Quiz
In which context are you MOST likely to encounter the term 'acre-foot'?
FAQ
Frequently Asked Questions
It is primarily a US customary unit. Countries using the metric system typically use cubic metres, megalitres, or hectare-metres for similar large water volumes.
One acre-foot is approximately 325,851 US gallons.
It is almost exclusively used for water volume, particularly in hydrology, irrigation, and civil engineering contexts. It would be highly unconventional for other substances.
The correct plural is 'acre-feet', similar to 'foot' becoming 'feet'.