Irrigation & Water
Well Yield Calculator
Calculate well yield in GPM and daily capacity from a pump test.
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How to Use This Calculator
Run a timed pump test by pumping into a container of known volume or using a flow meter. Enter the total gallons pumped and the test duration in minutes. The calculator converts your test data into gallons per minute, per hour, and per day.
Why This Matters
Well yield determines whether your water source can support your irrigation system. A well that cannot keep up with demand causes pump cavitation, well damage, and crop stress. Testing during dry periods gives the most conservative and reliable estimate.
Methodology
GPM = Gallons pumped / Test duration (minutes). GPH = GPM × 60. GPD = GPH × 24. A proper sustained yield test should run 4-8 hours to account for aquifer drawdown. Short tests overestimate actual sustainable yield.
Common Mistakes to Avoid
- Running a pump test for only 15-30 minutes — short tests overestimate sustainable yield by 20-50%.
- Testing in spring when water tables are high instead of late summer when demand is greatest.
- Not monitoring drawdown — if water level drops steadily, the well may not sustain that rate.
- Sizing the irrigation system to maximum well yield with no safety margin for drought years.
Tips & Best Practices
- A sustained yield test should run at least 4-8 hours for accuracy.
- Well yield may decrease during drought — test during dry periods.
- Match pump size to actual well yield, not maximum pump capacity.