Convert sprinkler-zone GPM and coverage area to in/hr or mm/hr, reverse-solve flow or area, and calculate runtime and gallons for a target depth.
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GPM To Precipitation Rate Formula
Variables:
- PR is the GPM To Precipitation Rate (in/hr)
- GPM is the US liquid gallons per minute
- A is the area (ft^2)
To convert GPM To Precipitation Rate, divide 96.25 by the area in square feet, then multiply by the gallons per minute.
| Flow (GPM) | Precipitation Rate (in/hr) |
|---|---|
| 0.5 | 0.214 |
| 0.75 | 0.321 |
| 1 | 0.428 |
| 1.25 | 0.535 |
| 1.5 | 0.642 |
| 1.75 | 0.749 |
| 2 | 0.856 |
| 2.5 | 1.069 |
| 3 | 1.283 |
| 3.5 | 1.497 |
| 4 | 1.711 |
| 4.5 | 1.925 |
| 5 | 2.139 |
| 6 | 2.567 |
| 7.5 | 3.208 |
| 8 | 3.422 |
| 10 | 4.278 |
| 12 | 5.133 |
| 15 | 6.417 |
| 20 | 8.556 |
| Formula: Precipitation Rate (in/hr) = 96.25 × GPM ÷ Area(ft²). Table assumes Area = 225 ft². Conversion: 1 in/hr = 25.4 mm/hr. | |
How to Calculate GPM To Precipitation Rate?
The following steps outline how to calculate the GPM To Precipitation Rate.
- First, determine the gallons per minute.
- Next, determine the area (ft^2).
- Next, gather the formula from above = PR = GPM * 96.25 / A.
- Finally, calculate the GPM To Precipitation Rate.
- After inserting the variables and calculating the result, check your answer with the calculator above.
Example Problem :
Use the following variables as an example problem to test your knowledge.
gallons per minute = 300
area (ft^2) = 900
Frequently Asked Questions (FAQ)
What is the significance of the GPM To Precipitation Rate calculation in irrigation systems?
This calculation estimates average applied water depth over an area. It does not establish irrigation efficiency, distribution uniformity, infiltration or crop water needs.
How does the area size affect the GPM To Precipitation Rate calculation?
The larger the area, the lower the precipitation rate for a given flow rate in gallons per minute (GPM), as the water is spread over a larger surface. Adjusting the area size in the calculation helps in planning and optimizing irrigation for differently sized fields or zones.
Can the GPM To Precipitation Rate formula be used for any type of irrigation system?
The volume/area relationship applies to any defined wetted footprint. For sprinklers, use total simultaneous zone flow and avoid double-counting overlap. For drip irrigation, distinguish the wetted area from total field area. Actual distribution and application efficiency require separate measurements.
Is it necessary to adjust the GPM To Precipitation Rate for different seasons or weather conditions?
Yes, seasonal changes and varying weather conditions can significantly impact the water needs of plants. Adjusting the irrigation schedule and the gallons per minute (GPM) based on current conditions can help in conserving water while ensuring that plants receive the necessary hydration.
