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Orchard Yield Water Needs Estimator

The Orchard Yield Water Needs Estimator calculates the irrigation volume required to cover a target depth of water across an orchard after subtracting effective rainfall and allowing for irrigation-system efficiency. It is useful for seasonal water budgeting, pump-runtime planning, and comparing irrigation scenarios across different orchard areas.

The result is a volume estimate, not a crop-specific irrigation prescription. Actual orchard demand varies with crop type, canopy, soil, root depth, evapotranspiration, weather, salinity, and irrigation scheduling. Enter a target weekly depth that already reflects the agronomic water requirement you intend to meet.

Calculator inputs

acres
in/week
in/week
%
weeks
Result
—
total irrigation water to apply
Net irrigation depth—
Applied acre-inches—
Average applied volume per week—

1. Enter orchard area
Use the irrigated acreage covered by the water plan.

2. Set the target weekly depth
Enter the water depth you intend the orchard to receive each week.

3. Subtract effective rainfall
Use only rainfall expected to contribute to the root-zone water requirement.

4. Enter irrigation efficiency
Use the estimated percentage of applied water that reaches the intended root zone.

5. Choose the planning period
Enter the number of irrigation weeks, then review total gallons, acre-inches, and weekly volume.

Net depth = max(Target weekly depth − Effective rainfall, 0)
Gross applied acre-inches = Area × Net depth × Weeks ÷ (Efficiency ÷ 100)
Total gallons = Gross applied acre-inches × 27,154

One acre-inch is approximately 27,154 US gallons. The same target and rainfall values are assumed for each week in the entered period.

What the result means

The main result is the gross irrigation volume needed to deliver the net target depth after rainfall, adjusted upward for system inefficiency.

The conversion uses 27,154 gallons per acre-inch. Field losses and effective rainfall can vary, so local scheduling data should take priority when available.

Given

  • 25 acres
  • 1.4 in/week target water depth
  • 0.3 in/week effective rainfall
  • 85% irrigation efficiency
  • 12 weeks

Calculation
Net depth = 1.4 − 0.3 = 1.1 in/week.
Gross acre-inches = 25 × 1.1 × 12 ÷ 0.85 = 388.24 acre-in.
Gallons = 388.24 × 27,154 ≈ 10,541,553 gal.

Result
Total irrigation water to apply ≈ 10.54 million gallons.

The gross volume is higher than the net crop requirement because the calculation allows for 15% irrigation losses.

What does effective rainfall mean?

It is the portion of rainfall that actually offsets irrigation need in the root zone. Runoff, deep percolation, and poorly timed rain may reduce how much rainfall is effective.

Why does lower irrigation efficiency increase the answer?

When a smaller share of applied water reaches the target root zone, more gross water must be pumped or delivered to provide the same net depth.

Can I use monthly rainfall in the weekly field?

Convert it to a consistent weekly amount before entering it, or model the period in smaller segments. Mixing weekly target depth with monthly rainfall would distort the result.

What happens if rainfall exceeds the target depth?

The calculator sets net irrigation depth to zero rather than producing a negative irrigation requirement.

Does this calculate crop evapotranspiration?

No. You enter the target water depth directly. A crop-ET method can be used separately to determine that target before using this volume estimator.