Build a crop and period record, separate ET from rain-adjusted application, compare measured delivery and document variable water costs.
List crop group, growth stage, represented area and the period to review. Record the source and reference surface for ETo and the matching Kc. Use an average daily ETo for the chosen interval or split it into consistent shorter periods.
Multiply the entered reference ET by the matched crop coefficient and period. Review the depth and area-based volume. Keep this crop-water-use estimate separate from a timer setting or the volume expected from the supply.
Enter effective rainfall for the whole period and a supported application-efficiency estimate. Review net replacement and gross application separately. Check stored soil water, capillary contributions, stress and any leaching requirement before deciding whether this simplified budget is appropriate.
Use measured delivery to translate a chosen amount into runtime. Compare planned volume with actual meter change over a known interval. Apply the relevant variable water charge, keeping fixed fees, sewer charges and tier thresholds separately in the bill record.
Record actual irrigation, rainfall, meter readings and crop/soil observations for the same interval. Explain differences due to weather, crop stage, leaks, meter scope or rate changes. Preserve the original case, revise the relevant assumption and save the next review date.
Keep crop, stage, area, ETo/Kc sources, dates and units. · Keep the original budget, actual-use record and reasons for revisions.
Use Crop evapotranspiration to calculate daily ETc and period crop-water-use volume. · Use ET and effective-rain budget for a simplified crop-ET replacement calculation.
Convert the chosen volume or average depth into runtime using nominal or measured delivery as appropriate.
Use metered water mode to compare readings and calculate an entered flat variable volume charge.
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FAO’s crop-coefficient method estimates ETc from ETo and Kc. Coefficients vary with crop and stage; this tool accepts those inputs and does not run a weather-based ETo solver.
Effective rainfall is the useful portion of rain, not all measured precipitation. Net replacement may be zero; application losses are handled through an entered efficiency. A complete soil-water balance may require additional terms.
With ETo 5 mm/day, Kc 0.8, seven days and 100 m², ET is 28 mm or 2,800 L. Subtracting 8 mm effective rain gives 20 mm net; at an entered 80% efficiency, the gross depth is 25 mm or 2,500 L. These values are examples, not recommendations.
Multiplying a peak-day ETo across a whole season can overstate the period average.
A flat volume rate does not reproduce tiered, fixed or sewer charges.