Seasonal Water Budget & Your Whole-Season Need
Sizes supply
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Enter your crop's average ETc, season length, effective rainfall and system efficiency to get the total irrigation supply you need — crop water demand, the net irrigation depth and the gross volume in m³.
Enter your season
Next: plan ~2,698 m³ of water for the season; store/secure this in your pond/borewell, or pick a less thirsty crop if short.
Uses an average ETc — real demand peaks mid-season; size storage/pump for the peak month, not just the season total.
Seasonal water budget — key facts
- Crop water use
- avg ETc × season days
- Net irrigation
- crop water − effective rain
- Gross irrigation
- net ÷ system efficiency
- 1 mm over 1 ha
- = 10 m³ (10,000 L)
- Drip / sprinkler
- ~90% / ~75% efficient
- Peak demand
- mid-season, full canopy
- Size storage on
- the peak month, not average
- Privacy
- Runs in your browser; nothing uploaded
Plan the whole season's water, not just today's
Daily scheduling tells you what to apply now, but planning a season needs the full picture: how much water the crop will use from sowing to harvest, how much rain will help, and how much you must therefore supply yourself. The seasonal water budget sums crop water use (average ETc × season days), subtracts effective rainfall, and divides by system efficiency to size the total irrigation supply. That total is what you build storage, a pond or a pump around.
This tool returns your seasonal crop water demand, net irrigation depth, gross volume in m³, and the rain contribution. Remember that real demand peaks mid-season when the canopy is full, so size your storage and pump for the peak month rather than the average. Pair it with the Pan Evaporation ET, Effective Rainfall and Farm Pond tools to plan and store a season's water with confidence.
See the whole season
Total water the crop needs from sowing to harvest.
Credit the rain
Subtract effective rainfall to size real supply.
Account for losses
Gross volume includes your system's efficiency.
Plan for the peak
Size storage and pump for the mid-season peak.
Frequently Asked Questions
What is a seasonal water budget?+
It's the total amount of water a crop needs over a whole season, after subtracting what rain provides and after allowing for irrigation losses. The tool sums crop water use (average ETc × season days), takes off effective rainfall, then divides by system efficiency to size the total irrigation supply you must deliver.
How is seasonal crop water use calculated?+
Multiply the average daily crop evapotranspiration (ETc) in mm by the number of days in the season. For example, 5 mm/day over 120 days is 600 mm of crop water use. That seasonal depth is the starting point before rainfall and efficiency are taken into account.
What is effective rainfall?+
Effective rainfall is the portion of rain that actually reaches and is held in the root zone — runoff and deep drainage don't count. Subtracting effective rainfall from seasonal crop water use gives the net irrigation depth, the water you must add beyond what the sky provides.
Why divide by system efficiency?+
Not all applied water reaches the roots: surface methods lose more, drip less. Dividing the net irrigation depth by your system efficiency gives the gross depth you must actually pump or deliver. Drip is about 90% efficient, sprinkler ~75% and surface ~55%, so efficiency strongly affects total supply.
How do I turn the depth into a volume in m³?+
One millimetre of water over one hectare (10,000 m²) is 10,000 litres = 10 m³. Multiply the gross depth in mm by your area in hectares by 10 to get the seasonal volume in m³. The tool does this for you so you can size storage, a pond or a pump.
Why does demand peak mid-season?+
Real water demand isn't flat: it's low at the seedling stage, climbs as the canopy develops, and peaks at mid-season when the crop is at full cover and the weather is often hottest. Sizing only on the average understates the peak, so plan storage and pump capacity for the peak month, not the mean.
Should I size storage on the average or the peak?+
Size total seasonal supply on the budget, but size your storage and delivery rate on the peak month. A reservoir or pump that only meets average demand will fall short exactly when the crop needs water most, costing yield. Use the seasonal total for planning and the peak for capacity.
Can I use this for any crop or region?+
Yes. Enter your crop's own average ETc and season length, your local effective rainfall, and your system efficiency. The method — seasonal demand minus rain, divided by efficiency — applies to any crop in any climate. Adjust the inputs to your conditions for a realistic budget.
How accurate is the result?+
It's a sound planning estimate. The biggest sources of error are the average ETc and the effective rainfall, both of which vary with weather and stage. Use locally measured or recommended figures where you can, and treat the output as a budget to refine against in-season readings.
How does this fit with daily scheduling?+
The seasonal budget tells you the total to plan and store; daily scheduling tools tell you how much and how often to apply as the weather and crop stage change. Use this to size supply and storage, then the Pan Evaporation ET and Irrigation Water tools to run each irrigation.
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