Team Organic Mandya ·
Water Budgeting for Organic Farms: Plan Your Water Needs
Most farm water crises are predictable and preventable — farmers run out of water in April and May not because there was no warning, but because they never calculated how much water the farm actually needed vs what the borewell actually produces. A simple water budget — done once, updated seasonally — shows exactly when your water demand exceeds supply, how many days your farm pond buffer can cover the deficit, and whether a second borewell or additional storage is needed before you face a crop-destroying crisis. This guide walks through the full calculation.
Peak in April–May
When Karnataka farm water demand is highest — hot, dry, no rain, maximum crop evapotranspiration
Borewell yield test
Run the borewell for 4 hours continuously and measure actual yield — many borewells produce 30–50% less than claimed
10,000 litres/day
Approximate peak water need for 30 raised beds on 1 acre in peak summer
Water budget
One-time 2-hour calculation that prevents a farm water crisis every summer
How Do You Calculate Your Farm’s Total Water Demand?
Step 1 — Calculate irrigation demand for your crop beds:
For drip-irrigated raised beds in peak summer (April–May), Mandya district:
- Evapotranspiration (ET₀): 6–8mm/day in peak summer
- Crop coefficient for vegetables: 0.7–1.0 (multiply ET₀ × Kc for crop ET)
- Drip efficiency: 90–95% (divide crop ET by 0.92 for gross irrigation need)
Simplified for 30 beds (each 4ft × 30ft = 11.2 sq m, total 336 sq m):
- Peak ET: 8mm × 336 sq m = 2,688 litres/day crop need
- With mulching (reduces ET by 60%): 2,688 × 0.40 = 1,075 litres from soil surface
- Total daily irrigation: approximately 5,000–8,000 litres/day for mulched beds (includes losses)
Step 2 — Add domestic and livestock water:
- Farm household: 100–200 litres/day
- 2 desi cows: 60 litres/day per cow = 120 litres/day
- Daily domestic total: 220–320 litres/day
Step 3 — Calculate total peak daily demand: 5,000–8,000 + 220–320 = 5,220–8,320 litres/day peak demand
How Do You Measure Your Water Source Capacity?
Borewell yield test:
- Run the borewell pump continuously for 4 hours
- At the end of 4 hours, measure the recovery rate: stop pump; measure how fast the water level rises (use a string with a float)
- If the borewell recovers 2,000 litres in the first hour after stopping — yield is approximately 2,000 l/hr
- This is the sustainable yield — do not design farm water use above this
Farm pond capacity: Volume (litres) = Length × Width × Average depth × 1,000 At 10,000 litres/day withdrawal: divide pond volume by 10,000 = days of supply
| Water Source | Daily Yield Measurement | Typical Yield (Karnataka) |
|---|---|---|
| Borewell (200–300 feet depth) | Run pump 4 hours; measure recovery in 1 hour | 500–3,000 litres/hour depending on aquifer |
| Open well | Measure diameter and depth of water; measure how fast water drops when pumping | 300–2,000 litres/hour in good conditions |
| Farm pond (stored) | Volume calculation; loses 2,000–3,000 litres/day to evaporation in summer | Set by pond volume; not a daily renewable source |
| Canal water (irrigation command area) | Allocation days per season × hours per day × known discharge | Varies by command area and season |
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Visit Our Shop →How Do You Create a Monthly Water Budget?
| Month | Daily Demand | Borewell Supply (2,000 l/hr, 4 hrs/day) | Surplus / Deficit |
|---|---|---|---|
| June–September (monsoon) | 1,000–2,000 litres (rain supplements) | 8,000 litres available | Large surplus — charge farm pond |
| October–November (post-monsoon) | 3,000–5,000 litres | 8,000 litres available | Surplus — maintain farm pond charge |
| December–January (cool, low demand) | 2,000–3,000 litres | 8,000 litres available | Surplus |
| February–March (warming) | 5,000–7,000 litres | 8,000 litres available | Marginal surplus or balance |
| April–May (peak demand) | 8,000–12,000 litres | 8,000 litres available | Deficit of 0–4,000 litres/day |
| **April–May deficit covered by:** | Farm pond buffer storage | 5,00,000 litre pond ÷ 3,000 litre/day deficit = **167 days of buffer** | Comfortable coverage |
Key insight: Even a modest farm pond of 5,00,000 litres (20m × 12.5m × 2m) covers the April–May water deficit on a 30-bed farm for months — eliminating the summer water crisis that affects borewell-only farms.
Test Your Borewell in March Before You Need It in April
Many farmers discover their borewell is declining only when crops start dying in April. The right time to test is February or March: run the borewell for a full 4-hour test and measure recovery. If yield has dropped significantly from last year, you have 6–8 weeks to take action — add a drip-fed farm pond from existing storage, reduce crop area, or arrange alternative supply. A borewell test in April, when the water table has already dropped to its lowest point, gives you no time to respond. Schedule your annual borewell test on the first day of March every year.
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