Water Efficiency Calculator

Reference ET (inside greenhouse)

1.80 mm·day⁻¹

Adjusted Penman-Monteith using transmitted solar radiation and low internal wind speed.

Crop evapotranspiration (ETc)

2.79 mm·day⁻¹

Net crop demand = ETc × area ⇒ 65.8 gal·day⁻¹.

(89.2 m² growing area)

Annual external water requirement

2528 gal·yr⁻¹

Baseline (timer, non-PC, drain-to-waste): 40523 gal·yr⁻¹

Savings: 37995 gal (93.8%)

Daily & annual water budget

Technology impact summary

• Soil moisture sensor scheduling

  Savings: 36% less water vs. timer irrigation; 28.8% vs. ET scheduling.

  Climate: Mediterranean plastic greenhouse (Pisa, Italy) – Incrocci et al. 2021.

  Cost: DIY $50–$100; commercial multi-zone Wi-Fi systems $1,000–$1,500+. Low operating cost (batteries/data).

  Formula: Applied as a scheduling multiplier (1.0 for sensors vs. 1.35 timer).

  Reference: Incrocci, L. et al. (2021) Agronomy 11(12):2485; Al-Arab, M. et al. (2025) IoT lettuce trial.

• Pressure-compensating drip emitters

  Savings: Improves distribution uniformity to 90–95%, reducing over-irrigation by ~15–25%.

  Climate: Uniform benefit; independent of external climate. Greatest impact on long laterals/slopes.

  Cost: Emitters $0.28–$0.70 each (marginal increase vs. $0.15 non-PC). Requires fine filtration (120–150 mesh).

  Formula: Modeled via application efficiency (Ea = 0.95 vs. 0.80 for non-PC).

  Reference: Irrigation engineering design standards (ASABE EP405).

• Rainwater harvesting & storage

  Savings: Supplies 45–80% of annual irrigation demand (semi-arid Turkey to Mediterranean Antalya).

  Climate: Semi-arid Kirsehir (Turkey) and Mediterranean Antalya studies; high-value greenhouse peppers.

  Cost: Gutters $900+/96 ft span, storage $200 (barrel) to $30k+ (large cistern + pump). Operating $100–$500/yr maintenance.

  Formula: Supply-side subtraction: rainfall × roof area × 0.623 × 0.90 runoff coefficient.

  Reference: Boyacı & Kartal (2019); Punjab Agricultural University rainwater modeling; U.S. high tunnel trials.

  (Not applied – toggle above to include in scenario.)

• Closed-loop water recycling

  Savings: Reduces new water demand by 85–95% vs. drain-to-waste irrigation.

  Climate: Widely adopted in high-tech glasshouses (e.g., NatureFresh Farms, Ontario).

  Cost: High capex: drains, tanks, UV/ozone treatment, sensors. Hydroponic NFT benches $10–$20/ft².

  Formula: System efficiency factor Sₑff = 0.90 (new water = demand × (1 − Sₑff)).

  Reference: Protected agriculture best practice (FAO 2013); commercial case studies (NatureFresh Farms).