Climate and irrigation
Rainfall, evapotranspiration, frost and degree days over the last 20 years anywhere (NASA POWER), and an estimate of your crop's irrigation need.
Past averages, not a forecast
Reanalysis data with cells of about 50 km. The irrigation need is an average estimate for planning, not an irrigation schedule.
Cargando…
Calculation version:agri-water@1.0.0.
How to use it
- 1Mark the plot on the map or type its coordinates and check the climate of the last 20 years.
- 2Check the rainfall, reference evapotranspiration (ET₀), frost and degree days for each month.
- 3For irrigation, enter the crop coefficient (Kc) for each month, your system's efficiency and the area. You can carry the water over to the margin simulator.
How it calculates
- NASA POWER daily data (maximum and minimum temperature and rainfall) for the last 20 complete calendar years; monthly averages of the years with at least 90% of days with data.
- Daily Hargreaves ET₀ (FAO-56, equation 52) = 0.0023 × (Tmean + 17.8) × √(Tmax − Tmin) × 0.408 × Ra, where Ra, the extraterrestrial radiation, depends on latitude and day (FAO-56, equations 21 to 25).
- FAO monthly effective rainfall: 0.8 × P − 25 if P > 75 mm; otherwise 0.6 × P − 10 (never negative).
- Net irrigation = max(0, Kc × ET₀ − effective rainfall); gross = net / efficiency. 1 mm over one hectare is 10 m³.
Verifiable example
If the mean ET₀ in July is 150 mm, Kc is 1.2 and 50 mm of rain falls (20 mm effective), the net irrigation is 180 − 20 = 160 mm; with 80% efficiency, 200 mm, i.e. 2,000 m³/ha that month. These are example numbers, not those of a specific place.
Limitations
- Hargreaves is less accurate than Penman-Monteith, especially with strong wind or high humidity; to schedule irrigation use data from your agro-climatic network.
- Cells of about 50 km: they don't capture the plot's terrain, coast or microclimates.
- These are past averages, not a forecast: a dry year will need more water.