1. Irrigation Water Requirements Part 2
Penman Monteith Implementation

2. Irrigation Water Requirements
What it does
Monthly and seasonal irrigation water requirements
Peak ET values
What it doesn’t do
It’s not a scheduler
It doesn’t calculate daily ET values

3. Overview of IWR
Strictly in conformance with USDA-NRCS NEH Part 623 Chapter 2 Irrigation Water Requirements
IWR can calculate evapo-transpiration using two methods:
FAO 56 Penman Monteith
SCS Blaney Criddle (TR-21)
Strictly in conformance with USDA-NRCS NEH Part 623 Chapter 2 Irrigation Water Requirements
IWR can calculate evapo-transpiration using three methods:
Temperature
Radiation
SCS Blaney Criddle (TR-21)

4. What IWR does
IWR implements procedures for computing monthly and seasonal irrigation water requirements.
It is not capable of making daily irrigation water requirement estimates

5. Data Requirements
The TR-21 method uses average monthly temperature and average monthly precipitation
The temperature and radiation methods require additional data:
humidity
wind
solar radiation

25. Go to SPAW