Figure 4. Model evaluation for the reference period 1980–2009.

Validation against observational data is shown for mean annual discharge (uncertainty range from use of four precipitation data sets) (a), environmental flow requirements for three differing calculation methods (b) and country-level crop yields (calibrated for management intensity) for main staple crops and the respective top 30 producer countries, with chart symbols scaled by the country's cropland area (c). The coefficient of determination (R²) is shown along with the root mean square error in parenthesis (further details in Methods section 'Model validation').