One section of the FeliX model deals with water availability and usage, which carries consequences for agricultural yields and places exogenous limits on global (absolute) food production. The factor (γ) linking water availability to cropland yields is defined by the equation at right, where:
- f (Agricultural Water Withdrawal Fulfillment Factor) = 3.5 : a factor defining the strength of infrastructural limitations on agricultural water demand fulfillment.
- σ (Maximum Water Withdrawal Rate) : a variable function equivalent to Available Water Resources
- θ (Agricultural Water Demand) : total agricultural water demand, based on extent of rainfed & irrigated land
In the above plot, annual Agricultural Water Demand is shown in green. Industrial and Domestic Water Demand (orange) are grouped together. Historical data from the UN International Hydrological Programme (IHP) is used to calibrate demand. The blue line represents IHP historical data on global annual supply, including withdrawals from surface and groundwater and non-conventional sources such as desalination .
Despite anticipated improvements in water use efficiency (due especially to irrigation), agricultural water demand grows 62% by 2100. Overall, water demand grows 75%, while supply is projected to grow only 54%. Unaddressed, this deficit limits the Maximum Water Withdrawal Rate for agricultural activities, with a double-digit negative impact on agricultural yields, as shown by the factors at the bottom of the plot.
 Shiklomanov, I.A., Rodda, J.C.: World water resources at the beginning of the twenty-first century. Technical report, International Hydrological Programme (IHP) of UNESCO (2003)