Agricultural Water Use Efficiency (WUE) and Productivity (WP)
Published Online: 15 APR 2005
Copyright © 2005 by John Wiley & Sons, Inc.
How to Cite
Steduto, P. 2005. Agricultural Water Use Efficiency (WUE) and Productivity (WP). Water Encyclopedia. 3:558–560.
- Published Online: 15 APR 2005
Among the different sectors of society, agriculture represents the major water consumer. Rain-fed and irrigated agriculture uses water at various degrees of efficiency, resulting in different levels of productivity.
The general term efficiency (e) indicates the ratio of output to input of variables (Eq. 1) associated with transformation (e.g., of energy) or transport (e.g., of mass and energy) processes:
The efficiency term (e) has two peculiarities: (1) the units are nondimensional and (2) the values are always between the theoretical limits of 0 and 1. In water use, the efficiency (ew) has water amounts (e.g., volumes, quantities, or depth) in both input and output variables.
The general term productivity (p) still indicates a ratio of output to input of variables, as in Equation 1, but these output and input variables are not associated with transport processes and might be associated, but not necessarily, with a transformation process. The consequent peculiarities of the productivity term (p) do not match those of the efficiency term (e), that is, the units are dimensional, and the theoretical limits of 0 and 1 are lost. In water use, the productivity term (pw) has water amounts (e.g., volumes, quantities, or depth) only in the input. The output, instead, generally takes the form of quantities produced: physical (e.g., dry matter or final yield of crops, or meat or dairy products from animal husbandry, etc.), economic (e.g., gross income, net revenue, etc.), or any other form.
The efficiency term ew has to do more with the way water is used by the system, whereas pw has to do more with the outcome from the system per unit of water it consumes. Nevertheless, it turns out that a change in ew is reflected in a change in pw, implying that there is a link between ew and pw, though the reverse is not the case. Moreover, though pw cannot be strictly defined by Equation 1, it still resembles a sort of efficiency of the system to produce a given output for a given input. The undefined degree of commonality and distinction between ew and pw has led to some confusion in investigating agricultural water use.
- water use efficiency (WUE);
- water productivity (WP);
- agricultural-system analysis