*2.5. Value of Virtual Water Flows*

The value produced by one unit of water (value of virtual water, i.e., VVW) is an important indicator of the efficiency of water use in different sectors (unit: US\$/m3) (the average exchange rate over the period 1990–2016 was 1 US\$ = 60.4 Pakistan Rupee [39]). Due to the differences in the opportunity costs of green and blues water, we calculate an average value of blue virtual water of the studied commodities over 1990-2016 by diving the production value (unit: US\$/ton) by the blue VWC (unit: m3/ton) that is

$$\text{VVW}\_{i,t} = \text{NPV}\_{i,t} / \text{BVWC}\_{i,t} \tag{9}$$

where *VVWi*,*<sup>t</sup>* is value produced by one unit of blue water by commodity *i* in year*t*(US\$/m3), *NPVi*,*<sup>t</sup>* is the net production (it is the value of net production, where, Net production = Production—Feed—Seed [39]) value of each commodity *i* produced in year *t* and *BVWCi*,*<sup>t</sup>* is the blue virtual water content of each commodity *i* produced in year *t*. The values for *NPVi*,*<sup>t</sup>* for Pakistan are obtained from Reference [39], while *BVWCi*,*<sup>t</sup>* values are based on various sources described earlier in this section.
