3.3.2. Commodity-Wise Net Import of Blue and Green Virtual Water

The commodity-wise contribution of net VWI of blue and green water varies considerably in Pakistan (Figure 3). Wherein, blue net virtual water import was mostly negative and green net virtual water import was mostly positive. Pakistan's negative blue net virtual water import has been mostly dominated by blue net virtual water import via rice exports, which had an average annual blue net virtual water import of -5680 Mm<sup>3</sup> and accounted for an average share of 94% in the total annual blue net virtual water import over the study period (Figure 3a). Moreover, blue net virtual water import through rice has been rising over the years; from an annual average of <sup>−</sup>3547 Mm<sup>3</sup> over 1990–1999 it increased to <sup>−</sup>5271 Mm3 per annum during 2000–2009 and reached <sup>−</sup>9314 Mm3 per year during 2010–2016. The rise in negative net VWI through rice can be attributed to rising domestic production and decreasing share of domestic consumption of rice in the domestic production in Pakistan. Specifically, rice production in Pakistan increased at a rate of 4.3% per year, from 4.89 million tons in 1990 to 10.5 million tons in 2016. Both yield and area contributed to improving production [39]. The combined effect of these factors was a steady year-on-year increase in rice exports from Pakistan. So much so that during 2010, Pakistan exported a staggering 86% of the domestically produced rice to the international market [39].

The contribution of wheat trade towards blue net virtual water import of Pakistan, although relatively small, saw an unusual feature over the study period. During 1990–1999, blue net virtual water import due to wheat had been consistently positive due to the small but sustained net import of wheat by Pakistan. After 1999, however, Pakistan occasionally recorded negative net import of wheat, which lead to sizable negative contributions to the total blue net virtual water import of Pakistan. The reason for this fluctuation in blue net virtual water import through wheat trade over the years was lower production in some years or bumper crops in others and due to weather events and poor stock management [54,55].

The blue net virtual water import of Pakistan due to the rest of the crops like maize, other cereals, oilseed crops, palm oil, sugar, vegetables, fruits, tea and tobacco and livestock such as beef, mutton and poultry has been quite small over the study period (Figure 3a).

Several agricultural commodities have contributed towards green net virtual water import, of which the total contributions due to net imports of palm oil, tea, wheat, oilseeds and cotton have been positive, that is, Pakistan imported more green VW through the trade of these crops than it exported (Figure 3b). Palm oil, with the average yearly contribution of 89% (5465 Mm3/year), was the most dominant commodity. Interestingly, in some years like 1992 and 1999, the contribution of wheat towards green net VWI even surpassed the share of palm oil due to large volumes of wheat imports by Pakistan. Green net virtual water import due to rice trade was negative over the study period. The rest of the crops and livestock had small but predominantly negative green net virtual water imports.

The comparison between both panels of Figure 3 indicates that Pakistan has been exporting ever-increasing quantities of blue virtual water, while at the same time importing almost equal amounts of green virtual water, which in the end seems to have canceled out the effects on Pakistan's water resources. However, the transfer of blue virtual water to other countries through net virtual water export is far more valuable than the green virtual water transfers from other countries into Pakistan through net virtual water import.

**Figure 3.** Commodity-wise evolution of (**a**) blue and (**b**) green net virtual water import of Pakistan (1990–2016). Source: Authors' calculations based on data from Reference [39] (trade volumes) and sources mentioned in the Methods section (VWC).

Blue water is far more costly than the green water used for agricultural production; as for the former, there are considerable costs in terms of construction, maintenance and operation of dams and the related irrigation systems, which are usually born by the citizens of exporting countries. However, these costs are not adequately included in the price of blue water or reflected in the price of final products. In addition to economic costs, there are many environmental and social costs of ensuring steady supplies of blue water, which are seldom considered in the literature of virtual water trade. Exporting commodities heavily laden with blue water also reduces the domestic supply of this precious natural resource, intensifying any water shortage issues.
