| Abstract | Pakistan is one of the most arid country in the world with an annual rainfall less than 240 mm and total available fresh water is 130 BCM. Per capita water availability is reducing rapidly from 5,000 m3 in 1951 to less than 1,100 m3 currently. Agriculture sector as a major fresh water consumer in the country needs considerable work in the field of water management to conserve this precious gift of nature. In this regard, this research study was conducted on the latest concept of “water footprint (WF)” that is applied at district level of the Punjab province for two major crops, maize and cotton, grown under drip and conventional irrigation separately using historical data from 2010 to 2017. The calculations were done to determine green, blue, gray and white WF components of each crop. The impact of climate change from 2010 to 2017 on each WF component for both crops under drip and conventional irrigation at district level in the province was analysed. Economic water productivity of each component of WF for both crops under drip and conventional irrigation was calculated separately at district scale for each studied year.
Considering the whole province, average WF under conventional irrigation from the year 2010 to 2017 calculated for maize was 1676.010 m3/t (139.416 m3/t green, 936.212 m3/t blue, 298.693 m3/t gray and 301.689 m3/t white) and for cotton was 23231.108 m3/t (2908.659 m3/t green, 13456.607 m3/t blue, 3070.366 m3/t gray and 3795.476 m3/t white). Under drip irrigation average WF from the year 2010 to 2017 estimated for maize was 872.660 m3/t (87.926 m3/t green, 642.747 m3/t blue, 64.805 m3/t gray and 77.183 m3/t white) and for cotton was 12478.863 m3/t (1814.586 m3/t green, 8481.744 m3/t blue, 1135.946 m3/t gray and 1046.586 m3/t white). The total volume of water used as water footprints during the year 2017 under conventional irrigation for maize was 5424.51 MCM and for cotton was 27965.8 MCM. During the same year total volume of water consumed as WF under drip irrigation for maize was 4.674 MCM and for cotton was 5.069 MCM. Precipitation and mean relative humidity had more significant effect on green WF of maize, while blue and green WF of maize were more significantly affected by precipitation and mean maximum temperature under both irrigation systems. Total rainfall had more significant impact on green and blue WF of cotton, while only rainfall had significant effect on white WF of cotton grown under both drip and conventional irrigation. The analysis of economic water productivity resulted mean minimum and maximum EWP under conventional irrigation for maize were 0.0877 USD/m3 in Sargodha district and 0.19662 USD/m3 in Okara district, respectively; while mean minimum and maximum EWP under drip irrigation for maize were 0.2845 USD/m3 in district Vehari and 0.3520 USD/m3 in district TT Singh, respectively. Mean EWP of cotton under conventional irrigation was minimum as 0.0300 USD/m3 in district Muzaffargarrh and maximum as 0.0425 USD/m3 in district Sahiwal; while, under drip irrigation maximum EWP of cotton was observed in district Pakpattan as 0.0788 USD/m3 and minimum in district Muzaffargarrh as 0.0563 USD/m3. These analyses do not reflect only the importance but also the requirement of better water management in agriculture sector at grass root level to conserve this precious blessing of nature through introducing latest interventions and technologies into this sector like drip and sprinkler irrigation. |