The verification of Jevons' paradox of agricultural Water conservation in Tianshan District of China based on Water footprint

摘要

Agriculture is the basic unit that safeguards food security in the world and is also the sector that uses the largest amount of water in economic activities. In agriculture, vigorously promoting high-efficiency water conservation in agriculture is regarded as the most important way to solve the water shortage. However, many examples have shown that increases in irrigation efficiency may increase water consumption in a manner similar to that of the "Jevon's Paradox" during the energy-saving technology progress. The rebound effect has a substantial impact on the effectiveness of water conservation policies. It is of substantial value to understand the rebound effect of irrigation water to effectively conserve agricultural water consumption and to reveal and solve the water conservation dilemma in the dry areas. An empirical case study is presented based on the largest water conservation irrigation area in the Tianshan region (northwest China), an arid area, to test the rebound effect on the water conservation efforts in terms of its blue water footprint, which is also designated irrigation water consumption. Irrigation technology in this region has increased so that more than 47% of the agricultural area utilizes high-efficiency drip irrigation technology since the adoption of modern water conservation technologies in 1996, while flooding was the only type of irrigation previously used in this area. The results illustrate that since the implementation of high-efficiency water conservation irrigation in 1996, the agricultural blue water footprint has continued to rise, and the increase in the southern foothill (referred to as "the south") is greater than that in the northern foothill (referred to as "the north") of the Tianshan Mountains. The rebound effect for agricultural water consumption totaled 115% in the Tianshan region during the last 20 years, showing a "backfire phenomenon". It differs substantially in the southern and northern parts of the Tianshan region, totaling approximately 166% in the southern part and 83% in the northern part. The high-efficiency water-conservation and conservation technologies, characterized by drip irrigation systems since 1996, resulted in a significant improvement in productivity and thus, economic gain, while the water consumption per unit area shows no significant decrease. The differences in agricultural water consumption can be related to four main factors: (i) the scale of high efficiency water saving, (ii) the change of cultivated land area, (iii) variation in planting structure, and (iv) the increase of average yield per ha. This study found negative correlations between high efficiency water conservation and moderate intensity of agricultural water consumption. The expansion of the total cultivated land area, the continuous increase in the proportion planted to economic crops and the average yield per ha undoubtedly increased agricultural water consumption. This study concludes that the primary pathways for achieving the resource-based concept of water conservation are to continue to promote more efficient or "water-conservation" irrigation technologies (engineering aspects), jointly consider with water and land allocation (management aspects), adjust the planting structure (policy guidance aspects), and the appropriate pursuit of yield per unit area (agricultural technology aspects).