Irrigation water and energy saving in well irrigation district from a water-energy nexus perspective.

Agricultural irrigation involves both water and energy consumption, especially in well irrigation districts. These two processes are closely linked considering to the energy consumed when pumping groundwater. This study analyzes the relationship between agricultural water consumption and energy consumption in the well irrigation areas of Hebei province. During the period of 1980–2015, irrigation efficiency increased while agricultural irrigation energy efficiency gradually decreased. In 1980, 0.8 m³ of water and 0.12 kWh of electric energy was required for irrigation to produce 1 kg grain, while in 2015, 0.4 m³ water and 0.45 kWh electric energy was required. This phenomenon is primarily attributed to the decline of the groundwater table leading to a necessary increase in energy consumption for pumping of groundwater. This study aimed to analyze the effect of saving both energy and water as well as the increase in energy consumption due to the decline in the groundwater table. The results show that 75.6 billion kWh of electrical energy was conserved due to water saving measures while the decline of groundwater table has resulted in an energy consumption increase of 174.4 billion kWh from 1986 to 2015. Which means the decline of groundwater table not only offset the effect of energy and water saving measures but also consumed an additional 98.8 billion kWh of electric energy. Moreover, the results show that since 1997, the quantity of irrigation energy saved through water saving measures has not been able to offset the increase in irrigation energy consumption caused by the decline in the groundwater table, and this difference is increasing. Finally, due to the decline in the groundwater table, irrigation energy consumption per unit water volume increases exponentially and the cost of irrigation energy consumption will become a factor that cannot be ignored. As irrigation water use efficiency cannot accurately reflect the regional water saving effect, this study suggests considering irrigation energy use efficiency (IEUE) from a water-energy nexus perspective. [ABSTRACT FROM AUTHOR]