The North China Plain (NCP) is the largest groundwater irrigation area in China, with about 6.5 million hectares of cultivated land and more than 1 million irrigation wells. Totally there are about 20 billion m3 of groundwater that pumped for irrigation each year. The exploitation of groundwater in NCP leads to the continuous decrease of groundwater level. The average depth of groundwater is more than 20 m, and the deepest groundwater level is 100m beneath the ground surface. As the groundwater level is low, the energy use for pumping in NCP is huge, which leads to high carbon emission. This paper reveals the nexus of water-energy in NCP based on the experiments of agricultural irrigation wells. The volume of the pumped water and the energy is measured, and the correlations between the water and energy are established for irrigation wells of different depth. Based on the groundwater level of NCP and the location of irrigation wells, the total energy use for agricultural pumping is calculated. As a comparative study, this paper calculates the potential benefit of CO2 emission reduction, assuming the groundwater is pumped by a photovoltaic system instead of the state power grid. The results show that the photovoltaic pumping system can reduce CO2 emission by 1.87 million ton/year, comparing to the state power grid. The surplus electricity could replace thermal power and bring additional 2.67 million ton of emission reduction benefit per year.
Keywords nexus of water-energy, photovoltaic pumping, emission reduction, groundwater irrigation, North China Plain