Emergy evaluation of a pumping irrigation water production system in China

The emergy concept was used to evaluate a pumping irrigation water production system in China.A framework for emergy evaluation of the significance of irrigation water and its production process was developed.The results show that the irrigation water saved has the highest emergy value(8.73E+05 sej$J–1),followed by the irrigation water supplied to farmlands(1.72E+05 sej$J–1),the pumped water(4.81E+04 sej$J–1),with the lowest value shown from water taken from the local river(3.72E+04 sej$J–1).The major contributions to the emergy needed for production are the inputs of soil and water.This production system could contribute to the irrigated agriculture and economy,according to several calculated emergy indices:emergy yield ratio(EYR),emergy investment ratio(EIR),environmental load ratio(ELR),and environmental sustainability index(ESI).The comparative analysis shows that the emergy theory and method,different from the conventional monetary-based analysis,could be used to evaluate irrigation water and its production process in terms of the biophysical account.Additional emergy evaluations should be completed on different types of water production and irrigated agricultural systems to provide adequate guidelines for the sustainability of irrigation development.