Quantitative Analysis of Eco-economic Benefits of Urban Reclaimed Water Greening Based on Emergy Theory

Abstract

With an increased rate of urbanization and people’s interest in high-quality natural environments, urban green spaces are receiving increased attention. However, urban green spaces irrigation increases tap water consumption, wasting high-quality water. Using reclaimed water for irrigation can not only maintain the normal ecological and landscape functions of green spaces but also save water resources. The eco-economic benefits of using reclaimed water as irrigation water were evaluated in this paper. The composition of benefits was analysed, and a new quantitative method was proposed based on the emergy theory. This proposed method was used to calculate the costs of different irrigation water, the other use benefits of the saved tap water, and the benefits of scientific research, leisure and entertainment, carbon fixation and oxygen release, biodiversity protection, soil conservation and air purification. Taking Zhengzhou in 2018 as an example, the results showed that the cost of using reclaimed water to irrigate urban green spaces was 46% of the cost of using tap water. The total benefit of using reclaimed water to irrigate green spaces was $4.05 billion, which was three times the benefit of using tap water. The net benefit of using reclaimed water was $2.00 billion, while that of tap water was negative. Therefore, the advantages of using reclaimed water to irrigate urban green spaces are the low costs and high eco-economic benefits. The method proposed in this paper provides a quantitative basis for using reclaimed water to irrigate urban green spaces in cities with water shortages.