Integrating supply and beneficiaries into assessing the benefit of water purification service: a spatial flow perspective

Water purification service (WPS) helps to provide clean water to human wellbeing, which is a key factor for sustainability of water ecosystem. The supply-demand relationship of WPS has been widely discussed, but there still lacks a full chain analysis from its supply to benefit, making it hard to reflect WPS’s actual contribution to human society, and cannot guide the landscape management effectively.

This paper aimed to (1) reveal the full chain from supply to benefit of WPS from a spatial flow perspective; (2) propose differentiated landscape management strategies for optimizing the benefit of WPS in the Taihu Lake basin.

Taking Taihu Lake Basin as study area, this study proposed a framework of the benefit of WPS integrating supply and beneficiaries from the perspective of spatial flow. The supply of WPS was simulated using InVEST model, and the beneficiaries including local and downstream residents were identified based on hydrological path analysis. Finally, the benefit of WPS was assessed by the product of supply and beneficiaries.

The supply of WPS decreased from 5.55 × 10⁷ kg to 4.55 × 10⁷ kg during 2000–2020, with a decrease rate of 17.97%. The amount of beneficiaries, however, increased from 2.69 × 10⁹ person to 3.90 × 10⁹ person, increasing by 45.19%. The benefits of WPS showed a 25.35% increase from 2000 to 2020 in the Taihu Lake Basin, which resulted from the increase of beneficiaries rather than the supply, and was an unsustainable state. The upstream beneficiaries of WPS would be underestimated if the spatial flow was neglected, and a considerable difference exists between ‘potential’ and ‘actual’ benefit of WPS. Finally, based on supply, beneficiaries and benefit, Taihu Lake Basin was divided into eight sub-basins and corresponding governance suggestions were proposed for the improvement of WPS.

This study clarified the entire chain of WPS from its generation from ecosystem to meeting the demand of human society, and then incorporated the supply and beneficiaries into benefit assessment. It deepened the studies of ecosystem services from supply-demand relationship to the supply-to-benefit process, which provided a new insight for landscape sustainability science.