Comparing volumetric and impact-oriented water footprint indicators: Case study of agricultural production in Lake Dianchi Basin, China

Water Footprint (WF) assessment provides a basis for quantitative description and evaluation of water consumption and degradation related to human activities. Several different WF methods have been developed, which can be broadly divided into volumetric and impact-oriented approaches. The former, coming from the discipline of water resources management, has mainly focused on water resource consumption. The latter, coming from the discipline of life cycle assessment, has generally considered a wider range of environmental impacts associated with water use, including water degradation. The purpose of this paper was to investigate water use in agricultural production in the environmentally sensitive Lake Dianchi Basin. It was found that WF results had different tendencies depending on the WF assessment method chosen. From 2001–2012, volumetric WF results (20570 ∼ 75838 L kg⁻¹) showed an upward tendency, whereas impact-oriented WF results (1069 ∼ 1453 L H₂O-eq kg⁻¹) declined modestly over this period. In the Lake Dianchi Basin, the agricultural water degradation footprint (1047.2 ∼ 1410.9 L H₂O-eq kg⁻¹) far outweighed the water scarcity footprint (21.8 ∼ 45.6 L H₂O-eq kg⁻¹). There has been a history of agricultural production placing a heavy burden on the quality of catchment water resources. In particular, fertilizers applied to wheat crops contribute to aquatic eutrophication. Wheat cultivation contributed most to the agricultural WF in the Lake Dianchi Basin, followed by tobacco, pulses, and then other cereals. Reductions, over time, in the impact-oriented agricultural WF were explained by reductions in total fertilizer application in the basin, despite increased use of irrigation in some years. These results highlight the importance of considering both water consumption and degradation in a complete WF assessment. Further improvements in fertilizer use efficiency and waste water treatment are identified as priorities in the Lake Dianchi Basin to safeguard water resources.