To achieve the global temperature control target under the background of climate warming, it is necessary to establish a systematic carbon dioxide (CO₂) emission accounting method system in the field of water resources as soon as possible. In this study, the carbon dioxide emission equivalent analysis (CEEA) method for different water resource behaviors (WRBs) is proposed from four dimensions of development, allocation, utilization, and protection, and a function table of CEEA (FT-CEEA) for WRBs is constructed. The FT-CEEA includes CEEA formulae for 16 aspects in four categories of water resource development, allocation, utilization, and protection. The CEEA method is applied to 31 provinces in China. The results reveal that: (1) There are significant spatial differences in the carbon dioxide emission equivalent (CEE) of WRBs in different provinces of China under the influence of various factors such as water supply structure and natural conditions. (2) Reservoir storage, tap water allocation, and wastewater treatment are the main contributors to CEE in the categories of water resource development, allocation, and protection behaviors, respectively. (3) The water resource utilization behavior category has the most significant CO₂ emission and absorption effects, and industrial and domestic water utilization behaviors are the main sources of emission effects. (4) The overall CO₂ emission effect of WRBs is greater than the absorption effect. Measures such as increasing the proportion of hydroelectric power generation, improving ecological water security capacity, and strengthening the level of wastewater treatment and reclaimed water reuse are effective ways to promote the goal of carbon neutrality in the field of water resources.

Green and high-efficiency water resource utilization patterns hold paramount importance in promoting sustainable economic and social development, as well as in attaining the goal of carbon neutrality. Most research on water utilization efficiency have taken a general perspective to quantify it, neglecting independent relationships and green effects among water use sectors. This study proposed an integrated measurement model of green water resource utilization efficiency (GWRUE), combined with the carbon dioxide emission equivalent analysis method of water resource behaviors, and constructed an input–output indicator system of GWRUE from four dimensions: domestic, industrial, agricultural, and ecological water. The aim is to achieve the measurement of GWRUE towards carbon neutrality. In this paper, 18 cities in Henan Province were used as instances to carry out the study. The results show that (1) The CO₂ emission equivalent from multiple water use sectors in Henan Province showed a tendency of fluctuating reduction during the study period, from a peak of 21,090,100 tons in 2012 to a low of 12,351,900 tons in 2021, with large spatial variations, and the CO₂ emission effect existed in most cities, with Zhengzhou being the highest. (2) The GWRUE of domestic, industrial, and agricultural water in Henan Province and 18 cities exhibited an overall upward trend, while that of ecological water presented a downward trend and was at the lowest level among the four sectors. (3) Consolidated GWRUE in Henan Province tended to decrease and then increase; its value was 0.512 in 2011, 0.448 in 2017, and 0.586 in 2021, and most of its cities were at a Medium level. The findings of this study can serve as a theoretical and practical basis for improving the level of green and efficient utilization of water resources, as well as offer references for relevant water use sectors to formulate CO₂ emission reduction policies.