We are facing the water shortage crisis. To realise sustainable development, we should improve water-use efficiency (WUE). In this study, a cloud-compound fuzzy matter element-entropy combined model was constructed to evaluate WUE. The Huai river basin (HRB) was selected as the study area. The cloud model was used to select some indices and build the comprehensive evaluation index system (CEIS), which included the overall, agricultural, industrial, domestic and environmental categories. The compound fuzzy matter element model was used to calculate the comprehensive indicators of WUE of the HRB and its regions. The weight of each index in the CEIS was determined using the entropy model. The results showed that WUE of the HRB had an upward trend on the whole because of the enhanced emphasis on water resources by the international and national governments. However, the regional difference was obvious. The WUE of Henan province was higher than that of Jiangsu province. The imbalance of regional WUE is an international problem. By analysing the difference among regions, research can provide a reference for the decision making of the water resources management department.

As an important water conservancy project, it is necessary to evaluate its water supply benefit. Based on the emergy analysis theory, a reservoir water supply benefits evaluation model (RWSBEM) was established. Firstly, the emergy transformity of natural and engineering water body was calculated. Secondly, the water resource values (WRV) of different water users (industrial, agricultural, domestic, ecological) were calculated. Finally, combined with the water supply situation of the reservoir, the various water supply benefits of the reservoir were calculated. Taking Hekoucun reservoir as an example, its ecological water supply benefit is the largest and agriculture is the smallest, followed by industry and life. The results showed that the trend of WRV was domestic > industry > ecology > agriculture, which reflected the contribution and utility of water resources in different industries. Under the condition of current water resources, the planned water supply benefits of the reservoir can be guaranteed in the wet and normal years, but in the dry years, the ecological benefit will be reduced. Therefore, the industry water-saving needs to be further strengthened, and the interannual regulation function of the reservoir should be applied more effectively to maximize the comprehensive benefits of reservoir water supply.