In the perennial river, environmental base flow, associated with environmental flow, is the base flow that should be maintained within the river channel throughout the year, especially in the dry season, to sustain basic ecosystem functions and prevent the shrinkage or discontinuity of a river. The functions of environmental base flow include eco-environmental functions, natural functions, and social functions. In this study, we provided a method based on these functions; this method estimated the function values per unit area, introduced the scarcity coefficient, multiplied by the corresponding water area, and summed over to quantify the value of environmental base flow from 1973 to 2015 in the Wei River Basin, the largest tributary of the Yellow River in Northwest China. We observed that there was a positive correlation between the total value of environmental base flow and its water yield, whereas this outcome was completely different in the benefit per unit discharge of environmental base flow, which was closely associated with the shortage of environmental base flow. This method can thus present the considerable value of environmental base flow in monetary terms in a simple and effective way and lay the foundation for further reasonable protection levels of environmental base flow.

The rational allocation of ecological and economic water is a topic of high interest for water resource sciences. Taking into consideration the difficulties to maintain the basic ecologic functions of rivers, we propose a calculation model for compensation for agricultural economic losses by restoration of the healthy eco-hydrological sequences of rivers. Firstly, healthy eco-hydrological sequence of rivers was constructed by assessing the response relationship between hydrological processes and ecological functions of ecological base flow of rivers. Following, the ecological water shortage was analyzed qualitatively and quantitatively. Finally, the compensation for agricultural economic losses caused by restoration of healthy eco-hydrological sequence of rivers was calculated. Taking the Baoji section of the Weihe River as a case study, compensation for agricultural economic losses caused by the recovery of the healthy eco-hydrological sequence of rivers were calculated and further analyzed. The results show that the current water diversion in the area of study is excessive and the ecological water shortage is relatively obvious. The compensation for agricultural economic losses caused by the recovery of healthy eco-hydrological sequence of rivers mainly focus on the non-flood season, which is up to 218 million yuan for 2009 year.

Scientific and accurate assessments of the economic value produced by environmental flows are an important basis for the protection of environmental flows by means of economics. Because of the temporal and spatial variation characteristics of environmental flows, it is more appropriate to study the economic value produced by environmental flows using a temporal–spatial scale rather than static calculations. In the present study, we combine the major influencing factors to establish the temporal–spatial calculation methods of the economic value produced by environmental flows using the assessment techniques of resources and environmental economics. The results obtained for the Wei River show that the annual variation range of the total economic value is CNY 0.30–0.42 billion, and the unit economic value is 0.86–6.40 CNY/m³ during the non-flood season ranging from the years 1980 to 2017. In general, the monthly variation in the total economic value ranges from CNY 0.04 to 0.08 billion, and the unit economic value is 0.94–14.34 CNY/m³. Based on this result, the variation tendency of the total economic value is consistent with the changing trend of the environmental flows occurring in the river; however, the unit economic value presents a reverse pattern. Furthermore, the deficiency of environmental flows can lead to a significant increase in its unit economic value. This method presents a dynamic, small temporal–spatial scale assessment of the economic value produced by environmental flows. It can also provide theoretical support for the ecological compensation of environmental flow protection in rivers present in water shortage areas.