Refined allocation of water resources is an important means of sustainable water resources utilization. Based on General Water Allocation and Simulation (GWAS), this study uses a Geographic Information System (GIS) to construct spatial topological relationships. A fairness optimal minimum was set as the objective function. Total quantity control, water supply potential, and quality-divided water supply were set as constraint conditions. Considering the dynamic mutual-feedback relationship between the middle-lower-reaches reservoir and the upstream reservoir, this study refines the allocation of water resources combined with the characteristics of “long cane knots melons” in the Pishihang irrigation area. Results showed that at 50%, 80%, and 90% frequencies in the base year, 2025, and 2035, respectively, the water deficient ratio is 0. For continuous drought years at 90% frequency, all water users are faced with different degrees of water shortage. In water source structures, water diversion in the irrigated area is the largest, followed by local surface water; reclaimed water and shallow groundwater are used as supplements. In the case of consecutive drought years, the water shortage degree can be reduced through rational development of local water and additional external water transfer. The model has thus been well applied. This study provides a more accurate method for optimizing water resources allocation.

The agricultural water price depends on the agricultural water price affordability (AWPA) in each region. This study found that the logarithmic linear model had the best fitting effect through evaluating the grey situation decision model, which considered factors such as rainfall and output value per unit area. The contribution of each influencing factor was determined by the Lindeman–Merenda–Gold method. We established a new model to determine the water expenditure coefficient (WEC) by improving the way that the value of the WEC is assigned. Then, the AWPA in different regions was calculated. The results showed that the WEC was between 2.62% and 12.95%, and the AWPA price was between 0.058 and 0.52 yuan/m³ (0.0084 and 0.075 $/m³). The contribution of precipitation and output was 45.20% and 25.60%, respectively. The WEC and AWPA in northeast, northwest, and northern China are higher than those in southwest and southern China. The AWPA in the Yellow River Basin was higher than that in the Yangtze River Basin; however, the space for adjustment in the Yellow River Basin was slightly smaller than that in the Yangtze River Basin.

As China attaches increasing importance to its ecological environment, ecology-related industries have become essential to China’s national economy. However, in the current national economic accounting practice, the ecological industry (eco-industry) is not independent, and the ecological service value ecology creates is currently not within the scope of national economic accounting. To clarify the impact of the development of the eco-industry on the whole regional economy, this paper takes Beijing as the study area. For the first time, the input–output analysis method is adopted to differentiate the eco-industry as an independent sector. Moreover, the ecosystem services value is integrated into the eco-industry, and each coefficient is quantitatively analyzed from an industrial-chain perspective. The results show that the eco-industry exerts a good pulling effect on the regional economy. The inputs and outputs of the eco-industry clearly tend to focus on eco-environmental and public-service-related industries, followed by industries for which ecological development can create value. Judging from the entire regional economy, ecological investment significantly impacts both the education and financial industries. Ecological investment can promote socio-economic development, achieving a 1.318 increase in regional GDP per unit of eco-investment. The results imply that the development of the eco-industry in China should be boosted further and social capital investment should be attracted. Finally, this paper provides a scientific basis for policymakers to better understand the overall situation of both the eco-industry and industry linkages and guide them to develop relevant ecological investment strategies.

Water conservation in agriculture is one of the key measures for alleviating the imbalance between water supply and demand, and a comprehensive assessment of the economic effects of agricultural water conservation is crucial for advancing the implementation of water conservation policies. Based on a traditional CGE model, this study incorporates “water resources” as an intermediate input and couples it with a mathematical model of water conservation costs to accurately reflect the relationship between the physical quantity of water resources and their economic value. The study establishes eight water conservation scenarios to simulate the impact of varying levels of water conservation on macroeconomic aggregates, water savings, and water conservation costs, and analyzes the marginal costs and marginal benefits under different conservation intensities. The results indicate that agricultural water saving can significantly improve economic water-use efficiency and drive macroeconomic growth through industrial linkage effects; nevertheless, the scale of reallocation of water saved from agriculture to non-agricultural sectors is limited. As water-saving intensity increases, the rate of change in economic output of each sector gradually rises and then stabilizes during 2022–2030. Among all sectors, the secondary sector exhibits the largest output change rate, ranging from 0.7% to 3.0%, while the tertiary sector shows the smallest change rate, varying from 0.4% to 1.7%. Under scenarios J1–J7, the marginal cost of water saving rises from 19.2 m³ per yuan to 52.1 m³ per yuan, and the marginal output decreases from 81.1 m³ per yuan to 6.8 m³ per yuan. The pattern of marginal cost–benefit follows general economic principles. The economically reasonable water-saving threshold occurs where marginal cost equals marginal benefit, corresponding to a water-saving volume of 8.2 × 10⁸ m³ and agricultural water withdrawal of 43.9 × 10⁸ m³. The research findings can serve as a reference for high-quality water-saving agricultural development in irrigation districts of arid and semi-arid regions.