*4.3. Analysis of Regional Pollutant Emissions*

Figures 10–12 show COD, NH3-N, and Tp emissions from the industrial, municipal, and agricultural sectors, respectively. The discharge of pollutants does not exceed the maximum permissible discharge concentration of pollutants in freshwater waters of "the Liaoning Provincial Water Pollutant Discharge Standards for Coastal Areas", in addition, the discharge of various pollutants does not exceed the regional water environment capacity. Under the condition of implementing the optimal water resource allocation scheme coupled with ecological value factors, the emission of all kinds of pollutants in all sectors presented a downward trend over time. For the industrial sector, in region Wafangdian, the COD emissions were 502.10, 464.10, and 367.45 tons/year, NH3-N emissions were 78.48, 71.4, and 54.6 tons/year, and Tp emissions were 37.10, 33.56, and 26.17 tons/year in the three periods, respectively. For the municipal sector, COD emissions were: 1888.43, 1745.54, and 1382.01 tons/year, NH3-N emissions were 254.43, 231.49, and 177.00 tons/year, and Tp emissions were 54.27, 49.10, and 38.29 tons/year in the three periods, respectively. For the agriculture sector, COD emissions were 14,549.27, 13,448.37, and 10,647.61 tons/year, NH3-N emissions were 1217.00, 1107.25, and 846.64 tons/year, and Tp emissions were 326.32, 295.21, and 230.23 tons/year in the three periods. This is in line with the objectives of China's 14th Five-Year Plan, which states that "by 2035, the total emissions of major pollutants will continue to be reduced, the efficiency of resource use will be significantly improved, and the first demonstration zone of a beautiful China will be basically built". However, Tp emissions increased slightly in some areas. For example, in region Four Districts, Tp emissions of the municipal sector were 458.09, 470.13, and 504.49 tons/year in the three periods, respectively. This may be because the domestic sewage collection and centralized treatment system were not perfect. Therefore, improving the domestic sewage centralized collection and treatment system will not only reduce the discharge of pollutants but also solve the water shortage problem. In regions Four Districts and

Lvshunkou with high population density, the pollutants were mainly from the municipal sector, while the pollutants from the agricultural sector were relatively high in other regions. In some regions, the industrial sector consumed more water than the agricultural sector, but the sewage discharge was lower, which may be because the industrial sewage collection and treatment network is relatively perfect, and the sewage is generally discharged or reused after treatment.

**Figure 10.** Chemical oxygen demand (COD) emissions of various sectors: (**a**) industry; (**b**) municipal; (**c**) agriculture (tons/year).

**Figure 11.** NH3-N emissions of various sectors: (**a**) industry; (**b**) municipal; (**c**) agriculture (tons/year).

**Figure 12.** Tp emissions of various sectors: (**a**) industry; (**b**) municipal; (**c**) agriculture (tons/year).

#### **5. Conclusions**

This study established an inexact two-stage stochastic programming (ITSP) model of optimal allocation of water resources that couples water ecological value factors under uncertain conditions. This model is mainly to forecast and optimize the long-term prospects of Dalian, which is a typical water shortage in China. By integrating IPP and TSP methods, the model can manage uncertainties in interval values and probability distributions. By solving the ITSP model, on the premise of protecting the ecological value, the optimal allocation of water resources under different conditions to different water sectors and three periods was determined. In addition, data were also obtained on the lack of an aquatic ecosystem acreage, value of ecosystem service and the discharge of major water pollutants in various administrative regions. These results are constrained by the available water resources and provide the basis for the optimize the allocation of water resources and water quality management in Dalian. In addition, optimal allocation of water resources can improve the discharge of water pollutants in various administrative regions. The model results can be used to guide various departments in Dalian to formulate an optimal water resources allocation scheme by considering ecological value factors. The study findings provide the basis and support for Dalian to achieve the social and economic development goals, use water resources efficiently, and improve ecosystem quality through the optimized allocation of water resources.

The purpose of this research was to establish an ITSP model to create a water resources management system in Dalian that combines ecological value factors with the optimal allocation of water resources, so as to realize the coordinated development of social economic benefits and ecological benefits, and conducive to the synergistic efficiency of socio-economic and ecological water consumption, and it can also be applied to other regions with water shortages. Although the ITSP model can provide optimal preset schedules and adjustments under different scenarios, it cannot measure decision-making risks, nor does it assess the impact of different water sources and climate change on the availability of water resources. Therefore, there is still considerable room for improvement.

**Author Contributions:** Methodology, J.Z.; software, J.Z.; validation, J.Z. and C.M.; data curation, J.Z.; writing—original draft preparation, J.Z.; writing—review and editing, J.Z., C.M., S.H. and W.L.; project administration, S.H.; funding acquisition, W.L. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the Natural Science Foundation of China, grant number 72050001.

**Conflicts of Interest:** The authors declare no conflict of interest.
