# Dynamic Evaluation and Internal Driving Factors of Water Resources Green Efficiency in China
## 3 Materials and Methods
### Total Factor Productivity Index Model
#### 3.3.3 Unexpected Output Indicators and Disposability Analysis  
Based on the definition of the essence of green efficiency of water resources and the setting of the input index, this study divides the unexpected output index into water pollution emissions and carbon emissions. Water pollution emission includes agricultural non-point source pollution, industrial and domestic wastewater discharge. Agricultural non-point source pollution was estimated by means of unit investigation and evaluation method [55]. The coefficients of fertilizer application in farmland and livestock and poultry breeding were separately consulted from the handbook of fertilizer loss coefficient for agricultural pollution sources and the handbook of pollution discharging coefficient for aquaculture published in the first national pollution source survey. The coefficient of rural life and farmland solid waste refered to the practice of [PERSON] et al. [55]. The total carbon emissions were calculated by using the research method of [PERSON] [56] based on fossil energy consumption. Due to space limitations, the detailed calculation method will not be repeated here. Due to the differences in the characteristics of the unexpected output, this article analyzes the disposability of the unexpected output of the water resources green efficiency from the perspectives of pollution characteristics, treatment costs, and environmental regulations. (1) Disposability analysis of agricultural non-point source pollution:  
(a) Characteristics of agricultural non-point source pollution. Agricultural non-point source pollution in China has a single type, which mainly includes Chemical Oxygen Demand (COD), Total Nitrogen (TN) and Total Phosphorus (TP), the main cause of these pollution is agricultural inputs. Some scholars pointed out that China's reduction in agricultural non-point source pollution emissions can increase crop yields to a certain extent [57]. (b) Treatment cost of agricultural non-point source pollution. The existing experience and policy incentives show that agricultural non-point source pollution control has strong economic feasibility, such as biogas power grid, straw biomass power plants can bring certain economic benefits, which is inconsistent with the economic significance of weak disposability of unexpected output. (c) Regulations on agricultural non-point source pollution. Due to the late formulation and implementation of rural environmental policies in China, it is difficult to adapt to agricultural non-point source pollution with randomness, concealment and dispersion in a short time, resulting in the failure of environmental regulation on agricultural non-point source pollution, temporarily difficult to convert to weak disposability. Therefore, China's agricultural non-point source pollution is highly disposable. (2) Disposability analysis of wastewater discharge:  
(a) Wastewater discharge characteristics. Industrial production and residents' lives lead to wastewater discharge, but when the wastewater treatment technology and hardware construction do not meet the requirements of wastewater discharge, reducing the total amount of wastewaterdischarge will affect the industrial output value and the living quality of residents. (b) Treatment cost of wastewater. Wastewater discharge is polluted water produced at the end of production and through life, and treatment leads to increased costs. China has encouraged the use of reclaimed water as a substitute for water that is not in direct contact with the human body at the policy level, and has implemented it in some seriously water-scarce cities and high-water-consuming industries. However, there are still some limitations in the construction and operation of reclaimed water recovery systems, due to the large investment in the early stage and the imperfect urban infrastructure. (c) Environmental regulations for wastewater discharge. The impact of environmental regulation on economic development in China is uncertain.