# Study of the Dynamic Adaptive Calculation Method for River Water Environmental Capacity
## 3 Methodology  
### Problems with Traditional Methods  
Most of the research on WEC calculation focuses on the establishment of calculation models, influencing factors, analysis and determination of model parameters, and solution methods of algorithms. However, the model is difficult to adapt to changing environmental conditions, and rarely considers the impact of human activities, which makes the calculation results mostly stay in the simulation stage and difficult to apply to practice. In addition, most of the current research is under static conditions, and the research results under \begin{table}
\begin{tabular}{c c c c} \hline \hline
**ID** & **Functional Area Name** & **Length/km** & **Water Quality Target** \\ \hline
1 & Gansu and Shaanxi buffer zone & 72.4 & II \\
2 & Baoji agricultural water area & 43.9 & III \\
3 & Baoji City landscape area & 20 & III \\
4 & Baoji sewage control area & 12 & IV \\
5 & Baoji City transition zone & 22 & IV \\
6 & Baomei agricultural water area & 44 & III \\
7 & Yangling agricultural water use area & 16 & III \\
8 & Xianyang industrial water area & 63 & IV \\
9 & Xianyang landscape water use area & 3.8 & IV \\
10 & Xianyang sewage control area & 5.4 & IV \\
11 & Xianyang Xi’an transition area & 19 & IV \\
12 & Lintong agricultural water use area & 56.4 & IV \\
13 & Weinan agricultural water use area & 96.8 & IV \\
14 & Huayin enters yellow buffer zone & 29.7 & IV \\ \hline \hline \end{tabular} Note: Water quality classification standards according to “Surface Water Environmental Quality Standards” [37].  
\end{table} 
Table 1: Water function zoning and water quality target of Shaanxi section of Wei River. Figure 1: Overview of Shaanxi section of Wei River Basin. fixed conditions are mostly used to formulate plans, while the WEC will be affected by various factors in time and space, which is a dynamic process. Static and planned management schemes are difficult to cope with complex and changing environments and needs. After in-depth analysis, it was found that the traditional WEC calculation has the following problems:  
1. Limitations of traditional methods. Due to the differences in understanding of the definition of WEC, the differences in water quality models, the differences in simplification, and the different requirements for water quality standards, the WEC calculation method has different expressions, and its calculation demands, accuracy, and applicability are different. For different watersheds, based on the generalized conditions of each model expression, select and apply appropriate calculation formulas. The limitations of the WEC calculation method is significant. 2. Inability to adapt to changes in development. WEC is proposed based on the management of water function areas. It is not only related to the natural attributes of water bodies and pollutants, but also includes social attributes such as human needs for water body functions. Both natural and social attributes are dynamic. Factors, such as changes in spatial-temporal scale, changes in design frequencies, changes in functional requirements, and changes in calculation methods, all determine that WEC is a dynamically changing quantity. The traditional WEC calculation is static, making it difficult to accurately quantify the WEC. 3. The operability is not strong. The traditional method is mostly aimed at a specific research basin, a specific time scale, and a specific hydrological condition. Some deterministic models and parameters are used to calculate the WEC. When the basin, hydrological conditions, or pollutants change, the calculation results under fixed conditions cannot cope with the changing environment and needs, and the operability is not strong. 4. Parameter determination shows a lack of adaptability. The parameter determination of the traditional method lacks the basis, which cannot reflect the hydrological characteristics of the river and the dynamic characteristics of other natural factors, resulting in a lack of accuracy and applicability in the calculation results of WEC.