Water Environmental Capacity Calculation Research Articles

New framework for managing the water environmental capacity integrating the watershed model and stochastic algorithm

Integrated calculations of pollution load and water environmental capacity (WEC) are essential for effective water quality management. However, few studies have focused on the dynamic WEC and pollution load in a nonpoint source pollution (NPS)-dominant temperate monsoon watershed under changing rainfall conditions. In this study, a new framework based on the watershed model and WEC calculation with stochastic rainfall input (SR-WEC), was proposed to reveal the dynamic WEC and pollution load under changing rainfall conditions. Stochastic rainfall series was generated by a first-order Markov chain and gamma distribution, and further input into the Soil and Water Assessment Tool (SWAT) to explore the dynamic response of water quality to rainfall. The framework was applied to the Daning River watershed, Three Georges Reservoir Region, China. The results suggested that compared with the new SR-WEC, the traditional return period method with limited observed rainfall input would result in an underestimation of ideal WEC and NPS pollution load by 23% and 48% for TN and 48% and 51% for TP, respectively. Approximately 46% of the annual TN reduction and 51% of the annual TP reduction were concentrated from April to June in a relatively small area. The regression relationships between rainfall and the ideal WEC, pollution load and remnant WEC obtained by the SR-WEC were superior to those of the traditional method, with R2 values increasing from 0.005–0.797 to 0.718–0.989. Specific threshold (120 mm/month for the study area) was observed for the effect of rainfall on water quality, beyond which the remnant WEC of organic N would change from decreasing to increasing. The new framework proposed identifies the key periods and areas with consideration of uncertainty of rainfall on water quality, and provides basis for NPS pollution management.

Water Environmental Capacity Calculation Based on Control of Contamination Zone for Water Environment Functional Zones in Jiangsu Section of Yangtze River, China

In recent years, due to unsustainable production methods and the demands of daily life, the water quality of the Yangtze River has deteriorated. In response to Yangtze River protection policy, and to protect and restore the ecological environment of the river, a two-dimensional model of the Jiangsu section was established to study the water environmental capacity (WEC) of 90 water environment functional zones. The WEC of the river in each city was calculated based on the results of the water environment functional zones. The results indicated that the total WECs of the study area for chemical oxygen demand (COD), ammonia nitrogen (NH3-N), and total phosphorus (TP) were 251,198 t/year, 24,751 t/year, and 3251 t/year, respectively. Among the eight cities studied, Nanjing accounted for the largest proportion (25%) of pollutants discharged into the Yangtze River; Suzhou (11%) and Zhenjiang (12%) followed, and Wuxi contributed the least (0.4%). The results may help the government to control the discharge of pollutants by enterprises and sewage treatment plants, which would improve the water environment and effectively maintain the water ecological function. This research on the WEC of the Yangtze River may serve as a basis for pollution control and water quality management, and exemplifies WEC calculations of the world’s largest rivers.

Calculation of water environmental capacity of Puzhehei Lake

The calculation of water environmental capacity of Puzhehei lake is of great significance for preventing water pollution and protecting water ecological environment of Puzhehei Lake Basin. Based on the lack of hydrological and water quality data in Puzhehei Lake Basin, a large number of basic data were collected through pollution source investigation and water quality monitoring. On this basis, a twodimensional hydrodynamic water quality model of Puzhehei lake was established by using Mike21 model to simulate the migration and diffusion of pollutants into the lake. The current situation of pollution load in Puzhehei lake was analyzed, and the characteristics of water flow, hydrodynamic force and the migration and diffusion law of pollutants in Puzhehei Lake were analyzed. The results show that: ①the annual loads of COD, TN, TP and NH3-N in puzhehai Lake in 2018 are 4090.0t, 401.3t, 34.4t and 122.6t; ②Puzhehei lake is mainly non-point source pollution, and the difference of water environmental capacity between non rainy season and rainy season is very significant.

Calculation of water environmental capacity of large shallow lakes – a case study of Taihu Lake

Abstract Lake currents have an important impact on distribution of pollutant concentrations in large shallow lakes. Taking Taihu Lake as an example, in view of the characteristics of wind-driven water flow in the lake, this paper puts forward a water environmental capacity calculation method that uses wind direction and wind speed combined frequency to provide joint correction and pollution zone control for the designed hydrological conditions. In the study, the total length of the pollution belt was controlled to be 10% of the length of the study area, and a mathematical model of two-dimensional unsteady water quantity and quality in Taihu Lake was established. By analyzing the hydrological water quality characteristics and measured data of Taihu Lake in recent years, the flow field and concentration field were simulated and verified, the mathematical model and the plausibility of the parameters were calibrated. The water environmental capacity of Taihu Lake basin was calculated by this method. The calculated results showed that the water environmental capacity of chemical oxygen demand (COD), total phosphorus (TP), and total nitrogen (TN) in Taihu Lake were 113,331 t·a−1, 479 t·a−1 and 6,521 t·a−1. By providing a technical basis for total pollutant control and management in Taihu Lake basin, this study is conducive to the planning and management of water environment.

Water Environmental Capacity Calculation and Allocation of the Taihu Lake Basin in Jiangsu Province Based on Control Unit.

The water quality target management of the control unit is a convenient and direct technology for water environment management and the development direction of water environment management in China, involving control unit division and water environment capacity calculation. Taking the Taihu Lake Basin in Jiangsu Province as an example, we propose herein the basic principle of the division of a regional control unit in a plain river network and the method of analyzing the rationality of the control unit division. On this basis, the Taihu Lake Basin in Jiangsu Province was divided into 70 control units. To calculate the water environmental capacity in the plain river network area, we established a water environmental capacity calculation framework based on multiple targets of lakes and rivers, and proposed the goal of water quality “double compliance” of the water environmental functional zone and the assessment section. For this study, we calculated the regional water environmental capacity using the mathematical model of the Taihu Lake Basin’s water environmental capacity, and the water environmental capacities of the 70 control units were allocated by the weight coefficient method, which established water area and functional division length. The research results described herein were applied to the pollution permit management of the Taihu Lake Basin in Jiangsu Province. It provides important technical support for the establishment of a pollution permit system based on the total capacity to improve environmental quality.

A Review of Water Environmental Capacity Calculation

Water environmental capacity is an essential component of water environmental assessment and must be monitored and managed for economic, engineering, and human health reasons. Many efforts have been made to study methods for the calculation of water environmental capacity. This paper reviews available literature on water environmental capacity. The evolutionary history and application scenarios of major water quality models, and water environmental capacity calculation formulas are summarized. Through the analysis of calculation formulas for water environmental capacity, it is found that endogenous pollution factors influence the values of degradation coefficient K and retention coefficient R in water environmental capacity calculation though few studies consider such factors. Therefore, the quantification of endogenous pollution factors (particularly the rheological properties of bed sediments) is important and needs further study.

Calculation of water environmental capacity and pollutant sharing rate with water diversion: a case study of Qinhuai River

Abstract With an overall consideration of hydrology, water quality and pollution sources, and the pollution source area, which affect the water quality, the Qinhuai River basin has been simplified as a control unit. Based on the establishment of the control unit water environmental model, the most unfavorable hydrological condition has been set up. The model comprehensively considers the effects of boundary water quality and the response relationship between the water quality of a cross-section and the general population. The allowable discharge of each generalization outfall can be calculated by the response relationship, and the chemical oxygen demand (COD), NH3-N, and total phosphorus (TP) water environment capacity of the control unit can be obtained. As shown in the results: in the near future (2017–2019) with 35% sewage interception and 30 m3/s water diversion; in the long term (after 2020) with 82% sewage interception, the water quality can reach the standard. Combined with the measured calculation, the paper also has made a quantitative analysis of the sharing rate of the main tributary and sewage pump station pollutant flux in the control unit and the whole basin within the administrative district.

Calculation of Water Environmental Capacity in the Lower Reaches of the Lancang River Basin

The deterioration of water quality in the lower reaches of the Lancang River basin has attracted worldwide attention. Reasonable estimation of water environmental capacity (WEC) can effective implement the prevention and control of water pollution in the lower reaches of Lancang River basin. However, research on WEC was scarce in the Lancang River basin. In this study, a two-dimensional water quality model was established to calculate the WEC in the Jinghong-Guanlei segment located at the downstream of the Lancang River basin. The WEC of CODCr in the Jinghong-Guanlei segment with different design flow rates (90%, 75% and 50% hydrological guarantee flow rate) are 2.83, 3.05 and 3.32 million tons/year, respectively. Design flow rate plays an important role in the calculating the WEC in the lower reaches of the Lancang River basin. Influence of cascade dams operation on flow rate is minor. Therefore, cascade dams operation will not have a greater impact on the WEC of CODCr in the lower reaches of the Lancang River basin. The current water quality in the segment is fairly good. However, under the couple effects of climate change and cascade dams operations, there is an increasing trend of CODCr concentrations in the lower reaches of the Lancang River basin. Therefore, water quality monitoring and water pollution controlling should be strengthened in the long run. Research results will provide scientific basis for decision-making and implementation of regional water pollution control measures.

An Integrated Method for Accounting for Water Environmental Capacity of the River–Reservoir Combination System

The security of drinking water is a serious issue in China and worldwide. As the backup source of drinking water for the Changde City in China, the Huangshi Reservoir suffers from the threat of eutrophication due to the water quality of the reservoir ecosystem being affected by the tributaries that carry Non-Point Source (NPS) pollutants. The calculation of the water environmental capacity (WEC) can provide a scientific basis for water pollution control, which refers to the maximum amount of pollutants that the water can accommodate. In this paper, according to the hydrological characteristics of the river–reservoir combination system, a one-dimensional (1-D) water quality model and the Environmental Fluid Dynamics Code (EFDC) model were chosen to calculate the water environmental capacity of each functional zone in this basin. The quantity control of pollution from the tributaries was conducted based on the combined results of the water environmental capacity calculation from the EFDC model and a one-dimensional (1-D) river water quality model. The results show that total water environmental capacity of the tributaries included a chemical oxygen demand (COD) of 421.97 tons; ammonia nitrogen (NH3-N) of 40.99 tons; total nitrogen (TN) of 35.94 tons; and total phosphorus (TP) of 9.54 tons. The water environmental capacity of the Huangshi Reservoir region accounts for more than 93% of the total capacity. The reduction targets of the major pollutants in the Huangshi Reservoir and its four major input rivers, which are, namely, the Bamao River, the Longtan River, the Fanjiafang River, and the Dongtan River, have been determined to achieve the water quality objectives for the reservoir in 2020 and 2025. The results will be helpful for the local water quality management and will provide a valuable example for other similar water source reservoirs.

Uncertainty analyses on the calculation of water environmental capacity by an innovative holistic method and its application to the Dongjiang River

The estimation and allocation of water environmental capacity (WEC) are essential to water quality management and social–economic interests. However, there is inevitable uncertainty in the capacity estimation due to model conceptualization, data collection and parameter calibration. An innovative holistic approach was developed, which took both independence and relevance between parameters into account to analyze the uncertainties in WEC calculation and estimate the margin of safety. The Dongjiang River was taken as the case to demonstrate the method, focusing on the chemical oxygen demand and NH4+–N that were the two major water quality problems in the river. The results showed that the proposed holistic approach is very promising and applicable compared to traditional methods of uncertainty analysis.

Calculation of Water Environmental Capacity for a Eutrophicated Reservoir

This paper analyzed the concept of water environmental capacity and the relation between water environmental capacity and control of reservoir eutrophication. A method, which is based on evaluating the water quality status and variation characteristics of the reservoir, to calculate the water environmental capacity of eutrophicated reservoir was put forward. Taking Shizitan Reservoir as an example, the water environmental capacity for TN, TP and COD of this eutrophicated reservoir in China were calculated by the method. A method, which could be used in the areas of short of data, to determine the retention coefficients of TN and TP was put forward in this case. In addition, the pollution gross control of the reservoir was analyzed according to the water environmental capacity and the pollutants discharged into the reservoir. The results show that the methods which were put forward in this study could be used to calculate the water environmental capacity of eutrophicated reservoirs, and this study could provide scientific support to the water environmental management.

Water environmental capacity calculation based on uncertainty analysis: a case study in the Baixi watershed area, China

Abstract Water environmental capacity (WEC) is an important concept in environmental science. A basic theory applied in EIA (Environmental Impact Assessment), WEC is also an indispensable factor in District Environmental Planning and total water pollutant control planning. The results of most calculating methods for WECs are fixed values that correspond to designed conditions and are not practical WECs. Instead of a fixed value in calculating WEC, confidence probability and uncertainty analysis should be combined with the river model. Consequently, the feasible WEC in different hydrological periods can ensure the precision and reliability of the load allotment. In this study, a useful method, Monte Carlo simulation, was combined with a water quality model to calculate the WEC and quantify the impact of a range of input values on the WEC. A case study of nitrogen and phosphorus WEC calculation was conducted in the Baixi Reservoir watershed area in Ningbo City, Zhejiang Province, China. The results show that the WEC values of TN under 90% confidence probability were 5.30 T/period during the wet period, 8.35 during the dry period, and 9.83 during the middle period. In comparison, the values under 80% and 70% were 10.80, 16.39, 18.79, and 15.94, 23.99, 27.71 T/period, respectively. The WEC values of TP were also obtained. The uncertainty analysis- based WEC could help policy makers to set better goals for different hydrological periods, especially in an area dominated by non-point source pollutants.