Abstract
Since 2011, China has implemented its most stringent water management system to effectively protect water resources and guarantee socioeconomic development. More basin-scale water division schemes have been developed to act as references for basin-scale water resources management. Water dispatching during dry periods is an effective way to guarantee the water supply for the river basin, and is also an important component of basin-scale water resources management. Given this, the present study proposes a framework for the water dispatching of river basins during dry periods under the most stringent water management system in China. This framework mainly consists of the analysis and forecasting of rainfall and inflow, the dispatching requirements for the main water users, major reservoirs, and sections, as well as safeguard measures. The Jian River Basin in South China is presented as a case study. The total discharge of the Gaozhou Reservoir in 2017 was 25 million m3 more than the target discharge specified in the water dispatching scheme, and the total water storage utilization ratio during the dispatch period was 4.7% higher than the target utilization ratio. These factors demonstrate the effectiveness and applicability of the proposed framework.
HIGHLIGHT
The proposed framework for the water dispatching of river basins during dry periods provides reliable technical support for water use security under the most stringent water management system in China, and is demonstrated to be both effective and applicable.
INTRODUCTION
Water provides the foundation for both socioeconomic development and environmental protection (Yuan et al., 2021). The uneven spatiotemporal distribution of water resources usually causes regional water shortages, water pollution, and ecological degradation, particularly during dry periods. While China has a rapidly developing economy and a fast-growing population, it has fewer per capita water resources (He et al., 2019). Thus, determining how to coordinate the relationship between socioeconomic development and water resources utilization and protection is of great concern for the Chinese government. Given this, the most stringent water resources management system was implemented in China in 2011 to achieve a balance between ongoing regional socioeconomic development and the supply and protection of water, including the water in river basins.
Water dispatching during the dry period is an effective way to guarantee the water supply of a river basin. To implement the most stringent water management system and water distribution plan, coordinate the allocation of domestic, industrial, and ecological water use, and guarantee the basic ecological water use of rivers and lakes, it is necessary to establish a water dispatching framework characterized by a scientific target, rational allocation, optimal dispatching, and strong supervision at the river basin scale (Dung et al., 2021).
The most stringent water management system
The most stringent water management system includes the ‘Three Red Lines,’ i.e., (1) the red line for the total quantity of water use, (2) the red line for the water use efficiency, and (3) the red line for the pollutants released into water function areas (Li et al., 2015a, 2015b; Deng et al., 2016; Hong et al., 2017). It was issued by the Chinese central government as the annual ‘No. 1 Document’ in January 2011 to effectively improve the efficiency of water use and alleviate heavy water pollution. In detail, the red line for the total quantity of water use means controlling the country's total water use to be no more than 700 billion m3 by 2030; the red line for the water use efficiency means improving the water use efficiency to be at or close to the world's advanced level by 2030; finally, the red line for water pollution refers to the limitation of the total amount of major pollutants emitted into rivers and lakes to the assimilative capacity of the water function area, as well as the increased compliance of water quality in the water function area (Deng et al., 2016). A specified control target was set for the total water use on the national level, while lower-level governments are required to set their own water control targets according to the national water control target (Li et al., 2015a, 2015b). The ‘Three Red Lines’ policy has had profound impacts on water resources exploitation at the basin scale (Li et al., 2015a, 2015b), and has influenced the adaptive water resources management of China (Hong et al., 2017). The ‘No. 1 Document’ of 2011 is China's top authoritative policy on the national level, and outlines a plan to expedite water conservancy development and reform, as well as to achieve the sustainable use and management of water resources in the new development era of China (Liu & Yang, 2016).
Following the ‘Three Red Lines,’ water division schemes at the river basin scale have emerged nationwide. In Guangdong Province, Southern China, water division schemes of the four larger basins (i.e., Dongjiang, Beijiang, Hanjiang, and Jianjiang) have been issued by the provincial government. In the water division scheme of each basin, the total constrained water use for the regions along the river is specified, and the minimum flow and water quality target of each control section of the river are set according to the requirement of the most stringent water management system implemented by Guangdong Province. These provide important boundaries and guidelines for water dispatching at the basin scale.
Literature review
Water dispatching is an important aspect of water resources management, and alleviates the water supply-demand conflict by optimizing the allocation of limited water resources among regions (Xie et al., 2018; Fang et al., 2021). Currently, water dispatching mainly focuses on the optimal allocation of water resources from rivers (Zhang et al., 2020), reservoirs (Mujumdar & Nirmala, 2007), and watersheds (Martinsen et al., 2019). Moreover, via the use of classical and heuristic algorithms, the domestic and international models for water dispatching have developed from a single objective to multiple objectives. In terms of classical algorithms, dynamic programming (Shi et al., 2013), nonlinear programming (Shi et al., 2015), and multi-level programming (Rani et al., 2016) have been extensively applied to develop optimal water allocation schemes. However, as water dispatching moves toward a multi-regional and multi-objective (e.g., water ecology, generation, and shipping) endeavor, ‘dimensional disasters’ occur to some extent, and the process of optimization has become increasingly complicated (Guo et al., 2010). Compared with classical algorithms, heuristic algorithms (e.g., the ant colony algorithm (Nguyen et al., 2016), quantum particle swarm algorithm (Sun et al., 2009), and genetic algorithm (Tabari & Yazdi, 2014)) are characterized by stability, robustness, and easy parallelization, can effectively solve the problem of dimensional disasters and improve the accuracy of the optimized solution, and therefore support effective water resources management.
Water dispatching has received considerable attention, and has been applied in many river basins in China. For example, Liu et al. (2010) developed a water resources allocation model for the water dispatching of the Pearl River Delta that considers the three objectives of social, economic, and environmental benefits. Similarly, in a case study of the Huai River Basin, Zhang et al. (2020) proposed a multi-objective optimal water resources allocation model from the perspective of different water sources and water departments. Furthermore, Li et al. (2015a, 2015b) constructed a multi-dimensional critical regulation model that includes water resources, the ecological environment, society, the economy, and water-saving measures to conduct water dispatching in the middle reaches of China's Heihe River Basin.
Since the establishment of the most stringent water management system in 2011, China has achieved the sustainable utilization of water resources, and increasing numbers of studies have evaluated the effects of this system on water resources management (Shang et al., 2017; He et al., 2021). For example, Guo & Wang (2021) established a prediction model to evaluate the carrying capacity of water resources in China in 2030 under this water resources management system. Chen et al. (2018) constructed a rough set cloud model to assess the vulnerability of the water resources of the Huai River Basin in China, and indicated the existence of severe vulnerability despite the water resources management system. Nevertheless, research on how to conduct water dispatching in China under the most stringent water management system at the basin scale remains insufficient. Guan et al. (2020) presented a multi-objective optimal water allocation model based on the characteristics of the ‘Three Red Lines,’ and applied it to the reasonable allocation of water supply and demand in Qinzhou, Guangxi, China. However, there exists no water dispatching framework for use under the most stringent water management system at the river basin scale, particularly during dry periods. Therefore, this study proposes a framework of water dispatching during dry periods under the most stringent water management system, and the Jian River Basin in Guangdong Province, China is presented as a case study. The current study has the potential to improve the level of water resources management in China at the basin scale via the effective implementation of the most stringent water management system.
The framework of water dispatching during dry periods under the most stringent water management system
Water dispatching during a dry period involves water resources protection, water pollution prevention, and water environment management. To achieve effective water dispatching, the watershed authority employs its administrative power to achieve cross-departmental collaboration by facilitating organizational coordination, alleviating departmental conflicts, and promoting resource mobilization among all related departments. The framework in Figure 1 is detailed as follows.
Rainfall and inflow analysis
Rainfall and inflow analysis includes the analysis of historical rainfall, rainfall forecasts, and the analysis and forecasting of the interval water and reservoir inflow of the basin.
Dispatch plan
The dispatch plan contains the control of the total water withdrawal in the basin during the dry period, the scheduling principle, and the dispatching requirements for major reservoirs. Reservoir dispatching mainly involves the determination of the target water level and discharge in the dispatch period. In addition, the dispatch plan also contains the required flow of major hydrological stations, as well as the dispatching requirements of each dam and the water quality control targets of the important control sections.
Safeguard measures
The safeguard measures include the duties of each department, including supervision and inspection, information monitoring and reporting, dispatch reporting, and effect evaluation.
In the current study, the dry period is considered to be from October of the current year to March of the next year, and is also referred to as the dispatch period.
Analysis and forecasting of rainfall and inflow in the basin rainfall analysis and forecasting
Historical rainfall analysis
Based on observed historical rainfall data, the average annual rainfall of the basin in the whole year and that in the dry period are analyzed. Furthermore, the rainfall of each month in this year is compared with the historical average rainfall of the same month. The proportion of rainfall in a dry period (e.g., from January to March) is compared with that of the historical average.
Rainfall forecasting
The rainfall in September of the current year, as well as the total rainfall in the dispatch period of the basin, is forecasted according to the observed historical rainfall data, the rainfall from January to August of the current year, and the short-term climate forecast.
Historical inflow analysis and forecasting
The monthly inflow of the interval and major reservoirs is forecasted according to the observed hydrological data, the water balance between the upstream and downstream regions, the correlation of historical rainfall with runoff in a dry period, and the rainfall-runoff correlation using the typical year analysis, mathematical statistics, etc.
Historical inflow analysis
The time series of the historical and monthly inflow of the main reservoirs are analyzed according to the observed inflow of the hydrological control stations.
Inflow forecasting
The monthly inflow of the hydrological stations and major reservoirs in the dispatch period is forecasted in consideration of the total rainfall and rainfall pattern in the post-flood period according to the rainfall from January to August of the current year and the rainfall forecasting results in the later period.
Interval inflow forecasting is a medium- to long-term hydrological forecast, the uncertainty of which is high (Lan et al., 2018). Moreover, the factors that affect the inflow are complex. Therefore, the forecasting results may deviate from the actual situation. Water dispatching during a dry period should be based on the real-time adjustment and dynamic dispatching of rainwater conditions, the soil moisture conditions, and the water demand, and therefore ensures the rational and effective use of water resources.
Dispatch plan
Total water withdrawal control in the dispatch period
The cities in the basin should implement the ‘Three Red Lines’ policy for their annual water use and comply with the requirements for the allocated annual total water use according to the water division scheme of the basin. Furthermore, the water-use plans of the main trunk channels and the main water user should also be considered. The total amount of water withdrawal for each city in the basin should be in accordance with the amount specified in the water division scheme.
The government regards the control of total water withdrawal permits as an important control means by which to implement the total water consumption control targets. It strictly approves the water withdrawal requirements of water users and prevents unreasonable increases in water use. New water withdrawal is not approved when the city has reached the total water consumption limit; the approval of new water withdrawals is restricted in cities whose water withdrawal is close to the total water consumption quota.
Based on the historical time series and the forecasting of the flow and rainfall in the basin, the water dispatch plan provides the targets of the outflows of major reservoirs and discharges across the main control sections, as well as the water quality control targets during the dispatch period. The scheduling requirements for the downstream tide barrages are also determined. Furthermore, a dynamic dispatch mechanism and emergency response mechanism are established to ensure the successful completion of water dispatching during the dry period.
Dispatching principle
Via reservoir dispatching and the management of the main stream dams and major water users, the water resources of the river basin are reasonably allocated to ensure the safety of the water supply during the dry period. The dispatch plan should follow the following principles:
Priority should be given to meet both urban and rural domestic water needs, and to coordinate ecological, environmental, industrial, and agricultural water demands.
Reservoir dispatching should be mainly implemented for flood prevention and the water supply, followed by the benefits of power generation.
Sustainable water use and conservation should be coordinated, and the relationship between water resources utilization and protection should be balanced.
The water quantity and quality should both be controlled.
Regular scheduling should be combined with dynamic scheduling.
Dispatching requirements for major reservoirs
Determination of the target water level of the reservoir
According to the water level of the reservoir at the beginning of dispatching, as well as the corresponding storage capacity and the average inflow volume of the reservoir in September of the current year, the reservoir storage is controlled according to the average discharge in September, and the target water level of the reservoir at the end of September is then determined.
Reservoir discharge during the dispatch period
According to the monthly inflow and reservoir discharge rules, and combined with the forecasts of the reservoir and interval inflows and the water-use plan for the main water users in the basin, the monthly discharge of the reservoir is inferred from the control flow requirements of each control section during the dispatch period. The discharge of the reservoir is adjusted in real time according to the inflow, rainfall, and water demand of the basin, thereby ensuring that the discharge across the control section meets the control flow requirements.
Control flow of major hydrological stations
The water dispatch plan is used to determine the daily average flow and water quality control targets of the main sections and hydrological stations according to the forecast of the interval inflow and the water division scheme of the basin.
Water quality control targets of the important sections
The water dispatch plan should include the monitoring of the water quality of the main sections according to the water quality control targets of the important sections specified in the water division scheme.
Dispatching requirements of each dam
The dams in the main stream of the river basin should follow the principle of giving priority to the water supply, and should ensure that the daily average discharge will meet the required flow target of the main sections in the downstream region.
Safeguard measures
Water dispatching requires the concerted efforts of the upstream and downstream parties throughout the entire basin. All relative departments must actively cooperate and carry out their responsibilities, obey the unified dispatch of the watershed authority, and strictly implement the dispatch plan. The municipal governments in the river basin should be responsible for the control of the total water withdrawal in their administrative regions and the management of water quality target sections in accordance with the requirements of the dispatch plan promulgated by the provincial government.
Duty of each department
Under the guidance and coordination of the provincial department of water resources, and under the technical guidance of the provincial hydrological bureau, the watershed authority organizes the relative departments of the basin to implement the water dispatch plan during the dry period. The responsibilities of each relative department are described as follows.
Watershed authority
The watershed authority is responsible for the preparation and organization of the dispatch plan.
It is responsible for the establishment of a dynamic dispatching mechanism, and specifically for the real-time adjustment of the dispatch plan based on changes in water resources.
It is responsible for organizing relevant monitoring, inspection, and coordination work.
It is responsible for activating the emergency response mechanism to effectively respond to severe droughts in the basin and sudden water pollution events.
Municipal water affairs bureau
The municipal water affairs bureau organizes the county (district) water administrative department under its jurisdiction to execute the water dispatching work in the basin according to the prescribed authority.
Based on the dispatch plan, the municipal water affairs bureau formulates water dispatching targets and principles within the jurisdiction, and clarifies the dispatching principles of the main barrages and hydropower stations, the regulation of the water dispatch authority, and the management responsibilities.
According to the requirement of the most stringent water management system, the municipal water affairs bureau has strict control of the total water withdrawal, gives strict approval of water withdrawal permits, and outlines the strict use of water resources for consumption. No less than one on-site supervision and inspection should be conducted for important water users and each barrage. Those who take water without authorization should be dealt with in accordance with the law and regulations.
The municipal water affairs bureau is responsible for monitoring the water intake status of the major water users, main canals, and power stations, as well as the operation status of the barrages within the jurisdiction. It is also responsible for reporting the water intake information of the main water users in the area to the watershed authority.
The relative departments are coordinated to implement emergency dispatching, the supervision and inspection of the implementation of water dispatching within the jurisdiction are organized, and the bureau assists the watershed authority to carry out supervision and inspection.
The sewage outlets are set up and supervised, and the total amount of sewage discharged into the river is controlled by relative departments to ensure the safety of the water quality during the dry period.
The bureau strengthens water conservation and protection.
Municipal hydrological bureau
According to the requirements of the dispatch plan, the municipal hydrological bureau is responsible for the monitoring of the water quality and quantity of the main sections, and for submitting real-time information about the flow and rainfall to the watershed authority. It is also responsible for reporting the problems uncovered by monitoring in a timely manner. The municipal hydrological bureau also organizes the supervision and inspection of water dispatching. Moreover, it is responsible for the monitoring of the reservoir water level, discharge, and water quality, for collecting, sorting, and providing relevant flow and rainfall information, for analyzing the dispatching results, and for proposing suggestions for the modification of dynamic dispatching, etc.
Municipal environmental protection bureau
The municipal environmental protection bureau is responsible for the unified supervision of water pollution prevention and control within the jurisdiction, and, in accordance with the requirements of the dispatch plan, for urging the local government to take practical and effective measures to ensure that the water quality of the main sections in the river basin meets the standards.
Main canals and water users
All main canals and water users should strictly implement the dispatch plan and water-use plan, and should report the water use information to the municipal water affairs bureau in a timely manner in accordance with the information reporting requirements.
Main barrage
Each barrage must operate strictly in accordance with the requirements of the dispatch plan, and the relevant information on the flow of the barrage should be reported once a month to the municipal water affairs bureau on time.
Supervision and inspection
To ensure the accurate implementation of the dispatch plan and the effective implementation of various dispatching indicators, the watershed authority and the municipal water affairs bureau should strengthen the supervision and inspection work according to the following requirements.
Watershed authority
During the dispatch period, according to the required discharge of the reservoir, the watershed authority grasps whether the reservoir discharge meets the requirements in a timely manner. It organizes the hydrological branch bureau to monitor the discharge and water quality across the main sections, and uncovers the actual situation of water dispatching.
In addition, the watershed authority organizes the municipal water affairs bureau and the hydrological branch to inspect the main water users, the canal water intake, the water quality of the water function areas, the water sources in the river basin, the discharge process of the reservoir, the barrages in the main stream, etc.
Municipal water affairs bureau
The municipal water affairs bureau organizes the supervision and inspection of the implementation of the dispatch plan within the jurisdiction, and cooperates with the watershed authority to carry out inspections. It is necessary to strengthen the supervision and management of the main water users, the canals, and the barrage, and organize the inspections. The bureau should also strictly control water withdrawal and the total amount of sewage discharged into the river in accordance with the relevant ‘red lines.’
Information monitoring and reporting
Relative departments should strengthen the information monitoring and reporting of the dispatch. The specific requirements are as follows.
Municipal hydrological bureaus
The daily rainfall of the main stations and average flow of the sections in last month are reported to the municipal hydrological bureaus.
The water quality monitoring data of the reservoirs, dams, and control sections in the last month are reported to the watershed authority.
In cases in which the flow or quality of the control section is significantly lower than the requirements of the dispatch plan, or if a major water pollution accident occurs, this information is reported to the watershed authority in a timely manner as required.
Municipal water affairs bureau
The municipal water affairs bureau reports the water withdrawals and the monthly water withdrawal plans of the main water users, main canals, and power stations to the watershed authority.
It reports the water intake of the water users who are inspected regularly or irregularly to the watershed authority.
Main water users
During the dispatch period, the water withdrawal of the previous month and the monthly water withdrawal plan are reported to the municipal water affairs bureau. If the water withdrawal amount is greater than the original water withdrawal plan, the reasons are also explained.
Main barrage
The cascade dams report the daily flow and rainfall in the last month to the municipal water affairs bureau. If special circumstances that affect the implementation of the dispatch plan are encountered, the unexpected situation is promptly reported to the watershed authority in writing.
Dispatching report
During the dispatching process, the watershed authority must quickly and comprehensively grasp the dynamics of the water resources in the basin and notify the relative departments of the situation. A watershed water dispatch report is issued every month during the dispatch period, which informs the implementation of the dispatch plan. The main contents include the following:
The rainfall, the average flow of the section, and the daily average discharge, inflow, water level, and storage of the reservoir.
The water quality of the reservoir and the control sections, including the DO, BOD5, ammonia nitrogen, CODMn, and other quality indicators.
The water withdrawal of each water user and trunk canal.
Effect evaluation
The effect of water dispatching during the dry period should be evaluated at the end of the dispatch, and an evaluation report should be made. The effect evaluation should be organized by the watershed authority.
A case study in the Jian River Basin, South China
The Jian River is the largest river in the southwestern part of Guangdong Province, South China, and serves as the main water source for domestic use and the production water demands of Maoming and Zhanjiang cities (Figure 2). It has a total length of 231 km, a total drop of 220 m, and an average slope of 0.374%. The Jian River Basin has a total drainage area of 9,464 km2, an annual average total rainfall of 1,768 mm, and 8.5 billion km3 of water resources. The intra-annual distribution of rainfall is very uneven (e.g., rainfall in the dry period only accounts for 15%). Huazhou Station, located in the mainstream of the Jian River (Figure 2), is the controlling station of the basin with a drainage area accounting for more than 75% of the total drainage area of the entire basin. The Gaozhou Reservoir, the largest reservoir of the Jian River Basin with a drainage area of 1,022 km2 and a total storage capacity of 1.24 billion m3, consists of the Shigu Reservoir and Liangde Reservoir, and serves as the main water source for the domestic and productive water use in the downstream region.
To effectively improve the water use efficiency and promote sustainable water use, the government of Guangdong Province approved the water division scheme of the Jian River Basin in 2010, which is an important basis for water dispatching during the dry period. The water division scheme specifies the minimum discharge (i.e., control flow) and water quality control target of the main sections and the maximum water withdrawal (i.e., the total water withdrawal control) of each water user, and provides powerful information for the implementation of the most stringent water management system over the entire basin.
Based on the observed historical rainfall data from January to August 2017, as well as the short-term climate forecast of the Guangdong Meteorological Bureau, the Jian River Basin had a normal flow year in 2017, and the average precipitation from October 2017 to March 2018 was 250 mm.
The entire basin can be divided into three parts, namely parts A (the drainage area above Gaozhou Station), B (the drainage area between Gaozhou and Huazhou Stations), and C (the drainage area of the Gaozhou Reservoir; see Figure 2). Tables 1 and 2 present the time series of the historical inflows of the three parts of the basin during wet, average, and dry years.
Analysis of the inflow of the basin (m3/s).
Month . | High flow year . | Normal flow year . | Low flow year . | ||||
---|---|---|---|---|---|---|---|
Part A . | Part B . | Part A . | Part B . | Part A . | Part B . | ||
Flood period | Apr | 89.5 | 121 | 35.8 | 69.4 | 30.6 | 43.7 |
May | 93.6 | 166 | 70.4 | 135 | 51.7 | 89.1 | |
June | 147 | 228 | 107 | 173 | 69.5 | 104 | |
July | 145 | 290 | 86.1 | 165 | 53.1 | 102 | |
Aug | 166 | 272 | 100 | 193 | 62.2 | 121 | |
Sept | 115 | 235 | 69.3 | 124 | 43.0 | 71.8 | |
Average | 126.2 | 219.1 | 78.2 | 143.6 | 51.7 | 88.9 | |
Non-flood period | Oct | 97.0 | 154 | 28.4 | 45.0 | 16.6 | 26.4 |
Nov | 39.6 | 56.9 | 20.9 | 24.4 | 13.8 | 8.9 | |
Dec | 29.5 | 28.2 | 14.3 | 12.1 | 10.2 | 4.3 | |
Jan | 23.9 | 21.3 | 15.1 | 15.1 | 10.7 | 4.4 | |
Feb | 23.7 | 28.8 | 14.1 | 16.9 | 8.77 | 4.1 | |
Mar | 21.0 | 23.3 | 12.0 | 10.3 | 8.49 | 8.9 | |
Average | 39.4 | 52.4 | 17.5 | 20.7 | 11.5 | 9.6 |
Month . | High flow year . | Normal flow year . | Low flow year . | ||||
---|---|---|---|---|---|---|---|
Part A . | Part B . | Part A . | Part B . | Part A . | Part B . | ||
Flood period | Apr | 89.5 | 121 | 35.8 | 69.4 | 30.6 | 43.7 |
May | 93.6 | 166 | 70.4 | 135 | 51.7 | 89.1 | |
June | 147 | 228 | 107 | 173 | 69.5 | 104 | |
July | 145 | 290 | 86.1 | 165 | 53.1 | 102 | |
Aug | 166 | 272 | 100 | 193 | 62.2 | 121 | |
Sept | 115 | 235 | 69.3 | 124 | 43.0 | 71.8 | |
Average | 126.2 | 219.1 | 78.2 | 143.6 | 51.7 | 88.9 | |
Non-flood period | Oct | 97.0 | 154 | 28.4 | 45.0 | 16.6 | 26.4 |
Nov | 39.6 | 56.9 | 20.9 | 24.4 | 13.8 | 8.9 | |
Dec | 29.5 | 28.2 | 14.3 | 12.1 | 10.2 | 4.3 | |
Jan | 23.9 | 21.3 | 15.1 | 15.1 | 10.7 | 4.4 | |
Feb | 23.7 | 28.8 | 14.1 | 16.9 | 8.77 | 4.1 | |
Mar | 21.0 | 23.3 | 12.0 | 10.3 | 8.49 | 8.9 | |
Average | 39.4 | 52.4 | 17.5 | 20.7 | 11.5 | 9.6 |
Analysis of the inflow of the Gaozhou Reservoir (m3/s).
Month . | High flow year . | Normal flow year . | Low flow year . | |
---|---|---|---|---|
Flood period | Apr | 42.3 | 27 | 14.8 |
May | 54.4 | 38.5 | 22.1 | |
June | 72.7 | 57.1 | 34.5 | |
July | 78.6 | 53.3 | 38.3 | |
Aug | 85.3 | 59.4 | 36.7 | |
Sept | 70.7 | 44.2 | 26.8 | |
Average | 67.4 | 46.6 | 28.9 | |
Non-flood period | Oct | 51.4 | 28.7 | 18.2 |
Nov | 30.2 | 17.4 | 12.4 | |
Dec | 20.8 | 12 | 8.1 | |
Jan | 21.1 | 12.8 | 8.7 | |
Feb | 20.1 | 11.5 | 8.6 | |
Mar | 19.5 | 13.3 | 9.5 | |
Average | 27.3 | 16.0 | 10.9 |
Month . | High flow year . | Normal flow year . | Low flow year . | |
---|---|---|---|---|
Flood period | Apr | 42.3 | 27 | 14.8 |
May | 54.4 | 38.5 | 22.1 | |
June | 72.7 | 57.1 | 34.5 | |
July | 78.6 | 53.3 | 38.3 | |
Aug | 85.3 | 59.4 | 36.7 | |
Sept | 70.7 | 44.2 | 26.8 | |
Average | 67.4 | 46.6 | 28.9 | |
Non-flood period | Oct | 51.4 | 28.7 | 18.2 |
Nov | 30.2 | 17.4 | 12.4 | |
Dec | 20.8 | 12 | 8.1 | |
Jan | 21.1 | 12.8 | 8.7 | |
Feb | 20.1 | 11.5 | 8.6 | |
Mar | 19.5 | 13.3 | 9.5 | |
Average | 27.3 | 16.0 | 10.9 |
Inflow forecast
According to the observed rainfall from January to August 2017, as well as the total rainfall and rainfall type in the subsequent flood season, Table 3 reports the monthly interval inflow of the basin in the dispatch period.
The monthly average inflow forecast of the basin (reservoir excluded) in the dispatch period (m3/s).
Part . | Oct . | Nov . | Dec . | Jan . | Feb . | Mar . |
---|---|---|---|---|---|---|
A | 23 | 16 | 13 | 11 | 10 | 10.5 |
B | 36 | 22 | 11 | 12 | 10.5 | 10 |
Total | 59 | 38 | 24 | 23 | 20.5 | 20.5 |
Part . | Oct . | Nov . | Dec . | Jan . | Feb . | Mar . |
---|---|---|---|---|---|---|
A | 23 | 16 | 13 | 11 | 10 | 10.5 |
B | 36 | 22 | 11 | 12 | 10.5 | 10 |
Total | 59 | 38 | 24 | 23 | 20.5 | 20.5 |
It is predicted that the total water volume of the Gaozhou Reservoir will be 194 million m3 during the dispatch period. The monthly inflow of the Gaozhou Reservoir in the dispatch period is reported in Table 4.
The monthly average inflow forecast of the Gaozhou Reservoir in the dispatch period (m3/s).
Month . | Oct . | Nov . | Dec . | Jan . | Feb . | Mar . |
---|---|---|---|---|---|---|
Reservoir inflow | 25 | 15 | 10 | 10.5 | 10 | 11.5 |
Month . | Oct . | Nov . | Dec . | Jan . | Feb . | Mar . |
---|---|---|---|---|---|---|
Reservoir inflow | 25 | 15 | 10 | 10.5 | 10 | 11.5 |
In accordance with the water division scheme of the Jian River Basin, the annual water withdrawal of Maoming and Zhanjiang cities should not exceed 2.39 and 0.74 billion m3, respectively. In the dispatch period, the water withdrawals of the two cities will be 1.18 and 0.32 billion m3, respectively.
On September 6, 2017, the water level of the Gaozhou Reservoir was 85.07 m, and the corresponding storage capacity was 763.36 million m3. The average inflow of the Gaozhou Reservoir in September 2017 was predicted to have been about 52.4 m3/s, and the storage was predicted to have been controlled according to the average discharge of the reservoir in September (28 m3/s). The water storage capacity of the Gaozhou Reservoir at the end of September was 842 million m3, and the target water level of the reservoir is 86.5 m.
The dispatching of the Gaozhou Reservoir
According to the monthly interval inflow and the regular discharge of the Gaozhou Reservoir, and combined with the forecast inflows of the Gaozhou Reservoir during the dispatch period, as well as the plan of the water use in the basin, the required flows across the main sections were reversed to calculate the required daily average discharge of the Gaozhou Reservoir (see Table 5). As shown in Table 5, the required daily average discharge varied from the maximum discharge of 22 m3/s in December 2017, which was mainly due to the fluctuations of the reservoir inflow and downstream water use. The Gaozhou Reservoir is located in the southern humid region of China and has a subtropical monsoon climate. The reservoir inflow is mainly influenced by the uneven distribution of rainfall, and therefore exhibits fluctuations during dry periods.
The required daily average discharge of the Liangde Reservoir (Suidongkou) during the dispatch period.
Month . | Required daily average discharge (m3/s) . |
---|---|
Oct 2017 | 12 |
Nov 2017 | 19 |
Dec 2017 | 22 |
Jan 2018 | 14 |
Feb 2018 | 15 |
Mar 2018 | 15 |
Month . | Required daily average discharge (m3/s) . |
---|---|
Oct 2017 | 12 |
Nov 2017 | 19 |
Dec 2017 | 22 |
Jan 2018 | 14 |
Feb 2018 | 15 |
Mar 2018 | 15 |
The monthly discharge of the Liangde Reservoir at the tunnel entrance is the basic control for the discharge of the reservoir. The discharge can be adjusted in real time according to the rainfall in the basin and the water demand of the downstream region to ensure that the flow across the control section of the downstream region meets the flow requirements.
Based on the discharge series of the Liangde Reservoir (Suidongkou and East Bank Canal) and the Shigu Reservoir (North Canal and Main Canal), the monthly discharge of Suidongkou and the East Bank Canal of the Liangde Reservoir, and the north and main canals of the Shigu Reservoir controlled according to the tunnel entrance, the monthly discharge of the Gaozhou Reservoir during dispatching was determined (see Table 6). The discharge of the Gaozhou Reservoir increased from October to December 2017, and the maximum and total discharges were respectively 85.7 and 414.5 million m3. This was mainly attributed to the discharge of the Liangde Reservoir (Suidongkou), which accounted for 61% of the total discharge of the Gaozhou Reservoir in the dispatch period.
The discharge of the Gaozhou Reservoir in the dispatch period (104 m3).
Month . | Liangde Reservoir (Suidongkou) . | Liangde Reservoir (East Bank Canal) . | Shigu Reservoir (Main Canal) . | Shigu Reservoir (North Canal) . | Total . |
---|---|---|---|---|---|
Oct 2017 | 3,214 | 140 | 3,400 | 70 | 6,824 |
Nov 2017 | 4,925 | 40 | 1,900 | 45 | 6,910 |
Dec 2017 | 5,892 | 25 | 2,600 | 55 | 8,572 |
Jan 2018 | 3,750 | 20 | 2,100 | 45 | 5,915 |
Feb 2018 | 3,629 | 30 | 1,900 | 35 | 5,594 |
Mar 2018 | 3,884 | 130 | 3,550 | 75 | 7,639 |
Total | 25,294 | 385 | 15,450 | 325 | 41,454 |
Month . | Liangde Reservoir (Suidongkou) . | Liangde Reservoir (East Bank Canal) . | Shigu Reservoir (Main Canal) . | Shigu Reservoir (North Canal) . | Total . |
---|---|---|---|---|---|
Oct 2017 | 3,214 | 140 | 3,400 | 70 | 6,824 |
Nov 2017 | 4,925 | 40 | 1,900 | 45 | 6,910 |
Dec 2017 | 5,892 | 25 | 2,600 | 55 | 8,572 |
Jan 2018 | 3,750 | 20 | 2,100 | 45 | 5,915 |
Feb 2018 | 3,629 | 30 | 1,900 | 35 | 5,594 |
Mar 2018 | 3,884 | 130 | 3,550 | 75 | 7,639 |
Total | 25,294 | 385 | 15,450 | 325 | 41,454 |
Based on the analysis of the dispatch of the Gaozhou Reservoir during the dry period and the inflow of the reservoir in recent years, it was predicted that the water level of the Gaozhou Reservoir will have been about 86.5 m on September 30, 2017. Considering the inflow and discharge of the reservoir in this period, it was predicted that by March 31, 2018, the total water reduction of the Gaozhou Reservoir will have been 199 million m3, and the water level will have fallen to 82.7 m (see Table 7).
The forecasts of the water level and water storage of the Gaozhou Reservoir in the dispatch period.
Date . | Water level (m) . | Water storage (104 m3) . | Available water (104 m3) . |
---|---|---|---|
September 30, 2017 | 86.50 | 84,150 | 77,270 |
October 31, 2017 | 86.48 | 84,022 | 77,142 |
November 30, 2017 | 85.94 | 81,000 | 74,120 |
December 31, 2018 | 84.83 | 75,106 | 68,226 |
January 31, 2018 | 84.25 | 72,004 | 65,124 |
February 28, 2018 | 83.62 | 68,829 | 61,949 |
March 31, 2018 | 82.70 | 64,270 | 57,390 |
Date . | Water level (m) . | Water storage (104 m3) . | Available water (104 m3) . |
---|---|---|---|
September 30, 2017 | 86.50 | 84,150 | 77,270 |
October 31, 2017 | 86.48 | 84,022 | 77,142 |
November 30, 2017 | 85.94 | 81,000 | 74,120 |
December 31, 2018 | 84.83 | 75,106 | 68,226 |
January 31, 2018 | 84.25 | 72,004 | 65,124 |
February 28, 2018 | 83.62 | 68,829 | 61,949 |
March 31, 2018 | 82.70 | 64,270 | 57,390 |
In the case study, the inflow in the flood period of 2017 was comparable to that in the normal flow year, and the rainfall in the dry period was slightly less. From the perspective of ensuring the water supply and considering the most unfavorable factors, the inflow of the Gaozhou Reservoir was controlled in the dry period of 2017. This dispatch plan implements the constrained total water withdrawal of the normal flow year specified in the water division schemes of the basin, and the control flows of the Gaozhou, Huazhou, and Hejiang hydrological stations were obtained (see Table 8).
The water quality control targets of the main sections of the Jianjiang River after dispatching.
Month . | Gaozhou Station . | Huazhou Station . | Hejiang Station . | ||||||
---|---|---|---|---|---|---|---|---|---|
Current dispatch . | Discharge requried . | Current dispatch . | Discharge requried . | Current dispatch . | Discharge requried . | ||||
Dis (m3/s) . | Fre . | Dis (m3/s) . | Fre . | Dis (m3/s) . | Fre . | ||||
Oct 2017 | 35 | 71% | 35 | 25 | 96% | 25 | 15 | 88% | 15 |
Nov 2017 | 35 | 61% | 35 | 25 | 92% | 25 | 15 | 88% | 15 |
Dec 2017 | 35 | 44% | 35 | 25 | 77% | 25 | 15 | 62% | 15 |
Jan 2018 | 25 | 72% | 25 | 25 | 77% | 25 | 15 | 69% | 15 |
Feb 2018 | 25 | 69% | 25 | 25 | 72% | 25 | 15 | 44% | 15 |
Mar 2018 | 25 | 68% | 25 | 25 | 69% | 25 | 15 | 44% | 15 |
Water quality control target | III | / | III | III | / | III | III | / | III |
Month . | Gaozhou Station . | Huazhou Station . | Hejiang Station . | ||||||
---|---|---|---|---|---|---|---|---|---|
Current dispatch . | Discharge requried . | Current dispatch . | Discharge requried . | Current dispatch . | Discharge requried . | ||||
Dis (m3/s) . | Fre . | Dis (m3/s) . | Fre . | Dis (m3/s) . | Fre . | ||||
Oct 2017 | 35 | 71% | 35 | 25 | 96% | 25 | 15 | 88% | 15 |
Nov 2017 | 35 | 61% | 35 | 25 | 92% | 25 | 15 | 88% | 15 |
Dec 2017 | 35 | 44% | 35 | 25 | 77% | 25 | 15 | 62% | 15 |
Jan 2018 | 25 | 72% | 25 | 25 | 77% | 25 | 15 | 69% | 15 |
Feb 2018 | 25 | 69% | 25 | 25 | 72% | 25 | 15 | 44% | 15 |
Mar 2018 | 25 | 68% | 25 | 25 | 69% | 25 | 15 | 44% | 15 |
Water quality control target | III | / | III | III | / | III | III | / | III |
Note: ‘Dis’ represents discharge; ‘Fre’ represents frequency.
Based on the flow-frequency analysis of the historical daily average flow of the main sections in the dry period, the frequencies of the target flow in Gaozhou, Huazhou, and Hejiang Stations were found to be 44%–72%, 69%–96%, and 44%–88%, respectively.
According to the water quality control targets of the main sections in the water division scheme of the basin, the water quality of the Gaozhou Reservoir, as well as that of the sections including the Yangdipo Barrage, Jiangkoumen, Hexi, Shibi, Tangkou, Shadong, and Panlong, was monitored (see Table 9). Based on the results, the water quality of Xiaodongjiang has not yet reached the requirements of the water division scheme, and the water quality of the Shibi section was found to be in Class V or inferior to Class V for a long time, and improvements must be made.
The water quality targets of important control sections of the Jianjiang River Basin.
Control section . | Water quality target . | Monitoring item . | |
---|---|---|---|
Monthly . | Quarterly . | ||
Gaozhou Reservoir | Class II | Water temperature, pH, electrical conductivity, ammonia nitrogen, permanganate index, fluoride, chloride, sulfate, nitrate nitrogen, total phosphorus, total nitrogen, chlorophyll, transparency | Volatile phenols, cyanide, chromium (hexavalent), arsenic, mercury, selenium, lead, zinc, copper, cadmium |
Yangdipo | Class III | Water temperature, pH, electrical conductivity, ammonia nitrogen, DO, BOD5, permanganate index, fluoride, chloride, sulfate, nitrate nitrogen, total phosphorus, iron, manganese | |
Jiangkoumen | Class III | ||
Hexi | Class III | ||
Shibi | Class IV | ||
Tangkou | Class III | ||
Shatong | Class II | ||
Panlong | Class II |
Control section . | Water quality target . | Monitoring item . | |
---|---|---|---|
Monthly . | Quarterly . | ||
Gaozhou Reservoir | Class II | Water temperature, pH, electrical conductivity, ammonia nitrogen, permanganate index, fluoride, chloride, sulfate, nitrate nitrogen, total phosphorus, total nitrogen, chlorophyll, transparency | Volatile phenols, cyanide, chromium (hexavalent), arsenic, mercury, selenium, lead, zinc, copper, cadmium |
Yangdipo | Class III | Water temperature, pH, electrical conductivity, ammonia nitrogen, DO, BOD5, permanganate index, fluoride, chloride, sulfate, nitrate nitrogen, total phosphorus, iron, manganese | |
Jiangkoumen | Class III | ||
Hexi | Class III | ||
Shibi | Class IV | ||
Tangkou | Class III | ||
Shatong | Class II | ||
Panlong | Class II |
Evaluation of the water dispatching scheme during dry periods
Taking Huazhou Station as an example, the flow control target specified in the water dispatching scheme and the daily average flows during the dry periods in 2016 and 2017 were compared, as shown in Figure 3. As revealed in the figure, the daily average flow during the dry periods was 80.3 m3/s in 2016 and 79.94 m3/s in 2017, both of which were above the flow control target (25 m3/s). In addition, the monthly average flows from October 2016 to March 2017 were respectively 116.9, 163.0, 69.1, 41.5, 46.9, and 47.0 m3/s. It is evident all the monthly average flows during the dry periods were greater than the flow control target. These findings are similar to those for the monthly average flows in 2017 during dry periods, which were respectively 156.98, 62.62, 70.17, 79.20, and 56.43 m3/s from October 2017 to March 2018.
The discharge and inflow during the dry periods and the water storage at the end of the flood periods of the Gaozhou Reservoir in 2016 and 2017, as well the discharge, inflow, and water storage targets specified in the dispatching scheme, were also compared to evaluate the effect of the dispatching scheme. As shown in Figure 4, in 2017, the total water storage of the Gaozhou Reservoir was 1.02 billion m3, the total discharge during the dry periods was 0.44 billion m3, and the total water storage utilization ratio (i.e., the total discharge divided by the total water storage) was 43.94%. Although the total discharge of the Gaozhou Reservoir in 2017 was slightly less than the total discharge in 2016, it was 25 million m3 more than the discharge target specified in the water dispatching scheme. Furthermore, the total water storage utilization ratio (43.9%) during the dry periods in 2017 was greater than the target utilization ratio (39.2%), suggesting that the Gaozhou Reservoir had been effectively utilized and the water supply of the entire basin had been guaranteed during the dry periods after the implementation of the water dispatching scheme. The average flow process of Huazhou Station and the discharge and total water storage utilization ratio of the Gaozhou Reservoir demonstrate the effectiveness and applicability of the proposed framework.
The discharge and inflow of the Gaozhou Reservoir during dry periods and the water storage at the end of flood periods.
The discharge and inflow of the Gaozhou Reservoir during dry periods and the water storage at the end of flood periods.
DISCUSSION
The analysis suggests that the proposed framework has the potential to achieve broad collaborative governance among all related stakeholders in the river basin and guarantee the water supply for the entire basin during the dry period. However, regarding the water dispatching framework for use under the most stringent water management system, there are several difficulties/debates regarding its effective application; these can help deepen the understanding of the proposed framework.
First, the forecasting of available water resources in the dry period is difficult. The accurate forecasting of water resources is the foundation of the water dispatching framework because it is directly related to the total amount of available water resources. In the current framework, the inflow forecasts of the interval and reservoir mainly depend on the analysis of historical and precedent rainfall and water resources. The uncertainty exists largely due to the complex interaction of human activities and climate change, which results in great difficulties in the improvement of the accuracy of the medium to long-term water forecast over the entire river basin (Valipour et al., 2021). The real-time forecasting of interval and reservoir inflows is therefore required. The modern forecasting techniques and remote-sensing monitoring can be integrated and used to reduce the uncertainty in medium- to long-term water forecasting during the dry period, which should be strengthened.
Second, a water quantity and quality monitoring system should be fully constructed and implemented over the entire basin. The control flow and the water quality control targets of the main sections in the dry period are the greatest concerns of the water dispatch plan. In addition, the control of the water withdrawal of each water user is an important means by which to achieve the total water consumption control targets. The satisfied ratios of the control flow and the water quality control targets should rely on the measured water quality and observed discharge of the reservoir and the main sections. The water withdrawals of the main water users should also be monitored in real time. Consequently, a thorough water quantity and quality monitoring system is necessary, and is a prerequisite of verifying the effectiveness of the water dispatch plan.
Third, in addition to regular dispatching, a dynamic dispatching mechanism is also necessary and complementary. Limited by the current level of hydrological and meteorological forecasting technology, it is difficult to accurately estimate future flow and rain conditions in a river basin, and the discharge of the reservoir should be dynamically adjusted. Therefore, a dynamic dispatching mechanism is required to improve the scientificity and rationality of the dispatch plan, conserve and protect water resources, and ensure the safety of the water supply in the basin over the dispatch period. During the dispatch period, if the inflow and rain conditions of the basin, the inflow and outflow of the reservoir, the discharge across the important sections, and the water withdrawal situation are significantly different from the situations forecasted by this plan, the relative department should promptly report relevant information to the watershed authority. The watershed authority should then implement dynamic dispatching under the framework of the dispatch plan in conjunction with the municipal water affairs bureau and reservoir management units according to the most recent situation.
Finally, the current study proposed a framework for the water dispatching of a river basin during a dry period under the most stringent water management system. The effective application of this framework to water dispatching across an entire basin still faces substantial challenges. For instance, reservoir dispatching is complex and has more uncertainty, and the duty of each department in different basins will vary, which will hamper the implementation of the water dispatch plan. Therefore, the sustainability and widespread deployment of the framework should be further investigated.
The current study proposed a framework for the water dispatching of river basins during dry periods under the most stringent water management system in China, and the applicability of the proposed framework was demonstrated via a case study of the Jian River Basin in South China. This framework can be extended to other basins in China, which should have water division schemes issued by the provincial government; in the water division scheme, the total constrained water use for the regions along the river is specified, and the minimum flow and water quality target of each control section of the river are set according to the requirement of the most stringent water management system implemented by the local government. In addition, a water quantity and quality monitoring system should be implemented for the basins to monitor the flow and water quality of each control section. These measures will provide guarantees for the effective implementation of the proposed framework of water dispatching at the basin scale.
CONCLUSIONS
This study proposed a framework for the water dispatching of river basins during a dry period under the most stringent water management system in China, and the framework was demonstrated to be effective and applicable via a case study of the Jian River Basin in South China. In this framework, the precipitation, surface water, and reservoir inflow during a dry period are forecasted according to historical and precedent precipitation and reservoir water storage data. Based on this, the water dispatching and water quality control targets for the main control sections are determined, and the goals of water dispatching for reservoirs and dams in the main stream region are set. Moreover, the water withdrawal of each water-use sector is controlled. The responsibility of each governmental department should be clearly set to ensure the orderly and effective implementation of water dispatching.
ACKNOWLEDGEMENTS
The authors would like to express their gratitude to all the reviewers for their valuable recommendations, as well as the Xijiang River Basin Administration of Guangdong Province and the Guangdong Research Institute of Water Resources and Hydropower for their data support. This research was financially supported by the National Natural Science Foundation of China (Grant Nos. 51979043, 51861125203, 51822908, 51869004, and 51779279), the Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou) (Grant No. GML2019ZD0403), and the Natural Science Foundation of Guangdong Province (Grant Nos. 2021A1515010723 and 2021A1515010558).
CONFLICT OF INTEREST
The authors report no potential conflicts of interest.
DATA AVAILABILITY STATEMENT
All relevant data are included in the paper or its Supplementary Information.