Realizing the full reservoir operation potential during the 2020 Yangtze river floods

Abstract

Five severe floods occurred in the Yangtze River Basin, China, between July and August 2020, and the Three Gorges Reservoir (TGR) located in the middle Yangtze River experienced the highest inflow since construction. The world’s largest cascade-reservoir group, which counts for 22 cascade reservoirs in the upper Yangtze River, cooperated in real time to control floods. The cooperation prevented evacuation of 600,000 people and extensive inundations of farmlands and aquacultural areas. In addition, no water spillage occurred during the flood control period, resulting in a world-record annual output of the TGR hydropower station. This work describes decision making challenges in the cooperation of super large reservoir groups based on a case-study, controlling the 4th and 5th floods (from Aug-14 to Aug-22), the efforts of technicians, multi-departments, and the state, and reflects on these. To realize the full potential of reservoir operation for the Yangtze River Basin and other basins with large reservoir groups globally, we suggest: (i) improve flood forecast accuracy with a long leading time; (ii) strengthen and further develop ongoing research on reservoir group cooperation; and (iii) improve and implement institutional mechanisms for coordinated operation of large reservoir groups.

Full text

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Realizing the full reservoir
operation potential during the 2020
Yangtze river oods
Hairong Zhang1,2, Yanhong Dou3*, Lei Ye3*, Chi Zhang3, Huaming Yao1,2, Zhengfeng Bao1,2,
Zhengyang Tang1,2, Yongqiang Wang4, Yukai Huang1,2, Shuang Zhu5, Mengfei Xie6,
Jiang Wu4, Chao Shi7, Yufeng Ren1,2, Dongjie Zhang1,2, Biqiong Wu1,2 & Yufan Chen1
Five severe oods occurred in the Yangtze River Basin, China, between July and August 2020, and
the Three Gorges Reservoir (TGR) located in the middle Yangtze River experienced the highest inow
since construction. The world’s largest cascade-reservoir group, which counts for 22 cascade reservoirs
in the upper Yangtze River, cooperated in real time to control oods. The cooperation prevented
evacuation of 600,000 people and extensive inundations of farmlands and aquacultural areas. In
addition, no water spillage occurred during the ood control period, resulting in a world-record
annual output of the TGR hydropower station. This work describes decision making challenges in the
cooperation of super large reservoir groups based on a case-study, controlling the 4th and 5th oods
(from Aug-14 to Aug-22), the eorts of technicians, multi-departments, and the state, and reects
on these. To realize the full potential of reservoir operation for the Yangtze River Basin and other
basins with large reservoir groups globally, we suggest: (i) improve ood forecast accuracy with a long
leading time; (ii) strengthen and further develop ongoing research on reservoir group cooperation;
and (iii) improve and implement institutional mechanisms for coordinated operation of large reservoir
groups.
Floods are the most frequent natural disaster globally aecting countless lives and property1. Reservoirs, one of
the most ecient infrastructures in ood control2, were built extensively, such that, cascade-reservoir groups are
common in large basins, such as the Nile3, the Yangtze River (alias: Changjiang)4, the Yellow River5, etc. When
encountering a severe ood, cascade-order impounding of oods for cascade-reservoir groups can reduce the
ood control pressure of a single reservoir and improve the ood control ability of the whole basin6. However,
each reservoir must manage a balance between ood risk and economic benet such as power generation and
shipping, and benets gained from dierent reservoirs vary between each other7,8. According to the World
Commission on Dams9, most large reservoirs worldwide cannot produce benets the authorities are satised
with. As a result, the cooperation of cascade-reservoir groups has been extensively considered by hydrologists
and decision makers. However, the connection between hydrologists and decision makers is relatively weak,
although there are many studies on reservoir cooperation10–13, little feedback and reection has emerged from
users. In this work, we describe challenges, achievements and reections of the cooperation practice of the
world’s largest cascade-reservoir group in the upper Yangtze River when facing a ood larger than that with a
100-year recurrence interval.
e Yangtze River, the third-longest river in the world, plays an paramount role in the economy, energy, and
ecology of China14–17; it has a basin area of 1.8 × 106 km2 that serves a population of nearly 50 million people,
generates 40% of the China’s Gross Domestic Product (GDP), and outputs 30% of China’s grain. e Yangtze
River Basin is shown in Fig.1a, where the distribution of population density is developed by Socioeconomic
Data and Applications Center18. Reservoir groups on the upper Yangtze River are vital for ood control in the
middle and lower regions19,20. e largest cooperation system of reservoirs in the world is constructed in the
upper Yangtze River Basin, as shown in Fig.1b, which counts for 22 cascade reservoirs with a total ood control
OPEN
1China Yangtze Power Co., Ltd., Yichang 443133, China. 2Hubei Key Laboratory of Intelligent Yangtze and
Hydroelectric Science, Yichang 443133, China. 3School of Hydraulic Engineering, Dalian University of Technology,
Dalian 116024, China. 4Changjiang River Scientic Research Institute, Wuhan 430074, China. 5School of
Geography and Information Engineering, China University of Geosciences, Wuhan 430074, China. 6Kunming
Power Exchange Center Co., Ltd., Kunming 650011, China. 7Yunnan Power Grid Co., Ltd., Kunming 650011,
China. *email: dou.yhong@gmail.com; yelei@dlut.edu.cn
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capacity of 38.7 × 109 m321. e system takes the ree Gorges Reservoir (TGR; largest installed capacity in the
world) as the core reservoir, the cascade reservoirs in the lower Jinsha River, including Wudongde (7th), Xiluodu
(4th), and Xiangjiaba (11th), as the main reservoirs, and the cascade reservoir groups in the middle Jinsha River
(six reservoirs), Yalong River (two reservoirs), Min River (two reservoirs), Jialing River (four reservoirs), and
Wu River (four reservoirs) as the coordinating reservoirs.
Challenges
Severe oods of Yangtze river. Rainfall distribution is grossly inhomogeneous in both spatial and tem-
poral aspects in the Yangtze River Basin, beneting from its location in the subtropical monsoon climate zone
on the east coast of Eurasia22,23. As a result, oods occur frequently in the Yangtze River Basin and are usually
characterized by a strong sudden occurrence, signicant areal extent, and massive loss of lives and property24,25.
Figure1. (a) e geographical location, streams, reservoirs and population density of Yangzte River Basin
generated by ArcGIS 10.2. (b) Sketch map of 22 reservoirs on the upper Yangtze River included in the joint
operation until 2020, where the circles represent reservoirs.
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In 2020, ve severe oods occurred between July and August along the Yangtze River as shown in Fig.2. e
TGR, located in the middle Yangtze River, experienced the highest inow of 74,600 m3/s since its construction.
Among the ve numbered oods, 4th and 5th oods (from Aug-14 to Aug-22) were caused by two continuous
rainfalls characterized by long duration, high intensity, and overlapping rainfall elds which covered most of the
upper Yangtze River. During the rainstorm, the 5-day accumulated rainfall exceeded 400mm, meaning that half
of the average annual rainfall fell in just ve days. As a result, ood peaks of the upper Yangtze River tributaries
would encounter before entering the TGR and a ood larger than that with a 100-year recurrence interval would
be formed without reservoir operation.
Complex operating decision of super large reservoir groups. Cooperation of reservoirs in the main‑
stream and tributaries. According to the joint operation scheme, when a severe ood occurs, the TGR and
the 21 upstream reservoirs will coordinate with each other to control the ood. is means that the upstream
reservoirs would not only perform their own ood control tasks, but also reserve part of their ood control ca-
pacity, known as reserved ood control capacity, to cooperate with the TGR to mitigate ooding in the middle
and lower regions of the Yangtze River. e mainstream ood may be comprised of two or even more oods
in the tributaries owing to the numerous tributaries and their frequent ood encounters in the Yangtze River26.
Considering the complicated composition of mainstream oods, various cooperation schemes should be used
for the reservoirs on the mainstream and tributaries. Additionally, the distance between each reservoir group is
signicant as shown in Fig.1a, which increases the inherent uncertainty of ood routing and rainstorm displace-
ment direction forecasting. erefore, the real-time joint operation of the super large reservoir groups faces the
problem of how to determine the utilization order of the reserved ood control capacity, as well as how much
to use and maintain.
Impact on stable power supply. e cascade hydropower stations on the upper Yangtze River are the key
power sources of China27. e theoretical and exploitable hydropower resources in the Yangtze River Basin
are 2.68 × 109kW and 2.35 × 109kW, respectively, out of which the upper Yangtze River accounts for more than
90%. Considering the Xiluodu-Xiangjiaba-ree Gorges cascade stations as an example, these three stations
are responsible for power supply to nine of the most economically developed provinces and cities in China,
including Guangdong, Jiangsu, Zhejiang, and Shanghai28. However, when cooperating with the downstream or
mainstream reservoirs, the upstream or tributary reservoirs must reduce discharge to release the reserved ood
control capacity, leading to a decrease in the output of the hydropower stations and making it dicult to gener-
ate stable power as specied in the original generation schedule29–31. With respect to the status of the cascade
hydropower stations on the upper Yangtze River, erratic hydropower supply aects other power sources in the
power grid like dominoes, particularly by decreasing the output during the peak summer months. erefore,
the second problem that the real-time joint operation of super large reservoir groups faces is how to adjust the
generation schedule.
Impact on safe operation. During a severe ood, the increasing inow and exible discharge of reservoirs
quickly change the water levels of both upstream and downstream dams, impacting the safe operation of water
conservation projects32 and shipping transportation. Taking Xiangjiaba reservoir as an example, if the daily vari-
ation in the water level exceeds 4m, it leads to reservoir bank instability33, and if the water level variation is too
large in the downstream dam, shipping safety is aected8. erefore, precise control of water level variation is
necessary, particularly at night, adding additional uncertainties owing to fewer sta.
Figure2. Outow, inow, and water level of TGR during 2020 ood season.
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Coordination of multiple departments. Each reservoir included in the upper Yangtze River cooperation system
is responsible for multiple simultaneous missions, such as ood control, power generation, and shipping7,8, etc.
e operation of reservoirs aects the competition-relation benets of multiple departments34. For example,
when facing a ood, the objective of Changjiang Water Resources Commission (CWRC) of the Ministry of
Water Resources (i in the Fig.3) is mitigating the threat of ood to the protection objectives in the basin, such
as populated localities, factories and farmlands. For this purpose, impounding and/or discharging of reservoirs
will cause frequent changes of water level and ow, which aects shipping and power generation signicantly.
Both the Changjiang Waterway Bureau (CWB) of the Ministry of Transport and power grid corporations hope
to reduce the duration of such abnormal operation as much as possible (ii and iii in the Fig.3). Additionally, it
is necessary to consider maintenance schedules and upper limits of transmission for each hydropower station
(iv in the Fig.3). erefore, one problem reservoir cooperation decision making faces, is how to manage and
balance the objectives and requirements of multi-departments.
Achievements of cascade-reservoir cooperation
Flood control. To prevent the 1st, 2nd, and 3rd oods of the Yangtze River in 2020, 20.5 × 109 m3 of the
ood control capacity of the 22 joint-operation reservoirs was used, accounting for 53% of the total ood con-
trol capacity. On this basis, to prevent the 4th and 5th oods, the cascade reservoir groups cooperated on a large
scale again and held up 19.0 × 109 m3 of ood volume. ere is 8.2 × 109 m3 of ood volume held up by the 21
reservoirs upstream of the TGR, as shown in Fig.4, which prevented ood peak encounters of the Jinsha River
(Xiangjiaba Station), Minjiang River (Gaochang Station), and Jialing River (Beibei Station). As a result, before
the ood enters the TGR (Cuntan Station), the ood peak with a 90-year recurrence interval (87,500 m3/s) was
reduced to 20years (74,600 m3/s), the ood volume with a 130-year recurrence interval was reduced to 40years
(36.00 × 109 m3), and the peak river stage was reduced by 3m. In this manner, ood control pressure at the tail
of the TGR was signicantly mitigated. e other 10.8 × 109 m3 of ood volume was held up by the TGR, which
reduced the ood with a 50-year recurrence interval (40.00 × 109 m3) to an ordinary ood and avoided the uti-
lization of the Jingjiang Flood Diversion Area. e above ood control cooperation prevented signicant direct
property loss in the middle Yangtze River, such as the evacuation of 600,000 people and inundation of 330 km3
of farmlands and more than 70 km3 of aquaculture areas.
Hydropower generation. In response to ood control, power grid companies adjusted the hydropower
generation schedules of relevant reservoirs eciently and scientically to ensure stable power supply, ecient
use of water resources, and greater power generation. Taking the operation of the Xiangjiaba Reservoir during
the 4th and 5th ood as an example, the Xiangjiaba Reservoir had to reduce the discharge and hold the ood in
order to cooperate with the TGR, resulting in decreased ow through the turbine and the plummeting power
generation. e State Grid quickly adjusted the power generation schedule, that is, permitted the output of the
Xiangjiaba hydropower station to be reduced to 2.2 × 106 kW at 17:00 on Aug. 17, and subsequently, the output
was increased to the rated power at 9:00 a.m. on Aug. 19. During the entire process, no water spillage occurred.
As a result, the Xiluodu-Xiangjiaba cascade hydropower stations and the single station of the TGR generated
Figure3. e relationship between six types of water-related departments, where i to iv indicate the objectives
and/or requirements of each corresponding type of department for reservoir cooperation, and v indicates
the submission of the cooperation scheme ensemble from Cascaded Reservoir Operation Center (CROC) to
Flood Control and Drought Relief Headquarters (FCDRH) considering the above objectives and requirements.
e nal cooperation scheme is determined through multi-department consultation under the leadership of
FCDRH.
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electricity outputs of 3.20 × 1010 kWh and 1.67 × 1010 kWh, respectively in August 2020, which are 49% and
42%, respectively more than the 10-year average in the same period. In addition, the TGR hydropower station
generated electricity output of 1.12 × 1011 kWh in 2020, hitting a world record for annual output of a single
hydropower station35.
Safe operation. e water level variations of both the upstream and downstream dams met the correspond-
ing regulation during the ood control cooperation owing to the benet derived from the forecast of precipita-
tion and hydrology and the simulation of hydrodynamics and reservoir operation. e daily water level variation
of the Xiluodu and Xiangjiaba reservoirs were 4.95m (5m in regulation) and 3.73m (4m in regulation) respec-
tively, which is the largest since their construction. From July to September 2020, more than 4500 ships and 15
million tons of cargo successfully passed through the waterway in an orderly manner.
Reections
Real-time cooperation was adopted for cascade reservoir groups for controlling oods in 2020, realizing the full
reservoir operation potential. During the real-time cooperation, conventional operation schedules and regula-
tions are always not applicable. Below are three key reections from the reservoir operation during the 2020
Yangtze River ood.
Figure4. e triangles represent the hydrological stations; and naturalized and measured ows of major
hydrological stations in the upper Yangtze River during 4th and 5th oods, where the naturalized ow of the
stations on the Jinsha River (Xiangjiaba), Min River (Gaochang), Jialing River (Beibei), and upstream of the
TGR (Cuntan) is obtained using the Intelligent Changjiang Decision Support System (ICDSS) according to the
actual operational data of upstream reservoirs and considering the ood travel time and water balance.
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Accurate forecast of precipitation and ow. Technicians from the CROC of China Yangtze Power Co.,
Ltd. forecasted the extreme precipitation and oods two weeks ahead of the 4th ood qualitatively, 2 oods with
both peaks of more than 60,000 m3/s a week ahead qualitatively, and the discharge and appearance times of the
ood peaks 3–5days ahead quantitatively, using the system that is responsible for precipitation and hydrology
forecasting in ICJDSS (details can be seen in “Methods and materials” section). Owing to the lower accuracy
of the forecast with a longer leading time36, the forecast changed from qualitative estimation to quantitative
prediction with the gradual approach of the forecast target. e quantitative forecast performance is presented
in Table1.
Following the qualitative precipitation forecast of the next 7–14days, the water level of the TGR dropped from
163.36m on Jul-29 to 153.03m on Aug-14 (its ood limited water level is 145m) by pre-discharging; further,
17.75 × 109 m3 of the ood control capacity was reserved, accounting for 80% of the total ood control capac-
ity of the TGR, which ensured adequate preparation for ood control and time to adjust the power generation
schedule. Following the quantitative ood forecast of the next 3–5days, the reserved ood control capacity of
upstream reservoirs (mentioned in section“Complex operating decision of super large reservoir groups”) was
released to hold up a portion of the ood and stagger ood peaks through real-time joint operation.
Scientic cooperation of cascade reservoir groups. In recent years, research eorts on the joint oper-
ation and coordinated management of reservoirs in the upstream Yangtze River have continued to increase, and
the application of scientic cooperation of cascade reservoir groups has also been enriched.
In terms of a cooperation scheme, the ood control capacity of the reservoirs in the upper Yangtze River
is reserved for cooperation with other reservoirs, and the reserved capacity is gradually released based on the
ood season stages37,38 and the reservoir classications. Specically, (1) In the main ood season, the necessary
capacity is reserved to hold the possible oods, and gradually released when the inow shows a declining trend
during the post-ood season. (2) e release order of each reservoir depends on ood encounter situations,
its own ood control tasks, and its role in cooperation with the TGR for ood control of the middle and lower
Yangtze River regions.
In terms of real-time cooperation, existing technology is used to predict or identify the ood type39, whereas
the ood control capacity of cascade reservoirs is determined by regulating each type of ood in the entire basin
during the design stage. erefore, in the case where there is no need to prevent various ood types simultane-
ously, some reservoirs have surplus ood control capacity. e surplus capacity of upstream reservoirs share the
ood control tasks of the downstream reservoirs, and as a result, the water levels of the downstream reservoirs
can be raised to increase the benet without increasing the ood risk of the entire basin40. In this manner, reser-
voirs can be compensated by the capacity of each reservoir based on the relatively accurate forecast and the joint
operation pattern, so that the water levels of some reservoirs with signicant benets in the ood season can be
relatively high and exibly controlled without strictly following a single ood limit water level. For instance, with
the most signicant benets in the Yangtze River, the legislative ood limit water level of TGR ranges from 145.0
to 146.5m. Between the 3rd and the 4th ood, the water level of the TGR was reduced to 153.03m by maximum
discharge through turbines, rather than the ood limit water level of 145m with water spillage, as the upstream
reservoirs could hold up part of the ood41,42. In Fig.4, it can be observed from the dierence between the natu-
ralized and measured ows at the Xiangjiaba Station that the Xiangjiaba reservoir and its upstream reservoirs play
an important role in ood storage and ood peak staggering; at the Gaochang and Beibei Stations, the reservoirs
in the Min and Jialing Rivers also hold up part of the ood, so that the ood peaks of the Gaochang and Beibei
Stations with recurrence intervals of 40–50years (40,600 m3/s) and 10–15years (38,400 m3/s), respectively were
reduced to 10–15years (37,500 m3/s) and 10years (37,400 m3/s), respectively.
Regulations for multi-department coordination. e Yangtze River reservoirs can be exibly used to
realize the potential benets safely by joint operation, which is inseparable from the state macro-coordination
(state FCDRH) and the cooperation of the local governments (local FCDRH), the basin management organiza-
tion (CWRC), the transport department (CWB), hydropower stations and power grid companies. As an inter-
mediary of multiple departments, CROC is responsible for the technical support of generating an ensemble
of potential cooperation schemes and information transport and management. During the 4th and 5th ood,
the above departments held 10 consultations on matters including real-time hydro-meteorological monitoring
and forecast information, real-time joint operation of reservoirs, and temporary adjustment of the hydropower
generation schedule. Reservoirs discharged exibly in real-time, rather than strictly following rigid operating
schedules and regulations.
Table 1. Quantitative forecast performance during 4th and 5th oods in 2020.
No
Measured Forecasted Evaluation
Peak ow (m3/s) Peak time Leading time Peak ow (m3/s) Peak time Error of peak ow Error of peak time
4 62,000 Aug-15 5 day 50,000 Aug-16 −19.35% 1 day
1 day 62,000 Aug-15 0 0
5 74,600 Aug-20 5 day 62,000 Aug-20 −17.33% 0
1 day 74,600 Aug-20 0 0
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To ensure a scientic, unied, and coordinated operation of the cascade reservoir groups in the Yangtze River
Basin, a series of relevant regulations have been established in recent years. In the aspect of monitoring and
management, the institutional mechanism dedicated to information sharing, benets compensation43, and risk
control44,45 for the reservoir groups has been established. In terms of the administrative system, the coordination
mechanism dedicated to multiple departments involving water resources, power, shipping, and environmental
protection has been improved46 based on the existing ood control organization47. On the basis of continuous
improvement of the above mechanisms and systems, the legislation of the Law of the People’s Republic of China
on the Protection of the Yangtze River was promoted, which was promulgated on December 26, 2020, and came
into force on March 1, 202148.
Call for action
Largely drawing on the reections reported based on the reservoir cooperation during the 2020 Yangtze River,
we suggest the following action points to realize the full potential of the reservoir operation of the Yangtze River
basin and other basins with large reservoir groups in the world:
1. Improve ood forecast accuracy with a long lead time. Accurate ood forecast is the premise of joint and
precise operation of reservoir groups, adjustment of the power generation schedule, and multi-department
cooperation.
2. Continue to study the cooperation of reservoir groups. As the number of reservoirs included in the joint
operation increases constantly, new situations and challenges with new requirements will gradually become
prominent. It is necessary to conduct research on the cooperation of reservoir groups and to formulate
scientic counter measures.
3. Improve and implement regulations for the coordinated operation of large reservoir groups. A powerful
coordination regulation has the potential to guarantee eective implementation of the scientic operation
of super large reservoir groups.
Methods and materials
Decision making of reservoir cooperation in upper Yangtze River Basin includes three steps. Firstly, the prelimi-
nary ensemble of cooperation schemes is obtained by Cascaded Reservoir Operation Center (CROC) through
Intelligent Changjiang Decision Support System (ICDSS), powered by China Yangtze Power Co., Ltd. Secondly,
departments through rounds of consultation to determine the nal cooperation scheme. Finally, ICDSS reanalysis
will be used to summarize the experience aer the ood.
Intelligent Changjiang decision support system. Intelligent Changjiang Decision Support System
is vital for the reservoir groups to optimally achieve the comprehensive operation objectives of ood control,
power generation, shipping and ecology by building a tailored technology framework. ICDSS includes four
main components: a data acquisition and management system; a set of interlinked models and data-model-user
interactive interface; a socioeconomic evaluation system; and crisis management plans.
Data acquisition and management system. is system is responsible for automatic collecting and managing
unstructured data (e.g., hydro-meteorology data, operation data and grid load data) and semi-structured data
(e.g., operation regulations and instructions). In the upper Yangtze River Basin, there are 1005 hydrological sta-
tions (of which 372 are managed by local Hydrological Bureau and 633 by CRCC), 12,129 precipitation stations
(of which 730 are national stations, 11,000 are local stations and 399 are managed by CROC), and 37 national
ground-based radars. e failure rate of the above stations was 1.7% in the past three years.
Interlinked models and data‑model‑user interactive interface.
a. Simulation of upstream reservoir operation: e operation of cascade hydropower stations in the upper
Yangtze River changes the propagation characteristics of natural ow, as a result, the accuracy of hydrological
forecasting is aected. erefore, this system is responsible for mining rules of impounding and discharging
for upper reservoirs that is not included in joint operation and anticipating discharge of these reservoirs.
b. Hydro-meteorological forecast and discharge routing simulation49–52: e system is composed of the
Xin’anjiang model with 377 subunits, the one-dimensional hydrodynamic model, and the error correction
module. Each module of the system runs automatically but can also be supplemented by human–machine
interaction functions depending on the experience of the forecasters.
c. Optimal cooperation of cascade-reservoir groups with dierent leading time53–56: is system is responsible
for generating the optimal ensemble of reservoir cooperation based on hydro-meteorological forecast with
dierent leading time. e NSGA-II is used to obtain the optimal cooperation schemes and Pareto solutions
of corresponding objectives. Hedging theory and marginal benet theory are used to analyze the competition
between risk and benet. As the update of forecast information with dierent leading time, the ensemble of
reservoir cooperation is rolling executed.
Socioeconomic evaluation system. is system is responsible for evaluation and reanalysis the cooperation pro-
cess of cascade-reservoir groups. By analyzing the contribution of each reservoir in cascade-reservoir groups
to ood control, power generation, shipping and ecology, the inuence of man-made and natural factors in the
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comprehensive achievements is claried, and the operation scheme will be revised and improved based the re-
evaluation of results.
Crisis management plans. ere are 22 crisis management plans for failures of automatic control systems,
equipment and power, as well as kinds of accidents and emergencies.
Received: 18 August 2021; Accepted: 2 February 2022
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Acknowledgements
is work was supported by the National Natural Science Foundation of China (Nos. 51925902, 51909010)
and the Fundamental Research Funds for the Central Universities (No. DUT20RC(3)019). All data, models, or
code generated or used during the study are available from the corresponding author upon reasonable request.
Author contributions
All authors contributed extensively to the work presented in this paper. H.Z., Y.D., and L.Y. conceived of and
designed the paper. Y.D. and L.Y. performed some of the analysis and prepare the manuscript. H.Z., Y.D., and
C.Z. provided nancial support. H.Y, Z.B., Z.T., Y.W., Y.H., S.Z., M.X., J.W., C.S., Y.R., D.Z., B.W., and Y.C. con-
tributed to the real-time reservoir cooperation. All co-authors contributed to the editing of the manuscript and
to the discussion and interpretation of the results.
Competing interests
e authors declare no competing interests.
Additional information
Correspondence and requests for materials should be addressed to Y.D.orL.Y.
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