Downstream Residents Research Articles

Risk dynamics modeling of reservoir dam break for safety control in the emergency response process

Abstract Dam break is an accident that may heavily threat downstream residents' life and property safety, especially in China. As revealed by accident investigation statistics, both flawed organizational behavior and inadequate downstream resident risk awareness have affected the safety risk of reservoir dams. Multiple information transferring mode and dynamic processes perform with the characteristics of social-technical systems. Based on the system dynamics approach, this study proposed a risk causation model aiming for factor interactions involving organizational, human, and technical system levels. The derived simulation model represented the historical risk evolution process of Gouhou reservoir in China and the rationality of the proposed model was verified. To further improve the efficiency of the organizational response and monitor real-time dam safety, a software tool called Dam Emergency Response Aids (DERA) was constructed to evaluate the potential safety benefits of risk control measures, and to overcome the defects of static emergency plans. By integrating relevant professional modules and data, the mobile application (APP) has been applied on the Jinniu Mountain reservoir dam in Nanjing of China and helped to maintain its excellent safety operation until now. It shows that the risk dynamics model proposed can improve the abilities of dam operating management organization for more effective responses under emergency circumstances.

Hydropower dams, river drought and health effects: A detection and attribution study in the lower Mekong Delta Region

The upstream construction of hydropower dams may drastically intensify climate change impacts due to changing the natural river flood-drought cycle and reducing the amount of water that flows into the lower Mekong Delta river, leading to hydrological and environmental health impacts. However, until now the influence of drought on residents’ health in the lower MDR, where river drought is highly sensitive to recently built hydropower plants, has not been examined. The objectives of this study are, for the first time, to detect the health impacts of river drought on residents and to evaluate the contribution of hydropower dams to the impacts of drought on health in the lower Mekong Delta Region (MDR). We applied the multi-step approaches of a Detection and Attribution study. First, we detected the effects of the river drought on the risk of hospitalization using a Multivariable Fractional Polynomials algorithm (MFP). Second, we linked the long-term changes of the river water level (RWL) to the operation of the first hydropower dam in the upper MDR using the interrupted time-series model (ITS). Finally, we quantified the hospitalizations and related economic loss attributed to the river drought. The results show that the percentage changes in risk of all-cause, respiratory, and renal hospitalizations attributed to the river drought were 2%, 2%, and 7%. There were significant reductions in average level and trend of the RWL during the post-1995 period, when the first hydropower dam began operation in the upper MDR, even though the cumulative rainfall in the MDR had not changed. The all-cause hospitalizations attributed to the river drought were 1134 cases during the period 1995–2014, which resulted in total additional cost at two provincial hospitals of US $360,385. This current study demonstrates the link between hydropower dams, river drought, and health impacts. As the MDR is highly vulnerable to climate change, these findings about the devastating impacts of hydropower dams and environmental change have important implications for the lives of downstream residents.

Study on Environmental Risk Assessment and Control Countermeasures of Tailings pond in a Mountainous Area of North China

The safety and environmental accidents of the tailings pond are likely to cause pollution of surrounding soil and water bodies, and endanger the safety of life and production of surrounding residents. In this study, the analytic hierarchy process (ahp) was used to score environmental sensitivity and control mechanism reliability of tailings ponds. The environmental risk rating model was used to characterize the environmental risk rating of tailings pond. The risk level characterization and evaluation results show that the four tailings ponds were general risks to downstream residents and the environment. Suggestions on environmental risk control of the upstream tailings pond were put forward.

Reservoir dam operating risk dynamics modelling for safety control in the emergency response process

As revealed by the dam break accident investigation statistics, flawed organizational behavior determines the safety level of the reservoir dam. Its operating risk revolution process involves water, disaster, relief material dispatching, information interaction, and so on. The multiple information transferring mode and dynamic processes perform with the characteristics of the social-technical system, but little prior research on the risk causality can be found in such a view. The traditional risk analysis and assessment techniques based on linear accident model and the partial probability calculation cannot effectively satisfy the requirements for dam-break emergency decision-making in a dynamic and systematic way. Based on the system dynamics approach, this study proposed risk dynamics models aiming for risk interaction mechanisms involving organizational, human, and technical system factors leading to dam break. The models guided the development of a quantitative risk assessment tool to integrate relevant professional modules and data. The derived policy suggestions which guarantee the life and property of downstream residents can improve the abilities of dam operating management organization for more effective responses under emergency circumstances.

Flood Routing Process and High Dam Interception of Natural Discharge from the 2018 Baige Landslide-Dammed Lake

The outburst flood of the Baige landslide dam caused tremendous damage to infrastructure, unfinished hydraulic buildings, roads, and bridges that were built or under construction along the Jinsha River. Can downstream hydraulic buildings, such as high dams with flood control and discharge function, accommodate outburst floods or generate more serious losses due to wave overtopping? In this study, the unsteady flow of a one-dimensional hydraulic calculation was used to simulate natural flood discharge. Assuming a high dam (Yebatan arch dam) is constructed downstream, the flood processes were carried out in two forms of high dam interception (complete interception, comprehensive flood control of blocking and draining). Moreover, three-dimensional visualization of the inundation area was performed. Simulation results indicate that the Yebatan Hydropower Station can completely eliminate the outburst flood risk even under the most dangerous situations. This station can reduce the flood peak and delay the peak flood arrival time. Specifically, the flood peak decreased more obviously when it was closer to the upstream area, and the flood peak arrival time was more delayed when the flood spread further downstream. In addition, the downstream water depth was reduced by approximately 10 m, and the inundation area was reduced to half of the natural discharge. This phenomenon shows that hydraulic buildings such as high dams can reduce the inundation area of downstream farmlands and extend the evacuation time for downstream residents during the flood process, thus reducing the loss of life and property.

Investigation of influence of baffles on landslide debris mobility by 3D material point method

In mountainous terrain, landslide debris is a common occurrence around the world that can potentially result in catastrophic consequences to downstream residents and facilities. Arrays of baffles are increasingly used as energy dissipaters for the protection from debris flow due to their low cost and environmental impact. However, the development of a numerical tool for the rational design of such structures is still a challenge. In this work, a material point method computational framework is presented, using two contact models to describe the landslide debris movement and interaction with structures, respectively. Flume model experiments are adopted as calibration and good agreements are exhibited in flow kinematics between computed results and physical model tests. Simulations on an idealized scenario of landslide debris flow show how the baffle geometry/arrangement has key effects on the debris movement and deposition. The impact force in soil-structure interaction has also been studied, showing the ability of this method on evaluation force characteristics acted on baffle structures.

Examining the role of parasites in limiting unidirectional gene flow between lake and river sticklebacks.

Parasites are important selective agents with the potential to limit gene flow between host populations by shaping local host immunocompetence. We report on a contact zone between lake and river three-spined sticklebacks (Gasterosteus aculeatus) that offers the ideal biogeographic setting to explore the role of parasite-mediated selection on reproductive isolation. A waterfall acts as a natural barrier and enforces unidirectional migration from the upstream river stickleback population to the downstream river and lake populations. We assessed population genetic structure and parasite communities over four years. In a set of controlled experimental infections, we compared parasite susceptibility of upstream and downstream fish by exposing laboratory-bred upstream river and lake fish, as well as hybrids, to two common lake parasite species: a generalist trematode parasite, Diplostomum pseudospathaceum, and a host-specific cestode, Schistocephalus solidus. We found consistent genetic differentiation between upstream and downstream populations across four sampling years, even though the downstream river consisted of ~10% first-generation migrants from the upstream population as detected by parentage analysis. Fish in the upstream population had lower genetic diversity and were strikingly devoid of macroparasites. Through experimental infections, we demonstrated that upstream fish and their hybrids had higher susceptibility to parasite infections than downstream fish. Despite this, naturally sampled upstream migrants were less infected than downstream residents. Thus, migrants coming from a parasite-free environment may enjoy an initial fitness advantage, but their descendants seem likely to suffer from higher parasite loads. Our results suggest that adaptation to distinct parasite communities can influence stickleback invasion success and may represent a barrier to gene flow, even between close and connected populations.

Erosion-based analysis of breaching of Baige landslide dams on the Jinsha River, China, in 2018

The Yangtze River is one of the most important rivers in China due to its large basin size, the large population along the river, and the numerous large dams and reservoirs on the river. The Jinsha River, the upper reach of the Yangtze River, was dammed twice recently at Baige, Tibet, one on 10 October 2018 and the other on 3 November 2018 (UTC + 8). Accordingly, two large landslide dams, 61 m and 96 m in height to the lowest dam crest, were formed in a 3-week interval. Due to the large inflow rates at the time of damming, the barrier lake level rose rapidly, posing huge risks to the downstream residents and properties. In managing the landslide dam risk, one of the important tasks is to predict the dam breaching flood beforehand. This paper focuses on rapid prediction of the dam breaching hydrograph and breach geometric parameters of the two landslide dams. The predictions were made timely before the breaching of the two landslide dams using both erosion-based empirical equations and numerical simulation and were refined based on detailed field investigation at the site after breaching. Comprehensive field investigations were conducted to determine the geological structures of the landslide dams, characterize the erodibility of dam materials, and measure the final beach dimensions. The simulated dam breaching processes, outflow hydrographs, lake water level changes, and final breach dimensions were validated by field observations. Compared with the hypothetical scenario without a diversion channel on the second landslide dam, a diversion channel 15 m in depth successfully lowered the peak flood discharge by about one third and helped to mitigate the flood risk significantly. The analysis outcome serves as basis for warning and evacuation of the downstream residents and making appropriate engineering risk mitigation plans.

Optimize multi-objective transformation rules of water-sediment regulation for cascade reservoirs in the Upper Yellow River of China

Frequent occurrence of flood and ice disasters caused by river channel sedimentation in the Upper Yellow River of China has seriously threatened the lives and property of downstream residents, which has become the most challenging issues in harnessing the Yellow River. In this paper, we aim at optimizing water-sediment regulation that considers two cascade reservoirs (Longyangxia and Liujiaxia) as the regulatory bodies using one multi-objective model (sediment transport and hydropower generation) and two single-objective models (sediment transport only, and hydropower generation only). We propose an innovative approach (FSS-MOPSO) that hybrids the Feasible Search Space (FSS) with the Multi-Objective Particle Swarm Optimization (MOPSO) algorithm to search the optimal solutions for the multi-objective joint operation of cascade reservoirs. We analyze the transformation rules of water-sediment regulation among five objectives (hydropower generation, sediment transport, water supply, flood control and ice control) under various optimization schemes. The results indicate that the conflict between the hydropower generation objective and the sediment transport objective is prominent. An extreme case indicates that an increase in hydropower output by 2.31 billion kW·h (17.6% increase) would greatly reduce the amount of sediment transport (73.5% decrease) while only makes little effects on the other three objectives. The results demonstrate that the optimal water-sediment regulation not only can ensure to meet water demands in the future (2030) but can provide an important guideline to safely operate cascade reservoirs during ice and flood periods. The research findings contribute to the identification of the relationship among objectives and strategy recommendations on water-sediment regulation for efficient cascade reservoirs operation in the Upper Yellow River.

On the mechanical damage to tailings sands subjected to dry–wet cycles

The safety of tailings ponds is considered to be one of the greatest environmental challenges in the field of energy and mining engineering. Impacted by factors such as rainfall infiltration, recycling water, dry beach face evaporation, tailings sands close to the saturation line in tailings ponds are subject to frequent dry–wet (DW) cycles. DW cycles aggravate the potential for damage to the mechanical properties of tailings sands, reduce the safety of tailings ponds, and pose a threat to the life and property of downstream residents. However, the behavior of the mechanical properties of tailing sands subjected to DW cycles due to damage to the tailing sands is still poorly understood from a stability analysis perspective. Therefore, we have conducted laboratory tests, including direct shear and matric suction tests, on tailings sands under conditions of DW cycling to improve our understanding of the DW cycling process of tailings sands. Based on the test results, we propose an innovative damage mechanism of shear strength, cohesion, and internal friction angle of tailings sands in association with DW cycles. We also introduce the cumulative damage rate of cohesion (Dc) and the cumulative damage rate of internal friction angle (Dφ) parameters in order to determine the relationship between the number of DW cycles (n) and Dc, and between n and $$ {D}_{\varphi } $$ . Finally, the effect of number of DW cycles on the matric suction of tailings sands was analyzed. We found that with increasing number of DW cycles, the soil–water characteristic curve of tailings sands tended to shift to the left. The results of this study provide a foundation for understanding the mechanical behavior of tailings sands under conditions of DW cycles as well as guidelines for the prediction and mitigation of the stability of tailings ponds.

Bhutan’s Forests through the Framework of Ecosystem Services: Rapid Assessment in Three Forest Types

Forests in mountain ecosystems provide a diversity of services and goods in mountain landscapes, and the immediate utility of the forest to upstream residents must be balanced with the insurance forests provide for downstream residents in the form of, especially, the services of water regulation and soil stabilization. Little empirical data exist for Bhutan that confirm a causal link between upstream forest use and downstream security. To help to fill this gap, we summarize the results of two literature reviews related to forest ecosystem services and human well-being, using the framework of Bhutan’s Gross National Happiness (GNH). We report preliminary findings of three field-based assessments of forest ecosystem services on hillsides. We conducted an assessment of the perceptions of local residents about the forest ecosystem services in three distinct forest areas of Bhutan. The studies were carried out in high-altitude oak forests, forest management units (FMUs) in government reserve forests, and community plantations. We engaged villagers in focus group discussions and conducted key informant interviews. The strongest evidence in the literature for linkages between forests and GNH was found for the role forests play in socio-economic development and good governance, particularly through the community forestry program. Regulating services of forests were cited as crucial to several aspects of human well-being, but little empirical evidence was provided. To local residents in the three study locations, the provisioning services of forests were highly ranked, as were water regulating services. At the plantation sites, residents felt that the new forests did improve soil stability and water provisioning services. Cultural services were identified but not highly prioritized. Awareness of forest ecosystem services was high among participants in the study, but understanding of the causal links between forest use and human well-being was mixed. Lack of direct evidence about causal pathways between upstream forest condition and downstream security leaves gaps in our knowledge and even perpetuates myths and misconceptions about the role that forests play. We encourage further research at multiple scales and using mixed methods to test hypotheses on the linkages between forests and human well-being in mountain landscapes.

Dynamic characteristics of tailings reservoir under seismic load

Earthquake is one of the most important factors that leads to the liquefaction of tailings and to the instability of the tailings reservoir. Therefore, it is of great practical significance to study the instability mechanism of the tailings reservoir under seismic load. In this study, the dynamic characteristics of the tailings reservoir under seismic load were investigated by carrying out a model test on the dynamic characteristics of the tailings dam. A model test of tailings dam failure and the dynamic characteristics model of the tailings reservoir under seismic load were established. Additionally, the dynamic characteristics under a seismic load were investigated. Additionally, the correctness of the dynamic characteristics model of the tailings reservoir was verified by numerical calculation. Researches show that with the increase in input peak acceleration, pore water pressure, earth pressure, and the horizontal and vertical displacements of the dam monitoring points are gradually increased. However, the acceleration amplification factor shows a declining trend. In the process of increasing the input peak acceleration, the saturation line and the lifting speed increases gradually. There is no obvious slip surface in the failure of the tailings dam, and the overall sliding is shown by the failure mode. The tailings reach each of the downstream sections. The mud height increases to the peak value, and then decreases gradually until stagnation. The results of this study can provide the theoretical basis and reference values for the stability analysis of a tailings reservoir under a seismic load, and the results are of great significance for controlling the risk factors in the operation of tailings reservoir, reducing the risk of tailings production safety, preventing the occurrence of tailing pond accidents, protecting the property safety of the downstream residents and enterprises, maintaining social stability around the reservoir area and creating a good ecological environment.

Analysis of the Factors Influencing Willingness to Pay and Payout Level for Ecological Environment Improvement of the Ganjiang River Basin

China has continuously stepped up its efforts to protect the ecological environment of the Ganjiang River Basin. The government has played a leading role, but the residents, who have also played an important role in this issue, are often overlooked. Consequently, it is necessary and urgent to study the willingness of the residents, who are the direct stakeholders, to pay for the protection of the ecological environment of the Ganjiang River Basin. Based on a survey of 773 households, this study examines the downstream residents’ willingness to pay (WTP) and their payout levels. Using the payment card (PC) contingent valuation method (CVM), we measure the payment probability of the downstream residents and the amount they are willing to pay. Additionally, Heckman’s two-stage model is adopted for exploring the influencing factors of the surveyed residents’ WTP and payout levels and avoiding the possible presence of sample selection bias. The results showed that 75.03% of the surveyed residents are willing to pay for ecological compensation in the Ganjiang River Basin. The downstream residents are willing to pay an annual average amount of about $47.62/household for ecological compensation. The factors that significantly influence their WTP include the educational background, work type, residential location, and water quality and quantity. In the case of payout levels, the influencing factors include the education background, work type, household annual disposable income, and water quality and quantity. In addition, the factor of value recognition is marginal and significantly related to WTP and payout levels. The results of this empirical study have important policy implications and recommendations that the government should intensify its propaganda about the ecological value, increase investment in education, and establish a variety of ecological compensation payments, in order to protect and improve the ecological environment of the Ganjiang River Basin.

The Design and Implementation of Displacement Monitoring System for Tailings Dam

Abstract Non-coal mining generally produces a large amount of tailings, and tailings usually accumulate in the canyon between two mountains, and the downstream of the tailings is intercepted by the dam. The dam is called a tailings dam. The development of safety monitoring technology for tailings dam is accompanied by the history of dam construction. The safety of tailings dam is not only related to the normal operation of mining industry, but also to the life safety of downstream residents. Once the tailings dam break, the loss caused by the dam is inestimable. In this paper, the laser collimation system is used to monitor the displacement of the dam, and the center of light is measured by the center of gravity, and the laser beam is reconstructed by a lens. The method has the advantages of high accuracy and simultaneous detection of horizontal displacement and vertical displacement of tailings dam. It is a new monitoring technology for dam displacement and has good application prospects.

Awareness and Involvement of Downstream Residents Toward the Mitigation Plan of Dam Failure: A Case Study of Klang Gate Dam

Dam planning development is important to provide water source to human and the environment. However, this development also poses a huge risk in the case of dam failure caused by natural disasters or operational failures. As part of the development of a dam, a mitigation plan should be provided to analyze the impact and provide the escape plan for the public residing in the risk areas. Hence, the public should be involved in the preparation of the mitigation plan to ensure the effectiveness of the plan. The current study seeks to determine the level of awareness and involvement of the public, especially the downstream residents in the preparation of the mitigation plan. This study also discusses the dam development planning in relation to dam failure and public involvement. A survey was done to investigate the level of awareness and involvement of the downstream residents in the chosen area towards the mitigation plan of dam failure. The major findings are hoped to guide in identifying the appropriate tools to improve the awareness of downstream residents in facing emergency situations resulting from dam failures.

Dynamics of grazing rights and their impact on mobile cattle herders in Bhutan

Seasonal cattle movements have been an important part of the living cultural heritage in Bhutan for centuries. Herders migrate south every winter to graze their cattle on subtropical pastures and to work in orange orchards. They return north to their villages in spring to grow summer crops. However, the practice of transhumant agropastoralism is under increasing pressure on account of changes in land-use policies, climate change and a declining labour force as youth seek alternative livelihoods. This research investigated the impact of changes in land-use policy, with emphasis on the Land Act 2007, on current and future livelihoods of transhumant herders in Bhutan. During in-depth interviews with 24 transhumant herders and nine livestock advisors, and seven focus-group discussions with 64 participants including herders, downstream residents and development agency personnel, perspectives on this issue were gathered. Findings revealed a lack of herder awareness of changes in land-use policies and minimal consultation of herders during policy development. Confusion and uncertainty about the proposed redistribution of grazing rights and restrictions on herd movements have resulted in confusion and resentment and have created conflicts between upstream and downstream communities. Herders with no current alternatives are concerned about their future livelihoods, whereas others are leaving it to their children to decide their future. It is concluded that the motive behind nationalisation of rangeland is noble and timely, but there are flaws in the redistribution plan. Transhumant agropastoralism is already in decline and there is no need to push towards its end through legislation. Transhumant practices could be left to evolve towards what may be their natural end. Sudden stoppage of inter-district transhumance without offering meaningful alternatives to herders could result in negative environmental and socioeconomic impacts. In future, policy development needs to increasingly embrace science and be based on evidence. A genuine participatory process with citizen engagement could avoid the unintended negative impacts likely to be faced by transhumant herders with marginal land holdings, who depend on this production system for their livelihoods.

Growth conditions after recruitment determine residence-emigration tactics of female Japanese eels Anguilla japonica

Back-calculated annual growth of 156 yellow-phase female Japanese eels Anguilla japonica sampled from freshwater sites in the Tsuchikawa River, Kagoshima, Japan, were compared among eels from the upper reaches (“upstream emigrants”), large eels (≥240 mm) from the lower reaches (“downstream residents”), and small eels ( 3 years of age. Back-calculated annual growth of large eels captured in the lower reaches was significantly greater than that of eels in the upper reaches for the first 3 years after recruitment (age 0–2 years), and small eels in the lower reaches had intermediate growth. These results suggest that female eels in this river decide whether to emigrate or reside in the lower reaches approximately 3 years after recruitment, and that slower-growing eels emigrate upstream, whereas faster-growing eels reside downstream.

Glacier changes in the eastern Nyainqêntanglha Range of Tibetan Plateau from 1975 to 2013

Maritime-type glaciers in the eastern Nyainqentanglha Range, located in the southeastern part of the Tibetan Plateau, are an important water source for downstream residents and ecological systems. To better understand the variability of glaciers in this region, we used the band ratio threshold (TM3/TM5 for the Landsat TM /ETM+ and TM4/TM6 for Landsat OLI) to extract glacier outlines in ~1999 and ~2013. After that, we also generated a series of glacier boundaries and monitored glacier variations in the past 40 years with the help of the Chinese Glacier Inventory data (1975) and Landsat TM, ETM+ and OLI data. The total glacier area decreased by 37.69 ± 2.84% from 1975 to 2013. The annual percentage area change (APAC) was ~1.32% a-1 and ~1.29% a-1 in the periods 1975-1999 and 1999-2013, respectively. According to the lag theory, the reaction time is probably about 10 years and we discuss the variations of temperature and precipitation between 1965 and 2011. Temperature and precipitation increased between 1965 and 2011 at a rate of 0.34°C /10a and 15.4 mm/10a, respectively. Extensive meteorological data show that the glacier shrinkage rate over the period may be mainly due to increasing air temperature, while the increasing precipitation partly made up for the mass loss of glacier ice resulting from increasing temperature may also lead to the low APAC between 1999 and 2013. The lag theory suggests that glacier shrinkage may accelerate in the next 10 years. Small glaciers were more sensitive to climate change, and there was a normal distribution between glacier area and elevation. Glaciers shrank in all aspects, and south aspects diminished faster than others.

Seismology-based early identification of dam-formation landquake events.

Flooding resulting from the bursting of dams formed by landquake events such as rock avalanches, landslides and debris flows can lead to serious bank erosion and inundation of populated areas near rivers. Seismic waves can be generated by landquake events which can be described as time-dependent forces (unloading/reloading cycles) acting on the Earth. In this study, we conduct inversions of long-period (LP, period ≥20 s) waveforms for the landquake force histories (LFHs) of ten events, which provide quantitative characterization of the initiation, propagation and termination stages of the slope failures. When the results obtained from LP waveforms are analyzed together with high-frequency (HF, 1–3 Hz) seismic signals, we find a relatively strong late-arriving seismic phase (dubbed Dam-forming phase or D-phase) recorded clearly in the HF waveforms at the closest stations, which potentially marks the time when the collapsed masses sliding into river and perhaps even impacting the topographic barrier on the opposite bank. Consequently, our approach to analyzing the LP and HF waveforms developed in this study has a high potential for identifying five dam-forming landquake events (DFLEs) in near real-time using broadband seismic records, which can provide timely warnings of the impending floods to downstream residents.

Pesticide Use and Health Outcomes: Evidence from Agricultural Water Pollution in China

This paper provides the first quasi-experimental evidence that pesticides adversely affect health outcomes through drinking water by linking provincial pesticide usage reports from several Chinese statistical yearbooks (1998-2011) with the Chinese Longitudinal Healthy Longevity Survey (1998-2011). First, we follow a difference-in-difference-in-differences (DDD) framework to compare health outcomes between people who drink surface water and ground water in regions with high and low intensity of rice pesticide use before and after 2004, when China shifted from taxing agriculture to subsidizing agricultural programs. Second, we measure the downstream effect of pesticide use from upstream provinces. Our results indicate that a 10% increase in rice pesticide use unfavorably alters the index of dependence (ADL) by 2.51% and 0.33% for local and downstream residents (65 and older), respectively. This is equivalent to 168.8 and 55.89 million dollars in medical costs and offspring’s human capital losses, respectively (in total, 1.92% of rice production profits). Our results are robust to a variety of robustness checks and falsification tests.