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Abstract The transboundary Arun River Basin (ARB) spreads across Nepal and Tibet. Nearly 95% of the basin lies in Tibet through which the Pumqu River flows, forming the Arun River once it enters Nepal. The ARB has five large hydropower projects undergoing construction or planned for the future. Rainfall and earthquake‐induced landslides, landslide‐dammed lakes and landslide‐induced glacial lake outburst floods pose major risks to smooth operation of these projects. To safeguard upcoming hydropower projects, areas susceptible to landslides in the ARB must be identified. We used high‐resolution satellite imagery and open‐source tools to generate a multitemporal landslide inventory for the basin. The rigorously quality‐controlled inventory represents a yearly record of landslides from 2011 to 2020. A data‐driven approach was used to map areas susceptible to landslides within the ARB. The multitemporal landslide inventory combined with other readily available Earth observation‐based variables was used to create a landslide susceptibility map. The susceptibility analysis provides a valuable initial estimate of where landslides are likely to initiate. These landslide products could form the basis of more comprehensive local studies to inform hydropower project development.

Abstract Power system unreliability tracing model allocates the system's reliability index to individual components, identifying potential weaknesses. This study expands its scope by considering the impact of storage resources. Unreliable factors leading to load shedding are categorized into two groups: objective factors inherent to the component and insufficient storage resources. The latter requires a retrospective analysis of other components that caused unreliability previously. When allocating responsibility for load shedding at a certain time, it begins by allocating it among components based on differences between fixed expected output and actual supply. Expected output insufficiency is considered as the unreliable factor. This insufficiency due to insufficient storage resources is then decomposed into segments, each caused by excessive output in earlier instances of the same component. The expected output excess is attributed to the expected output insufficiency of other components in previous times, for which responsibility has been allocated to each component. Consequently, the expected output insufficiency at a particular time can be traced back based on a temporal recursive model, with the load shedding further allocated to components before that time. Case studies based on several systems demonstrate that the proposed model's allocation results are reasonable and more accurate than the traditional model.

Abstract Habitat loss and fragmentation are leading contributors to the endangered status of species. In 2006, the Nakai Plateau contained the largest known Asian elephant (Elephas maximus) population in the Lao People's Democratic Republic (Lao PDR), and the population was among those with the highest genetic diversity reported for Asian elephants. In 2008, completion of the Nam Theun 2 hydroelectric dam inundated much of the Plateau, resulting in the loss of 40% of elephant habitat. We studied elephant presence, movements, and the incidence of human–elephant conflict (HEC) on the Nakai Plateau and surrounding areas from 2004 to 2020, before and for 12 years after dam completion. To examine contemporary population dynamics in the Nakai elephants, we used genetic sampling to compare minimum population numbers, demography, and levels of genetic diversity from the wet and dry seasons in 2018/2019, 10 years after dam completion, with those reported in a pre‐dam‐completion genetic survey. After dam completion, we found a major increase in HEC locally and the creation of new, serious, and persistent HEC problems as far as 100 km away. While we were unable to compare estimated population sizes before and after dam completion, our data revealed a decrease in genetic diversity, a male‐biased sex ratio, and evidence of dispersal from the Plateau by breeding‐age females. Our results raise concerns about the long‐term viability of this important population as well as that of other species in this region. Given that hydropower projects are of economic importance throughout Laos and elsewhere in southeast Asia, this study has important implications for understanding and mitigating their impact.

Abstract Hydroelectric power has unusual technical characteristics that could become more valuable as the penetration of variable generation renewables grows, but its use for electricity generation is constrained by complex physical, safety, and socioenvironmental considerations. Hydroelectricity can therefore be difficult to represent in national‐scale energy models, and is frequently presumed to be either overly flexible or inflexible. While a few grid models address this complexity via detailed hydraulic process models, more simplified optimization and dispatch models could benefit from the use of empirical parameter values. In this study, we combine a new data set comprising 7.8 million flow‐hours of data from 2011 to 2016 at 158 dams across the United States with monthly and hourly generation data from the U.S. Energy Information Administration (EIA) to elucidate such empirical constraints for the continental United States. We introduce an approach for estimating power generation from hourly water discharge, then present regionally resolved interannual seasonal and diurnal generation patterns; frequency analyses of ramp rates; minimum and maximum generation rates; daily reversals; and load duration curves, all available interactively with a new data visualization tool. We suggest that due largely to hydropower's role as power generation that also serves non‐energy purposes, it acts as a predictable variable generator with constrained dispatchability, more like a supply side analog to demand response resources than like a battery. This observation is particularly relevant for high penetration renewable energy scenarios, given hydroelectric generators' expected value for grid stabilization and load balancing.

Abstract Lao PDR's push for large infrastructure‐led economic growth has been delivered through a significant amount of financial leverage and a build‐up of sovereign debt obligations. The government now finds itself in danger of a sovereign default. This article traces the roots of this debt crisis over the past decade, focusing particularly on the role of hydropower. A significant share of infrastructure lending to Laos has been through Chinese policy banks. We argue that over‐lending to dam projects focused on the domestic energy market has been at the core of Laos' debt situation. Through 2020 the Lao Government has undertaken a series of restructuring measures, including privatisation of state assets, engaging in debt renegotiations with China, and attempts to secure new short‐term credit. We outline a range of other options Laos has to reschedule or restructure their sovereign debt, and offer policy targeted recommendations focusing on reforms in the energy sector.

Abstract As ecological civilization construction receives growing attention in China, the eco‐friendliness of the power supply structure is becoming increasingly important. Thermal power and hydropower are the two major power sources in China. Hydropower has both positive and negative effects on the ecosystem. However, there are few studies on the comprehensive impact of hydropower on the ecosystem. Therefore, the main innovation of this article is to integrally and comprehensively study the impact of hydropower to propose recommendations for hydropower development. The study of hydropower's effects on the overall ecosystem including resources, the environment, and economic society reflects the integrity, and the simultaneous study of hydropower's positive and negative effects reflects the comprehensiveness. First, this paper constructs a system dynamics (SD) model that can analyze the impact of replacing thermal power with hydropower on the ecosystem and proposes an improved coupling coordination degree (CCD) model. Then, this paper takes the province of Fujian as an example for SD scenario simulation and proposes recommendations for each indicator in the ecology subsystem. Finally, this paper performs CCD analysis on subsystems of the ecology subsystem in different policy scenarios and provides suggestions for future hydropower development in Fujian. Results show that hydropower technology improvement and efficiency increase (HTIEI) is more conducive to the development of the overall ecosystem. The scientificity of the current hydropower policy in Fujian is proven through theoretical analysis, and further hydropower development proposals are proposed. This paper provides a basis for the formulation of power generation policies and promotes ecological civilization construction for Fujian. The proposed methods in this paper can also provide tools for policy research on clean energy power generation.

Abstract Freshwater is vital to much life on Earth and is an essential resource for humans. Climate change, however, dramatically changes freshwater systems and reduces water quality, poses a risk to drinking water availability and has severe impacts on aquatic ecosystems and their biodiversity. The direct effects of climate change, such as increased temperatures and higher frequency of extreme meteorological events, interact with human responses to climate change, which we refer to here as ‘indirect effects’. The latter possibly have even greater impact than the direct effects of climate change. Specifically, changes in land‐use practices as responses to climate change, such as adjusted cropping regimes or a shift to renewable hydroelectricity to mitigate climate change, can very strongly affect freshwater ecosystems. Hitherto, these indirect effects and the possibility of idiosyncratic outcomes are under‐recognized. Here, we synthesize knowledge and identify threats to freshwater environments in alpine and pre‐alpine regions, which are particularly affected by climate change. We focus on the effects of adapted agriculture and hydropower production on freshwater quality and ecological status, as these examples have strong indirect effects that interact with direct effects of climate change (e.g., water temperature, droughts, isolation of populations). We outline how failure to effectively account for indirect effects associated with human responses to climate change may exacerbate direct climate change impacts on aquatic ecosystems. If managed properly, however, human responses to indirect effects offer potential for rapid and implementable leverage to mitigate some of the direct climate change effects on aquatic ecosystems. To better address looming risks, policy‐ and decisionmakers must account for indirect effects and incorporate them into restoration planning and the respective sectorial policies.

Abstract Inflow forecasts play an integral role in the management and operations of hydropower reservoirs. In Scotland, the horizon of inflow forecasts is limited in range to approximately 2 weeks ahead. Additional forecast information in the sub‐seasonal to seasonal (S2S) range would allow operators to take proactive action to mitigate weather‐related risks, thereby improving water management and increasing revenue. The aim of this study is to develop methods of deriving skilful S2S probabilistic inflow forecasts for hydropower reservoirs in Scotland, without the application of a hydrological model. We forecast inflow for a case study reservoir using a linear regression model, trained on historical S2S precipitation predictions and observed inflow rates. Ensemble inflow forecasts generated from the regression model are post‐processed using Ensemble Model Output Statistics, to create calibrated S2S probabilistic forecasts. We evaluate forecast skill for 11 different horizons, using inflow observations. Probabilistic forecasts of weekly average inflow rates hold fair skill relative to climatology up to 6 weeks ahead (fCRPSS = 0.01). Forecasts of 28‐day average inflow rates hold good skill (fCRPSS = 0.19). The S2S probabilistic inflow forecasts are most skilful during winter, when there is greatest risk of reservoirs spilling. Forecasts struggle to predict high summer inflows even at short lead times. The potential for the S2S probabilistic inflow forecasts to improve water management and deliver increased economic value is explored using a stylized cost model. While applied to hydropower forecasting, the results and methods presented here are relevant to broader fields of water management and S2S forecasting applications.

Abstract Selective water release from the deeper pools of reservoirs alters the temperature of downstream rivers. Thermal destabilization of downstream rivers can be detrimental to the riverine ecosystem by disturbing the growth stages of various aquatic species. To predict this impact of planned hydropower dams worldwide, we present a framework called “FUture Temperatures Using River hISTory (FUTURIST).” The framework used historical records of in‐situ river temperatures for existing dams in the U.S. and remote sensing observations for those in other regions to train an artificial neural network (ANN) model that predicts temperature change between upstream and downstream rivers. Validation of FUTURIST‐modeled impacts for dams worldwide showed promising results with a root mean squared error of 2.5°C (0.9°C) and categorical accuracy of 63% (88%) during the summer (winter) season. The trained ANN model afforded prediction of the likely thermal impacts of 216 planned dams. Results suggest that during the summer season, 73% of future dams will potentially cool downstream rivers by up to 6.6°C. Winter season operations were predicted to consistently warm downstream rivers by temperatures of up to 2°C. Reservoirs that experience strong stratification have the most potential to impact downstream pre‐dam thermal regimes. For copious existing or planned dams worldwide that are yet to be mapped of their thermal impacts, FUTURIST provides an efficient path forward to carry out a global thermal assessment and design sustainable hydropower expansion plans so that the upcoming dams can be operated in a more eco‐sensitive manner than the existing ones.

Abstract River regulation or flow modification—the hydrological alteration of flow by dams and diversions—has been implicated as a cause of fundamental change to downstream aquatic ecosystems. Flow modification changes the patterns and functionality of the natural flow regime and has the potential to restrict population connectivity and gene flow in river‐dependent organisms. Since population connectivity and the maintenance of genetic diversity are fundamental drivers of long‐term persistence, understanding the extent flow modification impacts these critical attributes of genetic health is an important goal for long‐term conservation. Foothill yellow‐legged frogs (Rana boylii) were historically abundant throughout many western rivers but have declined since the onset of flow regulation. However, the extent to which R. boylii populations in rivers with altered flow regimes are maintaining connectivity and genetic diversity is unknown. Here, we use population genomics to investigate the impacts of flow alteration on R. boylii to explore their potential for long‐term persistence under continued flow modification. We found R. boylii in rivers with flow modification showed striking patterns of isolation and trajectories of genetic diversity loss relative to unregulated rivers. For example, flow modification explained the greatest amount of variance in population genetic differentiation compared with other covariates including geographic distance. Importantly, patterns of connectivity and genetic diversity loss were observed regardless of flow alteration level but were most prominent in locations with the greatest flow modification intensity. Although our results do not bode well for long‐term persistence of R. boylii populations under current flow regulation regimes, they do highlight the power of genetic monitoring for assessing population health in aquatic organisms.

Abstract The Greater Mekong Subregion is a transnational area bound together by the Mekong River basin and its immense hydropower resources, historically seen as the backbone of regional economic development. The basin is now punctuated by several dams, successful in attracting both international investors and fierce criticisms for their environmental and societal impacts. Surprisingly, no attention has been paid so far to the actual performance of these infrastructures: is hydropower supply robust with respect to the hydroclimatic variability characterizing Southeast Asia? When water availability is altered, what are the implications for power production costs and CO2 emissions? To answer these questions, we focus on the Laotian–Thai grid—the first international power‐trade infrastructure developed in the region—and use a power system model driven by a spatially distributed hydrological‐water management model. Simulation results over a 30‐year period show that production costs and carbon footprint are significantly affected by droughts, which reduce hydropower availability and increase reliance on thermoelectric resources. Regional droughts across the Mekong basin are of particular concern, as they reduce the export of cheap hydropower from Laos to Thailand. To put the analysis into a broader climate‐water‐energy context, we show that the El Niño Southern Oscillation modulates not only the summer monsoon, but also the power system behavior, shaping the relationship between hydroclimatological conditions, power production costs, and CO2 emissions. Overall, our results and models provide a knowledge basis for informing robust management strategies at the water‐energy scale and designing more sustainable power plans in the Greater Mekong Subregion.

Abstract Many river basins in the Global South are undergoing rapid development with major implications for the interdependent water‐energy‐food‐environmental (WEFE) “nexus” sectors. A range of views on the extent to which such natural‐human systems should be developed typically exists. The perceived best investments in river basins depend on how one frames the planning problem. Therefore, we propose an approach where the best possible (optimized) implementations of different river basin development scenarios are assessed by comparing their WEFE sector trade‐offs. We apply the approach to Tanzania's Rufiji river basin, an area with multiple WEFE interdependencies and high development potential (irrigation and hydropower) and ecosystem services. Performance indicators are identified through stakeholder consultation and describe WEFE sector response under scenarios of river basin development. Results show considerable potential exists for energy and irrigation expansion. Designs that prioritize energy production adversely affect environmental performance; however, part of the negative impacts can be minimized through release rules designed to replicate the natural variability of flow. The reliability of monthly energy generation is more sensitive to environmental‐oriented management than the cumulative annual energy production. Overall results highlight how sectoral trade‐offs change depending on the extent of development, something that may be difficult to regulate in the future, and that there are important basin‐scale interdependencies. Benefits and limitations of the approach and its application are discussed.

Abstract Data scarcity impedes a comprehensive impact assessment of the 38 dams currently proposed within the highly biodiverse central African nation of Gabon. Here, we present a multiple‐species MaxEnt distribution modeling approach to assess species richness for freshwater fishes at the landscape level and demonstrate its utility in identifying proposed dam sites in Gabon that fall in highly diverse areas. We modeled habitat suitability for 202 of Gabon's fresh and brackish water fish species based on georeferenced presence data from museum specimens and a set of ecologically meaningful environmental conditions. We removed poor performing species from the model and compiled the distributions of 114 well‐performing species to generate a new metric, the species pseudorichness index (pR), defined as the cumulative number of species that are highly suited to the habitat in a given segment of river. We used pR as a proxy for true species richness and use this metric to evaluate the distribution of freshwater fish diversity relative to the proposed dam development in Gabon. We found that more than 80% of the proposed dams in Gabon overlap with areas of high pR, implying that planned hydroelectric development in Gabon may disproportionately affect high diversity areas. These dams deserve more focused baseline assessments and conservation action. This approach provides a rapid way to initiate a landscape‐scale assessment of freshwater fish diversity to inform conservation decisions in areas that are species rich, but data poor.

Abstract Bhutan is recognized for conservation success under its pro‐environmental development philosophy Gross National Happiness (GNH). However, an increase in area coverage alone cannot track the true contribution of protected areas (PAs) to biodiversity conservation. Capturing PA dynamism by tracking PADDD (PA downgrading, downsizing, and degazettement) and gain events can be used as a more comprehensive evaluation method. Based on existing data, we tracked gain events, enacted and proposed PADDD events, proximate causes of PADDD, and gain and PADDD events trends in Bhutan from 1966 to 2016. We also compared PADDD events recorded in www.PADDDtracker.org with the primary data sourced for our study. We discussed the findings in light of four tenets of GNH: good governance, sustainable socioeconomic development, preservation, and promotion of culture, and environmental conservation. We identified 81 gain and 29 PADDD events. All 12 proposed policy downgrading events in 2004 were proximally caused by infrastructure development, while all degazettement (n = 6) in 1993 and all downsizing events (two in 1984 and one in 1993) were proximally caused by conservation planning. Overall the gain and PADDD events were episodic but policy downgrading events occurred only from 2002. Based on our country data, we recorded 4.8 times more PADDD events than was recorded in www.PADDDtracker.org where even some degazetted PAs were not recorded. All gain events and even PADDD events, excluding one enacted and 12 proposed policy downgrading events caused by hydropower projects were aimed to improve conservation thus aligning with tenets of GNH. However, as hydropower is the specific cause for all proposed PADDD, Bhutan should be concerned about PADDD. Our findings provide further evidence for the dynamic nature of PAs, the widespread nature of PADDD and difficulty in detecting it. Furthermore, they also suggest the need to conduct archival case studies to better detect PADDD and PA dynamism.

This paper reviews published estimates of water consumption from hydropower production and the methodologies applied. Published values range from negative to more than 115 000 m3 MWh−1. Most gross water consumption rates are in the range 5.4–234 m3 MWh−1, while most net values are in the range 0.2–140 m3 MWh−1. Net values are often less than 40% of the gross values, sometimes only 1% of the gross water consumption estimates. The extremely wide range in estimates is explained by an inconsistent methodology and the very site‐specific nature of hydropower projects. Scientific challenges, such as allocation from multipurpose reservoirs, and spatial assignments in river basins with several hydropower plants, affect the results dramatically and remain unresolved. As such, it is difficult to propose “typical values” for water consumption from hydropower production. This paper points out directions of research in order to prepare a consistent and improved methodology for the calculation of water consumption from hydropower projects. This should take into account the role of reservoirs in the provision of a large range of water services, as well as providing regulated power to the energy system.