Yadu Pokhrel

• PhD
• Professor (Assistant) at Michigan State University

Groundwater serves as a crucial freshwater resource for people and ecosystems, vital in adapting to climate change. Yet, its availability and dynamics are affected by climate variations, changes in land use, and excessive extraction. Despite its importance, our understanding of how global change will influence groundwater in the future remains limi...

The cumulative effects of constructed dams on the mainstream of the Mekong River and its tributaries are transforming the fundamental characteristics of the river regime with pervasive repercussions not only for natural systems but also for social systems and economies. In this context, the study addresses the issues identified above by coupling th...

Agricultural irrigation withdraws water from multiple resources, possibly causing water scarcity issues. Previous studies predominantly relied on observations or land-only simulations, and therefore generally ignored land-atmosphere interactions, or failed to separate the effects of irrigation from other forcings. Here we analyse the effects of his...

Global water models increasingly allow us to explore the terrestrial water cycle in earth-sized digital laboratories to support science and guide policy. However, these models are still subject to considerable uncertainties that mainly originate from three sources: (1) imbalances in data quality and availability across geographical regions and betw...

Global data have served an integral role in characterizing large-scale groundwater systems, identifying their sustainability challenges, and informing on socioeconomic and ecological dimensions of groundwater. These insights have revealed groundwater as a dynamic component of both the water cycle and social-ecological systems, leading to an expansi...

Irrigation rapidly expanded during the 20th century, affecting climate via water, energy, and biogeochemical changes. Previous assessments of these effects predominantly relied on a single Earth System Model, and therefore suffered from structural model uncertainties. Here we quantify the impacts of historical irrigation expansion on climate by ana...

Accurate reservoir representation in large‐scale river models remains challenging owing to limited access to data on reservoir operations. We contribute to model development by introducing a global machine‐learning based flood storage capacity (FSC) data set and a satellite‐based target storage reservoir operation scheme (SBTS). The FSC data set fo...

Crucial to the assessment of future water security is how the land model component of Earth System Models partition precipitation into evapotranspiration and runoff, and the sensitivity of this partitioning to climate. This sensitivity is not explicitly constrained in land models nor the model parameters important for this sensitivity identified. H...

Natural fluctuations in river flow are central to the ecosystem productivity of basins, yet significant alterations in daily flows pose threats to the integrity of the hydrological, ecological, and agricultural systems. In the dammed Lancang–Mekong River (hereafter LMR), the attribution of these large daily flow changes to upstream regions remains...

Irrigation rapidly expanded during the 20th century, thereby affecting climate via changes in water, energy, and biogeochemical cycling. Previous assessments of these historical climate effects of irrigation expansion predominantly relied on a single Earth System Model, and therefore suffered from structural model uncertainties. Here we quantify th...

Alleviating water scarcity is at the core of Sustainable Development Goal 6. Yet the timing of water scarcity in its onset and possible relief in different regions of the world due to climate change and changing human population dynamics remains poorly investigated. Here we assess the timing of the first emergence of water scarcity (FirstWS) and di...

Flow regimes in major global river systems are undergoing rapid alterations due to unprecedented stress from climate change and human activities. The Mekong River basin (MRB) was, until recently, among the last major global rivers relatively unaltered by humans, but this has been changing alarmingly in the last decade due to booming dam constructio...

Climate change is altering the hydrological cycle of coastal river basins due to changes in monsoon patterns. The agriculture of the west coast region of India is highly vulnerable to flooding due to an increase in extreme rainfall events and coastal inundation. Understanding the distribution of floods geographically and their likelihood of occurre...

Study region: The island of Taiwan. Study focus: This study presents long-term and high-resolution modeling of flood occurrence, interdecadal patterns of river-floodplain dynamics, and analysis of flooding during two typhoon events-Nari and Morakot over Taiwan. The modeling system combines a hydrological model (HiGW-MAT) and a river hydrodynamics m...

Droughts and floods are the main threats to the Lancang-Mekong River Basin (LMRB) . Drought mainly occurs during the dry season, especially in March and April, in the LMRB. The “dry gets drier” paradigm performs well in the LMRB, specifically in the Mekong Delta. Further, flood frequency and magnitude, which are determined by heavy rain, are also i...

This chapter assesses surface water changes due to climate change and human activities, by particularly examining runoff and streamflow. Changes in the hydrological cycle due to climate change and human intervention can lead to diverse environmental impacts and risks. Fresh water is the agent that delivers many of the impacts of climate change on s...

Numerical models are simplified representations of the real world at a finite level of complexity. Global water models are used to simulate the global water cycle and their outputs contribute to the evaluation of important natural and societal issues, including water availability, flood risk and ecological functioning. Whilst global water modelling...

Natural fluctuations in river flow are central to the ecosystem productivity of basins, yet significant alterations in daily flows pose threats to the integrity of the hydrological, ecological, and agricultural systems. In the dammed Mekong River, the attribution of these large daily flow changes to upstream regions remains mechanistically unexamin...

Research on assessing dams preparedness to mitigate hydrological extremes has grown under climate change and water conflicts. However, discerning the success or failure of these strategies remains challenging, especially in Transboundary Rivers. Here, we use a meta-analytic approach to examine 14 moderators of dam efficacy in flood and drought risk...

Dams have proliferated along the Mekong, spurred by energy demands from economic development and capital from private companies. Swift dam evolution has rendered many databases outdated, in which mismatches arise from differing compilation methods. Without a comprehensive database, up-to-date spatial assessment of dam growth is unavailable. Looking...

The recent surge in dam construction has sparked debates regarding their contribution to carbon neutrality and food security, focusing on trade-offs between production benefits and ecological drawbacks. However, how dams affect carbon emissions and land cover changes, including their spatial differentiations, remains unclear. We quantified spatiote...

Flow regimes in major global river systems are undergoing rapid alterations due to unprecedented stress from climate change and human activities. The Mekong River Basin (MRB) was, until recently, among the last major global rivers relatively unaltered by humans, but this is changing alarmingly in the last decade due to booming dam construction. Num...

Intensifying droughts under climatic warming are of widespread concern owing to their devastating impacts on water resources, societies and ecosystems. However, the effects of exogeneous drivers on regional droughts remain poorly understood. Using the Lagrangian method, atmospheric reanalysis data and climate projections from the Coupled Model Inte...

Terrestrial water storage (TWS) includes all forms of water stored on and below the land surface, and is a key determinant of global water and energy budgets. However, TWS data from measurements by the Gravity Recovery and Climate Experiment (GRACE) satellite mission are only available from 2002, limiting global and regional understanding of the lo...

Global water models are increasingly used to understand past, present and future water cycles, but disagreements between simulated variables make model-based inferences uncertain. Although there is empirical evidence of different large-scale relationships in hydrology, these relationships are rarely considered in model evaluation. Here we evaluate...

Coupled human‐water systems (CHWS) are diverse and have been studied across a wide variety of disciplines. Integrating multiple disciplinary perspectives on CHWS provides a comprehensive and actionable understanding of these complex systems. While interdisciplinary integration has often remained elusive, specific combinations of disciplines might b...

Existing scholarship hypothesizes a causal chain from climate change to resource availability constraints, to forced migration and conflict risks. Limited research, however, synthesizes findings about the efficacy of interventions to alleviate resources conflict in communities hosting climate migrants. This systematic literature review identified a...

Dams have proliferated along the Mekong, spurred by energy demands from economic development and capital 10 from private companies. Swift dam evolution has rendered many databases outdated, in which mismatches arise from differing compilation methods. Without a comprehensive database, up-to-date spatial assessment of dam growth is unavailable. Look...

Climate change will likely increase crop water demand, and farmers may adapt by applying more irrigation. Understanding the extent to which this is occurring is of particular importance in India, a global groundwater depletion hotspot, where increased withdrawals may further jeopardize groundwater resources. Using historical data on groundwater lev...

Terrestrial water storage (TWS) includes all forms of water stored on and below the land surface, and is a key determinant of global water and energy budgets. However, TWS data from measurements by the Gravity Recovery and Climate Experiment (GRACE) satellite mission are only available from 2002, limiting global and regional understanding of the lo...

Irrigation accounts for ~70% of global freshwater withdrawals and ~90% of consumptive water use, driving myriad Earth system impacts. In this Review, we summarize how irrigation currently impacts key components of the Earth system. Estimates suggest that more than 3.6 million km2 of currently irrigated land, with hot spots in the intensively cultiv...

The Mekong River basin (MRB) is a transboundary basin that supports livelihoods of over 70 million inhabitants and diverse terrestrial-aquatic ecosystems. This critical lifeline for people and ecosystems is under transformation due to climatic stressors and human activities (e.g., land use change and dam construction). Thus, there is an urgent need...

8 Floods are among India's most frequently occurring natural disasters, which disrupt all aspects of socioeconomic 9 well-being. A large population is affected by floods during almost every summer monsoon season in India, leaving 10 its footprint through human mortality, migration, and damage to agriculture and infrastructure. Despite the 11 massiv...

Water resources sustainability in High Mountain Asia (HMA) surrounding the Tibetan Plateau (TP)—known as Asia’s water tower—has triggered widespread concerns because HMA protects millions of people against water stress1,2. However, the mechanisms behind the heterogeneous trends observed in terrestrial water storage (TWS) over the TP remain poorly u...

Compound drought–heatwave (CDHW) events are one of the worst climatic stressors for global sustainable development. However, the physical mechanisms behind CDHWs and their impacts on socio-ecosystem productivity remain poorly understood. Here, using simulations from a large climate–hydrology model ensemble of 111 members, we demonstrate that the fr...

Global water models are widely used for policy-making and in scientific studies, but substantial inter-model differences highlight the need for additional evaluation. Here we evaluate global water models by assessing so-called functional relationships between system forcing and response variables. The more widely used comparisons between observed a...

Hydrogeologists are trained to think about belowground processes, and their importance is apparent to them. Other scientific disciplines have traditionally emphasized processes that occur on or above Earth’s surface, and thus groundwater’s roles sometimes go unnoticed in studies of weather, climate, and plant diversity and traits, among others. Ove...

There is a pressing need for a transition from fossil-fuel to renewable energy to meet the increasing energy demands and reduce greenhouse gas emissions. The Nepal Himalaya possesses substantial renewable energy potential that can be harnessed through hydropower projects due to its peculiar topographic characteristics and abundant water resources....

Hydrological alterations caused by booming hydropower dams in the Mekong River basin are disrupting aquatic ecosystems and local livelihoods, calling for an urgent rethinking of hydropower development. Alternative operating strategies of existing Mekong dams could help restore the natural hydrological regimes without affecting power generation.

Karnali River Basin (KRB) located in western Nepal has been experiencing increasing temperature and decreasing precipitation trends in recent decades, making the basin highly susceptible to droughts. Adaptation to future droughts requires insight into the characteristics of past droughts and their impacts on different sectors. This study assesses t...

South America has been developed from its coast to its hinterlands since the beginning of its Western colonization. However, to this point, no significant effort has been made to integrate its interior. Waterways transportation can be considered the most sustainable inland mode of transportation due to its low CO2 emissions per ton of cargo transpo...

Climate change is expected to exacerbate drought conditions over many global regions. However, the future risk posed by droughts depends not only on the climate-induced changes but also on the changes in societal exposure and vulnerability to droughts. Here we illustrate how the consideration of human vulnerability alters global drought risk associ...

Droughts that exceed the magnitudes of historical variation ranges could occur increasingly frequently under future climate conditions. However, the time of the emergence of unprecedented drought conditions under climate change has rarely been examined. Here, using multimodel hydrological simulations, we investigate the changes in the frequency of...

While there have been efforts to supply off-grid energy in the Amazon, these attempts have focused on low upfront costs and deployment rates. These “get-energy-quick” methods have almost solely adopted diesel generators, ignoring the environmental and social risks associated with the known noise and pollution of combustion engines. Alternatively, i...

Human-controlled reservoirs have a large influence on the global water cycle. While global hydrological models use generic parameterizations to model dam operations, the representation of reservoir regulation is still lacking in many Earth system models. Here we implement and evaluate a widely used reservoir parametrization in the global river-rout...

Hydropower dams have received increased global attention due to their detrimental socioenvironmental ramifications. Such attention has led to an increase in studies on the impacts of reservoir operation on river flow; however, a holistic understanding of the compounded effects of hydropower dams on different hydrological characteristics is lacking,...

Eurasia, home to ~70% of global population, is characterized by (semi-)arid climate. Water scarcity in the mid-latitude Eurasia (MLE) has been exacerbated by a consistent decline in terrestrial water storage (TWS), attributed primarily to human activities. However, the atmospheric mechanisms behind such TWS decline remain unclear. Here, we investig...

Although global- and catchment-scale hydrological models are often shown to accurately simulate long-term runoff time-series, far less is known about their suitability for capturing hydrological extremes, such as droughts. Here we evaluated simulations of hydrological droughts from nine catchment scale hydrological models (CHMs) and eight global sc...

Inland lakes have been increasingly impacted by climate change and human activities, leading to unprecedented environmental consequences. Among many rapidly changing lakes is the Tonlé Sap Lake (TSL) in Cambodia—Southeast Asia's largest inland lake—which is under growing threats from altered flows and inundation dynamics due to compounding effects...

Numerous studies have examined the reliability of various precipitation products over the Mekong River Basin (MRB) and modeled its basin hydrology. However, there is a lack of comprehensive studies on precipitation‐induced uncertainties in hydrological simulations using process‐based land surface models. This study examines the propagation of preci...

Human-controlled reservoirs have a large influence on the global water cycle. While global hydrological models use generic parametrisations to model human dam operations, the representation of reservoir regulation is often still lacking in Earth System Models. Here we implement and evaluate a widely used reservoir parametrisation in the global rive...

Rapid urbanization throughout the globe increases demand for fresh water and the ecosystem services associated with it. This need is conventionally met through the construction of infrastructure. Natural infrastructure solutions have increased to provide freshwater ecosystem services, but little global research has examined the intricate relationsh...

Declines in terrestrial water storage (TWS) exacerbate regional water scarcity and global sea level rise. Increasing evidence has shown that recent TWS declines are substantial in ecologically fragile drylands, but the mechanism remains unclear. Here, by synergizing satellite observations and model simulations, we quantitatively attribute TWS trend...

Tropical river fisheries support food security for millions of people but are increasingly threatened by hydropower development. How dams affect these fisheries remains poorly known in most regions. Here, we used a functional traits approach to evaluate the extent to which compositions of fishery yields in the Madeira River Basin, the largest sub‐b...

Droughts are anticipated to intensify in many parts of the world due to climate change. However, the issue of drought definition, namely the diversity of drought indices, makes it difficult to compare drought assessments. This issue is widely known, but its relative importance has never been quantitatively evaluated in comparison to other sources o...

Future flood and drought risks have been predicted to transition from moderate to high levels at global warmings of 1.5 C and 2.0 C above pre-industrial levels, respectively. However, these results were obtained by approximating the equilibrium climate using transient simulations with steadily warming. This approach was recently criticised due to t...

The Lancang–Mekong River (LMR) is an important transboundary river that originates from the Tibetan plateau, China and flows through six nations in Southeast Asia. Knowledge about the past and future changes in climate and water for this basin is critical in order to support regional sustainable development. This paper presents a comprehensive revi...

The diverse impacts of anthropogenic climate change in the spatiotemporal distribution of global freshwater are generally addressed through global scale studies, which suffer from uncertainties arising from coarse spatial resolution. Multi-catchment, regional studies provide fine-grained details of these impacts but remain less explored. Here, we p...

Reservoir expansion over the last century has largely affected downstream flow characteristics. Yet very little is known about the impacts of reservoir expansion on the climate. Here, we implement reservoir construction in the Community Land Model by enabling dynamical lake area changes, while conserving mass and energy. Transient global lake and r...

Daily floods including event, characteristic, extreme and inundation in the Lancang-Mekong River Basin (LMRB), crucial for flood projection and forecasting, have not been adequately modeled. An improved hydrological-hydrodynamic model (VIC and CaMa-Flood) considering regional parameterization was developed to simulate the flood dynamics over the ba...

Given growing energy demands and continued interest in hydropower development, it is important that we rethink hydropower to avoid detrimental socioenvironmental consequences of large dams planned in regions such as the Amazon River basin. Here, we show that ~63% of total energy planned to be generated from conventional hydropower in the Brazilian...

The intensification of soil moisture drought events is an expected consequence of anthropogenic global warming. However, the implication of 1.5–3 °C global warming on these events remains unknown over North Africa and the Sahel region, where soil moisture plays a crucial role in food security that largely depends on rainfed agriculture. Here, using...

Global water models (GWMs) simulate the terrestrial water cycle, on the global scale, and are used to assess the impacts of climate change on freshwater systems. GWMs are developed within different modeling frameworks and consider different underlying hydrological processes, leading to varied model structures. Furthermore, the equations used to des...

Global water models (GWMs) simulate the terrestrial water cycle on the global scale and are used to assess the impacts of climate change on freshwater systems. GWMs are developed within different modelling frameworks and consider different underlying hydrological processes, leading to varied model structures. Furthermore, the equations used to desc...

Understanding the timing, location and rates of recharge is important for sustainable groundwater management and effective management of groundwater-dependent ecosystems. This paper explores the spatiotemporal distributions of large- and small-recharge events in a composite watershed in the Great Lakes region and examines the impacts of climate, la...

Although global- and catchment-scale hydrological models are often shown to accurately simulate long-term runoff time-series, far less is known about their suitability for capturing hydrological extremes, such as droughts. Here we evaluated runoff simulations from nine catchment scale hydrological models (CHMs) and eight global scale hydrological m...

Change of flow Anthropogenic influence on climate has changed temperatures, precipitation, atmospheric circulation, and many other related physical processes, but has it changed river flow as well? Gudmundsson et al. analyzed thousands of time series of river flows and hydrological extremes across the globe and compared them with model simulations...

Terrestrial water storage (TWS) modulates the hydrological cycle and is a key determinant of water availability and an indicator of drought. While historical TWS variations have been increasingly studied, future changes in TWS and the linkages to droughts remain unexamined. Here, using ensemble hydrological simulations, we show that climate change...

Extraction of drainage networks is an important element of river flow routing in hydrology and large-scale estimates of river behaviors in Earth sciences. Emerging studies with a focus on greenhouse gases reveal that small rivers can contribute to more than half of the global carbon emissions from inland waters (including lakes and wetlands). Howev...

The hydrology of the Himalayan region, known as the water tower of Asia, is undergoing rapid transformations due to climate change and growing human influences, and it is known that this region is one of those most vulnerable to climate change. Numerous studies have examined the changes in the hydrology of Nepal, which includes a significant upstre...

Billions of people rely on groundwater as being an accessible source of drinking water and for irrigation, especially in times of drought. Its importance will likely increase with a changing climate. It is still unclear, however, how climate change will impact groundwater systems globally and, thus, the availability of this vital resource. Groundwa...

Globally, flood risk is projected to increase in the future due to climate change and population growth. Here, we quantify the role of dams in flood mitigation, previously unaccounted for in global flood studies, by simulating the floodplain dynamics and flow regulation by dams. We show that, ignoring flow regulation by dams, the average number of...

Global water models (GWMs) simulate the terrestrial water cycle, on the global scale, and are used to assess the impacts of climate change on freshwater systems. GWMs are developed within different modeling frameworks and consider different underlying hydrological processes, leading to varied model structures. Furthermore, the equations used to des...

Representation of subsurface hydrology in global land surface models has been advanced but outstanding challenges and opportunities remain, especially in better simulating lateral groundwater flow and aquifer pumping for irrigation. This study improves the representation of groundwater in the latest version of the Community Land Model (version 5) b...

Importance of evaluation of global hydrological models (gHMs) before doing climate impact assessment was underlined in several studies. The main objective of this study is to evaluate the performance of six gHMs in simulating observed discharge for a set of 57 large catchments applying common metrics with thresholds for the monthly and seasonal dyn...