Xi Xi Lu

National University of Singapore | NUS · Department of Geography

Wetlands play a critical role in the global environment. The Middle Yangtze River Basin (MYRB), known for its abundant wetland resources, has experienced notable changes resulting from the complex interplay of environmental factors. Therefore, we investigated the spatiotemporal characteristics of wetland ecological quality in the MYRB from 2001 to...

Central Asia (CA) is characterized by arid and semiarid climates and heavy dependence on agriculture and water resources for sustenance and economic stability. As a result, the region faces heightened vulnerability to the impacts of climate change associated with global warming. This vulnerability is exacerbated by the increasing occurrence of flas...

Ecological restoration efforts in less developed regions confront a sustainability challenge due to the undervaluation of their substantive benefits. Soil conservation, as a crucial ecosystem service supporting both ecological and socioeconomic systems in less developed regions, is often overlooked in estimating the benefits of restoration efforts....

Damming profoundly affects downstream flow‐sediment regimes, altering channel bar dynamics and thereby affecting floods and riverine biodiversity. Here, we investigate the response of bars to upstream damming by examining patterns, mechanisms, and impacts in the Middle Yangtze River (∼1,000 km). Over a decade of post‐damming observational data reve...

Mangrove forests serve as significant carbon sinks and play a crucial role in mitigating climate change. Currently, the response of mangroves to intensified climate change and human activities, and the factors that influence the magnitude of carbon storage in their sediments remain uncertain. To address these questions, two sediment cores were coll...

Lakes are important component of the regional carbon cycle and a significant sources of greenhouse gases (GHGs) to the atmosphere. However, the regional variations in carbon dioxide (CO2) and methane (CH4) emissions, as well as the factors regulating these emissions are poorly constrained. To investigate the regional GHG emission from lakes and the...

Many large estuaries are threatened by intensifying hypoxia. However, due to the limited duration of available observations, uncertainties persist regarding the level of contemporary hypoxia intensity in a longer-term context and the relative contributions of climate versus human factors. Here we present sediment records for the hypoxia intensity a...

Hydropower, although an attractive renewable energy source, can alter the flux of water, sediments, and biota, producing detrimental impacts in downstream regions. The Mekong River illustrates the impacts of large dams and the limitations of conventional dam regulating strategies. Even under the most optimistic sluicing scenario, sediment load at t...

Mangrove forests can help to mitigate climate change by storing a significant amount of carbon (C) in soils. Planted mangrove forests have been established to combat anthropogenic threats posed by climate change. However, the efficiency of planted forests in terms of soil organic carbon (SOC) storage and dynamics relative to that of natural forests...

This study investigates the effects of climate change on the sediment loads of the Ping and Wang River basins and their contribution to the sediment dynamics of the lower Chao Phraya River basin in Thailand. The various climate models under different Representative Concentration Pathways (RCPs) scenarios are employed to project sediment loads in fu...

Understanding the trajectories and driving mechanisms behind land use/land cover (LULC) changes is essential for effective watershed planning and management. This study quantified the net change, exchange, total change, and transfer rate of LULC in the Jinghe River Basin (JRB), China using LULC data from 2000 to 2020. Through trajectory analysis, k...

Riparian wetlands have suffered from degradation due to global climate change and human activities, which can alter flora and fauna community patterns and disrupt material cycles in the riparian zones. Hydrological connectivity identified by functional and structural connectivity is an important driving force of riparian ecosystems. However, the ro...

Climate change affects cryosphere-fed rivers and alters seasonal sediment dynamics, affecting cyclical fluvial material supply and year-round water-food-energy provisions to downstream communities. Here, we demonstrate seasonal sediment-transport regime shifts from the 1960s to 2000s in four cryosphere-fed rivers characterized by glacial, nival, pl...

Although saline aquatic ecosystems are significant emitters of greenhouse gases (GHGs), dynamic changes in GHGs at the sediment-water interface remain unclear. The present investigation carried out a total of four sampling campaigns in Daihai Lake, which is a eutrophic saline lake situated in a semi-arid area of northern China. The aim of this stud...

Microplastics are widespread in coastal and marine environments, and sediments serve as a sink for microplastics. In this study, four sediment cores were collected from the Kuala Gula Mangrove area. The abundance of microplastics in mangrove sediments ranged from 25–130 items/kg dry weight. The highest abundance of microplastic was observed at the...

The hyporheic zone, i.e. the groundwater-surface water interface within riverine/riparian ecosystems, plays a key role in water transport, energy flow and biogeochemical cycling at watershed scales. Water and heat exchange are fundamental processes regulating biogeochemical cycles in the hyporheic zones. To improve the understanding of hyporheic fl...

Soil erosion by water and loss of soil organic carbon (SOC) are two major contributors to global land degradation. However, the impact of soil erosion and its effect on SOC in the fragile, sensitive alpine ecosystem of the Tibetan Plateau, where climate change is amplified, is not well understood. We used the Universal Soil Loss Equation (USLE) ens...

In recent decades, the increasing frequency and magnitude of extreme hydrological events due to climate change and human activities have caused substantial economic losses and damages to human wellbeing. Here, we investigated the spatiotemporal variations of streamflow extremes (QE) and sediment load extremes (SE) in the Yellow River (YR) during 19...

Understanding the processes governing lateral terrestrial organic carbon transfer is confounded by the fact that organic carbon deposits on land have not yet been fully explored. Despite recent advances in understanding organic carbon deposition in aquatic ecosystems, the burial of organic carbon in dry depositional environments remains unclear. He...

The boom in water infrastructure in the Mekong Basin has raised concerns over the annual supply of water and sediment among its riparian communities. By consolidating various datasets, continuous series of sediment load data were estimated for several stations located within the Lower Mekong Basin. At Chiang Saen in Thailand, the nearest station to...

Sediment is of great importance for the Lancang-Mekong River (LMR) ecosystem, providing essential ecological services for local communities. Understanding sediment change and its driving factors are critical to the sustainable management of this large transboundary river system. Insufficient background knowledge of sediment dynamics driven by clima...

Rapid atmospheric warming since the mid-twentieth century has increased temperature-dependent erosion and sediment-transport processes in cold environments, affecting food, energy and water security. In this Review, we summarize landscape changes in cold environments and provide a global inventory of increases in erosion and sediment yield driven b...

The contribution of intermittent rivers and ephemeral streams (IRES) to the global carbon cycle has largely been overlooked. Flood events can impact hydrological processes, carbon (C) transport, and carbon dioxide (CO2) emissions. This study monitored river flow and sediment concentrations in an intermittent river during a flood event. Water sample...

Riverine islands are widespread fluvial landforms with exceptional economic and environmental values. However, anthropogenic pressures have further induced drastic changes worldwide in fluvial islands, which endanger fluvial organism habitation and enable potential ecological degradation. Here, the hydromorphodynamics on these prominent riverine la...

Glacial and proglacial erosion are important sediment sources in river basins. The retreat of many glaciers on the Tibetan Plateau has important implications on the supply of fresh water and sediment dynamics for downstream river basins. Despite the importance of water and sediment dynamics at these catchments, existing quantification of suspended...

Shallow eutrophic lake with submerged aquatic vegetation (SAV) has high primary productivity, but its diurnal variation of CO2 flux remains unclear. Moreover, algae bloom has become a serious environmental problem; however, its effects are still unclear. Thus, monthly measurement in Lake Ulansuhai, a shallow eutrophic lake in China, was conducted t...

Traditionally, morphological channel change is monitored using field observations such as cross-section measurements or bathymetry surveys. However, in basins with poor field data, it is difficult to monitor historical changes of the river channel. Using only water level and discharge data from the Lower Mekong Basin (LMB), we plotted the stage cur...

Monitoring and quantifying suspended sediment concentrations (SSC) in estuaries such as the Pearl River Estuary (PRE) provide crucial information for environmental processes, hydrological infrastructure, and navigation. Traditional SSC mapping based on in situ investigations lacks the spatial coverage necessitated by detailed analysis. In this stud...

The utilization of regional climate methods (RCMs) to predict future climate is an important study under the changing environment. The primary objective of the paper is to correct the temperature and precipitation simulations for the period of 1980–2005 and 2026–2098 in the Wei River Basin (WRB), to evaluate the performance of RCMs for the period o...

Shallow eutrophic lakes contribute disproportional to the emissions of CO2 and CH4 from inland waters. The processes that contribute to these fluxes, their environmental controls, and anthropogenic influences, however, are poorly constrained. Here, we studied the spatial variability and seasonal dynamics of CO2 and CH4 fluxes across the sediment-wa...

Cascade damming can shape land surfaces; however, little is known about the specific impacts of dam construction on watershed land cover changes. Therefore, we developed a framework in which remote sensing, transition patterns, and landscape metrics were coupled to measure the impact of dam construction on watershed land cover changes and landscape...

As an important soil and water conversation endeavor, the 'Grain for Green' project launched by the Chinese Central Government almost doubled the vegetation cover on the Loess Plateau between 1999 and 2013. The corresponding vegetation restoration considerably diminished slope erosion throughout the Loess Plateau, although erosion in gullies remain...

Soil organic carbon (SOC) and soil inorganic carbon (SIC) are key components of the global wetland soil carbon pool, which plays a crucial role in carbon cycling. However, research on carbon storage in riparian wetland soils, especially in inland steppe river environments impacted by human activities, is relatively scarce. Thus, we evaluated the SO...

Climate change will likely increase the total streamflow in most headwaters on the Tibetan Plateau in the next decades, yet the responses of runoff components to climate change and permafrost thaw remain largely uncertain. Here we investigate the changes in runoff components under a changing climate, based on a high‐resolution cryosphere‐hydrology...

Global warming-induced melting and thawing of the cryosphere are severely altering the volume and timing of water supplied from High Mountain Asia, adversely affecting downstream food and energy systems that are relied on by billions of people. The construction of more reservoirs designed to regulate streamflow and produce hydropower is a critical...

China has implemented the world's largest‐ever vegetation restoration program in marginal mountainous areas to sustain life on land. However, land competition between the demand for grain and the need for green has threatened sustainable vegetation restoration. Here, focusing on China's marginal mountainous areas with the highest density of slope c...

Mangroves are typically found in tropical coastal areas, and these ecosystems face deterioration and loss due to threats from climate and human factors. In this study, sediment cores were collected from human-planted mangroves in sub-tropical Ximen Island, China, and were determined for sedimentary phosphorus (P) species. The objective was to inves...

Glacial and proglacial erosion are important sediment sources in a river basin. The retreat of many glaciers on the Tibetan Plateau has important implications on the supply of fresh water and sediment dynamics for downstream river basins. Despite the importance of water and sediment dynamics at these catchments, existing quantification of suspended...

The Mekong River in Asia is one of the world's longest rivers. Although it has some of the highest levels of biodiversity and productivity in Asia, the water quality in the basin has recently deteriorated as a consequence of land use changes, dam reservoir construction, population growth, and climate change. For the first time, this study estimates...

Investigating the migration and transformation of carbonaceous and nitrogenous matter in the cryosphere areas is crucial for understanding global biogeochemical cycle and earth's climate system. However, water-soluble organic constituents and their transformation in multiple water bodies are barely investigated. Water-soluble organic carbon (WSOC)...

A large amount of plastic waste has been released into the environment during the increase in global plastic production in the 21st century. Microplastics (0.1 µm to 5 mm in size) existing in hydro-systems, especially in aquatic sediments, can enter organisms and then human body through food chain. This paper provided the preliminary observation re...

The Cambodian floodplains experience a yearly flood pulse that is essential to sustain fisheries and the agricultural calendar. Sixty years of data, from 1960–2019, are used to track the changes to the flood pulse there. We find that minimum water levels over 2010–2019 increased by up to 1.55 m at Kratie and maximum water levels decreased by up to...

The response of suspended sediment load to climate change has important implications for downstream ecosystems and biogeochemical cycles. Glaciers, permafrost, vegetation and hydrological processes are rapidly changing in high-altitude regions. However, there is currently no consensus about how and to what extent these factors will affect interannu...

The effect of reforestation on carbon sequestration has been extensively studied but there is less understanding of the changes that stand age and vegetation types have on changes in biomass carbon and soil organic carbon (SOC) after reforestation. In this study, 150 reforested plots were sampled across six provinces and one municipality in the Yan...

Mangroves are highly productive blue carbon ecosystems that preserve high organic carbon concentrations in soils. In this study, particle size, bulk elemental composition and stable carbon isotope were determined for the sediment cores collected from the landward and seaward sides of two mangrove forests of different ages (M1, ca. 60; M2, ca. 4 yea...

Surface water (SW)-Groundwater (GW) exchange plays a vital role in a prairie aquatic system and the biogeochemical cycling in such a system. Considering the inadequate understanding of damming on SW-GW exchange, a damming prairie river in Southeast Eurasian steppe was chosen to investigate variations of the SW-GW exchange and its influences on the...

Strong anthropogenic activities and climate change have caused distinct hydrology and sediment dynamics in river systems worldwide. Yet, the integrated picture of sediment discharge changes and quantitative attribution of these changes from a basin-wide perspective were limitedly understood. In this study, we quantified the variations of sediment d...

Muddied waters The climate of High Mountain Asia is becoming warmer and wetter. Li et al . present data showing that rivers originating in this region have experienced large increases in runoff and sediment fluxes over the past six decades, most dramatically since the mid-1990s. The authors project that sediment flux from those rivers could more th...

Accelerated glacier-snow-permafrost erosion due to global warming amplifies the sediment availability in cold environments and affects the time-varying suspended sediment concentration (SSC) and discharge (Q) relationship. Here, the Sediment-Availability-Transport (SAT) model is proposed to simulate dynamic SSC-Q relationships by integrating the se...

Study Region Panxi mining area (15061 km², located in Sichuan, China). Study Focus This study aims to delineate groundwater potential zones in mining areas using a new method based on the cusp catastrophe model (CCM) and principal component analysis (PCA). First, 13 indicators were selected from natural and anthropogenic dimensions, and a comprehe...

Gradual riparian wetland drying is increasingly sensitive to global warming and contributes to climate change. Riparian wetlands play a significant role in regulating carbon and nitrogen cycles. In this study, we analyzed the emissions of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) from riparian wetlands in the Xilin River basin to...

Suspended particulates and sediments are the main substances of lake organic pollutants and organic carbon, and their stable isotope research is of great significance for effectively identifying lake eutrophication. We select Lake Wuliangsuhai as our research site to measure and analyze the index, such as δ13C, C/N, total organic carbon (TOC, POC)...

Understanding extreme temperature variations is important for countries to manage risks associated with climate change. Yet, the characteristics of temperature extremes and possible climate change impacts have not been adequately investigated in Singapore. In this study, we attempted to do so by defining 14 extreme temperature indices (ETIs) for th...

The Cambodian floodplains experience a yearly floodpulse that is essential to sustain fisheries and the agricultural calendar. Sixty years of data from 1960–2019 are used to track the changes to the floodpulse there. We find that minimum water levels in 2010–2019 have increased by up to 1.55 m at Kratie and maximum water levels have decreased by up...

Terrestrial vegetation growth activity plays pivotal roles on regional development, which has attracted wide attention especially in water resources shortage areas. The paper investigated the spatiotemporal change characteristics of vegetation growth activity using satellite-based Vegetation Health Indices (VHIs) including smoothed Normalized Diffe...

While 1992 marked the first major dam – Manwan – on the main stem of the Mekong River, the post-2010 era has seen the construction and operationalisation of mega dams such as Xiaowan (started operations in 2010) and Nuozhadu (started operations in 2014) that were much larger than any dams built before. The scale of these projects implies that their...

Research on the ionic chemistry of rivers and weathering types provides the basis fo