River Barriers Research Articles

The Global Dam Watch database of river barrier and reservoir information for large-scale applications.

There are millions of river barriers worldwide, ranging from wooden locks to concrete dams, many of which form associated impoundments to store water in small ponds or large reservoirs. Besides their benefits, there is growing recognition of important environmental and social trade-offs related to these artificial structures. However, global datasets describing their characteristics and geographical distribution are often biased towards particular regions or specific applications, such as hydropower dams affecting fish migration, and are thus not globally consistent. Here, we present a new river barrier and reservoir database developed by the Global Dam Watch (GDW) consortium that integrates, harmonizes, and augments existing global datasets to support large-scale analyses. Data curation involved extensive quality control processes to create a single, globally consistent data repository of instream barriers and reservoirs that are co-registered to a digital river network. Version 1.0 of the GDW database contains 41,145 barrier locations and 35,295 associated reservoir polygons representing a cumulative storage capacity of 7,420 km3 and an artificial terrestrial surface water area of 304,600 km2.

Population structure and demographic history of two highly-trafficked species of pangolin in the Congo Basin.

African pangolins are hunted for their meat and for use in local traditional medicine, as well as for their scales, which are trafficked internationally, especially to growing Asian markets. Pangolin's population genetic structure can be used to trace the geographic origins of trafficked scales, but substantial sampling gaps across pangolins' ranges hinder these efforts. In this study, we documented population structure and dynamics in the two species of African pangolin, the white-bellied pangolin (Phataginus tricuspis) and the giant pangolin (Smutsia gigantea) in the underexplored Republic of Congo. Using the mitochondrial control region and two nuclear markers (beta-fibrinogen and titin), we identified high genetic diversity in both species. We document a distinct mitochondrial lineage of the white-bellied pangolin, which was most likely shaped by river barriers together with dynamics of forest refugia related to the climatic shifts during the Pleistocene. We detected population growth in the white-bellied pangolin coinciding with a dry period during the Pleistocene, suggesting some ability for this typically forest-dwelling species to persist under diverse environmental conditions. Using landscape genetics, we found all but one of the pangolins we sampled at bush meat markets originated locally. A single individual appeared to have been imported to Congo from Cameroon. These findings significantly contribute to our understanding of pangolin population biology and local trade dynamics. In addition, our data from a previously unstudied part of pangolins' ranges will help us to better understand international wildlife trafficking patterns and to target conservation and protection strategies for these highly vulnerable species.

Amazonian rivers are leaky barriers to gene flow in forest understory birds.

Ever since Alfred Russel Wallace's nineteenth-century observation that related terrestrial species are often separated on opposing riverbanks, major Amazonian rivers have been recognized as key drivers of speciation. However, rivers are dynamic entities whose widths and courses may vary through time. It thus remains unknown how effective rivers are at reducing gene flow and promoting speciation over long timescales. We fit demographic models to genomic sequences to reconstruct the history of gene flow in three pairs of avian taxa fully separated by different Amazonian rivers, and whose geographic ranges do not make contact in headwater regions where rivers may cease to be barriers. Models with gene flow were best fit but still supported an initial period without any gene flow, which ranged from 187 000 to over 959 000 years, suggesting that rivers are capable of initiating speciation through long stretches of allopatric divergence. Allopatry was followed by either bursts or prolonged episodes of gene flow that retarded genomic differentiation but did not fully homogenize populations. Our results support Amazonian rivers as key barriers that promoted speciation and the build-up of species richness, but they also suggest that river barriers are often leaky, with genomic divergence accumulating slowly owing to episodes of substantial gene flow.

Identifikasi Urutan Prioritas Penanganan dalam Pemeriksaan Kondisi Jembatan dengan Metode Bridge Management System (BMS)

One piece of infrastructure that has an important role in a road network is a bridge. Bridges are land transportation infrastructure that is useful for continuing roads through existing obstacles such as rivers, so the collapse of a bridge will reduce or hold up traffic, which means disrupting the smooth transportation of people and goods. A bridge is a structure that crosses a river or other traffic barrier, so the collapse of the bridge will reduce or hold back traffic, which as a result will disrupt the comfort of traffic and disrupt economic relations. The purpose of a bridge inspection is to ensure that the bridge is in a safe condition for road users and also to secure the investment value of the bridge. In this thesis, we will discuss the identification of bridge condition checks which are carried out directly by conducting field surveys.

Genetic structure and landscape effects on gene flow in the Neotropical lizard Norops brasiliensis (Squamata: Dactyloidae)

One key research goal of evolutionary biology is to understand the origin and maintenance of genetic variation. In the Cerrado, the South American savanna located primarily in the Central Brazilian Plateau, many hypotheses have been proposed to explain how landscape features (e.g., geographic distance, river barriers, topographic compartmentalization, and historical climatic fluctuations) have promoted genetic structure by mediating gene flow. Here, we asked whether these landscape features have influenced the genetic structure and differentiation in the lizard species Norops brasiliensis (Squamata: Dactyloidae). To achieve our goal, we used a genetic clustering analysis and estimate an effective migration surface to assess genetic structure in the focal species. Optimized isolation-by-resistance models and a simulation-based approach combined with machine learning (convolutional neural network; CNN) were then used to infer current and historical effects on population genetic structure through 12 unique landscape models. We recovered five geographically distributed populations that are separated by regions of lower-than-expected gene flow. The results of the CNN showed that geographic distance is the sole predictor of genetic variation in N. brasiliensis, and that slope, rivers, and historical climate had no discernible influence on gene flow. Our novel CNN approach was accurate (89.5%) in differentiating each landscape model. CNN and other machine learning approaches are still largely unexplored in landscape genetics studies, representing promising avenues for future research with increasingly accessible genomic datasets.

Analisa Penilaian Kondisi Jembatan Sarolangun Batang Tembesi Dengan Metode Bridge Manajemen System (BMS)

Bridges are an important part of a road network system because they have a significant impact if the bridge collapses or if it does not function properly. A bridge is a structure that crosses a river or other traffic barrier, so the collapse of the bridge will reduce or hold back traffic, which as a result will disrupt the comfort of the public in traffic and disrupt economic relations. A bridge is a structure that crosses a river or other traffic barrier, which as a result disrupts people's comfort in traffic and disrupts economic relations (Bridge Inspection Guidelines 2012). Bridges are built so that pedestrians, vehicle or train drivers can cross these obstacles. However, it turns out that there are many types of bridges which of course vary both in terms of structure, strength and even construction costs. The main components of a bridge are the unity of the road embankment structure approaching the bridge, the sub-bridge structure and the bridge super-structure (BMS, 1993). The main objective of this research is to analyze the condition of the Sarolangun Batang Tembesi Bridge by observing it visually, assessing the technical condition of the bridge, and determining the priority order for bridge maintenance based on its condition value. However, the database results produced in this bridge management system are only limited to screening and ranking results in preparing bridge management programs (Directorate General of Highways, Bridge Management Systems, (1993), "IBMS General Procedure Guide", BMS, Department of Public Works of the Republic of Indonesia.

Convolutional Neural Networks Facilitate River Barrier Detection and Evidence Severe Habitat Fragmentation in the Mekong River Biodiversity Hotspot

AbstractConstruction of river infrastructure, such as dams and weirs, is a global issue for ecosystem protection due to the fragmentation of river habitat and hydrological alteration it causes. Accurate river barrier databases, increasingly used to determine river fragmentation for ecologically sensitive management, are challenging to generate. This is especially so in large, poorly mapped basins where only large dams tend to be recorded. The Mekong is one of the world's most biodiverse river basins but, like many large rivers, impacts on habitat fragmentation from river infrastructure are poorly documented. To demonstrate a solution to this, and enable more sensitive basin management, we generated a whole‐basin barrier database for the Mekong, by training Convolutional Neural Network (CNN)–based object detection models, the best of which was used to identify 10,561 previously unrecorded barriers. Combining manual revision and merged with the existing barrier database, our new barrier database for the Mekong Basin contains 13,054 barriers. Existing databases for the Lower Mekong documented under ∼3% of the barriers recorded by CNN combined with manual checking. The Nam Chi/Nam Mun region, eastern Thailand, is the most fragmented area within the basin, with a median [95% CI] barrier density of 15.53 [0.00–49.30] per 100 km, and Catchment Area‐based Fragmentation Index value, calculated in an upstream direction, of 1,178.67 [0.00–6,418.46], due to the construction of dams and sluice gates. The CNN‐based object detection framework is effective and potentially can transform our ability to identify river barriers across many large river basins and facilitate ecologically‐sensitive management.

Spatial and temporal variations of seabed sediment characteristics in the inner Louisiana shelf

Although many studies have been performed in the northern Gulf of Mexico, there have been a paucity of high-resolution sediment data collected from seabed. New multicores were collected repeatedly at 4 fixed stations in the inner Louisiana shelf on March 12, 2021, July 7, 2021, November 20, 2021, and March 5, 2022, respectively, to study detailed spatial and temporal variations of surficial sediment. Being a very high sediment accumulation zone, Raccoon Island dredge pit and its nearby shelf were selected as our study area and additional six vibracores were collected inside and outside the pit for comparison. This study area is about 140 km west of the modern Mississippi Delta and 70 km southeast of the Atchafalaya Delta. A total of 624 samples from both vibracores and multicores were analyzed for this study. Spatially, our results show that sediment near Ship Shoal was the coarsest and sediment deposited in the pit was the finest. The organic matter was highest inside the pit and lowest near Ship Shoal. The carbonate content was the lowest near Ship Shoal. Temporally, surficial sediments were generally coarser in July and November of 2021 and finer in March of 2021 and March of 2022. Although the Mississippi and Atchafalaya Rivers supply a large amount of sediment during spring season, it takes time for the river-derived sediment to be delivered into the study area. Hurricanes Delta, Zeta and Ida passed this area and greatly impacted sediment transport in the years 2021 and 2022. The comparatively coarser sediment in July and November of 2021 were likely related to the resuspension of some coarse sediment by these hurricane events. Besides the river supply, Ship Shoal and barrier islands are nearby localized sandy sources and inner Louisiana shelf is a widespread mud source. This spatial heterogeneity of surficial sediment interplays with the timing of Mississippi and Atchafalaya River flood season and hurricanes and together dictates the sediment texture. This research on a filled-up dredge pit can benefit future evaluation of the safety of existing oil infrastructure and the feasibility of building new pipelines and platforms after dredging activities. Our results also shed light on the study of river- and hurricane-impacted sediment transport in muddy and mixed-texture passive continental margins around the world.

Bidirectional connectivity in fishways: A mitigation for impacts on fish migration of small hydropower facilities

Abstract Most freshwater fish need to move freely through rivers to complete their life cycles. Thus, river barriers (e.g. dams, culverts and gauging stations) may delay, hinder or even block their longitudinal movements, affecting fish conservation. The most widespread solution to allow upstream fish migration are fishways, whereas downstream migration is basically facilitated through spillways, turbines or specific solutions such as bypass systems. So far, studies and scientific discussions concerning bidirectional movements through fishways are scarce and focused on large dams and reservoirs, mainly with large migratory species such as salmonids, rather than smaller facilities and lesser known species. This study investigated bidirectional movements through a small run‐of‐the‐river hydropower plant with a pool‐and‐orifice type fishway, using the Iberian barbel (Luciobarbus bocagei), a potamodromous cyprinid, as the target species. Passive integrated transponder and radio tracking data were collected over 4 years and combined to characterize upstream and downstream movements. The study focused primarily on fish movements through the fishway, but also estimated the multiple associated routes of passage. The results show diverse fish movements with inter‐ and intra‐annual variability, with several individuals performing bidirectional movements and even some fish returning over the years. The documented movements and observations indicate that fishways can serve as an effective bidirectional migration corridor for fish, potentially enhancing the conservation efforts for potamodromous species. This study supports the decision to use fishways as an overall mitigation tool to reduce the impact of small hydropower facilities on fish.

New Records of Species Taeniopteryx hubaulti Aubert, 1946 and Taeniopteryx schoenemundi (Mertense, 1923) (Plecoptera: Taeniopterygidae) in Serbia

Species Taeniopteryx hubaulti Aubert, 1946 and T. schoenemundi (Mertense, 1923) have been emphasized as endangered or vulnerable species in several European countries due to their local and limited distribution. More intensive research of these species on the territory of Serbia was conducted from 2011 to 2022. Taeniopteryx hubaulti was registered in seven localities. Five of these localities (Brusnička and Jerma rivers, the spring of the Raška River, and two localities on Grza River, spring and tufa barriers) were recorded as new sites of this species in Serbia. Two localities (Barska River and Lisinski Stream) had already been known from previous studies. The species T. schoenemundi was recorded in four new localities (Dulenska, Visočica, Temštica, and Trnavska rivers). Both species were found in waters with high oxygen concentration, relatively uniform low water temperature, and variable values of hardness, electrical conductivity, and pH values, with a small amount of inorganic nutrients. Considering the rare occurrence and prominent importance of these species as biological indicators of water quality and climate change, their findings have a great deductive value. This research represents an important contribution to the insight into the distribution of T. hubaulti and T. schoenemundi species.

The Effects of Channelization with Low In-Stream Barriers on Macroinvertebrate Communities of Mountain Rivers

The effects of channelization with low in-stream barriers in mountain rivers on macroinvertebrate communities are still weakly recognised. We aimed to assess the differences in structure and density of benthic macroinvertebrates between two north Carpathian mountain rivers: one channelized with a cascade of concrete sills and the other one with block ramps. Water was collected five times for physicochemical analysis. Macroinvertebrate fauna and fine bottom sediments were collected three times (spring, summer, autumn) from different habitat types: glides, runs, pools and riffles of the estimated channel surface. The in-stream barriers altered the channel gradient and flow velocity, reducing the area of pools and riffles as well as extending the area of glides with slow current velocities, associated with the highest rate of fine sediment deposition. Channel modifications induced a general shift of investigated fluvial systems toward lentic habitat conditions. Macroinvertebrate communities characteristic of slow-flowing rivers and pools became dominant, while those characteristic for the riffles of mountain rivers were confined to only small areas. The studied section of the Porębianka River channelized with block ramps exhibited greater diversity in the macroinvertebrate community between habitats and significantly higher macroinvertebrate density than the Mszanka River which was channelized with concrete sills.

Understanding the impact of barriers to onward migration; a novel approach using translocated fish

River catchments worldwide are heavily fragmented by anthropogenic barriers, reducing their longitudinal connectivity and contributing to the decline of migratory fish populations. Direct impacts of individual barriers on migratory fish are well-established, but barrier impacts on onward migration are poorly understood, despite their relevance to evidence-based, catchment-scale, management of threatened species. This study investigated the upstream spawning migration of 352 acoustic tagged river lamprey (Lampetra fluviatilis), translocated upstream of two key barriers (R2: n = 60 & 59; R3: n = 59 & 52) compared to a control group (R1: n = 61 & 59), across two contrasting (dry and wet, n = 180 and 172) years in the River Yorkshire Ouse, England, to reveal the impact of barriers on the onward migration of upstream migrating fish. Release further upstream increased the degree of catchment penetration, with median distance upstream of R1 56.1% and 68.6% greater for lamprey released at R2 and R3 respectively. Median delays at the two downstream-most main river barriers by the control group were 23.8 and 5.4 days (2018/19) and 9.3 and 11.4 days (2019/20). However, impacts of delay were only observed on the time to reach spawning habitat, time to reach final assumed spawning location and speed of movement in one upper catchment tributary during 2019/20 whilst they were only observed on time to reach spawning habitat during 2018/19 and on assumed spawning location distance during 2019/20 in the other. Ultimately, limited impacts of delay at barriers on onward fish migration post-passage were observed but median catchment penetration was increased with consecutive release upstream. This study demonstrated the importance of a true understanding of barrier impacts to inform catchment-wide planning, evidence vital for management worldwide. Although the findings of this study do support the use of trap and transport as a measure to remediate barrier impacts on migration, fish passage engineering improvements or barrier removal, at structures shown to be the most inhibiting to fish migration should be considered the best and most sustainable option to improve barrier passage.

Effect of thermo-velocity barriers on fish: influence of water temperature, flow velocity and body size on the volitional swimming capacity of northern straight-mouth nase (Pseudochondrostoma duriense).

Water temperature and flow velocity directly affect the fish swimming capacity, and thus, both variables influence the fish passage through river barriers. Nonetheless, their effects are usually disregarded in fishway engineering and management. This study aims to evaluate the volitional swimming capacity of the northern straight-mouth nase (Pseudochondrostoma duriense), considering the possible effects of water temperature, flow velocity and body size. For this, the maximum distance, swim speed and fatigue time (FT) were studied in an outdoor open-channel flume in the Duero River (Burgos, Spain) against three nominal velocities (1.5, 2.5 and 3m s-1 ) and temperatures (5.5, 13.5 and 18.5°C), also including the changes between swimming modes (prolonged and sprint). Results showed that a nase of 20.8cm mean fork length can develop a median swim speed that exceeds 20.7BL s-1 (4.31 m s-1 ) during a median time of 3.4s in sprint mode, or 12.2BL s-1 (2.55 m s-1 ) for 23.7s in prolonged mode under the warmest scenario. During prolonged swimming mode, fish were able to reach further distances in warmer water conditions for all situations, due to a greater swimming speed and FT, whereas during sprint mode, warmer conditions increased the swim speed maintaining the FT. In conclusion, the studied temperature range and flow velocity range influence fish swimming performance, endurance and distance travelled, although with some differences depending on the swimming mode. The provided information goes a step forward in the definition of real fish swimming capacities, and in turn, will contribute to establish clear passage criteria for thermo-velocity barriers, allowing the calculation of the proportion of fish able to pass a barrier under different working scenarios, as well designing of the optimized solutions to improve the fish passage through river barriers.

Three-dimensional migratory behaviour of European silver eels (Anguilla anguilla) approaching a hydropower plant.

The global population of European eel (Anguilla anguilla) is rapidly declining, and migration barriers in rivers are believed to be one of several key causes. While progress has been made in the development of bypass solutions, they are often constructed based on a limited knowledge of swimming behaviour. A bypass close to the stream bed is often recommended at fish passage facilities to accommodate downstream eel migration. The results of this recommendation are poorly studied, and the few studies that exist show varying bypass efficiencies. The current study used acoustic telemetry with depth sensors to explore the three-dimensional migratory behaviour of downstream-migrating silver eels. The eels were tracked as they approached a hydropower plant with a state-of-the-art angled bar rack and full-depth bypass. Downstream and upstream swimming differed in preferred vertical and lateral positions. During periods of local downstream movement, the density of observations was largest in the upper middle section, away from the river boundaries and in higher velocities. Conversely, when moving upstream, eels tended to avoid the upper layers of the middle part of the river, swimming closer to the riverbed and using the bank areas to a greater extent. Downstream-moving fish swam higher in the water column during night and in turbid conditions (high discharge). When approaching the impassable bar rack and the full-depth bypass, the eels searched most intensely but not exclusively along the bottom third of the rack, often exploring at new depths after changing direction. The impediment passage efficiency was 100% when both bypass solutions were considered. The study provides knowledge of the swimming behaviour of silver eels, which is relevant for the design of bypass solutions for eels at migration barriers.

River fragmentation and barrier impacts on fishes have been greatly underestimated in the upper Mekong River

River barriers reduce river connectivity and lead to fragmentation of fish habitats, which can result in decline or even extinction of aquatic biota, including fish populations. In the Mekong basin, previous studies have mainly focused on the impacts of large dams but ignored the impacts of small-scale barriers, or drew conclusions from incomplete barrier databases, potentially leading to research biases. To test the completeness of existing databases and to evaluate the catchment-scale fragmentation level, a detailed investigation of river barriers for the whole Upper Mekong (Lancang catchment) was performed, by conducting visual interpretation of high-resolution remotely sensed images. Then, a complete catchment-scale barrier database was created for the first time. By comparing our barrier database with existing databases, this study indicates that 93.7% of river barriers were absent from the existing database, including 75% of dams and 99.5% of small barriers. Barrier density and dendritic connectivity index (DCID and DCIP) were used to measure channel fragmentation within the catchment. Overall, 50.5% of sub-catchments contained river barriers. The Middle region is the most fragmented area within the Lancang catchment, with a median [quartiles] barrier density of 5.34 [0.70–9.67] per 100 km, DCIP value of 49.50 [21.50–90.00] and DCID value of 38.50 [9.00–92.25]. Furthermore, since 2010, distribution ranges of two representative fish species Schizothorax lissolabiatus (a rheophilic cyprinid) and Bagarius yarrelli (a large catfish) have reduced by 19.2% and 32.8% respectively, probably due in part to the construction of river barriers. Our findings indicate that small-scale barriers, in particular weirs and also small dams are the main reason for habitat fragmentation in the Lancang and must be considered alongside large dams in water management and biodiversity conservation within the Mekong.

Environmental DNA reveals a mismatch between diversity facets of Amazonian fishes in response to contrasting geographical, environmental and anthropogenic effects.

Freshwater ecosystems are among the most endangered ecosystem in the world. Understanding how human activities affect these ecosystems requires disentangling and quantifying the contribution of the factors driving community assembly. While it has been largely studied in temperate freshwaters, tropical ecosystems remain challenging to study due to the high species richness and the lack of knowledge on species distribution. Here, the use of eDNA-based fish inventories combined to a community-level modelling approach allowed depicting of assembly rules and quantifying the relative contribution of geographic, environmental and anthropic factors to fish assembly. We then used the model predictions to map spatial biodiversity and assess the representativity of sites surveyed in French Guiana within the EU Water Framework Directive (WFD) and highlighted areas that should host unique freshwater fish assemblages. We demonstrated a mismatch between the taxonomic and functional diversity. Taxonomic assemblages between but also within basins were mainly the results of dispersal limitation resulting from basin isolation and natural river barriers. Contrastingly, functional assemblages were ruled by environmental and anthropic factors. The regional mapping of fish diversity indicated that the sites surveyed within the EU WFD had a better representativity of the regional functional diversity than taxonomic diversity. Importantly, we also showed that the assemblages expected to be the most altered by anthropic factors were the most poorly represented in terms of functional diversity in the surveyed sites. The predictions of unique functional and taxonomic assemblages could, therefore, guide the establishment of new survey sites to increase fish diversity representativity and improve this monitoring program.

Wasted and excess energy in the hydropower sector: A European assessment of tailrace hydrokinetic potential, degassing-methane capture and waste-heat recovery

Hydropower is the giant of the renewable energy sector, and a well-established source of energy. In order to reduce the impacts of new barriers in rivers, the retrofitting of existing facilities with new technologies is deserving a great attention, especially when hydropower technologies are hybridized with other energy devices. In this study a European-scale assessment is carried out to quantify the potential associated to the exploitation of the excess (and wasted) energy sources in existing hydropower facilities. Three sources of energy are assessed: 1) the hydrokinetic energy of the tailrace water flow and the potential energy associated to the unexploited head below Pelton units, 2) the thermal energy of the cooling system of the electric generators and 3) the chemical energy of the degassing methane. Considering the available technology, 5.0 TWh/y of heat could be generated by exploiting the thermal energy of the cooling system. 2.4 TWh/y of electricity could be generated by harnessing the hydrokinetic energy at the tailrace; this would correspond to thousands of micro hydropower plants 100 kW each), and would avoid new installations in natural freshwater systems. Degassing methane is relevant at the global scale, especially in tropical reservoirs. In Europe 5,950 tons/year of degassing methane could be theoretically captured, since minor methane emissions from reservoirs occur. R&D activities are ongoing to overcome the current technological limitations and high installation costs. Different novelties are included in this study: for the first time, a continental assessment is carried out on this topic, establishing methodologies that could be implemented at any regional scale. For each technology, a literature review is carried out to collect data and case studies. Data to estimate the number of units and the operating range of Francis, Kaplan and Pelton turbines in Europe, and equations to estimate the degassing methane emissions, are provided. These data can be used for similar large scale assessments.

Comment on Souza and Perez Filho (2019) “Late Holocene coastal dynamics, climate pulses and low terraces in the coast of the state of São Paulo, southeast Brazil”

Souza and Perez Filho (2019) inferred two transgressive events in the Late Holocene record of lower Ribeira de Iguape River and Ilha Comprida barrier, Southeastern Brazil, based on luminescence ages and paleoenvironmental interpretation of four columnar sections. In the present paper, we discuss inconsistencies on the methods applied and sample design adopted by those authors, which lead to an incorrect model of coastline evolution for the region over the time period covered by the dates obtained. The dataset presented by Souza and Perez Filho (2019) allows the reinterpretation of the deposits studied as regressive and fits into previous models of regional coastal evolution.

Geography vs. past climate: the drivers of population genetic structure of the Himalayan langur

BackgroundContemporary species distribution, genetic diversity and evolutionary history in many taxa are shaped by both historical and current climate as well as topography. The Himalayas show a huge variation in topography and climatic conditions across its entire range, and have experienced major climatic fluctuations in the past. However, very little is known regarding how this heterogenous landscape has moulded the distribution of Himalayan fauna. A recent study examined the effect of these historical events on the genetic diversity of the Himalayan langurs in Nepal Himalaya. However, this study did not include the samples from the Indian Himalayan region (IHR). Therefore, here we revisit the questions addressed in the previous study with a near complete sampling from the IHR, along with the samples from the Nepal Himalaya. We used the mitochondrial Cytochrome-b (Cyt-b, 746 bp) region combined with multiple phylogeographic analyses and palaeodistribution modelling.ResultsOur dataset contained 144 sequences from the IHR as well as the Nepal Himalaya. Phylogenetic analysis showed a low divergent western clade nested within high divergent group of eastern lineages and in the network analysis we identified 22 haplotypes over the entire distribution range of the Himalayan langurs. Samples from the Nepal Himalaya showed geographically structured haplotypes corresponding to different river barriers, whereas samples from IHR showed star-like topology with no structure. Our statistical phylogeography analysis using diyABC supported the model of east to west colonisation of these langurs with founder event during colonisation. Analysis of demographic history showed that the effective population size of the Himalayan langurs decreased at the onset of last glacial maximum (LGM) and started increasing post LGM. The palaeodistribution modelling showed that the extent of suitable habitat shifted from low elevation central Nepal, and adjoining parts of north India, during LGM to the western Himalaya at present.ConclusionThe current genetic diversity and distribution of Himalayan langurs in the Nepal Himalaya has been shaped by river barriers, whereas the rivers in the IHR had relatively less time to act as a strong genetic barrier after the recent colonisation event. Further, the post LGM expansion could have had confounding effect on Himalayan langur population structure in both Nepal Himalaya and IHR.

Research Progress on Shotcrete for Construction Applications: A Scientometric Review

Considerable research has been carried out on shotcrete for rock supports in tunneling and mining. This study used a novel approach based on scientometric analysis of shotcrete’s bibliographic data to determine its essential components. Knowledge mapping, co-occurrence, and citation analysis are the most difficult parts of current research. The information needed to complete the study was retrieved from the Scopus search engine. There were 1267 articles considered, and the VOSviewer program was used to analyze. Important publishing sources, keyword analysis, writers that have the most contribution in terms of citations and publications, the most-cited articles, and the regions most actively engaged in shotcrete research were identified throughout the data review process. Also, shotcrete’s current applications and main limitations were explored. In addition to its applications in tunneling and mining, shotcrete can also be used for refractory linings, soil stabilization, structural restorations, and the construction of river barriers, swimming pools, shell structures, domes, and even buildings. However, the durability performance of shotcrete is poorer compared to conventional concrete. In this regard, additional in-depth research is needed to strengthen the durability features of shotcrete. The graphical description and quantitative contribution of scholars and countries in this study might help academics build collaborative projects and disseminate new ideas and methods.