Brahmaputra Basin Research Articles

Estimation of glacier-stored freshwater volume present in major tributaries of the Brahmaputra basin.

Estimation of the glacier-stored freshwater is important to understand the water security in the Himalayan region. While previous work has studied the western and central Himalayan glaciers, the eastern counterpart received less and more scattered attention. In this study, an attempt is made to quantify the total glacier-stored freshwater in the Brahmaputra basin and later compared with previous global models. Using open-source tools such as COSI-Corr and the Himalayan Glacier Thickness Mapper (HIGTHIM), the surface velocity and thickness of 1075 glaciers (> 1 km2) in the Brahmaputra basin were estimated, resulting in a current ice-volume estimate of 283 × 109 m3. Based on the laminar flow model, the mean ice volume ranges from 8284 to 230,186 m3, with an average of 36,570 m3. Sub-basin-wise evaluations of the total glacier-stored freshwater availability in the basin were also conducted, revealing that the Siang (89.998 × 109 m3, 31.45%) and Lohit (84.371 × 109 m3, 29.49%) sub-basins have significantly larger ice volumes than others. The average mean ice volume for each sub-basin are as follows: Teesta (45,233 m3), Sankosh (45,552 m3), Manas (39,581.7 m3), Subansiri (40,922.4 m3), Kameng (41,241.2 m3), Siang (36,120.5 m3), Dibang (31,792.2 m3), and Lohit (30,340.6 m3). Teesta, Sankosh, and Manas exhibit relatively higher average mean ice volumes than others. In comparison with the global studies, the present study's findings are acceptable with ensemble ice-volume estimates considering an uncertainty of ± 17.35%. Therefore, these results serve as a primary input for assessing the future changes in water resources and hazards related to water in the Brahmaputra basin.

Application of GRACE-based satellite estimates in the assessment of flood potential: A case study of Gangetic-Brahmaputra basin, India.

The high frequency of flood occurrences and the uneven distribution of hydrological stations make it difficult to monitor large-scale floods. Emergence of the Gravity Recovery and Climate Experiment (GRACE) satellite system sets up a new era of large-scale flood monitoring without much reliance on in situ hydrological observations. The GRACE-derived flood potential index (FPI) exhibits its ability to monitor major events of 2003, 2004, 2007, and 2008 over the Indo-Gangetic-Brahmaputra Basin (IGBB). Precipitation and soil moisture are the major influencing factors of flood. However, the response of potential flooding to such parameters is little known. Pearson's lag correlation analysis is used to examine the response of the GRACE-based FPI to precipitation and soil moisture over the study region comparing seasonal time series of the variables. Results exhibited a 2-month lagged response of FPI to precipitation in the Upper Gangetic Yamuna Chambal Basin (UGYCB) and the Lower Gangetic Basin (LGB) and 1-month lagged response in the Lower Brahmaputra Basin (LBB). With context to soil moisture, a 1-month lag is observed in the Gangetic basins, and no lag is observed in the LBB. Event wise analysis of the lags portrays slightly varying lags for different events; however, it provides a picture on the interaction between these variables. This study also assesses the agreement between FPI and satellite-based river discharge, i.e. Dartmouth Flood Observatory (DFO) discharge. A good correlation (> 0.60) between the two is observed. Threshold values of FPI are determined for the LBB due to its annual flood frequency. The nearly similar accuracy of threshold FPI, determined using DFO discharge, in monitoring floods and the predictive skill measure of FPI for LBB to the previous studies demonstrates the utility of satellite-based discharge in the quantification of threshold FPI values for different percentile floods.

Aquatic insect diversity and distribution in Maguri Beel and Khamti Guali Beel wetlands, Upper Brahmaputra Basin, Assam, India

The investigation revealed the presence of a total of 16 species of aquatic insects in Maguri Beel and Khamti Guali Beel, two freshwater ecosystems, in Assam, India. The distribution and diversity of species present in the two wetlands with an account of physico-chemical water analysis and macrophyte distribution are discussed. Variation in the diversity indices of both the wetlands, illustrated key differences in diversity and distribution of aquatic insects in Maguri and Khamti Guali Beel.

Exploring climate shifts in the Ganga-Brahmaputra basin based on rainfall and temperature variability.

Climate change has a significant impact on the Ganga-Brahmaputra (GB) basin, the major food belt of India, which frequently experiences flooding and varied incidences of drought. The current study examines the changing trend of rainfall and temperature in the GB basin over a period of 30years to identify areas at risk with an emphasis on the Paris Agreement's mandate to keep increasing temperatures below 2°C. The maximum temperature anomaly in the middle Ganga plains recorded an increase of more than 1.5°Cyear-1 in 1999, 2005, and 2009. Some extreme events were observed in the Brahmaputra basin during 1999, 2009, and 2010, where a prominent temperature increase of 1.5°Cyear-1 was observed. The minimum temperature revealed an increasing trend for the G-B basin with an anomalous increase of 0.04 to 0.06°Cyear-1. The rainfall variability across the Ganga basin shows a rising tendency over the lower Ganga region while the Brahmaputra basin showed a downward trend. To identify the statistical relation between the Global climatic oscillations and regional climate, Standardized Precipitation Index (SPI) and Niño 3.4 were used. The wet and dry period estimation shows a rise in flood conditions in the Ganga basin whereas, in the Brahmaputra basin, an increase in drought frequency was observed. The correlation based on Niño 3.4 and SPI3 presents a negative relation for the monsoon season in the G-B basin revealing a situation of drought occurrence (SPI3 below 0) with increased Nino 3.4 values (El Niño above + 0.4C).

Molecular identification and phylogenetic relationship of fishes belonging to the Family Danionidae from Brahmaputra Basin, Assam, Northeast India.

The Northeast India, being part of two global biodiversity hotspot namely the Indo-Burma and Eastern Himalayan Hotspots supports a wide variety of rich aquatic biodiversity including fishes. The family Danionidae is a widely diverse group inhabiting the upper colder stretches of river although few are abundant in the lower stretches. The persisting similarity in the morphological appearance and body colouration within the members of this family seeks an integrated method to identify the species correctly. In the present study, the mt-DNA barcode was generated for correct identification and confirmation of the species. A total of nine mitochondrial cytochrome c oxidase subunit I gene sequences were generated for each species under the study. The pairwise distance values ranged from 0.09 to 9.11% within species and 9.06-32.71% between species. A neighbour-joining tree was constructed based on the Kimura 2 parameter model. Two major groups were observed where Danioninae formed a sister group to the Chedrinae and Rasborinae. The present study is a preliminary work to document and identify the species under the family Danionidae from Brahmaputra basin, Assam, using molecular tools and establish the phylogenetic relationship.

Evaluating the Snow Cover Service Value on the Qinghai–Tibet Plateau

The Snow Cover Service Value (SCSV) is an important component of the ecological assets of the Qinghai–Tibet Plateau (QTP). Exploring the SCSVs on the QTP is the key to maintaining the functions of climate regulators and Asian water towers, and it is also an important theoretical basis for maintaining the ecological security of ecological barrier areas. Using multi-source data such as daily and monthly observation data sets and related statistical yearbooks, an evaluation framework for the SCSVs on the QTP was constructed for the first time. The results showed that the average annual SCSV of the QTP from 2001 to 2020 was 6.99 trillion yuan, and the average annual climate regulation value was 5.81 trillion yuan, which was the most important SCSV. The Inner Plateau Basin, the Brahmaputra Basin, and the Yangtze Basin had the highest SCSVs, while the Yellow Basin had the lowest unit SCSV, where it was the most vulnerable area of snow cover resources on the QTP, and the SCSV of the Yellow Basin was significantly correlated with rainfall. The correlation between the SCSV and the temperature in the Indus and Ganges Basins was significant. The freshwater supply value of the snow in the Indus Basin and Tarim Basin was found to be able to reach 30% of the whole year in June, where it would be necessary to pay attention to the risk of flooding caused by snowmelt during the melting period. Finally, this paper discussed the strategies for the protection and development of snow resources in each basin based on the spatial distribution characteristics, seasonal variation characteristics, and influencing factors of the SCSVs. The research can provide reference for the rational allocation of snow resources and ecological protection on the QTP.

Climate dynamics and the effect of topography on snow cover variation in the Indus-Ganges-Brahmaputra river basins

The river basins of the Indus-Ganges-Brahmaputra (IGB) are characterized by rapid population growth, increased water demand, and rapid snow/ice melting, all of which combine to make these catchments especially vulnerable to climate change. Here, we present a comprehensive dataset (2003−2020) for precipitation, temperature and snow cover area (SCA) to investigate the spatio-temporal variability of important climate factors in relation to elevation and across three major sub-basins of the IGB. Improved MODIS (Moderate Resolution Imaging Spectro-radiometer) Terra and Aqua snow cover data are used to estimate regional snow cover, while Climate Hazards Group InfraRed Precipitation with Station Data version 2.0 (CHIRPS-V2.0) is deployed for precipitation, and MODIS Land Surface Temperature (LST) data are used to estimate temperature. The analysis reveals significant changes in precipitation, LST and snow cover throughout the IGB region together with a strong degree of spatial coherence between SCA and regional surface topography (R2 = 0.82).Maximum changes were observed in the Brahmaputra basin at mean annual precipitation (13.9 mm/year) and reduced SCA (155.4 km2/year) over the period studied. Similar trends are also evident, albeit with relatively lower absolute values in the other two basins, whereby the Indus basin evidences a significant reduction in annual SCA, averaging 82.2 km2/year with increased precipitation (3.12 mm/year) and LST. This investigation further highlights the relative influence of climate change factors and regional human activities in determining high-elevation changes in SCA. Most of the middle elevation regions of the Ganges experienced a significant reduction in SCA, with human impact contributing 82% of the observed variation, while climate factors are more prominent in the Indus and Brahmaputra basins. Understanding the dynamics of snow cover and its regional influencing factors is crucial to the more accurate evaluation of water resources and to defining appropriate mitigation and adaptation strategies for the coming decades.

Evaluation of Near Real-Time Global Precipitation Measurement (GPM) Precipitation Products for Hydrological Modelling and Flood Inundation Mapping of Sparsely Gauged Large Transboundary Basins—A Case Study of the Brahmaputra Basin

Limited availability of hydrometeorological data and lack of data sharing practices have added to the challenge of hydrological modelling of large and transboundary catchments. This research evaluates the suitability of latest near real-time global precipitation measurement (GPM)-era satellite precipitation products (SPPs), IMERG-Early, IMERG-Late and GSMaP-NRT, for hydrological and hydrodynamic modelling of the Brahmaputra Basin. The HEC-HMS modelling system was used for the hydrological modelling of the Brahmaputra Basin, using IMERG-Early, IMERG-Late, and GSMaP-NRT. The findings showed good results using GPM SPPs for hydrological modelling of large basins like Brahmaputra, with Nash–Sutcliffe efficiency (NSE) and R2 values in the range of 0.75–0.85, and root mean square error (RMSE) between 7000 and 9000 m3 s−1, and the average discharge was 20611 m3 s−1. Output of the GPM-based hydrological models was then used as input to a 1D hydrodynamic model to assess suitability for flood inundation mapping of the Brahmaputra River. Simulated flood extents were compared with Landsat satellite-captured images of flood extents. In critical areas along the river, the probability of detection (POD) and critical success index (CSI) values were above 0.70 with all the SPPs used in this study. The accuracy of the models was found to increase when simulated using SPPs corrected with ground-based precipitation datasets. It was also found that IMERG-Late performed better than the other two precipitation products as far as hydrological modelling was concerned. However, for flood inundation mapping, all of the three selected products showed equally good results. The conclusion is reached that for sparsely gauged large basins, particularly for trans-boundary ones, GPM-era SPPs can be used for discharge simulation and flood inundation mapping.

Irrigation-driven groundwater depletion in the Ganges-Brahmaputra basin decreases the streamflow in the Bay of Bengal

Ganges and Brahmaputra, two of Asia’s most prominent rivers, have a crucial role in Southeast Asia’s geopolitics and economy and are home to one of the world’s biggest marine ecosystems. Irrigation-driven groundwater depletion and climate change affect the Ganges-Brahmaputra’s hydrology, threatening the stability of the Bay of Bengal. Here, we quantify, using results from a land reanalysis, the impacts of a changing climate and intensive irrigation on the surface water flowing into the Bay of Bengal. The effects of such activities mostly occurring in the Ganges basin, either intensified or lessened depending on the area by the climatic conditions, decrease freshwater flow into the bay by up to 1200 m3/s/year. While the increase in precipitation in the Ganges basin reduces the effects of groundwater depletion on the streamflow, the decrease in precipitation and the snowmelt decline in the Brahmaputra basin exacerbate streamflow reduction due to groundwater depletion at the delta.

An application of adjusted livelihood vulnerability index to assess vulnerability to climate change in the char areas of Assam, India

In this paper, socio-ethnographic and Livelihood Vulnerability Index methods have been used as qualitative and quantitative methods respectively to measure vulnerability due to climate change. Three hundred and ninety four (394) numbers of households of Char inhabitants across the Brahmaputra Basin of Assam, India were interviewed during the period of May 2022 to September 2022. Access to food and housing were found to be the main drivers of vulnerability in almost all the Char areas. The study reveals that though ethnically a section of people is seen to be resilient in terms of flood; different geographical factors overpower such advantage, increasing the vulnerability of those households. Different factors affected the vulnerability status of the Char dwellers differently across the different locations. Additionally, apart from the different factors of vulnerability considered in the model used, the study also revealed that flood, erosion and geographical character of Char areas contributed to the creation of the differences in the degree of vulnerability. The results revealed that there is a need for different treatment for vulnerability reduction for Char dwellers in different locations and for which, the sub-indicators of vulnerability used in the study are needed to be studied carefully. Suggestions were also made on the scope for further study on this aspect.

Assessing snow cover patterns in the Indus-Ganga-Brahmaputra River Basins of the Hindu Kush Himalayas using snow persistence and snow line as metrics

This study investigates the utilization of snow persistence (SP) as a metric to assess snow cover patterns in the Upper Indus-Ganga-Brahmaputra (UIGB) river basins, an area notably susceptible to climate change. The objectives of the study are to establish seasonal snow persistence, calculate seasonal snow lines, and quantify the temporal trend of snow lines. It also underscores the importance of accounting for climate zones, elevation, and seasonal variations when investigating snow persistence. Furthermore, the study estimates the snow line elevation using the Regional Snow Line Elevation (RSLE) approach with remote sensing data. Over a span of 19 years (2003–2021), the analysis of SP% in UIGB basins indicates a notable reduction in the mean annual permanent snow zone area, decreasing by -2.61 %, -2.37 %, and -4.18 % from winter (DJF) to summer (JJA). The results uncover considerable fluctuations in snow cover across various climate zones and seasons. The impact of warming is clearly visible on snow cover, instigating a transition from permanent and seasonal snow zones towards intermittent and minimal or no snow zones. The seasonal analysis of the snow line from 2003 to 2021 illustrates fluctuation in the snow line for UIGB basins, from 2349 ± 117 m to 4802 ± 51.7 m, 3003 ± 286 m to 4871 ± 64.4 m, and 3238 ± 127 m to 5047 ± 73 m between winter and summer seasons, with the most significant fluctuation occurring in the Brahmaputra basin. A substantial increase in Snow Line Elevation (SLE) is observed for Ganga (6.67 m yr−1), and Brahmaputra (7.26 m yr−1) at the conclusion of the melting season. These findings offer invaluable insights for formulating targeted mitigation strategies in the snow accumulation regions of each river basin. They equip us with the ability to respond effectively to the spatiotemporal variability of snow cover caused by climate change.

Assessment and Mapping of Riverine Flood Susceptibility (RFS) in India through Coupled Multicriteria Decision Making Models and Geospatial Techniques

Progressive environmental and climatic changes have significantly increased hydrometeorological threats all over the globe. Floods have gained global significance owing to their devastating impact and their capacity to cause economic and human loss. Accurate flood forecasting and the identification of high-risk areas are essential for preventing flood impacts and implementing strategic measures to mitigate flood-related damages. In this study, an assessment of the susceptibility to riverine flooding in India was conducted utilizing Multicriteria Decision making (MCDM) and an extensive geospatial database was created through the integration of fourteen geomorphological, meteorological, hydroclimatic, and anthropogenic factors. The coupled methodology incorporates a Fuzzy Analytical Hierarchy Process (FAHP) model, which utilizes Triangular Fuzzy Numbers (TFN) to determine the Importance Weights (IWs) of various parameters and their subclasses based on the Saaty scale. Based on the determined IWs, this study identifies proximity to rivers, drainage density, and mean annual rainfall as the key factors that contribute significantly to the occurrence of riverine floods. Furthermore, as the Geographic Information System (GIS) was employed to create the Riverine Flood Susceptibility (RFS) map of India by overlaying the weighted factors, it was found that high, moderate, and low susceptibility zones across the country span of 15.33%, 26.30%, and 31.35% of the total area of the country, respectively. The regions with the highest susceptibility to flooding are primarily concentrated in the Brahmaputra, Ganga, and Indus River basins, which happen to encompass a significant portion of the country’s agricultural land (334,492 km2) potentially posing a risk to India’s food security. Approximately 28.13% of built-up area in India falls in the highly susceptible zones, including cities such as Bardhaman, Silchar, Kharagpur, Howrah, Kolkata, Patna, Munger, Bareilly, Allahabad, Varanasi, Lucknow, and Muzaffarpur, which are particularly susceptible to flooding. RFS is moderate in the Kutch-Saurashtra-Luni, Western Ghats, and Krishna basins. On the other hand, areas on the outskirts of the Ganga, Indus, and Brahmaputra basins, as well as the middle and outer portions of the peninsular basins, show a relatively low likelihood of riverine flooding. The RFS map created in this research, with an 80.2% validation accuracy assessed through AUROC analysis, will function as a valuable resource for Indian policymakers, urban planners, and emergency management agencies. It will aid them in prioritizing and executing efficient strategies to reduce flood risks effectively.

Soft sediment deformation structures from the Brahmaputra Basin: A window to the eastern Himalayan paleoseismicity and tectonics

The Brahmaputra foreland basin, is one of the most dynamic in terms of tectonism and sediment load, revealed a variety of seismically generated soft sediment deformation structures (SSDS) in the form of clastic dikes, sand sills and related micro-faults. The qualitative and quantitative parameters of these SSDS in the study area such as dimension, angle of intrusion to capping layer, cross-cutting relations, wall shattering, sand sills, and micro-faults seem to be caused by multiple strong seismic events. The causative earthquake with intensity (VIII-X), paleo-peak ground acceleration (0.55 g) and magnitude (M ≥ 7.0) might have caused liquefaction features in the study area. Along with the geometry of various SSDS and Optically stimulated luminescence (OSL) dates derived for the clastic dikes indicate the oldest possible age for the seismic event as 0.94 ka. Further, the intensity and age obtained for the present study indicates a possible near seismic source like Kopili Fault Zone, Mishmi Thrust, and neotectonic lineament with trend NW-SE, which can be traced as micro faults and in clastic dikes. Liquefaction potential studies in the area indicate the likelihood of very high liquefaction potential (>45) with ground failures regardless of earthquake size or epicentral distance. The present study highlights the importance of SSDS for establishing paleoseismology in tectonically active regions where surface ruptures are sporadic due to dense alluvial cover and most of the active faults are blind.

Temporal and spatial changes in hydrological wet extremes of the largest river basin on the Tibetan Plateau

Global warming accelerates the rate of inter-regional hydrological cycles, leading to a significant increase in the frequency and intensity of hydrological wet extremes. The Tibetan Plateau (TP) has been experiencing a rapid warming and wetting trend for decades. This trend is especially strong for the upper Brahmaputra basin (UBB) in the southern TP. The UBB is the largest river on the TP, and these changes are likely to impact the water security of local and downstream inhabitants. This study explores the spatial-temporal variability of wet extremes in the UBB from 1981–2019 using a water- and energy-budget distributed hydrological model (WEB-DHM) to simulate river discharge. The simulated results were validated against observed discharge from the Ministry of Water Resources at a mid-stream location and our observations downstream. The major findings are as follows: (1) the WEB-DHM model adequately describes land-atmosphere interactions (slight underestimation of −0.26 K in simulated annual mean land surface temperature) and can accurately reproduce daily and monthly discharge (Nash-Sutcliffe efficiency is 0.662 and 0.796 respectively for Nuxia station); (2) although extreme discharge generally occurs in July and is concentrated in the southeastern TP, extreme wet events in the UBB are becoming increasingly frequent (after 1998, the number of extreme days per year increased by 13% compared to before) and intense (maximum daily discharge increased with a significant trend of 444 (m3s−1) yr−1), and are occurring across a wider region; (3) Precipitation is more likely to affect the intensity and spatial distribution of wet extremes, while the air temperature is more correlated with the frequency. Our wet extreme analysis in the UBB provides valuable insight into strategies to manage regional water resources and prevent hydrological disasters.

Decoding the control of active tectonics on the sedimentary budget of a Himalayan River basin: Insights from Sr and Nd isotopic compositions (87Sr/86Sr, εNd) of bed sediments

The interaction between climate and tectonics chiefly governs the erosion and sedimentary budget in the tectonically active Himalayan Mountain chain. In the present study, the relative contribution from the various litho-tectonic units of the Himalaya to the sedimentary budget of the Teesta River System (TRS) (a major tributary of the Brahmaputra system) has been deciphered using the Sr and Nd isotopic compositions (87Sr/86Sr, εNd) of bed sediments. The possible controlling factors for such observed sedimentary provenance have also been assessed. The discharge-weighted sediment transport amount has been translated into the quantification of the erosion rate in the basin. The 87Sr/86Sr and εNd values in the silicate fraction of bed sediments range from 0.74867 to 0.90529 and − 24.3 to −13.9, respectively. In the Teesta main channel, 87Sr/86Sr and εNd show large variability ranging from 0.74867 to 0.82288 and −21.8 to −13.9, respectively along its entire course. This large variability indicates changes in sediment sources i.e., Higher Himalaya and Lesser Himalaya. These data sets show that >60 % of TRS sediments are derived from the Lesser Himalaya, indicating a higher physical erosion over the catchments in the Lesser Himalaya. Our assessment suggests that the sedimentary budget of the Teesta Basin is chiefly governed by higher exhumation as well as the vertical uplift rate of the lesser Himalaya sector of the study area (due to the presence of Rangeet duplex) coupled with focused precipitations. Based on the sediment discharge method, we estimate the erosion rate in the Teesta basin to be 1.7 ± 0.5 mm/yr, which yields a total annual sediment flux of ~41.4 ± 12.4 Mtons. This estimate is comparable to other Himalayan River basins like the Ganga basin, however, lower than the erosion hotspots such as the Brahmaputra basin (Namche Barwa and eastern Syntaxis region) and Indus basin (western Syntaxis region). The obtained erosion rate of the Teesta basin seems to result from the active tectonics in the Sikkim sector of the Himalaya.

Ecology and Diversity of Small Indigenous Fishes in Four Fishing Sites of Upper Brahmaputra Basin, Assam, India

Small Indigenous fishes constitute important fishery resource of Assam, but doesn’t finds its place in capture fishery. Collection of these species is chiefly from their wild habitat and thus the study of these habitats become very important. The four sites selected for study namely Bogibeel, Madhupur, Maguri Beel and Sessa are well known fishing sites of Upper Assam known to record higher fish catch. These sites harbour variety of small indigenous fishes for both food and ornamental value. In our study we have recorded 41 different species of fishes of which 13 belonged to Family Cyprinidae. Channa bleheri and Ailia coila were the two Near Threatened (NT) fish found during the study. Systematic studies of the habitat directly or indirectly like studying the gut content of fishes will give significant information.

Gridded precipitation products on the Hindu Kush-Himalaya: Performance and accuracy of seven precipitation products

Climate change is expected to change precipitation and temperature patterns, which will impact the hydrological regime in Asia. Most river systems in the region originate from the Hindu Kush-Himalayas, and the altered precipitation patterns pose a threat to their sustainability, making it a major concern for planners and stakeholders. Obtaining accurate data on precipitation distribution is crucial for water accounting, which poses challenge. To address this, gridded precipitation products developed from satellite imagery and modeling techniques have become a viable alternative or addition to observed rainfall. However, the accuracy of these products in the region is uncertain. In this study, we aim to evaluate and compare the seven most commonly used precipitation products for the regions to address this gap. The study evaluated seven rainfall products, namely APHRODITE, TRMM, CHIRPS, PERSIANN-CDR, CMORPH, WFDEI, and GPCC by comparing daily, dekadal, and monthly rainfall data to 168 stations data in six countries and 11 river basins in the HKH region. The analysis used four continuous statistical indicators (Pearson correlation coefficient, Bias, Root Mean Square Error, and Nash–Sutcliffe Efficiency coefficient) and two categorical indicators (Probability of Detection and False Alarm Ratio). APHRODITE consistently performed well in several basins with high r values and low RMSE values, but had positive or negative bias values in different basins. CMORPH had the lowest positive bias value in the Ganga_Brahmaputra basin, while GPCC showed the largest r value and lowest RMSE value in the Sindha basin. CHIRPS performed well in Afghanistan, but had positive bias values. GPCC performed well in Myanmar and Pakistan, but had negative or positive bias values. APHRODITE performed consistently well in Nepal, but had negative bias values. Overall, the performance of different gridded precipitation products varies depending on the country and type of evaluation.

Regional Rainfall Frequency Analysis in the Lower Brahmaputra Basin

Regional Rainfall Frequency Analysis in the Lower Brahmaputra Basin

Ornamental Fish Diversity of some Wetlands in Nimati, Jorhat, Assam

The main sources of air-breathing and attractive fish species in the Brahmaputra basin are the wetland or the floodplain lakes. A significant number of riverine species are transported in the wetland areas by the flood impulse of the Brahmaputra and its tributaries. Various types of ornamental fish can be found in the marshes of Assam. There are numerous wetlands nearby Brahmaputra River in the Nimati Ghat of the Jorhat district of Assam. Many riverine species use wetlands as breeding and feeding areas. Unfortunately, the fish population in wetland areas is declining as a result of habitat destruction. The present communication deals with the ornamental fish diversity in some wetlands nearby Nimati, Jorhat. The study was conducted in three important wetlands of Nimati, Jorhat District namely Borsola, Sarala and Gohain beel during monsoon season. A total of 56 ornamental fish species from different genus has been recorded from the wetlands. The fish found in these wetlands are a source of livelihood to the local population. Some fish are utilized for therapeutic purposes as well.

Brief communication: Rapid ∼ 335 × 106 m3 bed erosion after detachment of the Sedongpu Glacier (Tibet)

Abstract. Following the 130 ± 5 × 106 m3 detachment of the Sedongpu Glacier, south-eastern Tibet, in October 2018, the Sedongpu Valley, which drains into the Yarlung Tsangpo (Brahmaputra) River, underwent rapid large-volume landscape changes. Between December 2018 and 2022 and in particular during summer 2021, an enormous volume of in total ∼ 335 ± 5 × 106 m3 was eroded from the former glacier bed, forming a new canyon of up to 300 m depth, 1 km width, and almost 4 km length. The 2021 erosion peak happened through massive but still gradual retrogressive erosion into the former glacier bed. Several rock–ice avalanches of in total ∼ 150 ± 5 × 106 m3 added to the total rock, sediment, and ice volume of over 600 × 106 m3 (0.6 km3) that has been exported from the basin since around 2017. The recent erosion volumes at Sedongpu are by order of magnitude equivalent to the average annual denudation volume of the entire Brahmaputra basin upstream of the location where the river leaves the Himalayas. This high-magnitude low-frequency event illustrates the potential for rapid post-glacial landscape evolution and associated hazards that has rarely been observed and considered at such high intensity so far.