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Diatoms (Bacillariophyta) of the world’s highest aquatic environments from the Western Himalayas, India

Pardhi Samadhan, Thiruvalan Thiruvalan, Thacker Mital, Alakananda B., Karthick Balasubramanian

Oceanological and Hydrobiological Studies

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2023

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Vol. 52, No. 2

172--205

EN

The present study is a preliminary taxonomic surveyof diatom assemblages from one of the highest mountainranges in the Western Himalayas – Ladakh. 37 sampleswere collected from 19 different sampling sites at altitudes ranging from 3100–4552 amsl. The diatom communities were representative of habitats such as lakes, streams, and hot springs from high altitudes. The dominant diatomsare studied using light microscopy and identified using valve morphometrics. The study enlists a total of 74 taxa belonging to 40 genera along with photomicrographic plates. Commonly-found species of high-altitude hot springs habitats were Gogorevia exilis and Denticula thermaloides.Reimeria sinuata, Fragilaria vaucheriae, Gomphonella cf.olivacea, Encyonema ventricosum, Lindavia biswashanti,Diatoma moniliformis, and Denticula valida were commonly occurring species in stream, river and lake habitats. Further analysis and putative novel species from this high-altitude environment will be described in future publications.

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Neural network based hybrid ground motion prediction equations for Western Himalayas and North Eastern India

Dhanya J., Raghukanth S. T. G.

Acta Geophysica

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2020

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Vol. 68, no. 2

303--324

EN

This work aims at developing a hybrid ground motion prediction equation (GMPE) for spectral acceleration in Western Himalayas and North-Eastern India. The GMPE is derived using an efcient nonparametric modelling based on neural network algorithm. In this study, owing to sparsity in the recorded ground motions (498 recordings) for the region, the available information is combined with 13,294 records from the well-tested NGA-West 2 database. For the methodology adopted in the study, regional fags are assigned to the records. Thus, given a magnitude, distance, shear wave velocity, fault type and region, the model is able to predict the possible spectral acceleration. The developed GMPE is observed to be unbiased with respect to region. Further, the inter- and intra-event standard deviations are also in acceptable ranges. It is observed that developed GMPE for Western Himalayas and North-Eastern India is able to capture all the known ground motion characteristics. Additionally, the GMPE is compared with the existing GMPE for rock-type soil condition available for the Western Himalayas and North-Eastern India. Furthermore, applicability of the developed GMPE model in estimating hazard is analysed by obtaining the uniform hazard response spectra for Delhi and Guwahati.

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Dynamics of suspended sediment load with respect to summer discharge and temperatures in Shaune Garang glacierized catchment, Western Himalaya

Kumar R., Kumar R., Singh S., Singh A., Bhardwaj A., Kumari A., Randhawa S. S., Saha A.

Acta Geophysica

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2018

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Vol. 66, no. 5

1109--1120

EN

The observed and predicted rise in temperature will have deleterious impact on melting of snow and ice and form of precipitation which is already evident in Indian Himalayan Region. The temperature-dependent entities like discharge and sediment load will also vary with the observed and predicted rise posing environmental, social and economic threat in the region. There is little known about sediment load transport in relation to temperature and discharge in glacierized catchments in Himalaya mainly due to the scarcity of ground-based observation. The present study is an attempt to understand the suspended sediment load and transportation in relation to variation in discharge and temperature in the Shaune Garang catchment. The result shows strong dependence of sediment concentration primarily on discharge (R2 = 0.84) and then on temperature (R2 = 0.79). The catchments with similar geological and climate setting were observed to have comparatively close weathering rate. The sediment load was found to be higher in the catchments in eastern and central part of Indian Himalayan Region in comparison with western part due to dominance of Indian Summer Monsoon leading to high discharge. The annual physical weathering rate in Shaune Garang catchment was found to be 411 t km−2 year−1 which has increased from 327 t km−2 year−1 in around three decades due to rise in temperature causing increase in discharge and proportion of debris-covered glacierized area.

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Dynamical downscaling approach for wintertime seasonal-scale simulation over the Western Himalayas

Tiwari P., Kar S., Mohanty U., Dey S., Sinha P., Raju P., Shekhar M.

Acta Geophysica

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2014

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Vol. 62, no. 4

930--952

EN

The performance of RegCM4 for seasonal-scale simulation of winter circulation and associated precipitation over the Western Himalayas (WH) is examined. The model simulates the circulation features and precipitation in three distinct precipitation years reasonably well. It is found that the RMSE decreases and correlation coefficient increases in the precipitation simulations with the increase of model horizontal resolutions. The ETS and POD for the simulated precipitation also indicate that the performance of model is better at 30 km resolution than at 60 and 90 km resolutions. This improvement comes due to better representation of orography in the high-resolution model in which sharp orography gradient in the domain plays an important role in wintertime precipitation processes. A comparison of model-simulated precipitation with observed precipitation at 17 station locations has been carried out. Overall, the results suggest that 30 km model produced better skill in simulating the precipitation over the WH and this model is a useful tool for further regional downscaling studies.

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Fish diversity in different habitats in the streams of lower middle Western Himalayas

Johal M., Krishan-Tandon Kewal, Kumar-Tyor Anil, Kumar-Rawal Yogesh

Polish Journal of Ecology

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2002

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Vol. 50, nr 1

45-56

EN

The present study was carried out in the lower middle Western Himalayan streams in the Indian state of Himachal Pradesh of the three river basins namely the Ghaggar, the Sutlej and the Yamuna. The main aim was to study fish assemblage structure/composition, fish diversity in different habitats and the habitat preference of the fishes. The different habitats like pools, riffles, runs and rapids were sampled over a 2 km stretch at all the sites with the help of cast net of 1 cm mesh size having a diameter of 1-2 meter on a fixed day every month between mid morning and late afternoon. All the sites when broadly delineated at level-1 fall into type - B except site II that is an F - type stream. A total of 23 species belonging to four orders were recorded of which the cyprinids were the most dominant group. According to Shannon-Weawer diversity index, the pool habitat supports greater diversity (H' = 0.72-0.97), Runs (H' = 0.24-0.87) and riffles (H' = 0.22-0.81) have diversity very near to each other at all the sites whereas rapids have significantly lower fish diversity (H' = 0.00-0.58). The pool is the preferred habitat for most of the cyprinid fishes recorded in the present study especially the minnows.