Ganga Basin Research Articles

Electrical Moho and upper mantle metasomatism in the Archaean Bundelkhand craton of the Indian peninsular shield

The Bundelkhand Craton (BKC), one of the Archaean nuclei in the north central part of the Indian shield, has a lesser surface exposure compared to other cratons. Recent magnetotelluric (MT) study in the Central Ganga Basin (CGB) showed NNE-SSW extension of the cratonic block as a transverse ridge and delineated a shear zone within the buried section of the BKC. In the present study, we extend the MT profile to further south with 19 broadband MT sites in the exposed BKC to complement the lithospheric electrical resistivity architecture. Two-dimensional (2-D) geoelectric structure down to 100 km is obtained from inverse modelling of the distortion corrected MT impedance tensors together with the 31 sites in the CGB. The resulting geoelectric model reveals a flat and sharp resistivity contrast at 40–42 km depth, the electrical Moho (e-Moho), separating highly resistive Bundelkhand massif and moderately conductive upper mantle. The 2-D model also brings out two shear zones represented by near-vertical moderately conductive zones within the massif, indicating zones of amalgamation of different fragments of the pre-Bundelkhand craton. In contrast to other major cratons of the Indian shield, the present MT study has delineated a moderately conductive upper mantle beneath the BKC. In view of the estimated low mantle heat flow along with relatively flat topography, we infer metasomatism of the mantle lithosphere by percolation of fluids. We hypothesize that infiltration of fraction of water (H2O) in nominally anhydrous mantle minerals as hydrogen (H) bonded to structural oxygen (O) originated from the subducted oceanic slab has altered the mantle rheology and metasomatized the lithosphere.

Studies on age profile of Common carp, Cyprinus carpio (Linnaeus, 1758) from the Tons River, India

Heavy fishing affects the population by the exploited section of the stock in riverine water bodies. Cyprinus carpio is very frequently cultured in the Ganga basin especially middle and lower stretches of the river due to its plasticity nature (survival rate), fast growth rate, high market demand, consumer preference and very simply availability of seed (example fry and fingerlings). C. carpio is highly adaptable to a suite of environmental conditions. Age composition, age and growth of C. carpio were studied during February 2019 to 2020 January from fish landing centre at Sirsa, Prayagraj, Uttar Pradesh, India. The hard part, key scales were studied for estimation of age and growth in the present study because of easy availability. A total of 548 specimens in length ranges between 97 to 687 mm and age classes of 0+ to 9+ were estimated in the river. The fish attained mean length of 203, 325, 413, 478, 529, 565, 594, 621 and 643 mm, respectively at the end of 1+ to 9+ years of the life cycle. The maximum growth was observed in first year with 203 mm of the life span. The result also indicated that the age composition and growth rate of C. carpio in the invaded waters of the Tons River is very appropriate to the fishes.

Age and growth assessment of the near-threatened fish Rita rita (Siluriformes: Bagridae) in the Ganges basin

Introduction: Rita rita is a freshwater catfish under threat of extinction, mainly from loss of breeding and nursing grounds. A reliable method for age and growth estimation is needed by fishery managers. Objective: To identify the best body structure for age and growth estimation. Methods: We assessed estimates precision based on Average Percent Error (APE), Coefficient Variation (CV), and Percent Agreement (PA) between readers separately analyzed each calcified structure. We used 390 fish samples from three rivers, Ganga, Yamuna and Ramganga, from September 2018 to August 2019. Results: The three indicators favored the use of vertebrae for age estimation; the growth band seems to be annual and formed from May to September. The growth equations were Lt = 90.19(1-e-0.145(t+0.51)) for Ganga; Lt = 91.19 (1-e-0.14(t+0.59)) for Yamuna and Lt = 89.63 (1-e-0.15(t+0.68)) for Ramganga. Conclusion: This species reaches moderate growth in these rivers, where vertebrae are the recommended age estimation structure, followed, in case of need, by sectioned otoliths, whole otoliths and opercular bones. Pectoral spines should be avoided, especially in older fish.

Application of paleo-structural and seismic sequence stratigraphy analysis to determine the potential plays within the Proterozoic sequence of the Ganga Basin, India

Gas discovery in Nohta-2 well from Proterozoic Rohtas plays in Vindhyan Basin, south of Ganga Basin has been a significant lead to suggest that Proterozoic sediments underneath Ganga Basin could be prospective. With this in view, the Govt. of India (GOI) acquired 1350 LKM (Line kilometer) of 2D regional seismic lines to image the Proterozoic sediments for the first time within the basin under National Seismic Program (NSP). The present study is carried out to understand the paleo structures, the nature of the sedimentary sequences, and the trapping mechanism to further visualize the prospectivity of the Proterozoic sequence within the basin. The paleo-tectonic and seismic sequence stratigraphy analysis reveals that the Proterozoic sediments were deposited in the passive margin setting in shallow marine and tidal conditions with several progradations and retrogradation cycles. Precisely, it is noticed that the Proterozoic sediments experienced two stages of progradations and retrogradations. That was followed by a long non-depositional hiatus (>500 Ma) spanning from the Paleozoic to Mesozoic ages which led to a regional unconformity throughout the basin as well as other local unconformities and hydrocarbon traps within the Proterozoic sediments. Four giant structural traps (>300 km2) and one combination trap (>500 km2) are identified within Neo-Proterozoic to Meso-Proterozoic sequence and are expected to be prospective. However, with more exploration efforts and additional data, these traps may lead to a paradigm shift in exploration strategy and discoveries in near future within the basin.

Heavy metal profile, mobility, and source characterization in size-fractionated bed-sediments of River Ganga, India

Sediment quality assessment is vital while assessing the quality of rivers since sediments can alter the water quality depending on pH, redox conditions, and other physico-chemical characteristics. The present study aims to assess the heavy metal concentration in the size-fractionated sediments of River Ganga, and ascertain the sources of contamination in upper Himalayan stretch of around 300 km. The bed sediments of River Ganga were collected from Gomukh, Bhojwasa, Gangotri, Jhala Bridge, Chinyalisaur, Devaprayag, and Rishikesh; and these were size-fractionated in the range of 0–75, 75–150, 150–200, 200–250, 350–300, 300–450, 450–600 μm particle size to determine the concentration of heavy metals associated with each range of particle size using Atomic Absorption Spectrophotometer (AAS). The mean concentration of the metals in the sediments varied in the order Al (126 g/kg) > Fe (68 g/kg) > Cr (79 mg/kg) > Zn (67 mg/kg) > Pb (59 mg/kg) > Ni (38 mg/kg) > Cu (36 mg/kg) > Cd (2 mg/kg), and representing more affinity of metals with finer particle size of sediments. Contamination Factor and Metal Enrichment Factor indicated that sediments in the lower stretch were contaminated and enriched with many toxic metals. Geo-accumulation index, Sediment Pollution Index, and Pollution Load Index revealed that the sediments of Chinyalisaur, Devaprayag, and Rishikesh were moderately to strongly polluted and are progressively getting deteriorated by metals, thus, classifying these locations as hotspots of contamination. The major sources of Al and Fe were found to be natural; whereas Cr, Zn, Pb, Ni, Cu and Cd were mainly contributed by anthropogenic sources. The study stresses for immediate interventions to control further contamination by restricting addition of wastewater directly to River Ganga, or through other streams in Ganga basin.

Increasing Flood Frequencies Under Warming in the West‐Central Himalayas

AbstractThe west‐central Himalayan River basins face significant damage caused by extreme floods annually. We selected the upper Ganga basin (UGB), the west‐central Himalayan basin, to demonstrate how maximum cumulative storm and total rainfall received during monsoon control the extreme flow variability. In addition, the downscaled CMIP6 data sets were used for projections of extremes. The results suggest that historically Alaknanda basin receives a relatively higher magnitude of monsoon and storm rainfall than the other regions in the UGB, which manifested into significant extreme flow variability at the Alaknanda outlet. The extreme flows at the UGB outlet are projected to be more frequent under warming scenarios. The nonstationary flood frequency magnitudes are higher than those obtained from the stationary frequency method, implying a need for a review of return periods used in the designs of flood control structures in the region.

Estimation of groundwater storage loss for the Indian Ganga Basin using multiple lines of evidence

We used remote sensing data, field observations and numerical groundwater modelling to investigate long-term groundwater storage losses in the regional aquifer of the Ganga Basin in India. This comprised trend analysis for groundwater level observations from 2851 monitoring bores, groundwater storage anomaly estimation using GRACE and Global Land Data Assimilation System (GLDAS) data sets and numerical modelling of long-term groundwater storage changes underpinned by over 50,000 groundwater level observations and uncertainty analysis. Three analyses based on different methods consistently informed that groundwater storage in the aquifer is declining at a significant rate. Groundwater level trend indicated storage loss in the range − 1.1 to − 3.3 cm year−1 (median − 2.6 cm year−1) while the modelling and GRACE storage anomaly methods indicated the storage loss in the range of − 2.1 to − 4.5 cm year−1 (median − 3.2 cm year−1) and − 1.0 to − 4.2 cm year−1 (median − 1.7 cm year−1) respectively. Probabilistic modelling analysis also indicated that the average groundwater storage is declining in all the major basin states, the highest declining trend being in the western states of Rajasthan, Haryana and Delhi. While smaller compared to the western states, average groundwater storage in states further towards east—Uttar Pradesh, Bihar and West Bengal within the basin are also declining. Time series of storage anomalies obtained from the three methods showed similar trends. Probabilistic storage analysis using the numerical model vetted by observed trend analysis and GRACE data provides the opportunity for predictive analysis of storage changes for future climate and other scenarios.

EVOLUTION OF FLUVIAL TERRACES OF ALAKNANDA AND ITS TRIBUTARIES AND IMPRINTS OF NEOTECTONISAM IN UPPER GANGA BASIN, GARHWAL HIMALAYA, PARTS OF CHAMOLI TEHRI UTTAKASHI & PAURI DISTRICT UTTAR PRADESH (UTTRARKHAND) INDIA

The Geomorphological study in in Alaknanda and its tributaries Ganga basin Garhwal Himalya parts of Chamoli Tehri Uttarkashiand Pauri district Uttar Pradesh (Uttrarkhand with special reference to fluvial terraces has been studied . An area about 10000 Sq.kms in parts of QA sheet 53Jand 53 N on 1:1000000/ 1:50000 scale of has been covered. The area of Upper Ganga basin genetically comprised of terraces of three domains, viz. glacial, fluvio-glacial and fluvial which represent distinct environment of sedimentation of Pleistocene, late Pleistocene and Holocene time during Quaternary period. The glacial terraces are identified at an average elevation of 1150 m above m.s.l, the fluvio-glacial terraces at an average elevation of 975m above m.s.l, and fluvial terraces at an average elevation between 650 to 900 m above m.s.l, The area of Upper Ganga basin consists of Alaknanda,Bhagirathi,Bhilangna, Nandakini, Mandakini, Pindar, Dhauli- Ganga Bal- Ganga , Madhmeshwar Ganga and Berhi Ganga. Amidst these Alaknnda is trunk stream and other are tributaries. The Alaknanda is chracterised by six fluvial terraces followed by Bhagirathi with five terraces , Bhilangna Nandakini four terraces Mandakini /Pindar/Dhauli-Ganga /Balganga three terraces , Madhmshwar Ganga two terraces and Bberhi Ganga one terraces. The Badrinath temple is situated in glaciated trough valley of Alaknanda, which comprise of, four levels of the glacial terraces (lateral moraine), cirque moraine on mountain flanks and the terminal moraine at the base of valley. whereas Kedarnath in the upstream of Mandakini, where number of well developed cirques were identified on high mountain, they are mostly arm chair shaped hollows with a steep to vertical head walls, concave floor and a threshold, these cirques are noticed at an average height of about 4500 m. The Kedarnath temple is situated in glaciated trough valley on quaternary platform formed by coalescing of cirque, lateral moraine and terminal moraine. The-Himalayan thrust like Central thrust Srinagar thrust,, Alaknanda fault, Tons thrust show flattening dip suggesting that they lie at comparatively at shallow depth at short distance, down dip from their out crops, recent movements along the trace of these faults /thrust are not of high and longer magnitude but have considerably affected Quaternary terraces of glacial, fluvio-glacial and fluvial domain of Alaknanda and its tributaries. Beside drainage, river bed profile, landscape architect and over all morphogenetic expression of the area bears the impact of tectonic activity. The imprints of neotectonisam associated in the area indicate that these thrust /faults are active and have posed tectano-ecological problems, bears signatures of sinking of the area, mass wasting activities and neosiemic hazards. The study revealed that there is sharp curvilinear break in morphogenetic expression of the area In North of Wazri in Jamuna valley, North of Uttarkashi in Bhagirathi valley, around Tugnath and Chamoli and South of Joshimuth in Alaknanda valley, which appears to be due to horizontal movement of a sub - tectonic plates towards south, which is causative factor in dislocation in tectonic ecology of the area, it is matter of serious concerned and needs further attention.

Measuring Ganga basin groundwater for irrigation purposes

Measuring Ganga basin groundwater for irrigation purposes

Suitability of the Lower Ganga basin groundwater for irrigation, using hydrogeochemical parameters and land-use dynamics.

The northern Ganga basin is one of the most densely populated basins in the world. Most agricultural and industrial contaminants drained in the river length are likely to be accumulated in the lower part of the Ganga basin. In this study, we have used ten parameters obtained from 495 sampling locations, besides using long-term climate data (GLDAS_NOAH025_M) to understand the irrigation suitability using the TOPSIS model. Multi-criteria decision making (MCDM) model using TOPSIS has been used to make the best choices from the available finite number of alternatives based on their ranking. The entropy weights for the irrigation suitability parameters such as electrical conductivity (Ec), sodium adsorption ratio (SAR), magnesium hardness (MH), sodium percent (Na%), total hardness (TH), Kelly's ratio (KR), permeability index (PI), chloride concentration (Cl-), groundwater level fluctuation (GWLF), and the Lang factor (Df) are found to be 0.08, 0.14, 0.02, 0.02, 0.04, 0.08, 0.01, 0.32, 0.29, and 0.01, respectively. We find that SAR, Cl-, and GWLF control the water quality for irrigation in the Lower Ganga basin since these parameters have relatively higher entropy weights (more than 0.10). The results obtained from the computed performance index or the closeness coefficient show that the area percent having very good and good groundwater quality for irrigation in the Lower Ganga basin is 77.03% and 22.97% respectively. The land-use change dynamics for the between 2000 and 2015 estimated using the transition matrix shows a positive percentage change for settlement (133.50%), wetland (35.04%), and bare area (0.98%); however, several other classes such as the agriculture (- 0.85%), forest (- 0.49%), grassland (- 14.38%), sparse vegetation (- 11.39%), and water (- 4.12%) show a decreasing trend. The highest amount of percentage change was observed in settlement areas which were contributed by other land-use classes such as agriculture (694.43 km2), water (41.61 km2), forest (16.77 km2), and grassland (1.86 km2). The results may be useful to the concerned organization for the proper planning and management of water resource for sustainable development.

Evidence of multiple stocks of catfish, Rita rita (Hamilton), from the Ganges Basin on the basis of an integrated analysis of truss morphometrics, otolith microchemistry, and otolith shape

Context Management of Rita rita (Hamilton) in India is hampered by a lack of understanding of possible stock structure. Aim To investigate possible spatial stock structure of Rita rita in the Ganges Basin. Methods Independent analyses of landmark-based truss morphometry, otolith elemental analysis and otolith shape were conducted to investigate the stock structure of the catfish (Rita rita) from the Ganga River and its tributaries Yamuna and Ramganga. Key results Each of the stock-delineation approaches, namely, truss morphometrics, otolith elemental composition and otolith shape, showed significant differences among the fish groups from three sampling locations (P ≤ 0.003). Despite these differences, reclassification analyses showed variable (although all greater than random) reclassification rates (truss morphometry: 78%, otoliths elemental data: 98%, otolith shape: 50%). Conclusions An integrated view of the three analyses suggested spatial structuring and that there may be multiple stocks of Rita rita in the Ganges Basin. Implications Future investigations should consider possible variations in demographic parameters that may affect fisheries management. The multiple-lines-of-evidence approach taken in this study can serve as a template for studies of other species in any region.

Impact of Forestry Interventions on Groundwater Recharge and Sediment Control in the Ganga River Basin

Water related services of natural infrastructure will help to combat the risk of water crisis, and nature-based solutions involve the management of ecosystems to mimic or optimize the natural processes for the provision and regulation of water. Forested areas provide environmental stability and supply a high proportion of the world’s accessible freshwater for domestic, agricultural, industrial and ecological needs. The present work on “Forestry Interventions for Ganga” to rejuvenate the river is one of the steps toward the Ganga River rejuvenation programme in the country. The consequences of forestry interventions for Ganga will be determined on the basis of water quantity and water quality in the Ganga River. The study conservatively estimated the water savings and sedimentation reduction of the riverscape management in the Ganga basin using the Soil Conservation Service Curve Number (SCS-CN) & GEC, 2015 and Trimble, 1999 & CWC, 2019 methodologies, respectively. Forestry plantations and soil and moisture conservation measures devised in the programme to rejuvenate the Ganga River are expected to increase water recharge and decrease sedimentation load by 231.011 MCM·yr-1 and 1119.6 cubic m·yr-1 or 395.20 tons·yr-1, respectively, in delineated riverscape area of 83,946 km2 in Ganga basin due to these interventions. The role of trees and forests in improving hydrologic cycles, soil infiltration and ground water recharge in Ganga basin seems to be the reason for this change. Forest plantations and other bioengineering techniques can help to keep rivers perennial, increase precipitation, prevent soil erosion and mitigate floods, drought & climate change. The bioengineering techniques could be a feasible tool to enhance rivers’ self-purification as well as to make river perennial. The results will give momentum to the National Mission of Clean Ganga (NMCG) and its Namami Gange programme including other important rivers in the country and provide inputs in understanding the linkages among forest structure, function, and streamflow.

Riverscape Approach and Forestry Interventions for Ganga River Rejuvenation

Rivers have been degraded globally due to various reasons over centuries and limiting their ecological health and value, including Ganga River in India. Riverscape approach can provide relevant information on riverine resources needed in river restoration programmes. We propose a conceptual riverscape model to rejuvenate the holy river Ganga in India through forestry interventions after due consideration of ecological processes, mosaic of landforms, communities and environment within the large landscape of Ganga basin. The select riverscape area includes the area of 5 km and 2 km on either side of the river Ganga and important tributaries, respectively, all along the rivers in five stakeholder states of Uttarakhand, Uttar Pradesh, Bihar, Jharkhand, and West Bengal in the country. The width of the riverscape was taken from the maximum bank line in recent years on either side of river in the concerned state. However, all micro-watersheds in the hills of Uttarakhand state, being the origin place of river, have been included in riverscape area up to Haridwar. Here riverscape is a mosaic of different land uses viz., natural ecosystems, rural and agricultural ecosystems and built-up urban environment including flood plain and is an ecologically sustained system developed during the last 30 years due to river meandering all along the river. Geospatial modelling and GIS data on land use pattern, soil erosion rates, slope of the topography, etc. were used to classify riverscape area into high, medium and low priority areas to implement forestry interventions in delineated riverscape. Thereafter, forestry interventions were planned and carried out in three identified landscapes viz., Natural (forests), Agriculture (agroforestry), and Urban along with conservation activities. Forestry interventions in delineated riverscape are expected to increase water recharge and decrease the sedimentation load in the Ganga River and its tributaries.

Soft Sediment Deformation Structures in the Sediment Deposits of Ganga River and Its Oxbow Lakes in Parts of Indo-Gangetic Plain: Implications for Quake Proxies and Paleoseismicity Tracking

The Late Quaternary thick sedimentary fills of the Ganga basin predominantly consist of unconsolidated fluvial sandy deposits which are often intercalated with mud. These deposits at various places record the evidence of earthquakes, which occurred in the recent geological past. The evidence is contained and manifested in the form of Soft Sediment Deformation Structures (SSDSs). Saturated sediments/muds/soils are liquefied by earthquake tremors which either generate SSDS or produce structural discordance in the pre-existing sedimentary structures. The present study reports the occurrence of SSDS, e.g. load and associated flame structures, clastic dikes and sill structures, slump structures and sedimentary breccias, etc. from the Ganga River and adjacent oxbow lake sediment deposits. An attempt has been made to establish the origin of soft sediment structures of this region in accordance with its neotectonic history and in turn, identification of seismic structural proxies to delineate paleoseismic events in this region with futuristic implications. The preservation of soft sediment deformation structures in large numbers with multiple geomorphology and scale, in the river and adjoining lake sediments, is indicative of frequent earthquakes of high magnitude consequent to tectonic activism in the Himalayan region.

GEOMORPHOLOGY OF GARHWAL HIMALAYA, PARTS OF CHAMOLI TEHRI UTTAKASHI & PAURI UTTAR PRADESH (UTTRARKHAND) INDIA

The Geological and Geomorphological study in Upper Ganga basin has been attempted in parts of de Uttarkashi,Chamoli, Pauri and Tehri districts an area of 10000 Sq.kms in parts of QA sheet 53Jand 53 N on 1:50000 scale of Garhwal Himalaya U.P presently known as Uttrakhand State of Union of India. Out of total area of study, an area about 3500 sq.Kms has been selected for detailed Geological, Geomorphological and Sedimentological study. The area of Upper Ganga basin consisting of Alaknanda,Bhagirathi,Bhilangna, Nandakini, Mandakini, Pindar, Dhauli- Ganga Bal- Ganga , Madhmeshwar Ganga and Berhi Ganga The Alaknanda is chracterised by six terraces followed by Bhagirathi with five terraces , Bhilangna Nandakini four terraces Mandakini /Pindar/Dhauli-Ganga /Balganga three terraces , Madhmshwar Ganga two terraces and Bberhi Ganga one terrace,amidst these Alaknanda is trunk stream and others are tributaries. Geomorphologically the area is divided in to seven geomorphic units viz High relief formerly glaciated area, Structural hills, Denudational hills, Area of mass wasting, High level dissected fans, river Terraces and Present day flood plain of Alaknanda and its tributaries . These units area developed in response to lithology to erosional land depositional activities and tectonic in which they are embedded. Each unit is characterized by drainage, diagnostic geomorphic landform elements and features, photo charcters and morphogenetic expression. The other geomorphic features and elements identified in the area are point bar, channel bar, alluvial fans ,talus cone , rock cut terraces fan cut terraces , abandoned channel ,epigenetic gorges, strand lines landslides ,rock fall scree and scree slope, retreating scarp, abandoned cirque, arêtes, threshold, horn peak and glacial lake. The area genetically comprised of terraces of three domains, viz. Glacial, Fluvio-glacia and Fluvial which represent distinct environment of sedimentation of Pleistocene, late Pleistocene and Holocene time during Quaternary period. The Glacial terraces are identified at an average elevation of 1150 m above MSL, the fluvio-glacial terraces at an average elevation of 975m above MSL and Fluvial terraces at an average elevation between 650 to 900 m above MSL.

Subsurface Expressions of the Aravalli-Delhi Fold Belt in the Western Ganga Basin by Magnetotellurics

Subsurface Expressions of the Aravalli-Delhi Fold Belt in the Western Ganga Basin by Magnetotellurics

Adoption of Banana Production Technology Among Banana Growers in Vaishali District of Bihar

India’s banana ranks fi rst in production and third in area and Bihar ranks 7th in the country. Dwarf canvendish, Alpan, Chinia, Chinichampa, Malbhog, Muthia and Kothia are Bihar cultivars. The Vaishali district area around the ganga basin is known for its banana production. The study comprised 135 respondents from seven villages in Bidupur and Hajipur blocks of Vaishali District of Bihar. Correlation between knowledge and adoption of banana production technologies and profi le of banana growers were obtained. The fi ndings revealed that majority (66%) of the farmers had medium level of overall knowledge regarding recommended banana production technologies. In context of practice-wise knowledge it was found that most of the farmers had low knowledge level and majority (70%) of respondents had medium adoption of recommended technologies. High level of adoption was reported for practices like propagation method (82.67%), cutting-pruning and stacking (64.67%), irrigation management (59.33%) and selection of varieties (57.33%). Extension personnel and agriculture scientist might have enhanced production of banana through regular visit, training and guidance to farmers.\

Risk assessment of persistent pesticide pollution: Development of an indicator integrating site-specific characteristics

Detection of high pesticide concentrations in sediments and water often leads to prioritizing a site as being ‘at risk’. However, the risk does not depend on pesticide concentration alone, but on other site-specific characteristics also. We developed an indicator that identifies the ‘Level of Concern’ by integrating five such characteristics: (i) pesticide concentrations in surface and groundwater causing risks to ecological health (ii) impacts on human health, (iii) water scarcity, (iv) agricultural production, and (v) biodiversity richness. We applied this framework in an agricultural region of the Lower Ganges Basin in West Bengal, India. We measured concentrations of selected organochlorine pesticides (OCPs) in surface and groundwater within an 8 km2 area in 2019. Of 20 banned and restricted OCPs, 11 were detected as causing high risk to ecological health and 10 at concentrations above the Accepted Carcinogenic Risk Limit (ACRL) for humans. In the pre-monsoon, the mean concentrations of ΣOCPs in groundwater and surface water were 126.9 ng/L and 104 ng/L, in the monsoon they were 144.7 ng/L and 138 ng/L, and in the post-monsoon 122.1 ng/L and 147 ng/L respectively. In groundwater, no significant seasonal difference was observed in most pesticides. In the surface water, 7 pesticides were significantly higher in the monsoon and post-monsoon, which may be attributed to increased runoff as well as post monsoon application of OCPs. In September 2022 we again measured OCP concentrations in surface water and sediment. The mean concentration of 14 of the 20 measured OCPs were found to be significantly lower in the post-pandemic period compared to the pre-pandemic time. These lower pesticide concentrations may indicate a reduced use of OCPs in agricultural practices during the pandemic. This area was identified as being at the highest Level of Concern, even though the OCP concentrations alone conformed to general guidelines.

Improving approaches and modeling framework for assessing vulnerability of Asian leaf fish in the major river basin floodplains of India in changing climate

Asian leaf fish Nandus nandus (Hamilton, 1822) is a valued small indigenous freshwater fish (SIF) in inland waters with high food, and conservation importance but relatively less studied. We assessed the impact of regional climate variability for the first time on population attributes and breeding phenology and predicted its biological vulnerability through General Additive Model (GAM) in changing climatic scenario. We determined environmental cue, threshold biological condition and preferred climatic condition for breeding from lower Gangetic floodplains and Brahmaputra floodplain wetlands, India. We observed that female length at first maturity (LM50) was 10.5 cm for Brahmaputra basin and 10.8 cm for Ganga basin. Threshold Gonado-somatic index value for ready to spawn individuals (GSIspawn50) was estimated at 10.6 units for Brahmaputra and 8.11 units for Ganga basin. Temperature > 28 °C and rainfall >200 mm were found optimum for breeding in Ganga basin and temperature between 26 and 29 °C and monthly rainfall >150 mm were found optimum for Brahmaputra basin. Narrow GSIspawn50 temperature window indicated that the species is more vulnerable to climate change in Assam compared to West Bengal. Pearson correlation coefficient indicated a strong and significant correlation of gonado-somatic index (GSI) with rainfall and temperature in floodplain wetlands of both states. The population vulnerability ranged from moderate to highly vulnerable to climate change based on 14 designed attributes. Evidently, an innovative vulnerability framework developed for assessing the resilience of the species was an important effort in the Indian sub-continent. This will further help to quantify the climate induced risks which could serve as important database to develop the mitigation measures.

A novel weight-drop seismic energy source for subsurface characterization

Multichannel Analysis of Surface Waves (MASW) studies for subsurface characterization in Central Ganga Basin of India, where thick cover of alluvium absorbs most of the vibrations generated by a sledgehammer source, give low quality seismic data at large offsets and generally provide imaging depth lesser than 30 m due to low quality of dispersion curves at lower frequencies. Therefore, a novel seismic energy source is designed and developed to produce large amplitude surface waves even at longer offsets and for deeper depths of imaging using dispersion analysis of surface waves. The developed source for seismic data acquisition is low-cost, repeatable, portable, and easy to operate with no environmental impact. Unlike the sledgehammer source where the quality of surface waves generated also depends on the person hitting the metal plate, the seismic data quality from the novel weight-drop source is independent of the operator.The developed source is an impact type where a free-falling mass accelerated due to gravitational pull hits onto a base plate coupled with the earth generating vibrations in the ground. The performance of the source was evaluated in a field trial. A receiver array of 24-channel cabled geophones with 3 m spacing was planted on the ground. Seismic data were acquired using the source at 5 m negative offset inline from the first geophone. Seismic data were also recorded with the sledgehammer as a source for comparison. Five shot gathers for each source were acquired with the same acquisition geometry and source position.Shot gathers were analyzed and compared using trace attributes, 1D and 2D Fourier spectra, signal-to-noise ratio, relative energy, and dispersion images. The study shows that the developed source produces low frequency high amplitude signal and better dispersion image, notably in the lower frequency range, in comparison with the sledgehammer source. Therefore, the developed source is adapted to investigate deeper subsurface velocity structure with dispersion curve from high amplitude surface wave analysis. Moreover, the repeatability study suggests that the repeat shot gathers acquired from the developed source have remarkably high degree of similarity. Therefore, seismic data acquisition with the developed source does not require repeat shots for vertical stacking as often done in case of a hammer source. Sound pressure level measurement indicates that the developed source has no adverse environmental impact on the operator. From the field trial of the developed source, it is convinced that the source is cost-effective, portable, easy to operate and handle and is environmentally friendly.