Silting patterns in the reservoirs of small- and medium-sized earthen check dams in humid subtropical monsoon regions

Silting of reservoirs is a ubiquitous process whenever water is impounded. Despite substantial work on the rates of silting, the spatial pattern of silting in reservoirs is not clearly understood. While it is anticipated that the variability of silting increases with decreasing reservoir size, not much is known about siltation in subtropical humid regions affected by monsoon rainfall. This paper presents the initial results of geomorphic analysis of six earthen check dams in the Shiwalik foothills of the Himalayas (India) in areas that are inhabited by high proportions of disempowered populations. These check dams include three small-sized dams (Dhamala-II, Rel Majra and Sukhomajri-II) and three medium-sized dams (Bunga-I, Parachh-II and Siswan). Field data were collected from each reservoir. The methods used included spatial interpolations of bed depth and silt thickness in each reservoir, Structure from Motion photogrammetry to extract multiple channel cross-sections from photographic scans along tributary mouths, texture analysis of bed and bank materials, and visual observations of hill slopes around the check dams. Based on this study, silt tended to concentrate either in the middle portion of the reservoir or near the dam; however, silt accumulation did not always occur along the dam or in the deepest portion of the reservoirs. Areas located downstream from these check dams are heavily used for various human activities and the channel network has almost been eliminated. While these earthen check dams may be cost-effective tools for water conservation in economically marginalized areas, if abandoned, these structures may pose a physical hazard to downstream communities. © 2019 John Wiley & Sons, Ltd. © 2019 John Wiley & Sons, Ltd.     

Relationship between lipid distribution and geochemical environment within Champagne Pool, Waiotapu, New Zealand

The lipid biomarkers associated with various geothermal facies within Champagne Pool were investigated and compared with previous microbiological characterisation. Biomarker analysis revealed two distinct microbial communities spanning the margin of Champagne Pool: the first in the subaqueous domal stromatolites, subaqueous orange precipitate and spicular microstromatolites at the air-water interface, and the second in an acidic sinter from the overhanging ledge. Lipid biomarkers were detected in all facies and are consistent with previous microbiological analysis, suggesting that encapsulated biomarkers do record microbial community structure. Results suggest a microbial community principally comprising Aquificales, Thermodesulfobacteriales, Sulfolobus and Thermofilum populations in all facies. In the acidic sinter, additional bacterial (Actinomycetales and Planctomycetales), archaeal (Thermoplasmatales) and algal (Cyanidium caldarium) inputs were observed, the predominance of algal biomarkers suggesting that these organisms are major contributors to the microbial community in this facies. It is evident that local geochemistry plays a fundamental role in defining community composition and, consequently, microbial lipids entrained in Champagne Pool sinters, with metabolic activity of the microbial community reflecting the physicochemical conditions in each microenvironment.     

Estimation of Trophic State Index of Sukhna Lake Using Remote Sensing and GIS

The present study is focussing on that how Landsat 7 ETM⁺ can be effectively used for estimation of Trophic State Index for Sukhna Lake. Sukhna Lake in Chandigarh has undergone lot of changes in last few decades. The depth and area both reduced tremendously. The shrinkage of the lake is due to the siltation and inadequate water volumes flowing to it. The Trophic State Index has been estimated by using secchi disk transparency and Landsat 7 ETM⁺ data. The in situ observations for parameters like pH, DO were measured by using multiparameter water quality instrument TROLL 9500. The best tested interpolation technique has been used to generate in situ images. The results have shown that the lake is in Hypereutrophic condition since 2000.     

Bearing Capacity of Eccentrically–Obliquely Loaded Footings Resting on Fiber-Reinforced Sand

This paper presents the method proposed to calculate the bearing capacity of a square footing under oblique and eccentric oblique loading condition (satisfying both shear failure and settlement criteria) resting on fiber reinforced sand layer underlain by sand with geosynthetic/fabric sheet at the interface. Large direct shear tests were carried out to investigate the shear strength parameters of sand and randomly distributed fiber reinforced sand (RDFS) and soil-plastic fabric sheet bond. The ultimate bearing capacity of RDFS was determined using direct shear results. Non-dimensional charts proposed by Kumar (Behaviour of eccentrically–obliquely loaded footing on reinforced earth slab. Ph.D. thesis, University of Roorkee, Roorkee, India, 2002) were used to consider the contribution of plastic fabric sheet in increasing the bearing capacity. Also, for calculating the settlement, horizontal deformation and tilt at a given pressure the regression analysis of plate load test data have been carried out. The predicted values of ultimate bearing capacity, settlement, horizontal deformation and tilt are compared with the experimental values which are in good agreement with each other. There appeared to be an increase in the residual shear strength and angle of internal friction of RDFS.     

Tectonics or climate: What drove the Miocene global expansion of C4 grasslands?

Investigations into the most plausible causes which triggered the Late Miocene global expansion of C₄ grasslands have reached no consensus and are still being debated. The global decline in CO₂ levels in the Late Miocene has been thought to be the most common driver. Although C₄ grassland expansion was largely confined to the Late Miocene, their first appearance varied significantly in different parts of the Old and New world and therefore emphasizes role of local and/or regional factors may or may not be in combination with one or more global factors. The dynamic Himalayan orogen constitutes a significant global tectonic event that is believed to have affected global climate. Hence, a study of the Himalayan foreland basin sediments could help in gleaning out possible causes behind this major paleoecologic event, which could perhaps be directly or indirectly related. Stable carbon isotope analyses of a total of 141 pedogenic carbonates in the Mio-Pleistocene Siwalik paleosols of the Ramnagar sub-basin are coherent, providing a better insight into paleovegetational changes across the sub-basin on temporal and spatial scales. Furthermore, paleovegetational history during Oligocene is reconstructed from Dagshai paleosols exposed in the Subathu sub-basin. The isotopic results show dominance of C₃ vegetation pre-7 Ma and dominance of C₄ vegetation post-5 Ma. Percentage abundance of C₄ vegetation was less than 20 % pre-7 Ma but increased to more than 40 % post-5 Ma, reaching up to 100 % in the youngest analyzed sediments. There is exclusive dominance of C₃ vegetation during Oligocene. These results conform to the pattern of change in vegetation documented in other parts of the Himalayan belt. The global expansion of C₄ grasslands largely during Late Miocene have long been linked with then climate changes, particularly brought by declining atmospheric CO₂ level, large-scale fires, intensification of monsoon, seasonality, and aridity as demonstrated by various researchers. These major hypotheses explaining expansion of C₄ grasslands during Late Miocene are not very convincing due to significant shortcomings associated with them, for example, expansion of C₄ grasslands in non-monsoonal regions put serious constraints on the monsoonal intensification hypothesis. Likewise, aridity as being the primary driver of C₄ grassland expansion seems hard to support since there is no substantial evidence that could suggest global onset of arid conditions at about same geologic time, and some most arid periods, like the Triassic, show no evidence of C₄ plants. We suggest that the initial lowering of CO₂ below 450 ppmV created an environment for the beginning of C₄ vegetation, but the persistence of this threshold value for a considerable time during Late Miocene appears to be the probable cause of the Late Miocene global expansion of C₄ grasslands irrespective of their time of first appearance. It has been deduced through the correlation of Himalayan tectonic events with atmospheric CO₂ levels and paleovegetational changes since Upper Miocene times that it was indeed the Late Miocene continuous, intense tectonic instability of the Himalayas that significantly decreased atmospheric CO₂ levels and which perhaps played a key role in changing the nature of photosynthetic pathways.     

Robe’s restricted problem of 2+2 bodies with one of the primaries an oblate body

In this problem, one of the primaries of mass \(m^{*}_{1}\) is a rigid spherical shell filled with a homogeneous incompressible fluid of density ρ ₁. The smaller primary of mass m ₂ is an oblate body outside the shell. The third and the fourth bodies (of mass m ₃ and m ₄ respectively) are small solid spheres of density ρ ₃ and ρ ₄ respectively inside the shell, with the assumption that the mass and the radius of the third and the fourth body are infinitesimal. We assume that m ₂ is describing a circle around \(m^{*}_{1}\) . The masses m ₃ and m ₄ mutually attract each other, do not influence the motions of \(m^{*}_{1}\) and m ₂ but are influenced by them. We also assume that masses m ₃ and m ₄ are moving in the plane of motion of mass m ₂. In the paper, equilibrium solutions of m ₃ and m ₄ and their linear stability are analyzed. There are two collinear equilibrium solutions for the system. The non collinear equilibrium solutions exist only when ρ ₃=ρ ₄. There exist an infinite number of non collinear equilibrium solutions of the system, provided they lie inside the spherical shell. In a system where the primaries are considered as earth-moon and m ₃,m ₄ as submarines, the collinear equilibrium solutions thus obtained are unstable for the mass parameters μ,μ ₃,μ ₄ and oblateness factor A. In this particular case there are no non-collinear equilibrium solutions of the system.     

Multiwavelength study of the transient X-ray binary IGR J01583+6713

We have investigated multiband optical photometric variability and stability of the Hα line profile of the transient X-ray binary IGR J01583+6713. We set an upper limit of 0.05 mag on photometric variations in the V band over a time-scale of three months. The Hα line is found to consist of non-Gaussian profile and quite stable for a duration of two months. We have identified the spectral type of the companion star to be B2 IVe while the distance to the source is estimated to be ∼4.0 kpc. Along with the optical observations, we have also carried out analysis of X-ray data from three short observations of the source, two with the Swift –XRT and one with the RXTE –PCA. We have detected a variation in the absorption column density, from a value of  22.0 × 10²² cm⁻²  immediately after the outburst down to  2.6 × 10²² cm⁻²  four months afterwards. In the quiescent state, the X-ray absorption is consistent with the optical reddening measurement of   E ( B − V ) = 1.46  mag. From one of the Swift observations, during which the X-ray intensity was higher, we have a possible pulse detection with a period of 469.2 s. For a Be X-ray binary, this indicates an orbital period in the range of 216–561 d for this binary system.     

Geospatial modelling of flood susceptibility pattern in a subtropical area of West Bengal,India

Flood hazards are the most destructive among all natural disasters and are a constant threat to human’s life and property. Effective disaster risk reduction strategies can be improved by geospatial approach in the way of producing information and knowledge that are useful to plan truly effective actions for the protection from floods. This research aims to develop a quantified predictive model of flood susceptibility in the Ghatal and Tamluk subdivision of Medinipur district of West Bengal, India, by means of empirically selected and weighted spatial predictors of flood. The weighted prediction model is used to quantify the spatial associations between individual geospatial factors within the flood inundated study area. Yule’s coefficient and distance distribution analysis are used to assign weights to individual geo-factors, and finally weighted spatial predictors are integrated to a multi-class index overlay analysis to derive the spatially explicit predictive model of flood susceptibility. The resultant susceptibility model reveals that approximately 32.35 and 52.99% of the total study areas (3261.45 km²) are under the category of high-to-moderate flood susceptible zone. Quantitative results of this study could be integrated into the policy process in the formulation of local and national government plans for the future flood mitigation management and also to develop appropriate infrastructure in order to protect the lives and properties of the common people of the Medinipur district.     

The Lost Natural Wetlands of Punjab (India): An Inventory

Wetlands play a vital role in maintaining groundwater levels in an area. This is true for Punjab that was bestowed with several natural wetlands in the flood plains of its rivers. These natural wetlands have never been mapped and their existence has not been acknowledged. The large scale agricultural development in the state has made it India's leading food producing state. This development was done at the cost of certain ecologically sensitive parts, mainly the flood plains thus leading to the demise of wetlands. This paper is an attempt to retrace the lost wetlands that were existed in the flood plains of the three major rivers: Satluj, Beas and Ravi in the present day Punjab at the beginning of 20th century. A majority of these wetlands have not been documented so far and do not even have names. The purpose is to emphasize their elimination in addition to establishing a baseline dataset that can be a tool for wetland planning and management.