This study represents the first attempt to examine spatial and seasonal variations of the surface water budget by using the Gravity Recovery and Climate Experiment (GRACE) by measuring gravity ...anomalies on earth to estimate changes in Total Water Storage (TWS) content over the north-western region of the India including New Delhi and states of Rajasthan, Uttar Pradesh and Haryana, covering an area of 676,917 km2. The TWS (surface plus ground) and its changes were estimated from 2003 to 2012. Additionally, Global Land Data Assimilation System (GLDAS) variables were used to infer as to how TWS was partitioned into canopy water and soil moisture components. To evaluate monthly accumulated rainfall, Tropical Rainfall Measuring Mission (TRMM) data, processed by the Global Precipitation Climatology Center (GPCC) were used. By computing storage changes in GRACE, TWS, GLDAS land surface state variables and terrestrial-based water balance approach, we calculated groundwater storage changes. The time-series comparisons show good agreement between the GRACE satellite data, GLDAS model data and computed groundwater data. The change in soil moisture storage is less than that in saturated storage. Both the GRACE and calculated groundwater storage changes indicate storage loss in the range of 86.43 km3/y ± average of 10 years data (in terms of equivalent water thickness). The average groundwater loss for was calculated as 9.7 ± km3/y, states of Haryana as 9.7 ± km3/y, Rajasthan as 33.199 ± km3/y and Uttar Pradesh as 44.4827 ± km3/y. Our results are convincing of a credible GRACE hydrology data which can be handy in monitoring storage dynamics and water availability at regional scale. As GRACE data are available for virtually every region of the world, their application in conjunction with hydrological models will improve applications of hydrological studies which may lead not only to water balance closures, but also to sustainable water resource management at regional scale.
Morphotectonics is a discipline of geomorphology that explores how landforms are formed or modified by tectonic action. In the present study we uthe sed application of geospatial technology to ...evaluate the active deformation owing to Main Boundary Thrust (MBT) and Ramgarh Thrust (RT) in Outer part of Kumaun Lesser Himalaya. Active deformation inside river valleys is ascribed downcuttinging and incision of bedrock, offset of river channel, lateral migration of the river, and development of Knickpoints. Therefore, we used quantitative geo-mathematical analysis of The Gaula river basin using ASTER DEM along with survey of India Toposheet (1:50,000) supplemented by field observations. Four morphotectonic metrics, including the basin elongation ratio, the asymmetry factor, the channel sinuosity, and the hypsometric integral, were derived to examine the relative index of active tectonics (RIAT). We applied Stream Power Incision Model (SPIM) by analysing the steepness index (Ksn) using the stream power law. Additionally, a comprehensive evaluation of tributary streams of the Gaula watershed has been carried out to understand relative tectonic activity. Further we used Chi integral (χ) to measure transience dynamics and geometric disequilibrium of Gaula basin. We conclude that most sub-basins are tectonically enhanced, structurally organized and elongated in nature. The landform in the study area is largely controlled by presence of MBT, RT and subsidiary thrusts spread over in the vicinity. Based on our activity classes we concluded that approximately 31% of the area in Gaula river basin falls in very active whereas ∼34% is potentially active. Furthermore, we suggest that the results will be very useful for estimation of hazard potential zones in sub-Himalayan region of foothill zone of Kumaun Himalaya.
•We applied geospatial techniques for the assessment of active deformation within the MBT zone.•We used RIAT, SPIM, and Chi (χ) to evaluate active deformation.•Our analysis shows that ∼34% area of the basin is potentially active and 31% of very active.•We infer that a significant portion of sub-basins are elongated and tectonically active.
Geomagnetic excursions are short‐lived episodes when Earth's magnetic field deviates into an intermediate polarity state. Understanding the origin, frequency, amplitude, duration, and field behaviour ...associated with excursions is a forefront research area within solid Earth geophysics. Excursion events typically last a few thousand to tens of thousands of years; unlike full reversals, excursions are generally not recorded around the globe. We present here a new palaeomagnetic record (Geomagnetic excursions) from a lacustrine sediment sequence (at times, punctuated by undersized horizons of the gravels) with extraordinarily stable signals. Palaeomagnetic and rock magnetic investigations were performed on a 17‐m‐thick profile of unconsolidated sediments from Bagwalipokar palaeolake (Lat. 29°43′18″; Long. 79°28′42″; altitude 4167 ft), Binta Basin in the Kumaun Lesser Himalaya, situated in the zone of the active North Almora Thrust (NAT). A total of 540 oriented palaeomagnetic samples from 108 horizons (five samples per horizon) were collected from the section. The extrapolation of the optically stimulated luminescence (OSL) date indicates that the whole section was deposited between 45 and 2.5 ka. Magnetic remanence is predominantly carried by magnetite alone. Virtual Geomagnetic Pole (VGP) latitudes were determined using mean declinations and inclinations. Two geomagnetic excursions were observed at younger levels 11.6–10.5 m (15.5–14.7 ka) and 15–11.7 m (8.0–2.85 ka). These geomagnetic excursions correlate with the recently reported younger Hawaiian lava flow excursions. The youngest excursion from 8 ka may be attributed to the climatic event beginning at 8.2 ka cooling event of an oxygen isotope record of biogenic carbonate from palaeolake Riwasa in north‐western India that provides a history of the Indian Summer Monsoon (ISM) from ∼11 to 6 ka BP and also the North Atlantic glacial outburst flood and the slowdown of Atlantic meridional overturning circulation. However, further work is needed to verify this interpretation.
Two geomagnetic excursions were observed at younger levels 11.6–10.5 m (15.5–14.7 ka) and 15–11.7 m (8.0–2.85 ka) in the magnetostratigraphic column.
We present geodetically estimated crustal strain rates in Uttarakhand Himalaya, a region which has long been considered as a part of seismic gap. We processed and analyzed the GPS data, acquired from ...the sites enveloping all the litho-tectonic units from the Sub Himalaya in the south to the Tethys Himalaya in the north together with the major Himalayan thrust/fault systems. On the basis of the obtained dataset, we conclude that the maximum amount of crustal shortening takes place towards the hinterland in the vicinity of Main Central Thrust and Inner Lesser Himalaya which is also in agreement with high seismic activity in these sectors. The GPS velocities of the sites (Indian reference frame) show significant variation from the sub-Himalaya to the Tethys Himalaya. The Sub and Inner Lesser Himalayan parts exhibit low deformation rate in contrast to the maximum amount of deformation in the Inner Lesser and Higher Himalayan segments. The strain analysis reveals lateral variation with high strain zones (HSZ) and moderate strain zones (MSZ) within the compressional regime in the Uttarakhand Himalaya. The strain rate of 0.45 and 0.25 micro-strain/year is observed in the HSZ and MSZ respectively. By comparing the strain rate with the seismicity pattern for the past five decades, we suggest that the earthquakes in the HSZ are related with ramp structure of the MHT, whereas, part of accumulated strain in the MSZ is being released in form of the present day seismic activity.
Snout monitoring of the Gangotri glacier (Uttarakhand, India) during the ablation season (May to September) in years 2005 and 2015 by using rapid static and kinematic GPS survey reveals that the ...retreating rate has been comparatively more declined than shown by the earlier studies. Our study is based on the individual measurement by the remote sensing, added by the ground observations by using Differential global positioning system (DGPS) to determine the precise recession rate of the glacier at sub-centimeter level of accuracy. The GPS dataset show that the total average retreat along the snout has been 102.57 ± 0.05 m from 2005 to 2015 with an average rate as 10.26 ± 0.05 m/yr. Additionally, the shift in snout position was also measured through multi-temporal satellite data from 1989 to 2016. The results indicate that the Gangotri glacier snout has retreated by 585.62 ± 38.30 m during this period with an average retreat of 26.75 ± 4.36 m/yr from 1989 to 1999, 21.58 ± 3.77 m/yr from 1999 to 2009 and 14.60 ± 4.81 m/yr from 2009 to 2016. Such a decline in retreat is further confirmed by the satellite data set. A close examination of meltwater discharge and retreating rate (
r
2
= 0.95) show that both parameters are strongly correlated. Therefore, we suggest that a consistent decrease in meltwater discharge from 1999 to 2015 is in agreement with decreasing trend of retreating rate during the recent years. To determine the possible causes of decreased retreating rate, a relationship between debris thickness and melt rate was also established by ablation stakes. Further, we infer that the declining trend in the glacier retreat is not only controlled by prevailing weather conditions (rainfall and air temperature) but is also governed by increased debris cover on the glacier surface which prevents the ice to melt.
The study evaluates the impacts of India’s COVID-19 lockdown and unlocking periods on the country’s ambient air quality. India experienced three strictly enforced lockdowns followed by unlocking ...periods where economic and social restrictions were gradually lifted. We have examined the in situ and satellite data of NO2 emissions for several Indian cities to assess the impacts of the lockdowns in India. Additionally, we analyzed NO2 data acquired from the Sentinel-5P TROPOMI sensor over a few districts of the Punjab state, as well as the National Capital Region. The comparisons between the in situ and satellite NO2 emissions were performed for the years 2019, 2020 and up to July 2021. Further analysis was conducted on the satellite data to map the NO2 emissions over India during March to July for the years of 2019, 2020 and 2021. Based on the in situ and satellite observations, we observed that the NO2 emissions significantly decreased by 45–55% in the first wave and 30% in the second wave, especially over the Northern Indian cities during the lockdown periods. The improved air quality over India is indicative of reduced pollution in the atmosphere due to the lockdown process, which slowed down the industrial and commercial activities, including the migration of humans from one place to another. Overall, the present study contributes to the understanding of the trends of the ambient air quality over large geographical areas using the Sentinel-5P satellite data and provides valuable information for regulatory bodies to design a better decision support system to improve air quality.
This paper presents an insight on major ion chemistry and identification of solute sources in meltwater of Chaturangi glacier throughout the ablation period 2015 and 2016. The results indicate that ...meltwater is slightly acidic with Ca–HCO
3
and Mg–HCO
3
dominated hydrochemical facies. In meltwater, Ca
2+
and HCO
3
−
are the most dominant cation and anion, respectively. The Water Quality Index values show that the quality of meltwater is good for both the ablation seasons. An important factor governing the quality of water is the residence time for dissolving minerals from the rocks. Mineralogy of surrounding rocks and Gibbs plot suggest that the meltwater ionic concentration is mostly controlled by weathering of rocks with slight contribution from atmospheric aerosols. For meltwater, the average equivalent ratios of Na/Cl and K/Cl were calculated as 3.36 ± 1.29 and 2.29 ± 0.62 in 2015 and 1.39 ± 0.6 and 0.8 ± 0.2 in 2016, which are considerably higher than the marine aerosols (Na/Cl = 0.85 and K/Cl = 0.017), it also confirmed the less contribution of atmospheric input in meltwater. The petrographic analysis of surrounding rocks indicate positive relationship among the cations (Ca
2+
, Mg
2+
, Na
+
and K
+
) and mineral abundance. Our observations suggest that the bedrock mineralogy and weathering reactions together with amount and composition of atmospheric inputs are the main sources of ions, dissolved in the glacier meltwater. It might be due to rate of chemical reaction which leads decomposition of rocks and leaching of minerals into the meltwater. Additionally, the geology of the area plays a significant as the influence of geology and climate on water quality is observed by the quantity and types of dissolved materials and amount of the sediment carried by the streams. The elevated proportion of Ca + Mg in total cations and high Ca + Mg/(Na + K ratios, 1.47 ± 0.14 in the year 2015 and 1.44 ± 0.28 in 2016 clearly reveal that the ionic composition is primarily controlled by carbonate weathering and partly by silicate weathering. Further, the low Na + K/TZ
−
ratio (0.41 ± 0.02) and (0.22 ± 0.05) in 2015 and 2016, respectively also supports that carbonate weathering is main geochemical process controlling the hydrochemistry of meltwater. In addition, the ion denudation rate was calculated for both the years. The results show that the cation denudation rate of meltwater was 32.84 and 22.30 ton/km
2
/ablation during 2015 and 2016, respectively, whereas the anion denudation rate was found to be 205.43 in 2015 and 170.24 ton/km
2
/ablation in 2016.
The present study aims to investigate the palaeoenvironmental changes around Sattal Lake, Kumaun Lesser Himalaya spanning the last 1670 years. Based on multi proxy analysis (i.e., grain size, mineral ...magnetism, clay mineralogy, Total Organic Carbon (TOC) and carbon isotopes), supported by a robust radiocarbon chronology, three major environmental phases were identified. Warm, wet phases occurred between 1,150–650 cal yr BP and 260 cal yr BP to the present. These phases coincide closely with the Medieval Climatic Anomaly (MCA) and modern warming, respectively. These warm/wet events were due to elevated precipitation, resulting in high lake levels and an expansion of the lake margin, which were marked by lower δ13C values, comparatively higher sand concentration, TOC values and magnetic susceptibility (χlf). The inference of a modern warm phase is supported by high resolution instrumental data. The MCA, which is marked by elevated amounts of coarse grained (sand) detrital material, is inferred to be an interval of strengthened of monsoonal intensity, which correlates with available monsoon records from various continental paleoclimate archives. Following the MCA a cold and dry phase was observed to occur between 610 and 260 cal yr BP, corresponding to the Little Ice Age (LIA). The LIA, which was characterized by high silt and clay concentration, high δ13C, low TOC and reduced magnetic susceptibility (χlf), is inferred to represent an interval of low lake levels, likely reflecting an episode of weakened monsoonal intensity.
We present results of our investigations on 7.65 m long core sediments from the Khajjiar lake, Himachal Pradesh, aimed at reconstructing palaeoclimate variability in the climatically sensitive region ...affected by both ISM (Indian Summer Monsoon) and IWM (Indian Winter Monsoon). Based on the multi-proxy approach, including organic geochemistry (carbon isotopes), magnetic susceptibility as primary proxies and inorganic geochemistry (major oxides) with grain size analysis as secondary proxies, climate of the mid-late Holocene (∼4600 yr) has been established on centennial to millennial scale. The chronology of the sediments is constrained by five AMS radiocarbon dates. The sedimentological data reveal variations in sediment grain size related to palaeo-precipitation. The first high resolution multi-proxy record from the Khajjiar lake core indicates less humid conditions during ∼4600–4185 cal yr BP except an extreme peak of dry and arid climate at around ∼4370 cal yr BP. Intensified monsoon with more wet and humid conditions has been interpreted during ∼4185–3790 cal yr BP. ∼3790–3300 cal yr BP, ∼2845–2115 and ∼1555–405 cal yr BP, and ∼2990–2845 cal yr BP and fluctuations are observed from ∼2115 to 1555 cal yr BP. The results suggest two major climatic phases corresponding with the 4.2 ka and Roman Warm Period (RWP). A regional comparison of mid-late Holocene climate records reveals a broad synchronicity, but with considerable spatial variation. The timing and duration of climate events varied across regions.
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