Current Science

K. H. V. Durga Rao ¹, V. Venkateshwar Rao ¹, V. K. Dadhwal ¹, J. R. Sharma ¹, R. Jyothsna ¹

Affiliations
1 National Remote Sensing Centre, Indian Space Research Organisation, Balanagar, Hyderabad 500 037, IN

Abstract

This communication discusses quantifying basin-scale water wealth by transformation from the presently adapted basin terminal gauge site run-off aggregation to distributed hydrological modelling approach. In this study, an attempt was made to propose modifications to simple monthly water balance model using time-series land-use grids derived from the temporal remote sensing satellite data to compute run-off at basin scale. This approach will help in studying runoff and water resources availability with limited meteorological parameters. The study was aimed at computing mean annual water resources in the Godavari Basin, India during the last 18 years (1990-91 to 2007-08) using the proposed approach and to compute availability of water resources during extreme wet and dry rainfall conditions in the basin. The land-use grids were integrated with soil textural, digital elevation and command area grids to compute hydrological response unit grids. Groundwater, reservoir flux, domestic and livestock water consumption and industrial water consumptive use were computed using the spatial data and integrated in the model environment to compute run-off. The model was calibrated and validated using observed discharge data at various prominent gauge stations in the basin. Long-term water resources availability in the basin was computed using the developed methodology.

Keywords

Climate Change, Hydrological Modelling, Remote Sensing, Water Resources Availability.

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A. Senthil Kumar ¹, V. Keerthi ¹, V. K. Dadhwal ¹, A. S. Kiran Kumar ²

Affiliations
1 Geophysical and Special Products Group, National Remote Sensing Centre (ISRO), Balanagar, Hyderabad 500 037, IN
2 Space Applications Centre (ISRO), Jodhpur Tekra, Ahmedabad 380 015, IN

Abstract

With the inclusion of a hyperspectral imager (HySI) sensor on the Indian Mini Satellite (IMS-1) Earth observation mission and subsequently near identical hyperspectral sensor on the Chandrayaan-1 lunar mission, 64-band hyperspectral data from both these missions have provided the user community rich information to explore new algorithms to exploit sensorspecific parameters and to interpret and/or classify the features in multi-resolution frame. In this article, methods to improve spectral uniqueness present in the HySI by analysing adjacent bands' spectral overlaps, by implementing spectral deconvolution and reconstruction techniques are presented. Similarly, the use of multi-resolution approach for fast searching of standard spectral library end-members for better discrimination of hyperspectral pixel data are also discussed along with applications in Earth and lunar surface hyperspectral image interpretation. These spectral analyses techniques are useful in discriminating subtle differences in spectral signatures that help study the origin of secondary craters and gullies/ landslides on the lunar surface.

Keywords

Lunar Surface, Multi-resolution Approach, Spectral Deconvolution, Spectral Overlap.

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Rajashree V. Bothale ¹, P. V. N. Rao ¹, C. B. S. Dutt ¹, V. K. Dadhwal ¹, Devesh Maurya ¹

Affiliations
1 National Remote Sensing Centre (ISRO), Hyderabad 500 037, IN

Abstract

In this article, spatio-temporal dynamics of snowmelt in Antarctica from 2001 to 2014 using OSCAT and QuikSCAT scatterometer data is presented. Melting over Antarctic ice sheet can influence shelf dynamics and stability. Here, we have utilized the sensitivity of scatterometer data to detect the presence of liquid water in the snow caused due to melt conditions. After analysing decadal data, a spatial and temporal variation in the average backscatter coefficient was observed over the shelf areas. An adaptive thresholdbased classification using austral winter mean and standard deviation of HH polarization is used which takes into account the spatial and temporal variability in backscatter from snow/ice. Significant spatiotemporal variability in melt area, duration and melt index was observed. Around 9.5% of the continent experienced melt over the study period. Larsen C and George VI shelves had maximum melt duration. The high correlation between melt duration obtained from satellite data and the positive degree day validates the efficacy of the melt algorithm used in the analysis and sensitivity of OSCAT data in detecting presence of water due to melt. There is seasonal and spatial variation in melt onset. Based on MI, 2004-05 was the warmest summer over the continent with 2011-12 being the coldest summer. Consistent and intensive melting was observed over Amery, Larsen C, George VI, Lazarev and Fimbul shelves. Melting of sporadic nature was observed over Ronne-Filchner, Ross and Riiser-Larsen shelves. The East Antarctic shelves experienced large melt during the study period. This article presents the suitability of OSCAT in melt identification and status of melt over the continent.

Keywords

Ice Shelves, Scatterometer Data, Spatiotemporal Dynamics, Snowmelt.

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K. H. V. Durga Rao ¹, V. Venkateshwar Rao ¹, V. K. Dadhwal ¹, P. G. Diwakar ¹

Affiliations
1 National Remote Sensing Centre, Indian Space Research Organisation, Balanagar, Hyderabad 500 037, IN

Abstract

The recent floods in the Kedarnath area, Uttarakhand are a classic example of flash floods in the Mandakini River that devastated the country by killing thousands of people besides livestock. Though the duration of the event was small compared to other flood disasters in the country, it resulted in severe damage to property and life. Post-disaster satellite images depict that the river banks were eroded completely along the Kedarnath valley due to the flash floods and few new channels were visible. Extreme erosion took place in the upstream portion of Kedarnath, besides the breach of Chorabari Lake and deposition of debris/sediments in the valley. Hydrological and hydraulic simulation study was carried out in the Mandakini River using space-based inputs to quantify the causes of the flash floods and their impact. Chorabari Lake breach analysis was carried out using Froehlich theory. Flood inundation simulations were done using CARTO DEM of 10 m posting in which the combined effect of lake breach and high-intensity rainfall flood was examined. As the slopes are very steep in the upstream catchment area, lag-time of the peak flood was found to be less and washed-off the Kedarnath valley without any alert. The study reveals quantitative parameters of the disaster which was due to an integrated effect of high rainfall intensity, sudden breach of Chorabari Lake and very steep topography.

Keywords

Flash Floods, Flood Inundation Simulation, Hydrological Modelling, Lake Breach.

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S. Dasgupta ¹, I. C. Das ¹, S. K. Subramanian ¹, V. K. Dadhwal ¹

Affiliations
1 National Remote Sensing Centre, ISRO, Hyderabad 500 625, IN

Abstract

Monthly, seasonal and annual hydrologic signals obtained by Gravity Recovery and Climate Experiment (GRACE mission) satellites are analysed and compared with storage variables of soil moisture signatures of Monsoon Asia Integrated Regional Study (MAIRS) mission and groundwater level information of Central Ground Water Board, to observe depletion trends of groundwater in the Gangetic plain, at regional scale. While the seasonal time-series showed seasonality in the groundwater storage change, the annual trends depict a decline in this region. Further, the results showed that groundwater storage had declined at a rate 3.33 mm/month from 2005 to 2010. These time-series comparisons of storage variables have agreeable R² (coefficient of determination) and r (correlation coefficient) at various temporal cycles.

Keywords

Groundwater Storage Change, Satellite Missions, Soil Moisture, Storage Variables.

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T. Watham ¹, S. P. S. Kushwaha ¹, N. R. Patel ¹, V. K. Dadhwal ²

Affiliations
1 Indian Institute of Remote Sensing, ISRO, Dehradun 248 001, IN
2 National Remote Sensing Centre, ISRO, Hyderabad 500 625, IN

Abstract

Studies on CO₂ and water vapour exchange in natural and man-made vegetation are necessary for quantifying their role in landscape-level carbon budget. The present study investigated variations in carbon and water vapour fluxes and monthly net ecosystem exchange (NEE) over a 9-year-old mixed forest plantation (Holoptelea integrifolia, Dalbergia sissoo, Acacia catechu and Albizia procera) in Terai Central Forest Division of Nainital district, Uttarakhand using January to September 2013 eddy covariance data. During leafless period (i.e. January), the plantation acted as a net carbon source (i.e. positive NEE) with daily mean release of 0.35 g C m^-2 day^-1, while from leaf onset to growing period (i.e. April to September), it acted as a sink (i.e. negative NEE) due to carbon uptake by an increasing number of leaves. The monthly mean daily NEE was noticed to be increasingly more negative in each subsequent month until September. The diurnal trend in NEE closely followed the variations in the intensity of photosynthetically active radiation. The diurnal NEE in all months was related to vapour pressure deficit with time-lag. Maximum daytime uptake (-29.5 μmol m^-2 day^-1) and night-time release of CO2 (8.2 μmol m^-2 day^-1) was observed in July. Monthly mean of daily NEE over plantation continuously increased from February and was highest (-5.74 g C m^-2 day^-1) in September. Rectangular hyperbolic function provided reasonably good fit between NEE and PAR. Ecosystem parameters (μ and P_max) of the light response curve also followed the canopy development trend.

Keywords

Carbon Dioxide, Eddy Covariance, Mixed forest Plantation, Water Vapour.

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P. Hari Krishna ¹, K. R. L. Saranya ¹, C. Sudhakar Reddy ¹, C. S. Jha ¹, V. K. Dadhwal ¹

Affiliations
1 National Remote Sensing Centre, ISRO, Balanagar, Hyderabad 500 037, IN

Abstract

Deforestation is one of the greatest threats to the world's forest ecosystems. The present study has utilized remote sensing and GIS techniques to quantify changes in forest cover and to map patterns of deforestation in Andhra Pradesh, India during 1930-2011. Andhra Pradesh has the second largest recorded forest area and ranks sixth with an actual forest cover amongst all Indian states. Forest cover maps from seven temporal datasets were prepared based on interpretation of multi-source topographical maps and satellite data. A representative set of landscape indices has been used to study landscape-level changes over time. The mapping for the period of 1930, 1960, 1975, 1985, 1995, 2005 and 2011 indicates that the forest cover accounts for 85,392, 68,063, 46,940, 45,520, 44,409, 43,577 and 43,523 sq. km of the study area respectively. The study found the net forest cover declined as 49% of the total forest area during the last eight decades. The annual rate of estimated deforestation during 2005-2011 was 0.02%. Annual rate of deforestation of teak mixed forests was relatively higher (0.76) followed by mangroves (0.58%), semi-evergreen forests (0.43%), dry deciduous forests (0.21%), moist deciduous forests (0.09%) and dry evergreen forests (0.07%) during 1975-2011. The landscape analysis shows that the number of forest patches was 3,981 in 1930, 5,553 in 1960, 8,760 in 1975, 9,412 in 1985, 9,646 in 1995 and 10,597 in 2011, which indicates ongoing anthropogenic pressure on the forests. The mean patch size (sq. km) of forest decreased from 21.5 in 1930 to 12.3 in 1960 and reached 3.9 by 2011. The analysis of historical forest cover changes provides a basis for management effectiveness and future research on various components of biodiversity, climate change and accounting of carbon.

Keywords

Collateral Data, Deforestation, Landscape Metrics, Remote Sensing.

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Sourav Das ¹, Abhra Chanda ¹, Suparna Dey ¹, Sanjibani Banerjee ¹, Anirban Mukhopadhyay ¹, Anirban Akhand ¹, Amit Ghosh ¹, Subhajit Ghosh ¹, Sugata Hazra ¹, D. Mitra ², Aneesh A. Lotliker ³, K. H. Rao ⁴, S. B. Choudhury ⁴, V. K. Dadhwal ⁴

Affiliations
1 School of Oceanographic Studies, Jadavpur University, 188 Raja S. C. Mullick Road, Kolkata 700 032, IN
2 Indian Institute of Remote Sensing, 4, Kalidas Road, Dehradun 248 001, IN
3 Indian National Centre for Ocean Information Services, Kukatpally, Hyderabad 500 090, IN
4 National Remote Sensing Centre, Balanagar, Hyderabad 500 042, IN

Abstract

The spatio-temporal variability of sea-surface temperature (SST), photosynthetically active radiation (PAR), chlorophyll-a (Chl-a), particulate organic carbon (POC) and particulate inorganic carbon (PIC) was evaluated in the Arabian Sea (ABS) and Bay of Bengal (BoB), from July 2002 to November 2014 by means of remotely sensed monthly composite Aqua MODIS level-3 data having a spatial resolution of 4.63 km. Throughout the time period under consideration, the surface waters of ABS (27.76±1.12°C) were slightly cooler than BoB (28.93±0.76°C); this was observed during all the seasons. On the contrary, the availability of PAR was higher in ABS (45.76±3.41 mol m^-2 d^-1) compared to BoB (41.75±3.75 mol m^-2 d^-1), and its spatial dynamics in the two basins was mainly regulated by cloud cover and turbidity of the water column. The magnitude and variability of Chl-a concentration were substantially higher in ABS (0.487±0.984 mg m^-3), compared to BoB (0.187±0.243 mg m^-3), and spatially higher values were observed near the coastal waters. Both POC and PIC exhibited higher magnitudes in ABS compared to BoB; however, the difference was substantially high in case of POC. None of the parameters showed any significant temporal trend during the 12-year span, except PIC, which exhibited a significant decreasing trend in ABS.

Keywords

Marine Ecosystems, Oceanographic Parameters, Remote Sensing, River Basins, Spatio-Temporal Variability.

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C. Sudhakar Reddy ¹, K. V. Satish ¹, S. Vazeed Pasha ¹, C. S. ¹, V. K. Dadhwal ¹

Affiliations
1 National Remote Sensing Centre, Indian Space Research Organization, Balanagar, Hyderabad 500 037, IN

Abstract

Andaman and Nicobar Islands are part of Indo- Burma and Sundaland global biodiversity hotspots. This study provides spatial information on forest types, deforestation and associated land-use changes in Andaman and Nicobar Islands during 1976 to 2014. Satellite remote sensing and geographical information system (GIS) techniques have been used to analyse forest cover changes, rate of deforestation and to map patterns of forest cover distribution in Andaman and Nicobar Islands. Classified maps prepared for 1976, 1989, 1993, 2000, 2006 and 2014 indicate that the forest cover accounts for an area of 7086.1 (85.9%), 6969.2 (84.5%), 6941.1 (84.1%), 6934.6 (84.1%), 6617.8 (80.2%) and 6407.3 sq. km (77.7%) respectively. It was found that the area occupied by evergreen forests is very high, consisting of 3065.1 sq. km (32.2%) followed by semi-evergreen (1531.6 sq. km), moist deciduous (1133.4 sq. km) and mangrove forest (677.2 sq. km) in 2014. There is large-scale deforestation in Andaman and Nicobar Islands which has been estimated as 678.8 sq. km during the last four decades. The loss of forest cover is high in moist deciduous forests which has been estimated as 312.2 sq. km in Andaman Islands; whereas in Nicobar Islands, the highest loss was found in evergreen forests (244.6 sq. km). The rate of deforestation in Andaman and Nicobar Islands was high during 2000-2006 (0.78) indicating major influence of the tsunami of 26 December 2004. The annual rate of deforestation from 2006 to 2014 was 0.40. The geospatial analysis of areas of forest cover change provides baseline information for restoration and conservation planning.

Keywords

Andaman and Nicobar Islands, Deforestation, Forest, GIS, Remote Sensing, Land Use.

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K. H. V. Durga Rao ¹, A. Shravya ¹, V. Venkateshwar Rao ¹, V. K. Dadhwal ¹, P. G. Diwakar ¹

Affiliations
1 National Remote Sensing Centre, Indian Space Research Organisation, 500 037, IN

Abstract

The recent flood in Machak River, Madhya Pradesh, India is a distinctive paradigm of flash floods that washed off rail tracks and killed a number of passengers besides incredible damage to Indian Railways and to the surrounding villages. This shows the vulnerability of bridges/culverts to flash floods in the country. Flash floods devastated the Machak River during the midnight of 4 August 2015 due to heavy rainfall in the catchment. The duration of flooding was small with less lead-time. Narrow river sections could not accommodate the peak discharge causing severe flooding in floodplains. Hydrological and hydro dynamic simulation was studied in the Machak River using space-based inputs to quantify the causes of flash floods and its impact. Satellite-based rainfall (GPM and IMD's WRF merged product) was used in hydrological modelling in the absence of field rainfall and discharge data. Flood inundation simulations were done using CARTO digital elevation model of 10 m resolution. Inundation extent, depth of inundation, and velocity of flow at different reaches were examined. As the slopes were steep in the upstream catchment area, the lag-time of the peak flood was found to be less and washed off the Machak rail culvert without any alert. The study reveals that quantitative parameters of the disaster are due to high intensity of rainfall, drainage congestion and sudden change of slopes across the catchment.

Keywords

Hydrological Simulation, Hydrodynamic Modeling, Machak River, Rail Accident.

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C. Sudhakar Reddy ¹, C. S. Jha ¹, G. Manaswini ¹, V. V. L. Padma Alekhya ¹, S. Vazeed Pasha ¹, K. V. Satish ¹, P. G. Diwakar ¹, V. K. Dadhwal ¹

Affiliations
1 National Remote Sensing Centre, Indian Space Research Organisation, Balanagar, Hyderabad 500 037, IN

Abstract

This study provides application of Resourcesat-2 AWiFS satellite imagery for forest burnt area assessment in India. AWiFS datasets covering peak forest fire months of 2014 have been analysed. The total burnt area under vegetation cover (forest, scrub and grasslands) of India was estimated as 57,127.75 sq. km. In 2014, 7% of forest cover of India was affected by fires. Of the major forest types, dry deciduous forests are affected by the highest burnt area, followed by moist deciduous forests. Among the biogeographic zones, the highest forest burnt area was recorded in Deccan followed by North East and Western Ghats. The highest burnt area was recorded in Odisha followed by Andhra Pradesh, Maharashtra, Chhattisgarh, Tamil Nadu, Madhya Pradesh, Telangana, Jharkhand, Manipur and Karnataka. Spatial analysis shows that 232 grid cells in India have a burnt area greater than 20 sq. km. The database generated would be useful in ecological damage assessment, fire risk modelling, carbon emissions accounting and biodiversity conservation.

Keywords

AWiFS, Forest Fire, Forest Type, India, Remote Sensing.

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Rajashree V. Bothale ¹, S. Anoop ¹, V. V. Rao ¹, V. K. Dadhwal ², Y. V. N. Krishnamurthy ¹

Affiliations
1 National Remote Sensing Centre (ISRO), Hyderabad 500 037, IN
2 Indian Institute of Space Science and Technology, Thiruvananthapuram 695 547, IN

Abstract

Snow fork and ground penetrating radar at 200 MHz were used for snow depth, wetness and density measurements towards understanding the relationship between melt/freeze conditions derived from spaceborne Advance Scatterometer (ASCAT) and Oceansat-2 Scatterometer (OSCAT), and field observations. The observations were acquired at Larsemann Hills, East Antarctica in austral summer of 2015-16 during the 35th Indian Scientific Expedition to Antarctica. The field observations of wetness correlated well with identified dry and percolation zones showcasing different behaviours of density and wetness. Ice firn was observed at 50-55 cm depth, even in dry zone. Melt onset and number of melt days based on ASCAT varied spatially and temporally over the years and correlated well with positive degree day (PDD) for automatic weather station data located at the Indian Antarctic station, Bharati. Backscatter measurements by OSCAT showed that winter backscatter reduced with accumulation for both dry and percolation zones, but increased in the later part of winter in the percolation zone. A positive but low correlation was observed between ASCAT backscatter to accumulation and the surface mass balance from regional atmospheric climate model (RACMO2.3). A high correlation of 0.78 was observed between reduction in backscatter due to liquid water content and PDD, which coincides with field observations of wetness. The observations serve as baseline to monitor melt conditions and stability of existing ice sheet.

Keywords

Ground Penetrating Radar, Ice Firn, Snow-Fork, Scatterometer, Snowpack Characteristics.

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P. Chandrasekhar ¹, K. Chandra Mouli ², D. P. Rao ³, V. K. Dadhwal ⁴

Affiliations
1 National Remote Sensing Centre, Indian Space Research Organisation, Hyderabad 500 037, IN
2 F. No. 505, Prashant Towers, Alkapuri, Hyderabad 500 035, IN
3 F. No. 402, Manasasarovar Apartment, Kalyan Nagar, Hyderabad 500 038, IN
4 Indian Institute of Space Science and Technology, Thiruvananthapuram 695 547, IN

Abstract

A number of magnetic zones, faults, lineaments and domal structures were interpreted based on the analysis of aeromagnetic data. Magnetic basement depth and thickness of the sediments were computed by means of quantitative interpretation techniques. A number of alternate basement ridges/highs/uplifted blocks and depressions/lows/downthrown blocks were also delineated. The lithological variations, major folding and faulting patterns, circular spectral anomalies and other geological structures were interpreted from IRS-1C satellite data. The tectonic framework and deformational history of the basin were deduced. The results obtained from the interpretation of aeromagnetic and satellite data were then integrated and the potential zones of hydrocarbon deposits and vulnerable areas for earthquake occurrence were derived.

Keywords

Aeromagnetic and Satellite Data, Basement Depth, Hydrocarbons, Earthquakes.

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