Contrasting lipid biomarkers in mountain rivers in the Nepal Himalayas:Organic matter characteristics and contribution to the fluvial carbon pool

The Nepal Himalayas is the source of many glacial and spring-fed river systems crisscrossing the moun-tainous terrain.There is an increasing recognition of small mountain rivers(SMRs)to have a significant combined export of dissolved and particulate organic carbon to the global carbon flux.We analyzed flu-vial sediments from two SMRs and compared the results with two large mountain rivers(LMRs)in Nepal.We investigated the organic matter(OM),its compositional variability,and seasonal export using a suite of lipid biomarkers,namely n-alkanes,n-alkanoic acids,n-alkanols,and sterols.The SMRs indicated a similarity in lipid distribution and were affected by a strong seasonal variability.The LMRs showed a dis-tinct contrast in the distribution of lipids in suspended sediments.Bedload sediments in SMRs were derived from diverse sources with weak terrigenous dominance all-year-round compared to the sus-pended load.Functional lipids(n-alkanoic acids and n-alkanols)were the major constituents in SMR sed-iments,indicating better preservation.In contrast,n-alkane concentration dominated over other fractions in suspended sediments retrieved from LMRs.The biomarker trends differentiate SMRs from LMRs with lower transformed/degraded OM in SMRs.A common observation was the strong presence of even carbon compounds in short-chain n-alkanes in SMR bedload sediments and their predominance in suspended sediments in LMRs.Such an unusual trend is attributed to specific biomarker sources from the catchment and ongoing processes in fluvial systems.Topsoil colonized by fungal species under moist acidic condi-tions and autochthonous bacteria contributes to the organic matter pool in shallow SMRs.In LMRs,the contribution from thermally mature sedimentary hydrocarbons and the diagenetic reduction of n-alkanoic acids to n-alkanes are additional contributors to the allochthonous carbon pool.The differences in lipid concentrations,their distribution,seasonality,and the size of rivers suggest differential preserva-tion/degradation of the organic matter pool and their importance in contributing to the carbon budget.     

Characteristics of meteorological droughts in northwestern India

This study analyses regional drought characteristics (frequency, severity, and persistence) of meteorological droughts occurred in the northwestern parts falling under arid and semiarid regions of India with mean annual rainfall ranging between 100 and 900 mm. A drought is defined as a season or a year with rainfall less than 75% of corresponding mean at a place. Long-term monthly rainfall records (1901–2013) of 90 districts of north-west India located in the states of Punjab, Haryana, Rajasthan and Gujarat are used in the analysis. The percentage departure of seasonal rainfall from long-term average rainfall has been used for identification of onset, termination, and quantification of drought severity. The average frequency varied from once every 3–4 years. The westerly districts have an average drought return period of 3 years, while districts lying toward the east had droughts once every 4 years. Only four of the 90 districts in the study area experienced droughts once every 5 years. Persistent droughts of 2, 3, and 4 year duration occurred widely. Severe droughts occurred in the years 1904, 1905, 1911, 1918, 1931, 1939, 1985, 1986, 1987, 1993, and 2002, with an average frequency of severe drought events of one in 10 years. The analysis presented in this paper improves understanding of the regional drought characteristics and will inform drought mitigations and strategies in these arid and semiarid areas.     

Activity of radon (<Superscript>222</Superscript>Rn) in the lower atmospheric surface layer of a typical rural site in south India

Analysis of one year measurements of in situ radon (²²²Rn) and its progenies along with surface air temperature, relative humidity and pressure near to the Earth’s surface has been carried out for the first time at the National Atmospheric Research Laboratory (NARL, 13.5^°N and 79.2^°E) located in a rural site in Gadanki, south India. The dataset was analysed to understand the behaviour of radon in relation to the surface air temperature and relative humidity at a rural site. It was observed that over a period of the 24 hours in a day, the activity of radon and its progenies reaches a peak in the morning hours followed by a remarkable decrease in the afternoon hours. Relatively, a higher concentration of radon was observed at NARL during fair weather days, and this can be attributed to the presence of rocky hills and dense vegetation surrounding the site. The high negative correlation between surface air temperature and activity of radon (R = – 0.70, on an annual scale) suggests that dynamical removal of radon due to increased vertical mixing is one of the most important controlling processes of the radon accumulation in the atmospheric surface layer. The annual averaged activity of radon was found to be 12.01±0.66 Bq m^?3 and 4.25±0.18 Bq m^?3 for its progenies, in the study period.     

Validation of a satellite-based cyclogenesis technique over the North Indian Ocean

Indian region is severely affected by the tropical cyclones (TCs) due to the long coast line of about 7500 km. Hence, whenever any low level circulation (LLC) forms over the Indian Seas, the prediction of its intensification into a TC is very essential for the management of TC disaster. Satellite Application Centre (SAC) of Indian Space Research Organization (ISRO), Ahmedabad, has developed a technique to predict TCs based on scatterometer-derived winds from the polar orbiting satellite, QuikSCAT and Oceansat-II. The India Meteorological Department (IMD) has acquired the technique and verified it for the years 2010–2013 for operational use. The model is based on the concept of analogs of the sea surface wind distribution at the stage of LLC or vortex (T1.0) as per Dvorak’s classifications, which eventually leads to cyclogenesis (T2.5). The results indicate that the developed model could predict cyclogenesis with a probability of detection of 61% and critical success index of 0.29. However, it shows high over-prediction of the model is better over the Bay of Bengal than over Arabian Sea and during post-monsoon season (September–December) than in pre-monsoon season (March–June).     

Optimal Underground Extraction of Coal at Shallow Cover Beneath Surface/Subsurface Objects: Indian Practices

Summary  Considering ground instability problems of underground coal mines at shallow covers, this paper reviews and describes problems of optimal extraction of coal stuck below surface/subsurface constraints at Indian coal fields. Importance of thickness and quality of inter-burden between the working horizon and surface/subsurface constraints is discussed from a ground movement point of view during optimisation of coal recovery by underground mining beneath the constraints. A CIMFR, formerly CMRI idea, known as Wide Stall Method, was found suitable to overcome the limitations of non-effective-width based optimisation of recovery of coal, trapped in pillars below surface/subsurface objects, at shallow cover. The involved rock mechanics concept and three successful field trials of the Wide Stall Method under three different geo-mining conditions of the country are also briefly given in this paper. Author’s address: Rajendra Singh, Central Institute of Mining and Fuel Research (CIMFR, formerly CMRI), Barwa Road, Dhanbad, 826001 Jharkhand, India     

Simulating land use for protecting food crop areas in northeast Thailand using GIS and Dyna-CLUE

Journal of Geographical Sciences - Land use in the northeast region of Thailand has changed dramatically in the past two decades. These changes are mainly due to the government policies, which...     

Relationship of drought frequency and severity with range of annual temperature variation

The frequency and severity of occurrence of meteorological droughts in different climatic regions depend on regional climatic factors. This study has made an effort to explore the relationship of range of annual temperature variation at a given place with the frequency of occurrence of drought and the maximum magnitude of seasonal rainfall deficit (i.e., severity). The seasonal rainfall refers to sum of monsoon season (rainy season) rainfall in India. The monthly precipitation data of 113 years (1901–2013) for 256 stations in different parts of India have been used to estimate the return period of meteorological drought at different stations. The daily normal values of observed maximum and minimum temperatures from 40 years of records have been utilized to estimate range of temperature variation (θ_R) during the year at each stations. In various parts of India, the θ_R ranges from 10 °C in humid regions to 40 °C in arid regions. The various climatic regions have been experiencing maximum deficiency of annual rainfall ranging from 30% (humid) to 90% (arid). The results reveal that places exhibiting θ_R values between 40 to 30 °C face more frequent droughts with average frequency of once in 3 to once in 6 years. The occurrence of extreme and severe drought events is more frequent in the regions with higher values of θ_R compare to that in lesser values of θ_R. The regions with θ_R values between 30 to 25 °C mostly face severe and moderate events having the average drought return period of 6–9 years, and the occurrence of extreme droughts in these regions is rare. Furthermore, regions with θ_R?<?20 °C face moderate droughts only with an average return period of 14 years. This study divulges that the average return period and magnitude of deficiency of drought events have notable relationship with the range of temperature variation during the year at a given place.

     

Integrative approach of RS and GIS in characterization of land suitability for agriculture: a case study of Darna catchment

Land elements like slope, soil depth, land use/land cover, water holding capacity, soil texture, soil erosion, elevation, potential of hydrogen, etc. determine the suitability for agriculture. Land suitability analysis is a one of the methods of assessment of detecting inherent capacities, potential and suitability levels of the lands for agriculture, and was utilized with the same land elements in this study. A multi-criterion decision making approach using IRS P6 LISS-IV satellite dataset within a GIS environment was used to identify suitable areas for agriculture in the Darna catchment. Experts’ opinions, literature review, and correlation technique were used to decide influencing criteria, assign scores to sub-criteria, and judgment formation in pairwise comparison matrix. All thematic layers of criteria were integrated with each other in GIS using the weighted overlay technique and generated agriculture suitability map into four classes according to FAO. About 23% of the area is under agriculture in the study region. This area can extend up to 69% under agriculture converting fallow land, scrub land, and sparse forest according to soil qualities with suitability levels, i.e., highly suitable (19%), moderately suitable (16%), and marginally suitable (34%). About 31% (19,219 ha) of reviewed area are classified in the class permanently “not suitable” for agriculture. Moderately and marginally suitable land requires the irrigation facility for efficient agriculture. This study emphasizes that about 46% area has potential as agriculture land and it will help improve the financial condition of the farmers.     

Use of geospatial technology for delineating groundwater potential zones with an emphasis on water-table analysis in Dwarka River basin,Birbhum, India

Dwarka River basin in Birbhum, West Bengal (India), is an agriculture-dominated area where groundwater plays a crucial role. The basin experiences seasonal water stress conditions with a scarcity of surface water. In the presented study, delineation of groundwater potential zones (GWPZs) is carried out using a geospatial multi-influencing factor technique. Geology, geomorphology, soil type, land use/land cover, rainfall, lineament and fault density, drainage density, slope, and elevation of the study area were considered for the delineation of GWPZs in the study area. About 9.3, 71.9 and 18.8% of the study area falls within good, moderate and poor groundwater potential zones, respectively. The potential groundwater yield data corroborate the outcome of the model, with maximum yield in the older floodplain and minimum yield in the hard-rock terrains in the western and south-western regions. Validation of the GWPZs using the yield of 148 wells shows very high accuracy of the model prediction, i.e., 89.1% on superimposition and 85.1 and 81.3% on success and prediction rates, respectively. Measurement of the seasonal water-table fluctuation with a multiplicative model of time series for predicting the short-term trend of the water table, followed by chi-square analysis between the predicted and observed water-table depth, indicates a trend of falling groundwater levels, with a 5% level of significance and a p-value of 0.233. The rainfall pattern for the last 3 years of the study shows a moderately positive correlation (R ² = 0.308) with the average water-table depth in the study area.