Papers by Mahendra Bhutiyani
The results of trend analyses of the discharge data of four rivers in northwestern Himalaya, name... more The results of trend analyses of the discharge data of four rivers in northwestern Himalaya, namely Beas, Chenab, Ravi and Satluj, are presented here and the impact of climate change in the last century is discussed. In the case of Satluj river, studies indicate an episodic variation in discharge in all three seasons on a longer timescale of about 82 years . Statistically significant decrease in the average annual and monsoon discharge and insignificant increase in winter and spring discharge, despite increasing temperatures during all the three seasons can also be seen. Decreasing discharge during winter and monsoon seasons in the post-1990 period, despite rising temperatures and average monsoon precipitation strongly indicates decreasing contribution of glaciers to the discharge and their gradual disappearance. On a shorter timescale of the last four decades of the 20th century, barring the Beas river, which shows a significantly decreasing trend, the other three rivers have shown a statistically insignificant change (at 95% confidence level) in their average annual discharge. Annual peak flood discharges show significant increasing trends in the Satluj and Chenab basins, significant decreasing trend in the Beas river and insignificant trend in the Ravi river. Notwithstanding these variations, the studies indicate an increase in the number of 'high-magnitude flood' events in the rivers in northwestern Himalaya in the last three decades.
This paper discusses the results of studies on sediment transport and the erosion rate in the Nub... more This paper discusses the results of studies on sediment transport and the erosion rate in the Nubra river carried out in hydrological years from 1986 to 1991.Discharge data of proglacial stream of the Siachen Glacier shows seasonal variation ranging from 0.26 × 10 6 m 3 d Ϫ1 in the beginning of the ablation season to about 23 × 10 6 m 3 d Ϫ1 in the peak ablation season. Suspended sediment mass in the Nubra River varies from 0.01 kg m Ϫ3 s Ϫ1 in the beginning of the ablation season to about 2-3 kg m Ϫ3 s Ϫ1 at its peak. A relationship is developed between daily suspended sediment transport and daily discharge. The total sediment load calculated from the data varies from 296 to 1287 tons km Ϫ2 (of the glacier basin area) per year. The erosion rate calculated from total sediment load which includes suspended sediment and bedload varies from 0.11 to 0.46 mm year Ϫ1 .The erosion rates in the Nubra basin are much lower than the Hunza basin in Western Karakoram Himalayas (1.8 mm year Ϫ1 ) which may be due to its geological setting consisting of highly erosion resistant rocks like diorites, granodiorites, granites and granite-gniesses. Tectonic upliftment and high relief give rise to comparatively higher erosion rates in Karakoram Himalayas. ᭧
Using available instrumental records, this paper examines the variation of precipitation from 186... more Using available instrumental records, this paper examines the variation of precipitation from 1866 to 2006 in the northwestern Himalaya (NWH). The study indicates no trend in the winter precipitation but significant decreasing trend in the monsoon precipitation during the study period. Periodicities on a multi-decadal scale (29-34 years and 58-64 years) obtained in power spectrum analyses point towards epochal behaviour in the precipitation series. Analyses of the temperature data show significant increasing trends in annual temperature in all three stations in the NWH during the data period. Warming effect is particularly noteworthy during the winter season. Negative relationships between mean winter air temperature and snowfall amounts recorded at different meteorological stations in this period reveal strong effect of rising temperatures on the decreasing snowfall component in total winter precipitation, reducing effective duration of winter on the windward side of the Pir Panjal Himalayan Range.
The study reveals significant rise in air temperature in the northwest Himalayan (NWH) region by ... more The study reveals significant rise in air temperature in the northwest Himalayan (NWH) region by about 1.6°C in the last century, with winters warming at a faster rate. The diurnal temperature range (DTR) has also shown a significantly increasing trend. This appears to be due to rise in both the maximum as well as minimum temperatures, with the maximum increasing much more rapidly. The results are in contrast to the findings in the Alps and Rockies where the minimum temperatures have increased at an elevated rate. Conforming to the global trends, the study confirms episodes of strong warming and cooling in the NWH in the last century. Real warming appears to have started from late-1960s and highest rate of increase was experienced in the last two decades. The study also shows teleconnections between temperatures and an epochal behaviour of the precipitation till late-1960s. These teleconnections seem to have weakened gradually since then and rapidly in the post-1991 period, indicating the waning effect of the natural forcings in this period.
The analyses of travel-time graphs obtained from 10 seismic refraction soundings taken across the... more The analyses of travel-time graphs obtained from 10 seismic refraction soundings taken across the length and breadth of the Chhota Shigri Glacier in the Pirpanjal Himalaya indicate that the depth of the glacier varies from 15 to 18 meters in its lower reaches to about 35 to 40 meters in the middle portion and it exceeds 55 meters in the higher reaches. The compressional wave (P-waves) velocities obtained for glacier-ice (3722 m/sec to 4133 m/sec), although slightly on the higher side, are generally in good agreement with the velocities obtained for glacier-ice in different parts of the world. The analyses also reveal that there are probably no englacial moraines within the glacier body. P-wave velocities obtained for underlying layer (5245 to 7950 m/sec) in the higher reaches indicate the presence of hard, unweathered granite or granite gneiss as bedrock. Comparatively lower P-wave velocities of about 4300 m/sec obtained for the underlying layer in the lower reaches possibly indicates the presence of highly eroded nature of the bedrock.
A 'Dirty snowfall' event was recorded at Field Research Station Dhundi (Altitude-3050 m) on 18th ... more A 'Dirty snowfall' event was recorded at Field Research Station Dhundi (Altitude-3050 m) on 18th and 19th March 1991. Because of its dark colour, this was reported as a 'Black snow' event by some heliskiers near Sonamerg in Kashmir Valley. It was thought to be related to burning oil wells in Kuwait in the aftermath of Gulf war which preceded it. Based on the data collected at this station and chemical analyses carried out in the laboratory, attempts were made to identify the cause of this precipitation. The data showed that this snow spell was abnormal as its density was 0.42 gm/cc, albedo was about 61% and had graupels as predominant crystal type. The chemical analyses of melted snow samples revealed the abnormally high concentration of suspended dust particles (1.15 to 1.5 gm/cc) which is comparable to flood waters of mountainous rivers. The concentrations of Cu, Mg, Ca, Zn, and Na were not abnormal as similar concentrations have been observed in fresh snow in other parts of the world. Total absence of sulphates and nitrates which are the byproducts of burning of crude oil and completely neutral nature of the meltwater samples ruled out the possibility of burning oil wells of Kuwait as their source. High concentration of dust particles in these samples leads to the conclusion that a major desert dust storm in neighbouring Thar Desert could have given rise to 'dirty snow' precipitation in Pirpanjal and parts of Greater Himalayas. The movement of 'Western Disturbance' that yielded this snowfall event, as tracked from NOAA satellite pictures supports this argument.
The paper examines the magnitude of warming in Northwestern Himalaya during the period from 1866 ... more The paper examines the magnitude of warming in Northwestern Himalaya during the period from 1866 to 2006. The analyses of the temperature data show an average rate of increase of about 1.1 0 C/100 years during this period. Warming effect is particularly significant during the winter season. Winter temperature has shown an elevated rate of increase (1.4 0 C/ 100 years) than the monsoon temperature (0.6 0 C/ 100 years), due to rapid increase in both, the maximum as well as minimum temperatures, with the maximum increasing much more rapidly. Statistically significant decreasing trends (at 95% confidence level) in the monsoon and overall annual precipitation during the study period are indicated. In contrast, the winter precipitation has shown an increasing but statistically insignificant trend (at 95% confidence level). Rising winter air temperatures have caused decreasing snowfall component in total winter precipitation on the windward side of the Pirpanjal Range. The studies also indicate reduced the duration of winter by about two weeks in the last three decades. Role of anthropogenic activities influencing climate change in last three decades can not be ruled out. Archer DR, Fowler HJ. 2004. Spatial and temporal variations in precipitation in the Upper Indus Basin, global teleconnections and hydrological implications. Hydrology and earth System Sciences 8(1): 47-61. Baines PG, Folland CK. 2007. Evidence for rapid global climate shift across the late 1960s. Journal of Climate 20: 2721-2744. Beniston M. 1997. Variation of snow depth and duration in the Swiss Alps over the last 50 years: Links to changes in large-scale climatic forcings. Climatic Change 36: 281-300. Beniston M, Diaz FD, Bradley, RS. 1997. Climatic change at high elevation sites: an overview. Climatic Change 36: pp. 233-251. Beniston M. 2003. Climatic change in mountainous regions: A review of possible impacts. Climatic Change 59: 5-31. climate variability over monsoon Asia as revealed by some proxy sources. Mausam 52 : 9-22. Brönnimann S. 2002. Picturing climate change. Climatic Research, 22: 87-95. Brown TB, Barry RG, Doesken NJ. 1992. An exploratory study of temperature trends for Colorado Paired Mountain-High plains Stations.
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Papers by Mahendra Bhutiyani