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Multi-model assessment of glacio-hydrological changes in central Karakoram, Pakistan

Journal of Mountain Science 2021年第8期18卷 1995-2011页

作者： Javed HASSAN CHEN Xiao-qing rijan bhakta kayastha NIE Yong Key Laboratory of Mountain Hazards and Earth Surface Process Institute of Mountain Hazards and EnvironmentChinese Academy of SciencesChengdu610041China China-Pakistan Joint Research Center on Earth Sciences CAS-HECIslamabad45320Pakistan University of Chinese Academy of Sciences Beijing100049China Himalayan Cryosphere Climate and Disaster Research Center(HiCCDRC)Department of Environmental Science and EngineeringSchool of ScienceKathmandu UniversityKavrepalanchowk45200Nepal

The multi-model assessment of glacio-hydrological regimes can enhance our understanding of glacier response to climate *** improved knowledge can uplift our computing abilities to estimate the contributing components of the river *** study examined and compared the hydrological responses in the glacier-dominated Shigar River basin(SRB)under various climatic scenarios using a semi-distributed Modified Positive Degree Day Model(MPDDM)and a distributed Glacio-hydrological Degree-day Model(GDM).Both glacio-hydrological models were calibrated and validated against the observed hydro-meteorological data from 1988–1992 and 1993–*** and precipitation data from Shigar and Skardu meteorological stations were used along with field estimated degree-day factor,temperature,and precipitation *** results from both models indicate that the snow and ice melt are vital contributors to sustain river flow in the ***,MPDDM estimated 68%of rain and baseflow contribution to annual river runoff despite low precipitation during the summer monsoon,while GDM estimated 14%rain and baseflow ***,MPDDM calculated 32%,and GDM generated 86%of the annual river runoff from snow and ice *** simulated river discharge with 0.86 and 0.78 NSE for calibration and validation,***,GDM simulated river discharge with improved accuracy of 0.87 for calibration and 0.84 NSE for the validation *** snow and ice melt is significant in sustaining river flow in the SRB,and substantial changes in melt characteristics of snow and ice are expected to have severe consequences on seasonal water *** on the sensitivity analysis,both models’outputs are highly sensitive to the variation in ***,compared to MPDDM,GDM simulated considerable variation in the river discharge in climate scenarios,RCP4.5 and 8.5,mainly due to the higher sensitivity of GDM model outputs to temperature *** i

关键词： Modified Positive Degree Day Model(MPDDM) Glacio-hydrological Degree-day Model(GDM) Glacio-hydrological Modelling Climatic Variation Snow and ice contributions

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Study of thermal properties of supraglacial debris and degree-day factors on Lirung Glacier,Nepal

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Research in Cold and Arid Regions 2018年第5期10卷 357-368页

作者： Mohan Bahadur Chand rijan bhakta kayastha Graduate School of Environmental Science Hokkaido UniversitySapporo 060-0810Japan Himalayan Cryosphere Climate and Disaster Research Center(HiCCDRC)Kathmandu UniversityDhulikhel 45200Nepal

The extensive debris that covers glaciers in the ablation zone of the Himalayan region plays an important part in regulating ablation rates and water availability for the downstream region. The melt rate of ice is determined by the amount of heat conducted through debris material lying over the ice. This study presents the vertical temperature gradients, thermal properties in terms of thermal diffusivity and thermal conductivity, and positive degree-day factors for the debris-covered portion of Lirung Glacier in Langtang Valley, Nepal Himalaya using field-based measurements from three different *** measurements include debris temperatures at different debris thicknesses, air temperature, and ice melt during the monsoon(2013), winter(2013), and pre-monsoon(2014) seasons. We used a thermal equation to estimate thermal diffusivity and thermal conductivity, and degree-day factors(DDF) were calculated from cumulative positive temperature and ice melt of the measurement period. Our analysis of debris temperature profiles at different depths of debris show the daily linear gradients of-20.81 °C/m, 4.05 °C/m, and-7.79 °C/m in the monsoon, winter, and pre-monsoon seasons, respectively. The values of thermal diffusivity and thermal conductivity in the monsoon season were 10 times greater than in the winter season. The large difference in these values is attributed to surface temperature and moisture content within the debris. Similarly, we found higher values of DDFs at thinner debris for the pre-monsoon season than in the monsoon season although we observed less melting during the pre-monsoon season. This is attributed to higher cumulative temperature during the monsoon season than in the pre-monsoon season. Our study advances our understanding of heat conductivity through debris material in different seasons, which supports estimating ice melt and discharge from glacierized river basins with debris-covered glaciers in the Himalayan region.

关键词： Lirung Glacier Himalaya debris-covered glacier degree-day factor thermal conductivity temperature gradient

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Predictions of future hydrological conditions and contribution of snow and ice melt in total discharge of Shigar River Basin in Central Karakoram,Pakistan

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Research in Cold and Arid Regions 2017年第6期9卷 599-612页

作者： Javed Hassan rijan bhakta kayastha Ahuti Shrestha Iram Bano Sayed Hammad Ali Haleem Zaman Magsi Himalayan Cryosphere Climate and Disaster Research CenterDepartment of Environmental Science and EngineeringSchool of ScienceKathmandu UniversityNepal Department of Earth Sciences Karakoram International University Gilgit-Baltistan 15100Pakistan

The high mountains of Hindu-Kush Karakoram and Himalaya(HKKH) contain a large volume of snow and ice, which are the primary sources of water for the entire mountainous population of HKKH. Thus, knowledge of these available resources is very important in relation to their sustainable use. A Modified Positive Degree Day Model was used to simulate daily discharge with the contribution of snow and ice melt from the Shigar River Basin, Central Karakoram, Pakistan. The basin covers an area of 6,921 km2 with an elevation range of 2,204 to 8,611 m a.s.l.. Forty percent of the total area is glaciated among which 20% is covered by debris and remaining 80% by clean ice and permanent snow. To simulate daily discharge, the entire basin was divided into 26 altitude belts. Remotely sensed land cover types are derived by classifying Landsat images of 2009. Daily temperature and precipitation from Skardu meteorological station is used to calibrate the glacio-hydrological model as an input variable after correlating data with the Shigar station data(r=0.88). Local temperature lapse rate of 0.0075 °C/m is used. 2 °C critical temperature is used to separate rain and snow from precipitation. The model is calibrated for 1988~1991 and validated for 1992~1997. The model shows a good Nash-Sutcliffe efficiency and volume difference in calibration(0.86% and 0.90%) and validation(0.78% and 6.85%). Contribution of snow and ice melt in discharge is 32.37% in calibration period and 33.01% is validation period. The model is also used to predict future hydrological regime up to 2099 by using CORDEX South Asia RCM considering RCP4.5 and RCP8.5 climate *** future snow and ice melt contributions in both RCP4.5 and RCP8.5 are 36% and 37%, respectively. Temperature seems to be more sensitive as compared to other input variables, which is why the contribution of snow and ice in discharge varies significantly throughout the whole century.

关键词： positive degree day factor simulated discharge daily meteorological variables debris covered ice clean ice

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Hydro-Chemical Characterization of Glacial Melt Waters Draining from Langtang Valley, Nepal

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Journal of Water Resource and Protection 2015年第8期7卷 605-613页

作者： Anisha Tuladhar rijan bhakta kayastha Smriti Gurung Ahuti Shrestha Department of Environmental Science and Engineering Kathmandu University Dhulikhel Nepal

A detailed analytical study of the physico-chemical parameters of melt water draining from glaciers of Langtang Valley with an elevation ranging from 1395 m a s l to 4200 m a s l in Rasuwa district, Nepal was carried out in order to study the seasonal and altitudinal variation in hydro-chemistry along the Langtang River and glacial melts from the Lirung and the Khimsung Glaciers. The study was carried out during 6 - 10 April and 30 June-3 July, 2014 at 11 sites. A total of 22 composite samples were collected. The concentration of cations and anions of the Langtang Valley were found in the order Ca2+ > K+ > Na+ > Mg2+ and , respectively. Significant seasonal variation in electrical conductivity (EC), turbidity, dissolved oxygen (DO), calcium (Ca), sodium (Na), magnesium (Mg), chloride (Cl), sulphate (SO4) and total phosphorus (TP-PO4) and altitudinal variation in EC, total dissolved solids (TDS), DO and Na was found out. The concentrations of the heavy metals (As, Al, Mn, Zn, Cd, Cr) were below the detection limit except Fe (0.5 to 18.1 mg/l), which was highly variable. Calcium carbonate weathering was found out to be the major source of dissolved ions in the region. The elemental ratios (Ca/Si and K/Na) were typical of glacial melt water and the low Na/Cl and K/Cl ratios indicated major contribution from atmospheric precipitation to the observed dissolved ions of melt waters. The study showed an increase in the concentration of cations as compared to previous studies, which could be attributed to increasing weathering rates due to temperature increase. Elevated concentration of NO3 and TP-PO4 compared to previous studies show the effect of human impact in the region. Differences in the melt water composition between the debris covered and clean type glacier was found out.

关键词： Hydro-Chemistry Langtang River Weathering Process Glacier Melt Water

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Effect of debris on seasonal ice melt (2016−2018) on Ponkar Glacier, Manang, Nepal

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Research in Cold and Arid Regions 2020年第5期12卷 261-271页

作者： Reeju Shrestha rijan B.kayastha Rakesh kayastha Himalayan Cryosphere Climate and Disaster Research Center(HiCCDRC)Department of Environmental Science and EngineeringSchool of ScienceKathmandu UniversityDhulikhel 45200Nepal

Supraglacial debris is widely present on glaciers in alpine environments and its distribution greatly affects glacier *** present study aims to determine the effect of debris on glacier ice melt on Ponkar Glacier,Manang District,*** estimated ice melt under various debris thickness using Energy Balance(EB)model and conductive heat flux methods,which are compared with in-situ *** stakes are installed on the glacier at different debris thickness of 11−40 *** data from March 2016 to May 2018 are obtained from the Automatic Weather Station(AWS)installed on the glacier surface at an elevation of 3,881 m *** the energy balance *** surface temperature and different debris depths are also measured on the *** calculated ablation rates from the conductive heat flux method are 0.9,1.62 and 0.41 cm/d on pre-monsoon,monsoon and post-monsoon,respectively,with mean debris thermal conductivity 1.04 W/(m∙K).The net radiation shows little variation between the seasons,while turbulent heat flux varies in the *** heat flux was found to be highest in post-monsoon season due to a larger temperature gradient between surface and air.

关键词： debris-covered glacier thermal conductivity energy flux Ponkar Glacier ice melt Hindu-Kush Himalaya

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Assessment of Sediment Load of Langtang River in Rasuwa District, Nepal

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Journal of Water Resource and Protection 2016年第1期8卷 84-92页

作者： Aastha Chhetri rijan B. kayastha Ahuti Shrestha Himalayan Cryosphere Climate and Disaster Research Center Department of Environmental Science and Engineering Kathmandu University Dhulikhel Nepal

This paper assesses the sediment load of the glacier fed Langtang River, Nepal from April 2014 to March 2015. Water samples were collected from the centre of the river with a frequency of two samples per each sampling day using the Depth Integration Technique (DIT) on daily basis in the monsoon season, weekly in the pre- and post-monsoon seasons and bi-monthly in the winter season. Suspended sediment concentration (SSC) is calculated from the water samples using filtration followed by oven-drying, and a rating curve is used to calculate daily discharge of the Langtang River. The annual sediment yield is 109,276.75 tons and 37.69, 11.52 and 5.54 tons of sediment is transported per day in the pre-monsoon, post-monsoon and winter seasons, respectively. There is a very high value of 872.86 tons per day in the monsoon season, which contributes the highest sediment load among all of the seasons comprising 83% of the total sediment transport. Diurnal cycle of sediment discharge is clearly seen with higher sediment discharge during the evening than the morning and reaching maximum values of 41.1 kg·s-1 and 61.5 kg·s-1, respectively. A clock-wise hysteresis loop has been obtained for discharge and sediment discharge where sediment flux is higher in the early monsoon than in the late monsoon for a corresponding discharge.

关键词： Sediment Load SSC Discharge Depth Integration Technique Langtang River

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Study of annual mass balance(2011–2013) of Rikha Samba Glacier, Hidden Valley, Mustang, Nepal

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Research in Cold and Arid Regions 2016年第4期8卷 311-318页

作者： Sanjaya Gurung Bikas C. Bhattarai rijan B. kayastha Dorothea Stumm Sharad P. Joshi Pradeep K. Mool Himalayan Cryosphere Climate and Disaster Research Centre Kathmandu University Dhulikhel 45200 Nepal International Centre for Integrated Mountain Development Lalitpur 44700 Nepal

Although Himalayan glaciers are of particular interest in terms of future water supplies, regional climate changes, andsea-level rises, little is known about them due to lack of reliable and consistent data. There is a need for monitoring theseglaciers to bridge this knowledge gap and to provide field measurements necessary to calibrate and validate the resultsfrom different remote sensing operations. Therefore, glaciological observations have been carried out by the CryosphereMonitoring Project （CMP） since September 2011 on Rikha Samba Glacier in Hidden valley, Mustang district in westernNepal in order to study its annual mass balance. This paper presents the first results of that study. There are 10 glaciers inHidden Valley, named G1, G2, G3, up to G10. Of these, G5 is the Rikha Samba Glacier, which has the largest area （5.37km2） in this valley and the highest and lowest altitudes （6,476 and 5,392 m a.s.l., respectively）. The glacier mass balancediscussed in this paper was calculated using the glaciological method and the equilibrium line altitude （ELA）. The glaciershowed a negative annual point mass balance along the longitudinal profile of its lower part from September 10, 2011 toOctober 3, 2012. Stake measurements from October 4, 2012 to September 30, 2013 indicated a negative areal average ofannual mass balance ？0.088±0.019 m w.e. for the whole glacier. Based on these observations, the ELA of the Rikha SambaGlacier is estimated at 5,800 m a.s.l. in 2013. This negative balance may be due to rising air temperatures in the region,which have been incrementally rising since 1980 accompanied by little or no significant increase in precipitation in thatperiod. The negative mass balance confirms the general shrinking trend of the glacier.

关键词： ablation accumulation climate change glacier mass balance Himalayan glacier

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