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 avai...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 scenarios.Predicted 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.展开更多
The multi-model assessment of glacio-hydrological regimes can enhance our understanding of glacier response to climate change.This improved knowledge can uplift our computing abilities to estimate the contributing com...The multi-model assessment of glacio-hydrological regimes can enhance our understanding of glacier response to climate change.This improved knowledge can uplift our computing abilities to estimate the contributing components of the river discharge.This 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 1993–1997.Temperature and precipitation data from Shigar and Skardu meteorological stations were used along with field estimated degree-day factor,temperature,and precipitation gradients.The results from both models indicate that the snow and ice melt are vital contributors to sustain river flow in the catchment.However,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 contribution.Likewise,MPDDM calculated 32%,and GDM generated 86%of the annual river runoff from snow and ice melt.MPDDM simulated river discharge with 0.86 and 0.78 NSE for calibration and validation,respectively.Similarly,GDM simulated river discharge with improved accuracy of 0.87 for calibration and 0.84 NSE for the validation period.The 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 availability.Based on the sensitivity analysis,both models’outputs are highly sensitive to the variation in temperature.Furthermore,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 change.The integration of an updated melt module and two reservoir baseflow module in GDM is anticipated to advance the representation of hydrological components,unlike one reservoir baseflow module used separately in MPDDM.The restructured melt and baseflow modules in GDM have fundamentally enriched our perception of glacio-hydrological dynamics in the catchment.展开更多
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 det...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 seasons.Field 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.展开更多
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 ...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.展开更多
文摘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 scenarios.Predicted 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.
基金the Himalayan Cryosphere, Climate and Disaster Research Center (HiCCDRC), Kathmandu University for constant support throughout the researchfunded by The Second Tibetan Plateau Scientific Expedition and Research Program (STEP)(Grant No. 2019QZKK0904)+3 种基金supported by the Comprehensive Investigation and Assessment of Natural Hazards in China-Pakistan Economic Corridor (Grant No. 2018FY100500)Ministry of Science and Technology Basic Resources Survey Project (2018FY100506)International Science andTechnology Cooperation Program of China (No. 2018YFE0100100)the National Natural Science Foundation of China (41925030 and 41661144028)
文摘The multi-model assessment of glacio-hydrological regimes can enhance our understanding of glacier response to climate change.This improved knowledge can uplift our computing abilities to estimate the contributing components of the river discharge.This 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 1993–1997.Temperature and precipitation data from Shigar and Skardu meteorological stations were used along with field estimated degree-day factor,temperature,and precipitation gradients.The results from both models indicate that the snow and ice melt are vital contributors to sustain river flow in the catchment.However,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 contribution.Likewise,MPDDM calculated 32%,and GDM generated 86%of the annual river runoff from snow and ice melt.MPDDM simulated river discharge with 0.86 and 0.78 NSE for calibration and validation,respectively.Similarly,GDM simulated river discharge with improved accuracy of 0.87 for calibration and 0.84 NSE for the validation period.The 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 availability.Based on the sensitivity analysis,both models’outputs are highly sensitive to the variation in temperature.Furthermore,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 change.The integration of an updated melt module and two reservoir baseflow module in GDM is anticipated to advance the representation of hydrological components,unlike one reservoir baseflow module used separately in MPDDM.The restructured melt and baseflow modules in GDM have fundamentally enriched our perception of glacio-hydrological dynamics in the catchment.
基金the HKH Cryosphere Monitoring Project implemented by the International Centre for Integrated Mountain Development (ICIMOD)supported by the Norwegian Ministry of Foreign Affairs
文摘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 seasons.Field 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.
文摘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.