Nature reflects our nature are 5749 m , 5094 m a . s . l . and 2.5 km2 , respectively . k | ltlaDa
Ageta et al . ( 1984 ) and Steinegger et al ., ( 1993 ) have analyzed photographs of crevasse walls at different altitudes . The glacier terminus was also surveyed in 1982 ( Ageta et al ., 1984 ). Since 1985 successive pit observations were carried out at 5350 m a . s . l . in the accumulation zone of the glacier ( Iida et al ., 1987 ; Ozawa , 1991 ). Shallow ice cores ( several meters in depth ) have been extracted at a neighboring altitude in 1991 ( Shiraiwa , 1993 , Yoshimura et al ., 2000 and 1996 ; Fujita et al ., 2006 ). Distinct dirt layers formed during a dry season ( Iida et al . 1987 ; Kohshima , 1987 ; Yoshimura et al ., 2000 ) were utilized as clearly discernable annual markers in pits and ice cores of this glacier . Dirt layers on crevasse walls appeared more clearly than those in pit / ice cores because the concentration of dirt materials and algal cells growing on them occurred wherever meltwater and abundant light were available ( Yoshimura et al ., 2000 ). Dirt layer spacing of crevasse walls is converted to a net balance ( mm w . e .) by use of a density-depth relation of firn ( Iida et al ., 1984 ). The depth ( 22 m ) at which the Tritium peak of 1963 was found in the ice core drilled in 1982 ( Watanabe et al ., 1984 ) coincided with the depth of the layer counted as 1963 ( 21.7 ) in the crevasse wall analysis by Ageta et al . ( 1984 ). This implies that , therefore , that the crevasse wall could be used as an alternative for an ice core as long as its dirt layers spacing can be measured precisely . The deepest ice core ( 60 m to the bedrock ) was extracted in 1982 ( Watanabe et al ., 1984 ) from this glacier . Depth of pits , the height of crevasse walls , length of ice cores , estimated age , observed altitudes , and data sources are summarized in Table 1 .
The glacier fluctuation was studied both by photogrammetry and ground survey . Fujita et al . ( 1998 ) surveyed Yala Glacier terminus in September 1994 , May , and October 1996 and found that the retreat rate and surface lowering has accelerated in recent years . Fujita et . al . ( 2001 ) studied Yala glacier in Langtang Valley to clarify the variations of the glacier in 1994 and 1996 and concluded that the shrinkage tendency of the glacier has been accelerated in the 1990s .
Takeuchi et al ., ( 2000 ) studied on characteristics of cryoconite holes on Yala glacier . Results suggested that cryoconite holes on this glacier were shallow and unstable because the albedo of the glacier surface was reduced by much darkcolored material . Motoyama and Yamada ( 1989 ) studied hydrology of Langtang Valley during the 1987 monsoon – post-monsoon season . Murakami et al ., ( 1989 ) studied the permeability coefficient of water on snow and firn at the accumulated area of Yala Glacier and a linear relation was found between density and the logarithm of the permeability coefficient while a discontinuity was seen at a density around 600 kg / m ³. Ozawa and Yamada ( 1989 ) studied the contribution of internal accumulation to mass balance and conditions of superimposed ice formation on Yala Glacier based on data obtained by field observations conducted in August to October 1987 . Baral et al ( 2014 ) found that the calculated mass balance of Yala Glacier from 10 November 2011 to 3 November 2012 was – 0.89 m w . e . Acharya and Kayastha ( 2019 ) also studied the mass and energy balance of the Yala Glacier and found that the cumulative mass balance of the Yala Glacier for the 2011 – 2017 period was negative at -4.88 m w . e . The mean annual glacier-wide mass balance was -0.81 ± 0.27 m w . e . with a standard deviation of ± 0.48 m w . e .
3.5 Dhaulagiri Region
Rikha Samba Glacier is the most studied glacier in the Hidden Valley , Dhaulagiri region in Mustang district , Nepal . Besides glacier mass balance hydrological , meteorological and other glaciological studies had been carried out in the Hidden Valley . Nakawo ( 1976 ) studied on bubble pattern of a glacier near Tukche Peak in Hidden Valley , Mukut Himal in the monsoon season , 1974 at about 100 points of the lower half of a glacier near Tukche Peak . Shrestha et . al . ( 1976 ) studied the climate of Hidden Valley by setting up a temporary station at a height of 5055 m during the monsoon in 1974 . Fujii ( 1976 ) studied periglacial phenomena in Hidden Valley which was found to occur between the forest line and snow line in Hidden Valley . Fujii and Higuchi ( 1976 ) reported on ground temperature and its relation to permafrost occurrence in the Khumbu region and Hidden Valley and the result indicated that permafrost occurred above 5000 m in the Hidden Valley . Higuchi ( 1977 ) studied the effect of nocturnal precipitation on the mass balance of the Rikha Samba glacier , Hidden Valley , and concluded that the present position of the terminus of the glacier had a relation to the tendency of precipitation in that area to occur frequently at night . Higuchi et . al . ( 1978 ) studied observation of snow particles at Hidden Valley during the monsoon season at Base Camp ( 5055 m ) and Camp III ( 5610 m ) from July 2 to August 28 , 1974 .
3.5.1 Rikha Samba Glacier
Rikha Samba Glacier ( 28o 50 ’ N , 83o 30 ” E ) is the most studied glacier in Hidden Valley , Kali Gandaki Basin . The
Nature and Social Concern Society 29