Monitoring spatio-temporal glaciers retreat and advances in Bhagirathi Basin, Gharhwal Himalayas using Remote Sensing Data

In this study, 29 glaciers of the Bhagirathi basin, Garhwali Himalayas, have been monitored using remote sensing (RS) satellite images for more than a decade. Bhagirathi basin has sub-basins, namely Bhagirathi, Bhilangana, Pilang, Jahnvi, Jalandhari, and Kaldi. The glaciers area > 5 km 2 has been considered apart from a few small glaciers to estimate glaciers retreat and advances. Landsat satellite images of 2000 and 2015 have been used to estimate areal extent change in glaciers. ASTER DEM has been used for extraction of glaciers terrain features such as elevation, slope, area, etc. It is observed from the analysis that Bhagirathi sub-basin has a maximum glaciated area of ~ 35% and Pilang has the least with ~ 3.2%, whereas Kaldi sub-basin has no glacier. In this region, out of 29 glaciers, 25 glaciers have shown retreat while 4 glaciers have shown advancement and resulting the total glacier area loss of ~ 0.5%, while the retreat rate varies from ~ 0.06 m/yr to ~ 19.4 m/yr. Dokarni glacier has maximum retreat rate (~ 19.4 m/yr), whereas, Dehigad has maximum advancing rate (~ 10.1 m/yr). Glaciers retreat and advance have also been analysed based upon terrain parameters and observed that north and south aspect orientations have shown retreat, whereas the area change is highly correlated with glacier length. The study covers more than 65% of the total glaciated area and as per our knowledge based on the existing literature; this is one of the initial exhaustive studies to cover the highest number of glaciers in all sub-basins of the Bhagirathi basin.

在这项研究中，对加尔瓦尔喜马拉雅地区的巴吉拉蒂河流域的29条冰川利用遥感卫星图像进行了长达十多年的监测。巴吉拉蒂河流域包含多个子流域，分别是巴吉拉蒂、比朗加纳、皮朗、贾恩维、贾兰德里和卡尔迪。除了一些小型冰川外，还考虑了面积大于5平方公里的冰川，以评估冰川的退缩和前进情况。利用2000年和2015年的陆地卫星图像来估算冰川面积的变化。利用先进星载热发射和反射辐射仪数字高程模型（ASTER DEM）提取冰川的地形特征，如海拔、坡度、面积等。通过分析发现，巴吉拉蒂子流域的冰川覆盖面积最大，约为35%，皮朗最少，约为3.2%，而卡尔迪子流域没有冰川。在该地区的29条冰川中，有25条冰川出现退缩，4条冰川出现前进，导致冰川总面积减少约0.5%，退缩速率从约0.06米/年到约19.4米/年不等。多卡尼冰川的退缩速率最大（约19.4米/年），而德希加德冰川的前进速率最大（约10.1米/年）。还根据地形参数对冰川的退缩和前进进行了分析，发现朝北和朝南的方向出现了退缩，而面积变化与冰川长度高度相关。这项研究涵盖了超过65%的冰川总面积，据我们基于现有文献的了解，这是对巴吉拉蒂河流域所有子流域中数量最多的冰川进行的首批详尽研究之一。