Guo Wanqin

Assessment and Simulation of Glacier Lake Outburst Floods for Longbasaba and Pida Lakes, China

Abstract Longbasaba and Pida lakes are two moraine-dammed lakes located at the headwaters of the Geiqu River, a tributary of the Pumqu River in the Chinese Himalayas, at an elevation of about 5700 m. The minimum distance between the two lakes is 24 m and their difference in elevation is about 76 m. Breach risks were assessed on the basis of field surveys carried out in the summers of 2004, 2005, and 2006. Empirical formulae for breaching of moraine dams and the BREACH model for earthen dam failure were employed to simulate the breach properties and hydrograph of floods at the breaching site of the dam from the two lakes. The modeling showed that an outburst flood from Longbasa-ba and Pida lakes would last for about 5.5 hours and have a peak discharge of about 3–5 × 104 m3/s at about 1.8 hours after the beginning of the outburst.

Recent shrinkage and hydrological response of Hailuogou glacier, a monsoon temperate glacier on the east slope of Mount Gongga, China

Temperate glaciers are more sensitive to climate changes than polar or continental glaciers, and can drive remarkable runoff variation in local water catchments. Here we present recent glacier shrinkage and runoff change for Hailuogou glacier, a typical monsoon temperate glacier on the east slope of Mount Gongga (Minya Konga), China. The surface area of Hailuogou glacier has decreased by 3.5% (0.92 km(2)) between 1966 (aerial photographs) and 2007 (ASTER images). Flow measurements at a stream gauge about 500 m down-glacier commencing in 1994 display a remarkable increase in annual runoff (mostly during July September) since 1999. Annual runoff over the same period in a non-glacierized but forested subcatchment (9.17 km(2)) did not experience significant change. By separating the daily rainfall component from the daily total discharge, monthly catchment water-balance series were calculated for the period 1994-2005, which shows an increasing trend of glacier storage loss. We concluded that air-temperature rise (with a trend of +0.2 degrees C (10a)(-1) between 1988 and 2005, recorded at nearby weather stations) has had an increased effect on glacier mass loss and river runoff change during the past 20 years.

Using Remote Sensing Data to Quantify Changes in Glacial Lakes in the Chinese Himalaya

Abstract To assess changes in glacial lakes in the Chinese Himalaya, 2 inventory phases were conducted on the basis of 278 aerial survey topography maps from the 1970s and 38 Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images from the 2000s. In the past 30 years, the number of glacial lakes has decreased, from 1750 to 1680 (a decrease of 4.0%), whereas the average area of glacial lakes expanded from 166.48 to 215.28 km2 (an increase of 29.7%). Between 3400 and 6000 m, glacial lake areas expanded at rates of 2–84% in almost all 100-m elevation bands, and the dominant expansion rates at different elevations were inversely correlated with glacier area retreating rates to some degree. Glacial lake expansion was a dominant contributor to the increase in glacial lake area, accounting for about 67% of the net changes in lake area, whereas newly formed lakes accounted for the remaining 33%.

Glacier changes in the Koshi River basin, central Himalaya, from 1976 to 2009, derived from remote-sensing imagery

Abstract We use remote-sensing and GIS technologies to monitor glacier changes in the Koshi River basin, central Himalaya. The results indicate that in 2009 there were 2061 glaciers in this region, with a total area of 3225 ±90.3 km2. This glacier population is divided into 1290 glaciers, with a total area of 1961 ±54.9 km2, on the north side of the Himalaya (NSH), and 771 glaciers, with a total area of 1264 ± 35.4 km2, on the south side of the Himalaya (SSH). From 1976 to 2009, glacier area in the basin decreased by about 19±5.6% (0.59±0.17%a–1). Glacier reduction was slightly faster on SSH (20.3 ±5.6%) than on NSH (18.8±5.6%). The maximum contribution to glacier area loss came from glaciers within the 1-5 km2 area interval, which accounted for 32% of total area loss between 1976 and 2009. The number of glaciers in the Koshi River catchment decreased by 145 between 1976 and 2009. Glacier area on SSH decreased at a rate of 6.2 ±3.2% (0.68 ±0.36% a–1), faster than on NSH, where the rate was 2.5 ±3.2% (0.27±0.36% a–1) during 2000-09. Based on records from Tingri weather station, we infer that temperature increase and precipitation decrease were the main causes of glacier thinning and retreat during the 1976-2000 period. Glacier retreat during the 2000-09 period appears to be controlled by temperature increase, since precipitation increase over this period did not offset ice losses to surface melting.

Changes in Glacier Volume in the North Bank of the Bangong Co Basin from 1968 to 2007 Based on Historical Topographic Maps, SRTM, and ASTER Stereo Images

Abstract Heterogeneous mass wastage has been found across the northwestern Tibet Plateau, and both slight positive and negative average mass budgets were observed using different data sets during the past decades. The north bank of the Bangong Co Basin partly covers the Western Kunlun Mountains and Karakoram Mountains. The assessment of glacier mass budget in this region over a long period is of particular interest to understanding the regional diversity of the mass changes of glaciers. Changes in glacier mass in the area of concern were assessed by differentiation of digital elevation models (DEMs) from the earliest available topographic maps, the Shuttle Radar Terrain Mission (SRTM), and the Advanced Space-borne Thermal Emission and Reflection Radiometer (ASTER) stereo images. Results show that glaciers in this basin have in general experienced a decelerated mass loss but with regional differences. Glaciers were found to have lost a volume of 4.45 ± 0.63 km3 from 1968 to 2007, corresponding to -0.18 ± 0.03 m a-1 water equivalent (w.e.) in the north bank of the Bangong Co Basin. Loss of glacier mass in this region from 1999 to 2007 was 0.11 ± 0.12 m w.e. a-1, which was approximately half the loss that occurred from 1968 to 1999 (-0.20 ± 0.01 m w.e. a-1). From 1968 to 1999, higher mass losses were found in the north with smaller losses in the south, while from 1999 to 2007 there was more loss of mass in the southeast and a somewhat balanced mass budget in the northeast.

Recent glacier and glacial lake changes and their interactions in the Bugyai Kangri, southeast Tibet

Abstract Glaciers in the Bugyai Kangri are located in a transition zone from southeast Tibet, where monsoonal temperate glaciers dominate, to inner Tibet, where continental glaciers dominate. Here we analyze glacier and glacial lake changes in this region using multi-year inventories based on Landsat images from 1981–2013. Results show that the total area of 141 glaciers in the region decreased by 30.44 ±0.89 km2 from 198.35 ±9.54 km2 (1980s) to 167.93 ±4.52 km2 (2010s). The annual area shrinkage rate (–0.48% a–1) is lower than that reported for southeastern Tibet but higher than that of inner Tibet. Both the number and total area of glacial lakes increased between 1981 and 2013. Among all lakes, proglacial lakes contribute most (~81 %) to the expansion. The total area of ten proglacial lakes increased by 150.3 ± 13.17% and of these ten lakes the four that expanded most sharply showed increased calving at their upper margins, resulting in more rapid retreat of lake-terminating glaciers than land-terminating glaciers. Owing to rapid calving, several lakes may undergo further growth in the near future, increasing the potential risk of glacial lake outburst floods.

Glacier changes since the early 1960s, eastern Pamir, China

Glaciers in the eastern Pamir are important for water resources and the social and economic development of the region. In the last 50 years, these glaciers have shrunk and lost ice mass due to climate change. In order to understand recent glacier dynamics in the region, a new inventory was compiled from Landsat TM/ETM+ images acquired in 2009, free of clouds and with minimal snow cover on the glacierized mountains. The first glacier inventory of the area was also updated by digitizing glacier outlines from topographical maps that had been modified and verified using aerial photographs. Total glacier area decreased by 10.8%±1.1%, mainly attributed to an increase in air temperature, although precipitation, glacier size and topographic features also combined to affect the general shrinkage of the glaciers. The 19.3-21.4 km3 estimated glacier mass loss has contributed to an increase in river runoff and water resources.

Glacier change in the western Nyainqentanglha Range, Tibetan Plateau using historical maps and Landsat imagery: 1970-2014

Glaciers in the western Nyainqentanglha Range are an important source of water for social and economic development. Changes in their area were derived from two Chinese glacier inventories; one from the 1970 1:50,000 scale Chinese Topographic Maps series and the other from Landsat TM/ETM+ images acquired in 2009. Analyses also included boundaries from 2000 and 2014 Landsat TM/ETM+ images. A continuing and accelerating shrinkage of glaciers occurred here from 1970 to 2014, with glacier area decreasing by 244.38 ± 29.48 km2 (27.4% ± 3.3%) or 0.62% ± 0.08% a–1. While this is consistent with a changing climate, local topographic parameters, such as altitude, slope, aspect and debris cover, are also important influences. Recession is manifested by a rise in the elevation of the glacier terminus. The shrinkage of glaciers with NE, N and NW orientations exceeded that of other aspects, and glaciers with SE and S orientations experienced less shrinkage. Changes in the average positive difference of glaciation (PDG) show that the western Nyainqentanglha Range has unfavorable conditions for glacier maintenance which is being exacerbated by a warming climate since 1970.

Glacier Changes in the Lancang River Basin, China, between 1968–1975 and 2005–2010

Abstract The Lancang River Basin (LRB) crosses from the higher inland Tibet Plateau to lower south Asia. Glaciers in upper reaches of the basin are significant reservoirs of freshwater and are considered to contribute substantially to the runoff of the Lancang River. In this study, we present the results of glacier inventories of the LRB and demonstrate its changes during the past 40 years, based on investigations conducted during two periods: the first (1968–1975) and the second (2005–2010) glacier inventory of China. Total area of the 423 measured glaciers in the LRB decreased by 98.50 ± 26.61 km2 from 328.16 ± 20.29 km2 in 1968–1975 to 229.66 ± 16.48 km2 in 2005–2010, indicating a loss in total glacier area of about 30% ± 8% during the past 40 years (at a mean area loss rate of 0.75% ± 0.2% a-1), which is comparable to glacier changes in other regions of high Asia. Southern glaciers in the LRB have experienced greater area loss than the northern inland Tibet regions, indicating more sensitivity of temperate glaciers to climate warming. The general warming trend but with less significant precipitation changes during the past 50 years (1960–2010), which has been confirmed by the observation of several meteorological stations across from the south to the north of the basin, could be one of the main causes accounting for the overall glacier recessions in the LRB.

Glaciers in China and Their Variations

This chapter summarizes recent glacier variations in China as investigated using remote-sensing methods. We find that glaciers in China have lost a tremendous amount of ice mass since the Little Ice Age maximum: area and ice volume have decreased by 26.7 and 24.5 % of the respective amounts of glaciers based on maps compiled during the late 1950s and 1980s. Chinese Glaciers have been in a general state of mass loss during recent decades as monitored by satellite remote-sensing methods over glaciers totaling one fifth of the glacier area in China. At present, the ability to monitor ice volume change and the surface velocity of glaciers by satellite is relatively new, but shows potential for glaciers having complex topographical conditions in the high mountains. This is an important research focus, in part because Chinese economic development is locally heavily impacted by changes in the glacier dynamical regime due to (1) glaciers’ role in supplying meltwater to most of the region and (2) potential for local glaciological hazards.