Gauligletscher drains into the Aare River in the Bernese Oberland of Switzlerand. The glacier is in the next valley north or the Oberaar Glacier, that is also retreating and important to hydropower. The Aare River is both has a complex scheme for generating hydropower and a simple system of run of river power stations
Alpiq Hydro Aare AG manages the Flumenthal, Ruppoldingen and Gösgen which use the power of the River Aare to generate 90 MW of electricity, without using significant reservoirs or altering flow. Kraftwerke Oberhasli (KWO) from the 1930’s through 1979 built a constellation of power plants, seven hydro dams, a natural lake and around 130 km of water carrying pipes. The total output of the KWO system is 1100 MW, equivalent of a large nuclear plant. This network supplies 7% of the hydropower for Switzerland. The glacier has been in rapid retreat since 2000, with the Swiss Glacier Monitoring Network identifying a retreat of 246 m from 1958-1990, 132 m from 1990-2000 and 864 m from 2000-2013.
KWO hydropower scheme for Aare River.
Google Earth 2007 image showing new lake that the glacier is calving icebergs in.
Here we use Landsat satellite imagery to examine the retreat, the formation of a new lake and the retreat from that lake during the 1990-2013 period. The Glaciers Online site has excellent images of the retreat of this glacier during the lake formation phase from Jürg Alean and Michael Hambrey. In each Landsat image Point A-D are fixed to provide a comparison of terminus change. In 1990 there is no lake at the terminus of the glacier, the terminus has a low slope ending at 2170 m. By 1999 a tiny lake can be seen forming at the northern side of the terminus as the glacier has retreated into a basin. By 2002 there are two small lakes at the north and south corner of the terminus. In 2007 the lake has coalesced into one lake that is 500 m wide and has a length of 600 m on the northern and southern margins and 250 m long in the middle, where ice is still calving into the lake as seen in the Google Earth image above. By 2013 the glacier has retreated out of the 800 m long lake, and terminates 100-150 m from the lake shore. The terminus in 2013 is approaching the base of a steeper slope with more crevassing. This region has thinned both in width, depth and has lost crevassing. The retreat will slow as the glacier retreats up the slope, but is not near an end.
Landsat image 1990
Landsat image 1999
Landsat image 2002
Landsat image 2007
Landsat image 2013
The Oberaar Glacier at the headwaters of the Aare River is one of the key glaciers whose runoff feeds the complex hydropower system built by Kraftwerke Oberhasli (KWO) from the 1930’s thorugh 1979. The Glacier ended in the artificial lake Oberaarsee created by damming the glacier outflow in 1932. Oberaarsee (O) is dominantly a glacier fed reservoir, which is evident in this 2002 image from Jürg Alean This dam is close to two other largely glacier fed reservoirs Grimselsee (G) and Raterichsbodensee (R). The upper watershed of the Aare provides ideal natural conditions for hydropower generation, abundant water, deep broad glacial valleys for water storage and a 1700 m elevation drop from the Oberaarsee down to Innertkirchen. KWO’s constellation of power plants, seven hydro dams, a natural lake and around 130km of water carrying pipes was completed only in 1979. The total output of the KWO system is 1100MW, equivalent of a large nuclear plant. The network that supplies 7% of the hydropower for Switzerland is fascinating as seen in the schematic below from KWO.
Oberaar Glacier has retreated 1500 meters since the building of the dam and now no longer reaches the shores of Oberaarsee. The glacier from 1953-1967 retreated at a rate of 42 meters per year, calving into the lake with the average depth of 17 meters. The presence of the lake enhanced retreat, the glacier velocity was 8 meters per year, while calving retreat was 42 meters per year. The lake did not cause the retreat though, as Gauligletscher the next glacier to the north has experienced a large retreat since 2000. The Swiss Glacier Commission’s retreat history indicate that by the 1970’s the glacier was in shallow water near the edge of the lake and retreat was minor. More recently though the lake is no longer enhancing retreat, the retreat rate has again risen to more than 20 meters per year from 1998-2010. The glacier has retreated 460 meters from the edge of Oberaarsee. By 2013 Landsat imagery indicates the glacier has retreated approximately 1 km from the lake, black arrow indicates terminus and red arrow the end of the stagnant zone. . The Swiss Glacier Commission monitored the glacier surface and found the lower section of the glacier below 2700 meters, thinned by 7.3 meters from 2001-2005 representing a volume loss of 13.5 million cubic meters. Given that lower glacier thickness averages somewhere close to 75-100 meters, this was 7-10% of the glacier lost in four years. Compared to the 1960’s the glacier near the terminus has slowed from 8 to 4 meters per year. It is evident that terminus tongue is thin nearly stagnant moving at 2 meters per year in 2005. The glacier thinning is rapid which is also indicated by the degree to which the lateral margin of the glacier is higher due to the higher debris cover. This occurs only during periods of rapid retreat. The retreat will continue due to the recent snow line rise that has reduced the area of the accumulation zone. The glacier has an icefall at 2800 meters and and above this at 3050 meters is a significant consistent accumulation zone; however not large enough to maintain the large lower elevation glacier tongue. This is similar to all Swiss Glaciers, the average mass balance from 2000-2010 has been consistently and substantially negative as reported to the WGMS, -0.8 meters per year. This has led to retreat of 98% of all glaciers in the Alps such as Maladeta, Italyand Ochsentaler in Austria. The Swiss have the best annual terminus survey system and the graph at bottom indicates the percent retreating in red, advancing in blue, and stationary in green. It is clearly a red tide. With glacier area loss the summer melt will decline and summer inflow to Oberaarsee will decline. The total annual inflow is determined by annual precipitation and is not changed by loss of glacier area. This decline in natural glacier storage is one reason KWO is contemplating expanding the reservoir storage of Grimselsee.
Sara Umaga Glacier drains into the Beas River in the Himachal Pradesh region of India. The glacier has retreated over 1600 meters since initial 1970. The glacier is also a key water source for hydropower, this will be detailed below. The glacier is 15 km long extending from 5600 m to 3900 m. The glacier has retreated at a rate of 44 meters/year from 1989-2004 (Kulkarni, 2005). The glacier is adjacent to the Chota Shingri Glacier which has retreated at a rate of 7 m/year from 1970-1989 and 27 m/year from 1990-2000. The retreat is the result of the rise of the equilibrium line, approximately the snowline at the end of the summer, where ablation equals accumulation. In the late 1980’s the snowline averaged 4700 m. In recent years the snowline has been a high as 5180 meters (Wagnon et al., 2007). This same rise has led to high snowlines on the Sara Umaga Glacier. In recent satellite images the snowline is above 4900 m, and the snowline is below where the ELA will be at the end of the melt season. The snowline and the head of the glacier are noted in the image below. This leaves only 20 % of the length of the glacier in the accumulation zone. In terms of area 25-30% of the area of the glacier has been above the current ELA. For a glacier to be in equilibrium at least 50% of the glacier must be in the accumulation zone. The Sara Umaga is retreating as it cannot sustain the large lower elevation ablation area. Retreat has revealed two vegetation trimlines. The older is a Little Ice Age trimline-the former the trimline is from the 1950-1970 period. This is an attempt to restore equilibrium. An examination of the heavily debris covered ablation zone indicates that the lowest 2.25 km of the glacier is stagnant and will melt away. The end of the stagnant zone is indicated by the green arrow and the change in thickness to the Little Ice Age lateral moraine by the brown arrow and the current terminus by the pink arrow.
. The lower section of the glacier is heavily debris covered which reduces melt rates. There is no apparent crevassing or convex shape to the glacier cross profile in the lower 2.25 km indicating stagnation. The debris covered section is not sensitive to soot deposition, as it is already sufficiently dark. The Glacier drains into the Beas River, which flows first through the Larji Hydropower project, which alters streamflow often leaving the stream below nearly dry. The Beas River is then impounded by the Pandoh Dam-and lake, third image below, which diverts water through a tunnel into the Saltuj (Sutlej) River, fourthimage, and thence the Bakrhra Dam at 1200 MW hydropower project. The tunnel from Pandoh is the largest tunneling project in Inida 13 km with a diameter of 8 m.
Larji Hydropower looking upstream to reservoir and beyond. Notice the influence of the dam on the river which is nearly dry below the dam on the date of the imagery near Markanada Temple.
Colonial Glacier is on the southwest side of Colonial Peak in the Skagit River Watershed, North Cascades of Washington. The North Cascade Glacier Climate Project has made six visits to this glacier over the last 25 years. Meltwater from this glacier enters Diablo Lake above Diablo Dam and then flows through Gorge Lake and Gorge Dam. These two Seattle City Light hydropower projects yield 360 MW of power. As this glacier shrinks the amount of runoff it provides during the summer for hydropower is reduced. In 1979 the glacier was clearly thinning, having a concave shape in the lower cirque, but still filled its cirque, there is no evidence of a lake in this image from Austin Post (USGS). The glacier had retreated 80 meters since 1955. In 1985 my first visit to the glacier there was no lake at the terminus. In 1991 the lake had begun to form, second image, but was less than 30 m across. The upper glacier was a smooth expanse of snow. By 1996 the lake was evident, and was 75 meters long. In 2001 the lake had expanded to a length of 125 meters. By 2006 the lake was 215 m in length, and had some thin icebergs broken off from the glacier front. Runoff to the Skagit River is impacted directly by the climate change and the resultant retreat of the glaciers. Three notable changes in North Cascade streamflow have occurred.
1) Alpine runoff throughout the North Cascades is increasing in the winter (Nov.-Mar.), as more frequent rain on snow events enhance melting and reduce snow storage Streamflow has risen 18% in Newhalem Creek and 19% in Thunder Creek despite only a slight decrease, 1% in winter precipitation at Diablo Dam, within 5 km of both basins. These basins are on either side of Colonial Glacier.
2)Spring runoff (April-June) has increased in both basins by 5-10% due to earlier alpine snowpack melting.
3)Summer runoff has decreased markedly, 27%, in the non-glacier Newhalem basin with the earlier melt of reduced winter snowpack. In Thunder basin runoff has in contrast increased negligibly, 4%. The difference is accounted for in part by enhanced glacier melting. The observed net loss of -0.52 meters per year in glacier mass spread over the melt season is equivalent to 2.45 cubic meters per second in Thunder Basin, 10% of the mean summer streamflow. This trend of enhanced summer streamflow by reduction in glacier volume will not continue as the extent of glaciers continues to decline.
The lower portion of Colonial Glacier is not moving. GPS readings on both rockpiles on the lower glacier indicated no movement from 1996-2006. In the picture above the lake is still small in 1996, lower right corner and the lower rock pile distant from the terminus. The first two images below are from 2006, the lower rock pile is near the terminus and the last image is 2007 the lake has expanded back to the lower rockpile. Additional rock outcrops have appeared in the midst of the upper glacier that were not present in 1991, indicating this glacier does not have a persistent accumulation zone and will not survive current climate.
In India the Gangotri Glacier is the largest glacier at the headwaters of the Bhagirathi River. The false-color image below provided by NASA shows the retreat of Gangotri Glacier, situated in the Uttarkashi District of Garhwal Himalaya. It is one of the larger glaciers in the Himalaya, and like all of the nearby Himalayan glaciers is retreating significantly. The Bharigrathi River has the Tehri Dam, a 2400 mw hydropower facility. With an area of 286 square kilometers Gangotri Glacier (Singh and others, 2006) provides up to 190 cubic meters per second of runoff for this river. Gangotri Glacier provides hydropower as it passes three hydropower plants generating 1430 MW, including the 1000 MW Tehri Dam and reservoir and maneri Bhali I and II, see map below. The Tehri also provides flood control, such as this past week of June 17, 2013. The Tehri Reservoir level rose 25 m within 48 hours which is a storage of approximately 1.3 billion cubic meters. Below is a view of the Tehri Reservoir, images of the dam and its operations are here.
Map from the Southeast Asian Network on Dams, Rivers and People
Gangotri Glacier retreated 26.5 meters per year form 1935-1971. From 1968-2006 the glacier retreated 800 meters, close to 20 meters per year (Bhambri et al, 2012). Srivastava et al (2013) indicate the retreat rate of 21 m/ year from 2004-2010. The glacier continues to thin and tributary inflow decline, while the thick heavily insulated by debris terminus retreat is slow. Srivastava (2012) published a report with numerous terminus pictures though they do not have a common reference point beginning on page 90. Where the river exits the glacier is referred to as Gomukh.
Here we compare both Landsat and Google Earth images during the 2000-2013 period. First the 2000 and 2013 Landsat images. A 2000 and 2013 landsat image pinpoint the terminus change, the yellow and red arrows converge on the 2000 location of Gomukh. The blue arrow indicates the mouth of a side valley from the east that is at the terminus in 2013 and actively cutting the face, which is not the case in 2000. The orange dots indicate the course of this stream. A 2006 Cartosat image from Bhambri et al (2012) can be compared to the 2010 and 2013 Google Earth images. In Google Earth the 2010 image gives a clear view of Gomukh which can be compared to the 2006 Cartosat image from Bhambri et al (2012). In 2000 and even 2006 this was not the case. A 2013 Google earth also indicates this point,with the glacier having retreated to the side valley from the east. The retreat from the location of Gomukh in 2000 to 2013 is 240-270 m, approximately 20 m per year as noted by Srivastava et al (2013) for a shorter interval.
2000 Landsat image
2013 Landsat image
2006 Cartosat image
2010 Google Earth image
2013 Google Earth image
2013 Google Earth image
This glaciers remains over 30 km long, and is not in danger of disappearing anytime soon. The lower section of the glacier is heavily debris covered, which slows melting. The debris cover prevents black carbon-soot from enhancing melt over most of the ablation zone. The upper reaches of the glacier extends above 6000 meters and remains snow covered even during the summer melt season June-August, as this is also a main accumulation season due to the summer monsoon. This is different from other alpine regions, where the melt season is also the dry season, here it coincides with the wet season and the accumulation season on the upper glacier. Compare the differences in hydrographs from Thayyen and Gergen (2009) Figure 3 and 4. The new snowcover on the upper glacier also limits the impact of black carbon or soot on ablation. The glacier is fed from avalanches off of the even larger area of mountains above 6000 meters adjacent to it. This is one of many glacier in the Himalaya that is being tapped for hydropower. The retreat is slower than that of nearby Malana Glacier and Samudra Tupa Glacier but similar to Durung Drung Glacier.