[Music] he [Music] [Applause] [Music] yeah it's a pleasure to give the talk here today um it will be rather broad overview talk because uh yeah I found it hard to to judge exactly the audience I was talking to um so the the title of my talk is the recent advances and future challenges in in understanding Asia's water tower so what I want to do is uh yeah of course there has been a very strong focus on on Glacier research so I would like to start with A Brief Review about that and then um also place the importance of glaciers in a more broader hydrological context and um at the end of the talk I also would like to uh you know just show you a few thoughts and images uh regarding the recent disaster in in utraan just a few slides of uh yeah of of the recent understanding of what happened during that event yeah so first a little bit about about the context you know we've all been been working on climate change issues during uh during the last last 20 years and I think things have changed um very rapidly in how we have how we are perceiving climate change so you know even already in in in 1912 uh it was it was quite clear that carbon dioxide was changing uh the climate on the globe and you can see that here on the left side this paper I think this is a New Zealand paper from New Zealand in 1912 uh where they already noted that you know the furnaces of the world are burning about two billion tons of coal each years and that that the amount of associated carbon dioxide you know had had the potential to raise the temperature on Earth so that was already known in 1912 and then when you look at at the right side you see an uh an an advertisement of uh Oil Company humble and ESO where they and this I think this is a newspaper somewhere in the 1960 60s where they proudly announced that the amount of oil that they produce every day has the capacity to melt 7 million tons of Glacier so I mean these kind of aters are nowadays unimaginable so that really means that climate change is is high on the political agendas and in the minds of people and I think science has played a very critical role in this so now let's go back a bit to the region um yeah I think most of you are are aware of the region it's a highly diverse region so it's it's very difficult to to generalize anything if you talk about this region so of course we have many different mountain ranges so we have the Himalayas the Tibetan Plateau the kunun Shan the karakoram the pamir the Hindu Kush and they all have very distinct ly different climates and they also respond different to climate change um we have a huge amount of glazes in this region um and also a lot of Perma Frost and in particularly the you know the research into the impacts of permafrost on the hydrological cycle is still in its infancy I would say in this in this particular region um then you know this this cryosphere feeds uh the huge river systems um that that have their origin in the mountains in in high mountain Asia and if you start at the at the West you know that we have the the Saria and the Amaria and they end up in the RLC they huge irrigation systems here that have initially started during the the Soviet era then we have of course the Indus and the ganis the Indus is the largest continuous irrigation system in the world and the ganis the brahmaputra the iradi the salvin makong yanga and Yellow River so these are all huge river systems and if you add up all the people that live in the river basins of of all of those Rivers it's about 25% of the global population so that doesn't mean that all of those people directly depend on on on glacial meltwater or on water from the mountains but it it does show that it is really important to understand climate change impacts in those water towers of the world um then of course here you can also see the the different countries and it it is also a geopolitically a very complex region um there are many transboundary rivers where water is shared between countries and U there are lot of lot of conflicts between upstream and downstream countries regarding you know Hydro power or water to be used for irrigation um then let's put this also a little bit in the global um context yugan already mentioned it in the introduction this is a research that we did last year and it was funded by National Geographic so National Geographic U together with Rolex they they had this this year of the mountains so on the one hand they organized the you know the highest Expedition meteorological expedition to to Mount Everest where they installed a number of weather stations up to an altitude of 8,000 meter and yeah they they funded all kinds of of more small scale research projects in the Everest region but in parallel they also ask us to uh to do a global assessment of uh of mountain regions and and uh you know uh indicate where mountains matter matter most so what we did is we we designed this water tower index and we said you know mountains are are very important if there is logically abundant Water Resources in the mountains itself so this can be glaciers or snow or rain or um Open Water um but there must also be a lot of demand for that water in the downstream regions um and that water there there must be no opportunities of that water to be delivered from the downstream regions themselves so if you have this uh you know a high Supply index so a lot of water in the mountains in combination with a high demand that cannot be supplied in the downstream regions itself then we consider a mountain range to be uh very important so in this way we kind of ranked all water towers based on a huge amount of globally available data sets we ranked all water towers in the world and you can see I won't go into all the details here but what you can see here is that for the different continents on the left side you can see the supply index um so that that says something about the amount of water resources that you find in the mountains itself and on the right you find the demand index so we look at different types of Demands the let's say the environmental flow uh the industrial water demand the domestic water demand and the irrigation water demand so what you see that there is a lot of variation so there are for example water towers or mountain regions that score very high in the supply index for example the Tibetan Plateau so there's a lot of Open Water there there's a lot of glaciers there um but there if you look at the demand side then you can see that the Tibetan Plateau scores um yeah in the demand side you can see that it's that the Tibetan Plateau has hardly any demand because the the population density there is very low so there's no demand for it so but if you look for example at the IND this Basin you can see it scores quite high on the supply side but it also scores high on the demand s side so this is an example of a water tower where where mountains are really really important so that is kind of the approach that we that we took in this study so now if you take look at the global picture so here you see the final water tower index in colors so the Bluer it gets the more important a water tower is and what we basically concluded that all of the key water towers in the world are found in uh high mountain Asia so and of particular importance then are the Indus the Amaria and the tarim because those are all areas where you have a lot of glaciers and Water Resources in the high mountains the downstream climates are Aid and there is a lot of demand for that water and in addition this is also a region where population is growing very rapidly in the future so these are also the areas which are very vulnerable so we also did this this vulnerability assessment so for all of those water towers we looked at different indicators of vulnerability uh we looked at a number of static indicators such as you know the hydropolitical tension um uh the Govern governmental Effectiveness um the the the the current water stress and then we also looked at the number at a number of more more Dynamic vulnerability indicators so how quick is the economy going to grow over the next uh couple of decades and how is the climate going to change and what we found is that the most important water towers in the world are also the most vulnerable ones so that was the key conclusion and and high mountain Asia is really Hotpot in this this regard yeah so far for the broad context then I would like to zoom a little bit in uh on the role of glaciers and the state of Glacier research in in high mountain Asia um I think the the the Visual Evidence that we have that things are changing rapidly um in the Himalaya or in any mountain range in in high mountain Asia is quite overwhelming um I often show this picture this is a picture taken by George mallery in 1921 um it was never clear whether George mallery actually was was the first to Summit Mount Everest because his body was found I think in 1924 but uh about 100 meters below the summit so people never knew whether he was on his way up or on his way down but at least he left us this this picture and this is on the north side of Mount Everest the Rong buo glacia and this is exactly the same picture in 2007 and there there's been obviously a lot of changes this picture has been taken also by a famous climber David brers and you can see here that this Glacier down wasted about more than 100 meters which is higher than the than the D Tower in the in the city of UT where I live and there are plenty of examples of this this is an example of the research Sketchman where we do a lot of research so this is in langtang um this is north of kandu um and what you can see here is is lon Glacier so on the left you see a picture taken by Tony Hagen in 1952 was a famous explorer and one of the first to uh to explore the Himalayas and on the right hand side you you see a picture taken by yob Steiner and with myself on the on the foreground and in the distance you see the Lum Glacier so you can see that now on the right hand side it's more like a like an empty bath top and all the IES disappeared while in 1952 um the the de cover Glacier was still filled to the rim of of the lateral Marines so it's clear that there are a lot of changes so this is another example again of Lon Glacier we recently found those those really old pictures so this is a picture from Arn Sneider from the 1970s so many of the maps in Nepal are famous Schneider Maps which are based on the photogrametry of that that he did back then so this is another example of you can can what you can see here is that um you know the ice that comes from the accumulation zone is still connected to the glacier Tong and if you look now you there's a big rock band in between and the and the glacier Tong actually gets gets no more nourishment from uh from Ice from high up so if we if you look at at the region as a whole how many Glaciers are there and uh and how does that relate to the to the global picture so this is a a paper by Danielle farinotti from 2019 published in nature geoscience so it shows that there are about uh about 95,000 glaciers in Asia about with an area about 100,000 square kilometer and uh a volume of of around 7,000 cubic kilometers so that is if you look at all the mountain glaciers in the world that is about 4% of the total ice volume so that may not sound large but uh yeah the big difference with all with many of the other regions is that this is a region which is very densely populated of course so a little history about the glacier research uh in the Himalayas I I think this really took off in uh yeah basically in in by the end of 2 2007 um the ipcc fourth assessment report was was published and in that report there were a number of very big errors so the the first error was that it was stated that glaciers in the Himalayas are receding faster than in any part of the world which which was not true because we we later saw that the glaciers in the Himalayas they they are they more or less response at an average rate compared to all the mountain ranges in the world and the biggest thing was that it was also stated that the likelihood of them disappearing by the year 2035 and perhaps sooner is very high if the Earth keeps warming at its current rate and its total area will shrink from 500,000 to 100,000 square kilometer by the year 2035 well that was obviously a very big error because the glaciers will not disappear by 2035 and um you know the the glacier extent was only around 100,000 square kilometer already in 2007 so what this illustrates is basically that these conclusions that made it to the ipcc report were based on on Gray literature and at the time there was hardly any research available about any peer review research available about about glaciers in in the Himalaya or hydrology so um this error also caused the you know the big problems for the ipcc it almost led to the uh the the chairman who resigned and it it also caused a lot of debate but the good thing was that it also generated a lot of funding for Himalayan research which I think we all have benefited from in the last in the last decade um yeah so these were some of the new stories that that happened after uh the publication of that IPC series report so the real story behind it was called Glacier gate Glacier estimates on thin ice um it also made it to to to to Dutch newspapers and to newspapers all over the world yeah so then there was also this this letter published by grae Graeme gley and and Jeff Cel and G kazer and case f f and they tried to to track the source of this this big error that was taken and they found that it it came from Gray literature published in WWF report and um yeah so so that that actually shows how important the role is that we have as scientist and to make sure that whatever we do is reproducible and published in in good journals luckily since then uh the amount of the amount of knowledge and peer-reviewed studies on glaciers has increased tremendously and it's unimaginable what we know now relative to about 10 or 15 years ago so let's first look at the mass balances so you probably all know what a glacier mass balance is it's the difference between the accumulation and the ablation and it tells you in what state a glacier is so this is kind of the the latest state-ofthe-art it's a study by David Sheen published in 2020 in frontiers of earth science and he uh yeah he combined a huge amount of digital elevation DMS Bas based on world viw a satellite imagery combined with AER U imagery and based on that he he quite accurately derived m balances and you see that here aggregated in uh cells of 55 by 55 hexagonal cells and you can see a very clear pattern that along everywhere along the southern Arc we see a strong negative Mass balances in the order of uh of 40 cm of water equivalent per year and we also see a very interesting place around the karakoram and the Western kunun Shan where glaciers seem to be gaining mass or yeah yeah at least are stable so that's also very interesting and I'll I'll come back to that later in the talk another another Benchmark study in this respect is the study byui the heck published in 2017 and uh what he did he tried to uh to analyze the flow velocity of glaciers and that's also very interesting because the patterns match very well with the mass balance patterns so what you see that all along the Himalayan arc on the southern part you see that Glaciers are slowing down between 2000 and 2017 but again in that area around the karakorum and the Western kunun Shan the Glaciers are accelerating so that is very clear that those signals M are matching so uh but this this DM all these these kind of studies are based on on on DMS and DM differencing and there have been been several Benchmark studies in this field and I've I've tried to to summarize them here so this all St by the study with Andy Cape who combined isot with srtm um and then there was Alex Gardner Julie Gardell Andy Cape did an update of his previous study then funny Brun who based it all on AER DMS and then the last study of David Sheen that I showed so what you can see is that there's quite the the numbers in red are the the average mass balance of whole high mountain Asia and there you can even for the entire region you can see there's still quite a lot of variation between the different studies and this is uh there are different reasons for this variation a key problem was of course for those studies that have used srtm is that that that's a basically a radar signal and the penetration of the radar into the ice is quite uncertain so that is one reason why there is seems to be a systematic error for those studies that have used the srtm as a as a reference DM but uh you you can see that slowly we are converging and if if you look now we are about for the whole high mountain Asia we have an average mass loss annually of about 0.2 meters of water equivalent per year um then a lot of lot of people and a lot of Studies have also been devoted to understanding this Korum anomaly or that you know that that one area that I just showed where the Glaciers are stable or seem to be gaining in Mass so what what we did last year uh did a kind of a a review study of you know what what are now the manifestations and mechanisms that cause this anomalous Glacier behavior in this in this region um but was interesting that that kenu it was one of the first who already uh detected that that Glaciers are are behaving anomalously in the Korum already in 2005 um he noted this so what we did in the review is yeah we looked at at different kinds of reasons what could potentially lead to this anomalous Glacier Evolution so on the one hand there are studies that say well it's it's all uh it is related to climate change and changes in large scale atmospheric forcing so the monsoon could be weakening or the position of the Westerly jet can shift to the north which draws uh you know colder air into the carac Corum which which in the summer which could be a reason we have been working ourselves uh in our group a lot on on the role of increased Irrigation in the region so I'll say a little bit more about that and how that perturbs the regional climate and as a result causes extra snowfall in the mountains um then the Korum also has very specific Glacier Properties so uh many many of the glaciers there are fed by avales with very steep accumulation areas and very very long and elongated Glacier tongs which is is distin different from what we find in the in the in the for example in the Himalayan Arc and the climate by itself is already different so in the Himalayas it's a monsoon climate so 80% of the precipitation Falls between June and August while when you go to the Korum and the Chan there is there is also a very strong precipitation contribution during winter so all of these processes together shape how the how the Glaciers are responding and have been responding in the past then a little bit about this irri hypothesis that we have been working on um this is work by Remco deok who was a postdoc in my group so our our hypothesis was that you know in particularly in the tarim Basin but also in the in the Indus and in the southern part there has been very strong increases in in irrigation and irrigated areas so in the tarim there has been a lot of uh groundwater pumping in the desert and a lot of green areas have popped up there so obviously all that water that comes from the groundwater is evaporated it um gets into the atmosphere and and changes the regional climate um so our hypothesis was that because uh of the fact that you get that additional moisture in the atmosphere that can potentially lead to more uh snowfall and more clouds in the mountains so more snowfall of course adds adds snow and ice to the glaciers and more clouds protects uh yeah causes less incoming shortwave radiation so that that that's a double effect which would favor Glacier Mass growth so here you can see an example of U of The Greening pattern in uh in high mountain Asia so these are ndvi Trends between 2000 and 2010 um so you can very clearly see particularly in the tarim Basin um that that there's a lot of irrigation uh areas there and we also used a moisture tracking model to to assess if that extra moisture in the atmosphere will also actually end up in the mountains so then we did some some model experiments with the with a weather model uh a Warf weather model and we um yeah what we did is we looked at uh the the role of irrigation and uh of course that has a temperature effect but also a precipitation effect and basically the main conclusion is if you include both that temperature and precipitation effect of additional irrigation then the simulated mass balance so we coupled this to a glacier model the simulated Mass balances they match quite well with the with the observe pattern so you do indeed see that in the karakoram and the Western kunun Shan there is an increase uh in mass balance yeah so this is this is more the very large scale patterns in in glacial response but U I also came to realize more and more in the last uh 10 years that if you really want to understand how the system works you also have to to look at the really small scale um and what we yeah we did a lot of research also with uh with drones and uavs and in particularly we looked at De covered glaciers because uh they are a particular feature of Himalayan glaciers and many of the tongs are covered in a thick layer of debris you can see a a picture here um the surface is very variable so we have ice Cliffs Lakes there is this debris on on top of the glacier so all of those things of course they have a big influence on how fast the glaciers melt so according to the theory um a very thin layer of debris and you see that on the plot on the bottom left very thin layer of debris actually accelerates the Melt because it darkens the surface so this is an albo effect it captures more shortwave radiation and it increases the Melt but very quickly when de layer gets more than 10 cmers or a few centimeters it's it it starts to insulate the ice from from melting so we tried to uh to investigate that with drones so we did a lot every half year we did drone flights over a number of Benchmark lases and we Tred to with those drones we can derive very detailed elevation models and a resolution of 20 cm or something and then when you subtract those elevation models between different time steps then um yeah you can can get a really detailed Insight in the in the in the spatial melt patterns so this is this is more the large scale what what what's the difference between the the de cover and the clean ice glaciers and what is interesting to note is that even though according to the theory the de cover Glaciers are supposed to melt at a at a less fast than the clean ice glacies and what you can see here is that they are even melting faster particularly during 2 and 2016 um so that is something that is that has been puzzling also so quite some scientists why are those de recovered glacies melting um as fast or maybe even faster than their clean clean I counterparts of course there are differences in elevations and you have to be careful in comparing it but this was quite a clear signal so what we what we saw with the Drone is um yeah this is an example of that very detailed elevation models that you you can generate you can really see all the details this is a this is a trend in the Melt over a period of uh I think over a period we started in 2013 and the last one was in 2018 so this is a melt pattern of that Lum Glacier so that's a same picture that I showed in the beginning uh these very old pictures so you can see that this pattern of melt is very variable so we see in general is red so this means that the tongue is losing mass but you can also see this this really big hot spots and even some areas where the yeah where we have a positive surface elevation change so what we found is that you know the those hotpots of melt those dark red places U sometimes the Melt there is is a factor 10 times higher as the average so on average it's about uh the glacier loses about uh 85 cm per year in thickness but in in some of those hot spots it can be a couple of meters or even up to 10 meters per year so we found that that those are areas where you have those ice Cliffs or those supr glal PS so these are they are really accelerators of mouth um uh that we find we also this is the Terminus of the glacier where we have a lot of exposed ice so it's quite interesting to see with this is all the different uh time steps that we have so we can really reconstruct how the whole uh terminal has has developed and withdrawn over the last uh last six years between 2013 and 2018 so you can see that it withdraw already in this case about 250 MERS in such a short period so we identified uh you know that those those glacial lakes and Ice Cliffs are important but then we we went even a step further because of course if you want to understand why there is so much much more melt at those ice Cliffs or lakes you have to understand the energy balance in detail uh for those places so it's a PhD student in my group and she worked with uh an Lees model and she modeled the turbulent fluxes in a a very high level of detail you can see here this is just a single ice Cliff where she has uh yeah and you can see here the potential temperature and you see how the heat is transported and how this cold ice cliff is being influenced also by edes that come from the opposite side on the right hand side you see also a spatial pattern of the of the net energy over the entire Glacier so you know when when you go um you know you if you really want to understand the fundamental processes you have to also go to these kinds of small scales so I think that's also so interesting about this kind of research you want to understand the general patterns but then you know when you zoom in and you zoom in and you Zo zoom in you find many interesting things at a very small scale as well so the last thing about glaciers which is really important I think is the uh uh that's also a lot of recent work is a lot of uh PR glacial lakes are developing in the Himalayas at the end of Glacier tongs and this is a this is a picture by Scott Watson I think it's uh the sopa uh Lake which is a famous Lake in in Nepal and this is uh the imja lake so what you can see is that there's a a lot of calving happening at the at the Terminus of this kind of glaciers and um yeah what you also see is that that glaciers which end up uh in a lake they are retreating much faster than than land terminating glaciers so the yeah it's clear that this carving plays a role but the exact mechanisms are are not really clear so this is work by Owen King and B and they looked at um at the difference between Lake terminating glaciers and land terminating glaciers for the whole region and so you see in the the orange lines are the lake terminating glaciers and the the black line is the the the green dotted line is the land terminating Glacier so you see that everywhere the lake terminating Glaciers are losing mass much faster than the land terminating glaciers so this is another key process in understanding the glacial response um now let's take a step back again to the to the whole region what what is going to happen in the future so there quite quite some studies uh have been published now so this is a study also that we did in our group that was published in nature in 2017 where we Tred to look at what what does the let's say the the the Paris agreement uh of 2015 where where all countries agree to try and limit the global warming to 1.5° what does that imply for the glaciers in Asia because that 1.5 degree is quite an arbitrary threshold so the first thing that we showed is if you know if the global warming is 1.5 degrees that means actually that in high mountain Asia the average warming is about 2.1 degrees so that that's a process called elevation dependent warming so it shows that you know the the high mountain Asia is even more sensitive to changes and that elevation dependent warming is also consistent in all RCP so if you go to more extreme scenarios you still see that the warming in mountains is stronger than the global average um yeah then just some quick results so what does that mean um let's say if if we are able to um constrain the global warming to 1.5 degrees that means we will still lose about 36% of the total Glacier mass by the end of the century that is what our our models showed us and if you go to more more realistic scenarios so RCP 4.5 or 6.0 it means that we will lose about 50% of the total ice volume by the end of the century so you can see this is quite a different conclusion than the ipcc report of 2007 which said that most of the glacies would have been gone by 2035 but still it's a pretty uh dramatic message then yeah as I said in the beginning you cannot generalize so here is is also the spatial patterns in in in change that that we modeled so um in the colors you see the temperature change uh so that's the pre-industrial minus the end of the century so what it does show is that the pamier the hindukush and the karakorum they show the strongest warming but there are other uh that's about 2.3 degrees and there are other regions where the warming is a bit less less less strong and then the pie charts they show the reduction in area under the 1.5 degre scenario so and then you have three different time slices 2040 20170 and 2100 and you can see um yeah how how the how the area is going to uh to retreat in the future there you also see quite some differences between the regions so in the for example in the Kilian Shan or Tibetan Plateau or Eastern Himalayas you see quite a strong reduction in area um but if you look in the Korum for example even though that warming there is the strongest you see that the area reduction is relatively small there's still 75% of the area left by the end of the century and that also has to do with the Glacier Properties so the glaciers in the Korum are huge Glacier tongs can be 30 or 4 40 km long and uh with 500 to 1,000 meter of of of thick ice so that just takes a a huge amount of time to respond to climate change and if you have smaller glaciers um the response time is much shorter so that's basically what you see here well I won't go into detail of this but these are the total projected ice volumes for all the different um uh mountain regions that we that we projected so in the the bottom right you can see the the differences for that's the total so for the entire region and um you can see the the black dotted line is the 1.5 degree uh projection and then uh in colors you see the projections of the different rcps so there's really a big difference uh between whether we are able to keep keep the global warming to 1.5 degree or whether we are going to to much more that has a very big impact on the total ice volumes yeah so so far the quite an overview of the glacier research in the region but let's go now uh to the hydrology um this was already a bit mentioned in the beginning so this is a paper we did already um more than uh 20 years ago now that was published in science and it was yeah also after that that ipcc report we actually thought well how important are the glaciers in the let's say in the greater scheme of things and the interesting thing was that no there's there's a lot of variation in how the how important the Glaciers are um if you look at the western part so what you what I show on the right is the the normalized Melt index which is a measure of how important melt water is in the overall hydrology so the main conclusion already then was in the Indus Glacier and snow melt are really important but if you go further to the east the Glaciers are not really important at least at the River Basin scale because there's so much Monsoon range which occur simultaneously with the Melt season that the contribution of glaciers Glacier melt to the overall River flow is relatively small so we also must keep that perspective so even though there has been a huge focus on Glacier research there are other parts of the hydrological cycle which are very critical as well so then there was a follow-up study by AR Luts in 2014 where we really tried to quantify the you know the spatial variation in meltwater contribution so this basically tells us the same story um in the three Maps you see the different contributions of glacial melt snow melt and Rain uh rainfall runoff and you can see if you are very far in the west high in the mountains in the koram glacier melt is very important um but if you look all along the Himalayan Arc you can see that you know the it's really the the rain contribution that drives the river flow um in the rivers um so this is a very recent review that came out in nature reviews by yungi at all and um that was also partly based on on our results and they looked also at the future runoff so in the top three plots you see for the upper indust Bas and upper ganji Basin and the upper brahmaputra Basin you see the different runoff projections so the gray bar is the uh total runoff under the current climate and then the PTR is the projected total runoff um you see the different colors so green is the base flow uh Pink is the rain runoff yellow is the snow melt and blue is the glacier melt so what you actually see is that for the future it looks it looks quite boring there's not in terms of average water availability not not much is going to change and it's getting a little bit wetter and that is a combination of you know an increase in glacial melt and an increase in precipitation that is projected by most most climate models so in terms of General water availability we we kind of concluded we don't have much to worry about over the next decades there will be plenty of water and most climate models predict an a stronger monsoon um so in you know on average the amount of water uh that comes down from the mountains will more or less stay the same or increase a little bit so in the bottom you see also the year of Glacier runoff Peak so this is the year when the glacier melt is contribution is largest um so that's also quite variable but you see it will take quite a lot of decades for most regions until we reach that point oh this is a bit uh yeah bit bit similar this is a Time series of the of the uh glacial runoff change that we find so you see that stays fairly constant for a long time and uh you know there are in the bottom that those are some results of the longt catchment of the the different contributions and how they change so what you can see between 2 and 2075 for this very small scale stud stud is that you know the the general pattern Remains the Same the glacial melt contribution is reducing in summer but the extra rainfall is compensating that um does that mean that there is no problem um or we we don't have to make adaptations I I don't think so there I think there are two two critical things that that may change in the future one is the seasonal shifts um one example of that I want I want to illustrate with this study uh of the upper indis Basin um so we did a detailed modeling study here and in those blue bars at the right side you see the change in projected runoff so that's a total runoff including all contributions and uh we've done that for several uh uh points where we also had runoff measurements in the Basin so you see those points on the on the right so what you generally see is that um in generally in general it gets wetter but in particularly in the second half of the century 2071 2100 you see a kind of attenuation of the river flow so the during the monsoon season the let's say the the runoff gets less and in the in the shoulder season there's there's much much more River flow so the snow melt comes earlier um there's less rain predicted in the in the in the summer season so those kinds of shifts we have to adapt to because of course U there are big agricultural areas Downstream that depend on water in specific months uh the other challenge is basically the increase in hydrological extremes so if Glaciers are retreating and perennial snow fields are reducing uh there's a a lot yeah the whole hydrological system changes so we get a lot more of exposed rock and uh the buffering role of the cryosphere disappears so the system basically accelerates and uh you know a drop of rain that falls ends up in the river faster than it used to be when it when it turned into snow ice became a glacier and slowly melted in periods when it's War when it was warm and there was no rain so this is a study by R vard um also for the Indus ganis and brahmaputra where he did a first order assessment of the potential changes in the peak runoff so what you see here is for the two climate scenarios the change in uh one 50 1 to 50 years um extreme runoff and you can see basically in particularly along the Himalayan Arc that you get a very strong increase in this peak flow and of course we all know and and this whole project is about that you know Peak flows and flooding um uh cause cause millions of Damages every year so the final part um what what we are also uh increasingly more interested in so on the one hand we have of course the physical changes uh in the system and climate change that changes you know the timing of water availability and that changes the peak flow but um maybe even a bigger water D bigger driver of of stress to the system can also be the socioeconomic developments so we started with this uh already a few years back and we C coupled our our physical models of the of the hydrological models from the mountains we coupled that to Agricultural and water demand models Downstream and what we try to to quantify is really how much of the irrigated agriculture really depends on snow and glacial melt water so we we yeah this this is one result from that that paper that was published in 2019 so in the the rivers are shown in colors and you can see there the mean annual contribution of snow and glacial M to discharge so that basically follows quite well of what I showed earlier so in the western part you see that that mwat has a very important contribution and in the in the eastern part it's much less and then in green you can see which yeah what you know how how much of the irrigation water supply actually comes from snow and Glacier melt so we track that water and we combine that with a yeah with with an advanced agricultural model Downstream to really try to attribute that and then again you see that in particularly the Indus is really a hot spot where a lot of the irrigation water comes directly from meltwater and that melt water is stored in a number of major reservoirs like tarella and mangala dams and they store that water and they Supply that huge irrigation system Downstream so if you look at the future I think uh there's this is again for for the three different basins um what we are going to see is a very steep population growth um which is projected for all three basins and we also see a very strong economic growth so people get richer and diets are changing uh people eat more calories per person um a lot more energy is required a lot more crop land is required so all of this together I think will will cause an exponential growth in the water demand in the future and that that that growth in in water demand I think is even a stronger impact than the climate changes that we are seeing so this is also recent work about where we try to um yet to estimate that water Demand by making detailed population projections we looked at different different scenarios uh you know where we looked at a scenario that focused purely on urbanization scenario that looked more from Highland to lowland migration and an scenario where we looked at south to North migration on the planes to avoid increasing heat stress so in all those cases we see a very rapid increase in in population and an Associated uh demand in water so the yeah the basically the takeaway point from my talk is I think we have had a lot of focus on Glacier research but we should also acknowledge that the the the full picture is much more complicated that we really have a lot of key unknowns in the mountain water cycle and of course everything is being driven by precipitation but still we know very little about precipitation at high altitude there are hardly any stations that measure precipitation or snowfall above three or 4,000 meters in the in the Himalaya or karakorum and of course that drives everything so a lot of strong conclusions are drawn but we we still have a very large uncertainty about the key hydrological input in the system which is press a then another another uh knowledge Gap I think are the snow Dynamics um we know quite quite little about you know snow accumulation snow sublimation which can be an important loss of snowfall the wind redistribution and the snow hydrology so the models that are being used in particularly the large scale ones they are quite simplistic in terms of how they deal with those snow Dynamics a third comp component is uh I think is evapor transpiration and Greening so we have a really strong focus on the cryosphere uh at high altitude uh or we look at the at the downstream Plains but a lot is happening in between the you know the the high mountain peaks above 6,000 meters and the plains at uh close to sea level so I think in the middle mountains we see a lot of there's a lot of evapor transpiration and Greening and that also has of course a huge potential to change the the whole water cycle in the mountains but very little research is being done into that field and finally I think uh yeah Chris andman is of course one of the key persons who's working on this the role of groundwater is also quite important uh you know in in Mountain hydrology and there there's only a limited limited amount of research being done into that field so more at a larger scale I think the key challenges that we have to deal with for the future is to understand and predict extremes and natural hazards um that's very complicated because of course then you also need to have accurate forcing and you need to understand you know it's all very probabilistic and which which events lead to which uh natural Hazard and what impact that Hazard has is very complex to to quantify systematically in particularly for larger regions and the last point is that I think the key is to to to to acknowledge also that it that the the increase in water demand is going to be a major challenge for the future and we need to adapt to that so yeah that was basically my my talk and then um if I still have the time I would like to give a few some thoughts on the utraan disaster um I was uh yeah that I followed also uh very closely and um I think it's it's also a good example of you know how we with collaborative science and with remote sensing we can very quickly um make some first assessments and try to understand uh what has happened very fast after after such an event has happened so you as you probably all know on 7 February um at uh at 10:30 in the morning a major deis flow was witnessed in close to chamoli and it destroyed for a large part the the re ganga Hydro power plant which was still under construction um so um yeah a lot of people immediately started to uh to to try and understand what happened there was a lot of lot of reports in the media uh first there was this story about a glacier burst which I think it's not really an a scientific term and there was stories of of Glacier Ice that hit the Hydro power plant directly and then there was other reports of Glacier Lakes somewhere Upstream in the nand Davy Basin that caused the flood and that caused the event and yet 100 100 people were missing there was a lot of damage so the big question is is is this now can you attribute such an event to climate change or is it just just bad luck and is it something that can just happen in in such extreme environments so what happened is that a few hours after the event and um there was already a satellite image available so this is a satellite image from from planner.com so they have this whole constellation of Dove satellites so those are tiny satellites and with that constellation they can can observe uh let's say almost every place on Earth with a resolution of I think three meter depending on which type of satellite it is uh every every few days so by coincidence there was an image right after the event and uh what you saw is here that it was in area about 20 kmers away so the Hydro power plant is that blue spot in the map and the red area is the source area so what what was found out quite quickly is that it was a catastrophic slope failure and that huge amount of rock mixed with ice came down and that this transitions into a debris flow on its way down and that was the cause of the destructive uh uh the destructive debris flow so here you can see some some different images so this is 6 February versus 9th February so you can see that um on the right hand side you see that whole Scar and uh was yeah it's it's a huge amount I guess think I have a better one here so you it's a it's a huge um it's quite large it's about 500 Metter in width and about a K ometer in length and I think over 100 meter in depth so that is a huge amount of rock and Ice that came down and the source area was about 5,500 MERS and it came down to 3,800 M so on the right hand side you see a kind of 3D visualization also with that planet image overlaid and then um you could see that but a big here are again some some difference DMS between May 20 15 and 2021 this is made by a b and Sim gcoin using padas imagery so you can really see that you know it is U on the right hand side you can see in in that red triangle is basically the the volume that was released so it's really uh 100 150 M thick and about a kilometer long that whole wedge came down so some initial energy calculations were also made by my colleague Jakob Steiner so if you assume uh the impact energy you yeah you calculated that the volume of ice and rock that came down was about 5.2 times 10 to the power of 10 kilograms of rock and ice and if you drop that over 1600 meters of elevation you get a huge amount of energy which is equal to 10 times the bomb on Hiroshima so you can imagine the amount of energy and D uction that that has caused um big question that many people had well then what was the source of all that water that came down because if this was just rock and ice but it can also be that you know there's uh a lot of ice remnants on the valley floor and uh yeah this this energy can actually liquefy uh what what it finds on its way so that is now the the current hypothesis but of course this is very very preliminary analysis I think it's a great example of you know what to of what remote sensing and high res high resolution remote sensing can now do in terms of uh of of identification of of natural hazards and uh that has a lot of potential and I think 10 years ago this would not have been been possible at all within a few days people reconstructed uh in a very collaborative way what what had happened thank you very much [Music]