What's in the news?

A news article on the Nature website posted on the 22^nd March 2011 looks at the people living alongside the Colonia River, in the Aysen region of Chilean Patagonia. Their significance is the threat they live under of sudden glacial lake outbursts from the above glacial mountains.

Whilst these lake outbursts are not uncommon globally (see this previous blog post), the region has experienced seven of these events since April 2008. Evidently, this is a much higher rate than seen anywhere else. During each of these seven outbursts, Lake Cachet 2 (of the Colonia glacier), has drained approximately 200 million m³ of water into the Colonia Lake and River in only a few hours. This has created a wave observed as far as 100 km downstream to the Pacific Ocean. The risks to the people of the Colonia River need no further explanation.

The Nature article uses the findings of a paper by Casassa et al. (2010), which has studied the floods to identify a primary cause.  The three year study ultimately found that the main cause was:

“...the repeated opening and closing of a tunnel 8 kilometres beneath the Colonia glacier, connecting Lake Cachet 2 above the glacier and Colonia Lake below it.”

Of course, this alone does not reveal the entire process of glacial lake outburst from the Colonia glacier. As a result, Casassa et al. (2010) found that climate change was the main culprit behind the frequency of these events. This happens as a result of the shrinking and thinning of the glacier in the past few decades, causing a weakening of the natural dam structure that the glacier forms. Thus the water moves between the two lakes with much greater ease. There seems little that can be done about this at present, although the paper offered some hope for the future:

“The researchers conclude that the discharges will continue until the ice has receded or thinned sufficiently to generate a permanent natural drainage channel.”

Figure 1. Ice-laden lake leading up to the Colonia glacier

Questionable impacts of glacier retreat on regional water security: dealing with uncertainties

Following on from the previous blog post, a paper by Archer et al. (2010) looks quite broadly at how the sustainability of water resources in the Indus basin might be altered by future changes in climate, as well as changes in socio-economic conditions. As was noted by the Indus water commissioner in the previous post, climate change effects on glacier shrinkage were suggested to be the primary cause of water scarcity. However, in this paper by Archer et al. it is argued that the impact of glacier retreat may be limited, especially when compared with other physical and socio-economic factors downstream of the Himalayan glaciers.

Agriculture in Pakistan is very much reliant on water which originates in the mountain sources of the upper Indus. As the authors note, these water resources are already highly stressed and are likely to get worse with projected rises in population. The paper considers the impact of climate change on these water resources in terms of three distinct hydrological regimes: a nival regime (dependent on melting winter snow), a glacial regime, and a rainfall regime. The mountainous sources of water are known to be affected by changes in temperature and in precipitation. The authors note that this is due to most of the runoff being derived from the melting of seasonal glacier snow and ice. Thus, any ablation of glaciers could quite easily affect water scarcity downstream.

Figure 1. The Indus basin

However, as the paper importantly notes, there is a great deal of uncertainty regarding how climate change might affect glaciers and river flow in the region. It cites several studies, which show regional conflicts with global patterns. Firstly, that summer temperatures (key for glacial melt) have actually fallen in the Karakoram between 1961 and 2000. Secondly, similar falls in temperature were found for the monsoon and pre-monsoon periods (April to May) in the Karakoram. Thirdly, that there have been significant increases in Upper Indus precipitation (both winter and summer) between 1961 and 1999. Fourthly, that extensive glacial mass balance records do not show shrinking glaciers. And finally, that in the late 1990s, there was widespread evidence of glacier expansion in the Karakoram.

With such conflicting evidence in the upper region of the Indus basin, it is unknown whether climate change will have a positive or negative effect on water resources in the region. The authors state that the hypothesis of reduced water resources relies on two assumptions: firstly that temperature and glacier melt are the primary impact on water resources, and secondly, that temperatures in the Upper Indus will rise in line with global climate predictions. As a result of this, they state that both of these assumptions are questionable. In particular, it is stated that river flow has been shown to not depend uniquely on glacier melt, but also rely on seasonal snowmelt and rainfall. This thus gives us the three hydrological regimes: nival, glacial and rainfall.

In the nival regime, the area of seasonal snow melt gives the largest contribution to downstream flow. This comes largely because the area of seasonal snow is much bigger than the perennial snow and ice. Of course, however, the area greatly reduces during the melt season. For this regime, winter precipitation has been shown likely to have the most significant impact on summer runoff. And unlike the glacial regime, there is a significant negative relationship between runoff and temperature on nival regimes. Archer et al. state that this:

“Can be explained by greater evaporative losses from the snow cover under higher temperatures and thus reduced runoff.”

As a result, the authors estimate that for a 2^oC rise in summer temperature, there would be an 18 percent reduction in runoff. However, the observed Karakoram decline in summer temperature would produce increased summer runoff.

In the glacial regime, the contribution to flow in the very high catchments is significant. However, the combined flow of these high catchments into the Indus represents an average of less than 30 percent. Here, there is a significant positive correlation between summer runoff and temperature. As well as this, winter precipitation doesn’t have such an influence. As such, spring and summer temperatures have the greatest impact on runoff. In this regime, runoff will rise initially with increased global temperature, but reduce sharply with declining glacier mass.

However, the findings of falling summer temperatures in the region mean that with this positive correlation between runoff and summer temperature, there is presently a downward trend in flow. The present and past behaviours of the Karakoram glaciers are noted in the paper:

“...glacier recessions were observed in almost all Karakoram glaciers for most of the 20th century until the mid-1990s. However, at lower elevations glaciers continued to decline. This seems to confirm that glacier loss is reduced in the Karakoram compared both with the neighbouring Himalaya and the Pamir mountains to the west.”

Finally, in the monsoon rainfall regime, the main influence falls over the southern plains and foothills of the Himalaya. Here, seasonal volume of runoff (as a result of rainfall) is lower than in the glacial and nival regimes. However, the monsoon rainfall produces more intense runoff and therefore highest flooding in the region. Therefore, this regime can be very important for water resources in the Indus basin. Yet as the paper states, the IPCC indicate that estimates of precipitation change hold great uncertainty, and that the impact of climate change on monsoon precipitation cannot be safely assumed.

In summary, based on the three regimes identified for the upper Indus basin, the paper shows that there appears to be little evidence for reductions in runoff and thus availability of water resources in the region. It must also be accepted, however, that much of this relies on uncertainty over glacier response to climate change in the Karakoram. Indeed, more recent past climate may not be a reliable guide to future change as well.

Whilst not the focus of this blog, it is important to mention briefly, the overall findings of the paper when physical and socio-economic conditions downstream are considered. Whilst the authors found inconclusive evidence of climate change causing reductions in runoff, they did find that several other factors had much greater influence on water resources further down in the Indus basin. Firstly, that urban growth and industrialisation will increase and demand further shares of the scarce water resources. Thus, economics plays an important role in water resource management, as large investment is needed to provide practical solutions whilst balancing the needs of security, health and education. Secondly, reservoir sedimentation means that water resources will diminish as storage is taken up by sediment. This problem will not reduce unless new reservoirs are built. Finally, the alternative of using groundwater in the spring for agriculture may soon have no practical use when the water tables fall from over pumping.

As can be seen, the issue of water scarcity in Pakistan’s Indus basin is very complex. The presence of and future changes to glaciers upstream is a very important part of the highly stressed water scarcity issues here. Only with greater knowledge of how these regional glaciers will react to global climate change, using past records and future modelling, will a truly certain answer be able to be given for these problems.

Changing glaciers and regional security

Focussing here on the human impacts of potential glacier loss, a 2009 Bloomberg article assesses the security risks associated with water scarcity, through looking at a report by the Asia Society. The article begins by stating that the water supplies of China and India are predicted to decline alongside the shrinking of Himalayan glaciers as a result of global climate change. This in turn is likely to begin or exacerbate regional conflicts.

This conflict, the author states, could come as a result of several factors. Asia contains half of the global population, yet has least water of any continent (with the superfluous exception of Antarctica). There exist problems of waterborne diseases throughout Asia, and these could certainly be amplified by water scarcity. As well as this, lack of fresh water could trigger mass migration and invigorate cross-border conflicts over water control. Evidently, there exist many potential sparks of conflict.

As well as this, the threat to agricultural production in the region is very real. Increased amplitude of dry and wet seasons caused by the influence of climate change on regional atmospheric patterns may overwhelm and destroy a proportion of crops. As well as this, any change in Asian crop yields (particularly China or India) would most certainly affect world food prices.

There is a particular problem in Pakistan, with approximately 77 percent of its water resources coming from outside of its borders. As a result of this situation, Pakistan holds a water treaty (since 1947) with India which guarantees sufficient supply. Of course, since that time, there have been several territorial and other disputes between the two countries. Most recently, Pakistan-based terrorists launched an attack on Mumbai in 2008. This further tension caused those in Pakistan to criticise the failures of India to always adhere to the treaty. Underlying all of this, they suggested, lay the long standing violent disagreement over the Kashmir region. These alleged abuses of the treaty in the past are particularly important when the population figures of 180 million presently (a tripling since 1950) and of a predicted 335 million by 2050 are seen.

The article then looks, albeit briefly, at the rapid melting of some Himalayan glaciers as a consequence of climate change and attempts to link this with the security issues. The author states that:

   

“Melting Himalayan glaciers now account for up to 70 percent of the summer flow of the Ganges River and about 55 percent of Asia’s other major river systems, according to the report. In 30 years, as the glaciers continue to retreat, the Indus and Mekong rivers could be dry during part of the year, the report said.”

Therefore, with the regional effects of climate change on temperature and a seemingly large degree of uncertainty regarding how the Himalayan glaciers will respond (unlikely uniformly), there is a great deal of potential danger associated with glacier retreat and water scarcity in the region.

In a separate article shown on the Policy Research Group website, much the same conclusions are found regarding the Pakistan example. The author, using World Bank estimates, shows that:

“... Pakistan’s Indus River will be negatively impacted by climate change, with incidents of flooding in the Indus basin expected to increase over the next 50 years. In addition, estimates suggest that there will be a 30-40% reduction in river flow over the next 100 years due to natural climatic and environmental changes.”

The article then notes that the Pakistani government, and more specifically the Indus water commissioner, feel the issue has received insufficient media coverage when compared to the potential damage that could take place. And looking at western media outlets, it would be hard to disagree with this assessment. Finally, the Indus water commissioner states belief in climate change as the primary driver of Pakistan’s water scarcity problems both now and in the future. However, as will be discussed in a following blog post, this is certainly not the belief of all scientists. Indeed, several have stated the exact opposite of this opinion.

Figure 1. View of the Indus River, fed from the glacial Himalayas

With regards to this last opinion of the Indus water commissioner; according to a weblog article by the Centre for Strategic and International Studies (CSIS) several officials in India believe that it is governmental mismanagement of water resources - and not climate change - that are responsible for water scarcity. Indeed, the article goes into slightly greater depth over the risk of conflict over water between Pakistan and India. It highlights the frustration of many of the rural poor in Pakistan regarding the observed extended dry spells, and a subsequent temptation to blame India for these droughts. Despite this desperation, there seems to be no evidence of this practice (according to the Indus water commissioner). Whilst cooperation on the water treaty has survived many of the previous disputes between the two countries, several militant Islamic groups have been seen to use this regional frustration for self gain. This threat of water cut-off by India is used by the militants to garner support for their wider agenda as well, which is in all probability aimed at destabilising the region.

It can be seen that water scarcity and regional security are very closely interlinked. Thus, with regional uncertainty of how glaciers may react to climate change, it is of wide ranging importance that greater certainty is achieved. Whilst this blog has looked more at the physical characteristics of past and future glacier change, it has been shown here that there is a inextricably linked human dimension to our knowledge of future glacier dynamics.