There have been numerous articles published on the hazards posed by gases trapped in Lake Kivu. The most recent were published in the New York Times and ScienceDaily.
However, some of these articles have been ill informed, alarming and to some extent factually incorrect.
While it is true that there are potential dangers posed by the gases dissolved in Lake Kivu, there are also many opportunities to be gained from exploiting the trapped gas in the lake with a view to achieving Rwanda’s development goals and simultaneously avoiding the saturation and explosion of these gases.
The Government of Rwanda is aware of all the potential dangers and is doing everything possible to mitigate them, and ensure safety of the population within the Lake Kivu environs.
All dangers currently associated with the lake are potential, and are by no means imminent. However, these need not be subject to so much speculation. Indeed, volcanoes pose a greater threat as witnessed by the 2002 Nyiragongo volcanic eruption, and are therefore more deserving of attention than speculative dangers.
The 2002 eruption of Nyiragongo volcano lasted for one day, destroyed a good part of the Town of Goma, including part of the international airport and the business centre.
Tens of thousands of people were made homeless and thousands evacuated. It is important to note that this eruption was not caused by any activity in the lake.
Despite the fact that lava from this eruption went into Lake Kivu, it had no adverse effects on the stability of the lake. Therefore, the danger of the volcano eruptions is more pertinent and should be the major issue to discuss as opposed to the speculative issue on effects of activities at the lake. In any case, no significant volcanic event has resulted in the lake ‘turning over’ for almost 1000 years.
Studies have shown that it would take a severe or strategically located volcanic event in the magnitude of a nuclear explosion to trigger a ‘turnover’.
We recognise well the various facets of risk in and around the lake. but we are actively developing the knowledge and understanding necessary to develop Lake Kivu’s potential, at the same time ensuring that what is done advances public safety as a top priority.
Our priority as governments, that have jointly accepted responsibility for coordinated and safe development of Lake Kivu, is clear.
We are forming the technical and scientific institutions needed to oversee the lake’s development with clear priorities of public safety, environmental safety and social benefits ahead of the commercial rights of developers. These will be backed by the necessary expertise, both local and international.
The program we have embarked on will run for fifty years to ensure that the lake is returned to a safe state of equilibrium with a risk level reduced by orders of magnitude.
Along the way we are sure that our regional energy problems will be resolved with cheaper, cleaner and more abundant energy for all. This is a valuable resource that can do much for the regional economy’s development
But perhaps a short lesson on Lake Kivu and its surrounds will assist with a deeper level of understanding that is necessary to dispel some of the myths and loose conjecture in the report.
Geography of Goma and Lake Kivu
Goma was referred to in the New York Times article by Josh Kron.
Goma in the DRC is a Town founded on layer upon layer of volcanic lava, perhaps as much as 500m deep and extending across a 50km front on Lake Kivu.
For at least the last 10 000 years, the twin volcanoes, Nyiragongo and Nyamulagira, have erupted and spilled trillions of tons of fast-flowing lava up to 25km southwards and up to 45km northwards to dam the rift valley and form the lake.
Further afield and sometimes overlain by the lava flows, fly lava and far-flung boulders have formed deep layers of usually nutrient-rich and porous soils which attracts high-density farming.
Because the free-flowing lava has established an extensive plain with these fertile soils between the hilly country to the east and west, the population of Goma and the surrounding plains has grown to a number almost a million.
The high rainfall in the area, often up to 3000mm per year that falls in two wet seasons, permits up to three crop harvest per year to sustain the subsistence farmers and their families.
Tropical forests have yielded timber and firewood that also helped sustain the burgeoning population.
The effect of Africa’s rifting, which is a widening split of the African continent both east and west of Lake Victoria, has been the creation of this western or Albertine rift measuring over 50km wide.
Lake Kivu formed in the rift, but was deepened by the damming effect of the twin volcanoes. Older volcanoes, now dormant, have left the imprint of seven high volcanic peaks in the Virunga mountains, home to the mountain gorillas, and many smaller creatures.
Other characteristics of the lava plains and the lake do affect human habitation. The heavy seasonal rains on the lava plains curiously do not create or sustain streams and rivers. Groundwater is difficult to access. The porous rock and soils absorb all the water which flows through deep underground channels into Lake Kivu.
These waters absorb both soluble gases (magmatic CO2 and H2S) and salts and carry them into the lake, sometimes entering through “springs” hundreds of metres below the lake surface.
The largest of these inflows enters Lake Kivu at a depth of about 250m and plays a significant role in the stratification of the lake’s deep waters.
Once in the lake, these salts and gases contribute to a unique system where the deep waters are denser than lake’s shallower and relatively fresh waters.
The lake waters are layered, according to density, and accumulate both magmatic CO2 and biogenic methane and carbon dioxide created by the anaerobic breakdown of organic sediment such as dead algae and fish.
The lake presently contains some 60-65 billion cubic metres of methane and five times that volume of carbon dioxide.
Since the lake has been progressively stabilising through this density stratification effect, its ability to carry and contain these billions of cubic metres of both methane and carbon dioxide has been established as an effective safety mechanism.
The lake has been in this quasi-stable state for hundreds of years despite numerous lava inflows and tectonic rifting events.
The lake at certain depths has reached about 60% saturated of its carrying capacity. But these gas accumulations are destined to create their own instability in time, by building up to a concentration where the gases fully saturate the deep lake waters.
In about 100 years, when they reach 100% saturated, these gas accumulations can spontaneously create an explosive degassing of the lake.
This degassing can occur locally as small shallow eruptions, as occasionally witnessed, or possibly over the whole lake in a major “turnover” event. An added danger is the potential of nature to prematurely trigger such degassing through a volcanic or major seismic event.
The fact that no major turnover has occurred for at least 900 years indicates that the lake has the capacity to absorb most such events and resist degassing events through its stability structures.
There is a reasonable expectation that the lake can continue to withstand the effect of such incidents for most of the next 100 years by which time the lake’s gas content will be nearing saturation at some depths.
This is where man is uniquely positioned to reverse nature’s trends by extracting much of the accumulating methane and hence remove the trigger component of any lake degassing.
Understanding lake science and development
The governments of Rwanda and DRC have joined in an effort to understand how they can reverse the gas accumulation of the last centuries. An expert group including top scientists and engineers involved in methane extraction and lake science has been advising both governments and has issued firm recommendations on gas extraction requirements.
They have set out the safest known, most environmentally friendly and technically efficient methods of reducing the gas load in Lake Kivu. Methane extraction can make the lake many times safer than it is at present.
The plan is extracting commercially valuable gas to provide a renewable and clean energy source to the teeming population around the lake.
The $3 million mentioned in the article is for the governments to jointly undertake a feasibility study into the extraction of gas to provide 200MW of gas-fired power within the following three years.
There are several technical proposals and options available for the lake but these must be viewed against their compliance to the technical requirements for gas extraction and for their economic efficiency. This development program is slated to cost up to $500 million.
The forests that remain on the many volcanic peaks are threatened by deforestation driven through slash and burn agriculture coupled with charcoal burners feeding the cooking needs of the cities like Goma and surrounding densely populated areas.
This is unsustainable and threatening the mountain forest habitat of the gorillas.
Methane gas can provide most of the energy to these communities more cheaply than charcoal through distributing both electrical power and even cheaper pipeline gas to homes and other users.
Lake gas can thus reduce the demand for charcoal significantly if it can be widely and economically distributed. Electrical power may be the energy of choice for the wealthier 10-15% of the population, but gas can be provided cheaper to city dwellers to provide essential cooking and lighting energy.
Responding to the article
The anecdotes provided by Josh Kron in the New York Times are topical and a sad reminder of the many dangers that loom over Goma.
Goma is one of planet Earth’s virtual crucibles, its horizon dominated by live volcanoes and its foreshore bounded by a lake that seems mysteriously threatening.
We have reports of pockets of gas in ditches and mysterious disappearances of swimmers and boats on the lake. However such reporting as this article, while necessary on a local level, is handled irresponsibly and unhelpfully in this forum of the international press.
On reading it, the article perpetuates the thought that this is a medieval mystery, as though these are victims of some ghoulish demon that stalks people on still moonless nights. Instead of downplaying such ill-founded sensation with practical answers, the author is playing on people’s fears.
What is needed is a set of practical explanations of the phenomena and similarly practical warnings and solutions to allow the people to avoid these dangers. Understanding the sources and manifestations of gas pockets is a clear basis for such safety education.
Explaining the phenomena
For example, with the death of Mr Masha (discussed in Josh’s article) percolation of carbon dioxide (not methane) to the ground surface is a common phenomenon in Goma.
The very structure of the volcanic plains on which Goma is built, and the water flows beneath the city is a start to this understanding.
The rock is porous, and porous to water means highly porous to gas. Most of the 2-3 cubic kilometres of rainwater that falls on the plains around Goma each year flows under the city into the lake, carrying magmatic carbon dioxide and salts with it into the depths of the lake.
As easily as this gas dissolves in water it can separate again, such as when pouring a soda from a bottle. Free gas can easily percolate up through to the surface. In the lava there will be more porous channels in some areas which can function like vents.
Being a denser-than-air gas it would accumulate in hollows and ditches if there is no wind to disperse it. For this reason one should not enter hollows and ditches, especially on calm windless days. In a few minutes exposure one can experience breathing difficulties and it’s well known that CO2 build-up as experienced by submariners leads to disorientation.
Where accompanied by oxygen levels below 10-15%, this can eventually result in fainting and eventually asphyxiation.
This happens to pilots whose aircraft compression systems fail unnoticed in flight at altitudes above 25 000 feet. The example of well-known golfer Payne Stewart was reported exactly ten years ago, where he and his crew perished from hypoxia. They simply fell unconscious and died in their seats before the fuel ran out.
Similar conditions occur in the lake itself, where there is an accumulation of 300 billion cubic metres of carbon dioxide in the lake water. Concentrations of dissolved gas reduce rapidly towards the water surface.
The deeper gas diffuses slowly upwards through the water from the depths towards the surface all the time, slowly. Any methane that makes it up to 60m depth or shallower is oxidised by dissolved oxygen to carbon dioxide.
This adds to the rising quantity of CO2 gas. Hydrogen sulphide (rotten egg smell) is also present in small quantities in the lake depths and will also be oxidised to weak sulphurous acid as it rises.
It is clear that the danger comes from carbon dioxide. By contrast methane and hydrogen sulphide can only be present at the surface as a result of eruptions from deep water or through gas extraction.
From the lake surface the dissolved carbon dioxide is also able to diffuse and escape into the atmosphere. Tens of millions of cubic metres diffuse out this way annually.
This is a slow process that occurs continuously and no visible bubbling occurs. Once again in windless conditions, particularly when they last for several days, this accumulation of CO2 on or near the surface of the water can reach the point that it is dangerous. This is particularly so for swimmers who breathe in “air” very close to the water surface.
Carbon dioxide is denser than air. People in boats are less susceptible and they may only feel mild discomfort or breathlessness in the same conditions.
All the same, people should avoid being on or near the lake, especially swimming, when the conditions remain very calm. Wind can disperse the problem into the atmosphere very quickly and make conditions quite safe within minutes.
Lessons learned and necessary precautions
Education is required for the lake-side population. Whether they are land-dwellers, swimmers or fishermen, the key to preventing loss of life is avoiding circumstances that raise the risk of asphyxiation.
Still and calm conditions on the lake, when there is not a breath of wind, allows accumulation of an invisible thin layer of carbon dioxide over the lake’s surface.
The same conditions on Goma’s volcanic plain allow pockets of carbon dioxide to accumulate in ditches and hollows.
An education scheme for children in schools should warn of these dangers and instruct them to avoid them until the winds return, even a light breeze disperses pockets or layers of gas. Both these dangers, in the lake and on land, dissipate within minutes with a fresh breeze blowing off the lake.
Fishermen too, many of whom are young children, need to be aware of the need to avoid fishing on still, calm nights or alternately to stand or otherwise elevate themselves at least a metre off the surface. Education must also play a part in boat safety.
Too many overloaded boats leave harbours in relative calm with less than 200mm of free-board, a highly unsafe practice when lake storms can blow in far less than the time taken to cross the lake. Lake safety regulation is needed on all water craft, particularly those carrying members of the public.
The provision of water is a clear priority which will benefit from the better availability of power and funding. Power plants also would have the ability to generate cleaner, more potable water from waste heat driven purification plants. One of our hopes is to deliver better quality of life and better safety.
The children also need to learn that there is no dark mystery that threatens them, and that through education and behaviour they can remain safe and unharmed. The so-called “mazuku” or “evil wind” is a misnomer and actually comes from the lack of wind.
The stories reporting deaths and disaster may well be valid, and must be reported completely and factually. But the interpretation and education that should accompany such stories is missing.
Omitting such key information is being irresponsible. We all need to be educated about Lake Kivu and safety. We all need our children to be safer.
Part of the mandate of the Bilateral Regulatory Authority in collaboration with the international expert team is to work out such education programmes and observe their effective implementation.
The author is Rwanda’s Minister of State for Energy