Saturday, August 29, 2009

Water problems in Nepal

There is a growing tendency to assign the cause of weather events that badly impact different populations to climate change, and thereby to add additional “evils” to those who generate “greenhouse gases.” I noted this last week about the story of the Nile Delta and the causes of erosion and lack of fertility that farmers are now seeing. As I showed the events have nothing to do with climate change or AGW, despite the bits of the story that implied that they were.

The events don’t even have to have happened yet. This week Oxfam International were pointing to the change in climate threatening the livelihood of the people of Nepal.
Nepal will likely suffer more frequent droughts because of climate change, Oxfam International said in a report released in Kathmandu. River levels will decline due to the reduced rainfall and glacial retreat, making it harder to irrigate crops and provide water for livestock.
Now here is the problem that I have with that last sentence. When there is precipitation in the mountains, it is either retained in the mountains as ice and snow, or it goes into the rivers where it is available for irrigation. If glaciers grow then less of that precipitation is available for irrigation, if glaciers retreat, that means that they are melting and not only not capturing the precipitation but are also providing some of their stored water to be available for irrigation. This supply of more water is a resource critically needed in China as well as Nepal, and provides the great rivers that flow from the Himalayas and are relied on by millions of people.

The report itself is a integrated mix of things that might happen if the global temperature increases by 2 degC by 2050 (35% of the Himalayan glaciers are projected to disappear) and a recent winter drought that has left many farmers without adequate food supplies.

However this has been a poor year for the monsoon in India, and Kumar et al have shown that the failure of the monsoon correlates with El Nino events – something that we are now moving into.

Thus the actual events that are reported in the Oxfam report have a cause that is likely not due to global warming but to a predictable and regular other cause. However, by combining the effects of the drought and the poor weather, with the predicted events that might occur with a dramatic increase in global temperature, a confusing picture of contradictory predictions has been built. Monsoons, sadly, have failed before, and for the same reason.

It is understandable that folk seek to find a scapegoat when the weather is inhospitable, however, as with other countries, an additional part of the problem in Nepal arises from the increase in population, particularly in the Kathmandu Valley. To solve the problem the government has just laid the foundation stone for a 26.5 km long tunnel to bring 170 million liters of drinking water a day (MLD) into the valley. It is known as the Melamchi Drinking Water Project and is due to be completed in 2013. The work is being carried out by a Chinese contractor. The valley needs some 240 MLD and can supply only 90 MLD, for the 2 million inhabitants of the valley. Most of the rain (it gets about 1.5 m/year) comes in the monsoon season between June and August.

It has not met with universal approbation and does not help those living in the hills. However they have other problems since while the communities live on the tops of the hills, the water is in streams in the valleys and so women and children can spend up to 4 – 6 hours a day just carrying water. There has recently been an innovation – called the Large Fog Collector (LFC)
The Large Fog Collectors (LFC) are constructed using 4 x 8 meter sheets of polypropylene mesh, which when suspended on a ridgeline resembles a large volleyball net. Warm air from the Bay of Bengal moves inland during the monsoon, where it intercepts the varied topology of the Himalayan foothills. As the air moves up into valleys at higher altitudes, it mixes with cooler air and condenses, forming fog. As fog passes through the fog collectors, water droplets cling to the weave of the mesh, and filter down into a discharge system that stores the water in 20,000 liter ferro-cement tanks. Water quality testing found that all parameters meet WHO guidelines. . . . . . . . Here six large fog collectors produce an average of 1700 liters of water per day for the villages 75 inhabitants.
Although relatively cheap they do require both maintenance and frequent fog which they get in Nepal, Peru and Chile.

The glaciers in the Himalayas occupy some 193,000 sq miles and at present the melting and retreat of the glaciers, which has been been going on since the end of the Little Ice Age, has accelerated since 1970. It is the melting of the glaciers that provides the water for the rivers and people that they serve, and provide a supply of water in the seasons that the rains don’t fall. It will be interesting to see if the changing global climate conditions of this century have any impact on the melt rate.

The nations that are served are thus in a bit of a cleft stick, since during the Little Ice Age the glaciers grew, and thus supplied less water to their dependants than they do now, so the current melting does have some benefits, that should be recognized.

But if it continues too long then the water resource will be gone - depending on how the temperature actually continues to rise, if it does, this is going to lead to a difficult conumdrum, though likely over a longer time period than is currently being used as a discussion point.

On the other hand (h/t Marc Morano) when Asia gets hotter, then in the past the glaciers have started growing again.
A group of Himalayan glaciers grew six-fold during much hotter summers, when temperatures rose steeply by six degrees Celsius in Asia, baffling geologists.

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