By Joseph J. Bailey, University of Nottingham, UK.
Rivers are the arteries of the world, carrying life-giving water to the organs that are the natural habitats and human settlements. An increase or decrease in flow can have disastrous consequences through droughts and flooding, thus ensuring a sustainable water supply is seen as a priority by many states worldwide. Despite the vast number of environmental problems dams can (and do) cause, they allow people to not only control water flow to the population in times of low or high supply/demand, but also produce energy through hydroelectric technologies. Whether or not to build a dam, and when to remove a dam, is, or at least should be, decided by comparing the environmental impact with the benefits of energy and water provision. The accumulated impact of building multiple dams within a watershed should also be considered, because this can result in lower water quality for humans, alongside inflated environmental impacts.
It is not surprising then that dams are highly contentions across all scales, from the local to the global. Indeed, they are one of the most contentious geopolitical issues in the world today, with international debates surrounding the Nile in Africa and within-country debates over Brazil’s Belo Monte and Madeira dams, to take just two examples. Dams have even been considered ‘powerful weapons of war’ in the Middle East. To sum up, dams are amongst the most important structures in the world because they safeguard the most valuable resource in the world for whoever owns it. Dams therefore hold great political, as well as hydrological, power and are understandably at the centre of many international debates and discussions.
Often in such debates and discussions, the owner of the upper reaches of a river, and any dams therein, holds vast amounts data about spatial and temporal water flow (discharge) in that region, and may closely guard those data from its neighbours, and from global data hubs. Those who hold the data have a political advantage when discussing the future for a particular river, and those downstream, who possess no or very little data on the upstream parts of the river flowing through their country, may struggle to apply any political pressure.
This issue of data sharing, or lack thereof, is discussed in a paper by Gleason and Hamdan (2015) in The Geographical Journal. They write how a novel remote sensing technique might be able to help with this using two case studies: the Brahmaputra and the Mekong (known as the Lancang in China). Both have featured in the news recently, with the opening of a Chinese dam in the upper reaches of the Brahmaputra in Tibet (e.g. Reuters Africa, Voice of America) and with the Mekong because of the many dam constructions completed recently or in progress (map and details at International Rivers; also see Al Jazeera). Both of these situations are very complicated, affecting millions of people in the countries concerned, as well as attracting international attention.
The aforementioned technique highlighted by Gleason and Hamdan (2015), and initially developed by Gleason and Smith (2014), is called ‘at-many-stations hydraulic geometry’ (AMHG). It uses remotely sensed data (from satellites) and recent advancements in geomorphic theory and aims to address the data shortfall many countries experience in relation to inaccessible watersheds. These are usually in another country, but the technique may also be of use in hard-to-reach areas within a country. While the model produces noteworthy inaccuracies compared to in situ gauge measurements, these data are obtainable by anyone and may at least partially fill a knowledge gap for some countries.
Perhaps through enabling countries without direct access to flow rate information of river stretches outside of their borders, data from remote sensing technologies will benefit a nation’s diplomatic standing with their neighbours. Such technologies are also likely to improve in the future with dedicated satellites for measuring river properties (see Gleason and Hamdan, 2015). This will overcome inaccuracies seen with AMHG, which, at present, may be an argument that countries owning upper reaches can use against those further downstream; that the data being used are not accurate enough to make a valid case for more or less water to be released downstream, for example.
However, whilst these new technologies will no doubt be able to assist with hydrological monitoring into the future and probably help with these often tense cross-border situations by enabling downstream countries, the ultimate challenges, as is already the case in many places at the moment, will be political and rely on the relationship between the countries concerned. This is because one country will always control the dam that stops and releases the water, even if their neighbour knows absolutely everything about the watershed concerned through remote sensing. There are many discussions to be had about who really owns rivers, containing arguably the most valuable resource on the planet, when they start in one country and flow into another. As climate change continues, and populations grow, water resources are likely to be stretched ever further and it may be prudent to attempt to resolve the issues discussed here sooner rather than later.
Gleason C. J. and Smith L. C. (2014). Toward global mapping of river discharge using satellite images and at-many-stations hydraulic geometry. Proceedings of the National Academy of Sciences, 111, 4788–91.
Gleason, C. J. and Hamdan, A. N. (2015). Crossing the (Watershed) Divide: Satellite Data and the Changing Politics of International River Basins. The Geographical Journal (early view).