Water is not confined to political borders. An estimated 148 states have international basins within their territory (OSU, n.d., 2008 data), and 21 countries lie entirely within them (OSU, n.d, 2002 data).
There are 276 transboundary river basins in the world (64 transboundary river basins in Africa, 60 in Asia, 68 in Europe, 46 in North America and 38 in South America).
185 out of the 276 transboundary river basins, about two-thirds, are shared by two countries. 256 out of 276 are shared by 2, 3 or 4 countries (92,7%), and 20 out of 276 are shared by 5 or more countries (7,2%), the maximum being 18 countries sharing a same transboundary river basin (Danube).
46% of the globe’s (terrestrial) surface is covered by transboundary river basins.
148 countries include territory within one or more transboundary river basins. 39 countries have more than 90% of their territory within one or more transboundary river basins, and 21 lie entirely within one or more of these watersheds. Read more
85% of the world population lives in the driest half of the planet.
783 million people do not have access to clean water and almost 2.5 billion do not have access to adequate sanitation.
6 to 8 million people die annually from the consequences of disasters and water-related diseases.
Various estimates indicate that, based on business as usual, ~3.5 planets Earth would be needed to sustain a global population achieving the current lifestyle of the average European or North American.
Global population growth projections of 2–3 billion people over the next 40 years, combined with changing diets, result in a predicted increase in food demand of 70% by 2050. Read more
In our article Introduction to Water Wheels we introduced Undershot and Overshot water wheels together with other alternatives.
Each different type of water wheel has its advantages and disadvantages as well as features which make them suitable or unsuitable for different situations. In this article we will present a detailed mathematical analysis looking at the maximum possible efficiency of the overshot and undershot designs of water wheel. Many thanks to retired radio physics lecturer Bill for sharing this work with us. Read more
A Water wheel (or Waterwheel) is a system for extracting usable power from the water flowing in a river or stream. Along with windmills, water wheels have being powering the milling of flour and other industry for hundreds of years. Waterwheels are still in common use in Nepal (25,000+), and India (over 200,000 waterwheels). Water wheels come in two main flavours: undershot, and overshot.
Historically the undershot water wheel was the commonest as it is the cheaper and simpler to build. It was used frequently by the Romans and the undershot water wheel is sometimes known as a Vitruvian water wheel after the Roman engineer Vitruvius. In this system the wheel is simply placed over a fast flowing river. The water hits paddles which protrude all around the wheel and therefore turns the wheel. This system can only be used where the flow of water is very fast as little of the energy of the water (around 20%) is used. Click here to read our article on run of river hydro power. Read more
The region of Mesoamerica is comprised by the southern states of Mexico and the seven countries of Central America. While Mesoamerica is rich in freshwater, the area is extremely vulnerable to changes which, in the medium to long term, could diminish its availability.
Such challenges such as waste, pollution and lack of governance pose serious threats to the precious supply of this resource. Non-governmental organizations from the region plan to denounce this situation at the 6th World Water Forum, taking place Mar. 12-17 in Marseille, France. Read more