IWRA Proceedings

Abstracta) introduction, World population will increase by 3 billion people over a few dozens years. This fact raises the question of global availability of foodstuff and particularly of increasing land surfaces dedicated to irrigation. This fact will also increase dramatically population suffering from water shortages. Moreover, in many cases, water resources are not available where needed. Increasing locally water resources at an affordable price (i.e. much lower than 1€/m3) will solve this problem. But, all existing solutions suffer from major flaws. Desalination costs around 1€/m3 and its energy consumption is greater than 3kWh/m3. Today, few traditional ground-based inter basin transfers can be carried out or even continued because they are difficult to implement and induce numerous problems downstream. Other exotic solutions (e.g. tankers) are very expensive (>2€/m3) or can be used only for limited quantities (1m3/s ~ 1 tanker of 100.000t/d). b) objective, Innovative alternative solutions should be considered. Available water at river mouths is abstracted upstream the salt wedge. It is then transported by underwater pipes parallel to the coast (across the sea for islands). At destination in coastal areas where 60% of the world population lives, it is distributed through the local network after usage-specific treatment (human consumption, industry needs or agricultural needs that account for 2/3 of global water consumption and require a very low price). c) methods, This patented system allows transportation of water in large quantities (from 1m3/s up to several dozens m3/s) over long distances (from a few dozens kilometers up to several hundreds). It is structured around a very flexible pipe that adapts to the seabed profile without preparation of the ground. It is laid on the seabed (typically at 200m depth) and ballasted by a “mattress”. d) results Projects transferring any volume over any distance can be considered: larger volumes require more parallel pipes beyond the two that always considered for security reasons; longer distances require intermediary pump stations which constitute so many abstraction or delivery points. This system is very competitive and is therefore a serious alternative to land transmission lines and to desalination plants. Its prices are low (from 0.1 up to 0.3€/m3 in most cases). Its energy consumption is less than 0.2 kWh/m3 in most cases, which is about 5% of the energy necessary for seawater desalination. Its construction can be conducted in 1 to 2 years. An over investment of 15% at the outset typically brings the flexibility to meet a 50% increase in demand over time. More than two dozens applications have been identified after a limited market study. They cover all continents and they total several thousand kilometers of pipes. e) conclusion The advantages of this system are manifold. Delivery of fresh water at an economical price satisfactorily meets large demands, especially agricultural uses. Low energy consumption makes it more environment friendly and less sensitive to energy price. It is simple and sturdy which allows operation by workforce with lower qualification, without external technological dependence.