Water is undoubtedly the most widespread and strangest element on the planet. Its multiform nature, liquid, solid and gaseous, allows it to convert from one condition into another and with a sudden change of state it can even be sublimated. It is the substance which forms oceans, permeates the atmosphere and even determines the formation of certain types of rocks: indeed, perennial glaciers should be considered as authentic rock formations. Its volume increases when it solidifies and this property, enabling ice to float, allows the present climatic balance and the spread of dry land. The physical characteristics of water are exploited to calibrate instruments that measure temperature, volume and mass. From the remotest times water has been at work moving water mills, in recent times with steam power, in the future supplying clean energy through fuel cells. All living beings are composed of and fed with water. Most of the species of our planet live in the sea whereas all the others colonized the land by absorbing the primordial ocean. By taking the liquid component away from all animal or vegetable organisms, the dry residue is negligible in comparison with the original weight of the organism. It was through the decomposition of the water molecules in the primordial seas by cyanobacteria that oxygen was released and our atmosphere was created. We are born in water but we can drown in water as well.

Water is always mixed with other substances because of its diluting property, yet it is a symbol of purity. It is a universal solvent, that can melt and coagulate. Thin and malleable, it carves out stone and destroys metals. By its strongly destructive power and weak building strength, it, constantly, shapes the earth eroding mountains, making grooves and digging caves. In damp areas, it falls as rain, condenses into frost and dew, falls as hailstones and assumes the impalpable and crystalline form of snow. In desert areas, minuscule water particles penetrate even the hardest stone that disintegrates in the cold night temperature when water freezes. Otherwise, in the heat of the day water surges to the rocky and sandy surface, transports and deposits salts or creates oxide layers creating the beautiful painted deserts, canyons and multicoloured dunes. Water energy shapes coasts, demolishes embankments and destroys forests and towns. Its weak and insinuating tenacity allows it to build geological formations, fill up valleys and enable plants to stand. It chisels and forms the landscape: in stone by accumulating rocky layers on the earth's surface; subterranean, infiltrating the deep tunnels and shaping an architecture of stalactites and stalagmites; ethereal in the skies by the continuous movement of the clouds. The weather would not exist without water. Indeed, it operates as a general thermal regulator with the masses and the streams of the oceans on a worldwide level and by the perspiration and evaporation on the skin of the human body. Water's perpetual flow and change engage the world in a vital cycle, involving the seas, the atmosphere and underground by filtering through everywhere and vitalizing everything.

Although the contrary is believed, water is widely spread over the universe. In the galaxy of Andromeda great vaporous water masses have been observed. Comets are 70% water and it is possibly because of the comets that water is present on earth. Although it is so widespread, water is enormously precious. In proportion, if we were to pour the total water of the globe into a five-litre tank the quantity of non-salty drinking water would be no more than a spoonful. If we ignored the water in the glaciers the proportion of drinking water would be reduced to just a drop. The geographic distribution of this quantity is so unequal that the largest areas are in conditions of complete aridity.

In 1992, the United Nations organized the World Conference on the Environment and Development in Rio de Janeiro with the participation of 178 governments and 120 heads of state. The importance of that meeting was such that it is described as 'The Earth Summit'. The Conference, that aimed to reconcile the dramatic world environmental conditions with the development and the welfare of people, issued three world conventions on the climate, on biodiversity and on desertification. Each of these conventions experimented an innovative approach to the question of development and technology and considered the necessity of taking into account and re-enhancing traditional knowledge and practices. More specifically, the United Nations Convention to Combat Desertification and the Degradation of Soils (UNCCD) founded a Science and Technology Committee composed of the most outstanding experts from all countries to argue the issue of an inventory and classification of such knowledge. Thus, the Convention Secretariat began a huge research activity in all of the approximately 200 member countries.

The work of synthesis (UNCCD, 1998a) based on the reports on traditional knowledge sent in by the different countries and by the experts specifically sent on missions, proposes an inventory of traditional knowledge in a 78-item list of techniques or practices classified into 7 different topics:

However an inventory with this structure and classification based on a separation of functions due to the need to present such a vast subject, risks weakening the theme and not catching the meaning and the way of operating of the traditional techniques. Thus, the Science and Technology Committee decided to continue to extend the research by setting up a special team of experts on the topic, which has drawn up the following definition:

Each traditional practice is not an expedient to solve a specific problem, but always a studied and often a multifunctional method involved in an integrated approach (society, culture and economy) closely linked to a concept of the world based on the careful management of local resources. Terracing, for instance, is a method used to protect slopes, replenish soils and harvest water. But it is also something else. It takes on an aesthetic value and works within a social organization and a shared system of values supporting it and based on it as well.

Modern technology aims at an immediate efficiency through a high specialization of knowledge supported by dominant structures able to mobilise resources external to the environment. Traditional knowledge proficiency is appreciable over long and very long periods by resorting to shared knowledge, created and handed down from one generation to another, and also to social practices, and it exploits renewable internal inputs. Thanks to modern technology, for instance, very deep wells have been dug out to pump water up to the surface. The results have immediately been visible, but have dried up bordering resources and sometimes by drawing water from fossil pockets, with the passing of time they completely exhaust them. On the contrary, traditional knowledge uses systems for harvesting meteoric water or exploits run-off areas by using the force of gravity or water catchment methods allowing the replenishment and increasing the durability of the resource.
Modern technological methods operate by separating and specializing, whereas traditional knowledge operates by connecting and integrating. According to the usual meaning of words such as forest, agriculture and town they are completely distinct from each other and meet similarly different needs: wood, food and housing. They correspond to specialized scientific systems: silviculture, agriculture and town planning. Local knowledge does not make an artificial distinction within the world of plants between the forest supplying commercial wood and tilled land supplying food (Shiva, 1993). Forests, fields and dwellings are unitary ecological systems. Forests and other marginal apparently non-productive areas, such as steppes and marshes, provide large quantities of food and water resources, and fodder and fertilizers for agriculture. They are also convenient to live in. The traditional town, in its turn, integrates with agriculture by replacing the forest in desert areas, by collecting fertilizers produced by the inhabitants' organic waste and through its production of water collected on the roofs. The humus thus produced in the fields provides the colloidal material indispensable to build adobe towns. The cavity resulting from the excavation is used as an impluvium for water, a ditch for the transformation of excrement into humus, a productive garden protected by the outside excavated walls. This is a continuous cycle of activities in which the result of one forms the basis for the next. The buildings, right down to the smallest detail, conform to this necessity.

This principle, so close to the way in which nature works, where everything that remains of a system is reused by other systems and the concept of waste and the possibility of resorting to external resources do not exist, has allowed human beings to survive throughout history. Multipurpose and multiuse techniques have guaranteed successful results even in harsh conditions. Collaboration and symbiosis resulting from the reuse of everything produced within a system have allowed autopoiesis (self-reproduction) and a self-propulsive development independent of exogenous or occasional factors.

By this logic, when a strong cohesion between society, culture and the economy is created, this leads to positive development leaps in history. The synthesis of traditional knowledge and social systems strengthens the proper use of all resources and, consequently, determines positive changes of status and builds rural or urban ecosystems. This is the process that generated the success of the great civilizations, built on the traditional techniques that led to their economic, social and monumental results. The prosperity of the magnificent Angkor civilisation is due to the digging of colossal canals and ditches surrounding human settlements with several concentric rings in north-eastern Cambodia, a traditional practice in use since prehistoric times. These landscape-shaping techniques are usually explained as drainage or irrigation systems, but this is too narrow an interpretation. Their use as a means of defence, owing to the ease with which the ditches could be crossed, is not a convincing reason. Only an understanding of their multipurpose use (van Liere, 1980) as water reservoirs in the cold season and as a protection against floods in the humid season, and of their value as a symbol and as a form of identification of the community can explain the success of this practice.

Aesthetic and ethic values complete the interaction between environmental, productive, technological and social aspects. Traditional procedures operate a harmonious fusion between the landscape and the traditional aesthetic canons. A device for collecting or conveying water is never a merely technical structure but it also has its own beauty. Fields in the oases are systems of production and relaxing places for contemplation as well. Little agricultural fields in desert areas are called gardens, just as in Southern Italy, eliminating the separation between the vegetable garden and the pleasure garden. Often, the works and procedures have a deep symbolic meaning and are a continuous game of suggestions and analogies between techniques, art and nature. Systems of water distribution in the Sahara are reproduced in carpet drawings and in women's hairstyles. They are part of a complex symbolism linked to life, fertility and the generations. Spiritual principles make rules sacred and guarantee their perpetuation as in the case of the African sacred woods with their restricted access and of the whole set of taboo-objects, practices which guarantee the regeneration of forests, the saving of environmental resources and the land as reserves for nature and human communities.

Therefore, traditional technique is an integral part of a strongly consolidated network of links and relations, supported by a global framework of signs and meanings. It works within a socially shared cultural structure: the historical system of science and local knowledge. It is therefore wrong to isolate each single technology, which is always highly contextualised, not only linked to an environmental situation, but to a precise historical moment and a complex social construction. These are decisive reflections in the perspective of the dissemination, the reproducibility and a modern re-proposal of these traditional practices. Really, the use of traditional technique is not always and everywhere successful. The practices known as slash and burn or as itinerant agriculture allowed the survival of human communities in perfect harmony with resources over a very long time. But, it can be disastrous if applied in a completely different environmental and demographic context.

Therefore, traditional knowledge should not to be understood as a series of devices replacing the usual knowledge background, since it can generate a new paradigm. Traditional and local knowledge do not suggest miraculous solutions, which would mean to follow the modernity logic, but put forward a method to be also re-proposed through modern technologies.

Before the industrial revolution, the modification of environment is carried out through knowledge and techniques which are the result of long-term collective experience. This knowledge, and specifically water management technologies, originates from people and is transmitted to people by recognizable and experienced actors. They are systemic (inter-sectorial and holistic), experimental (empirical and practical), handed down from generation to generation and culturally enhanced. Such a kind of knowledge supports diversity and enhances and reproduces local resources.

Each traditional practice is not an expedient to solve a specific problem, but always a studied and often a multifunctional method involved in an integrated approach (society, culture and economy) closely linked to a concept of the world based on the careful management of local resources.

Therefore, traditional technique is an integral part of a strongly consolidated network of links and relations, supported by a global framework of signs and meanings. It works within a socially shared cultural structure: the historical system of science and local knowledge.

The fact of not reducing traditional knowledge to a mere series of techniques means considering it as part of the overall environmental, productive and cultural conditions of the societies. The history of traditional water management technologies and local knowledge, therefore, becomes an investigation of the social groupings. The technological dimension of these formations is based on a series of resource usage practices that are an integral part of the cultural system and guarantee the maintenance of a relationship between the social groupings and nature. Such knowledge, technologies and environmental transformation devices supply people with a larger quantity of resources than the naturally available ones. Therefore, the advantages increase, thus guaranteeing optimal life conditions that can undergo further positive changes. Those communities that are in harmony with the resources remain stable for a very long time. Deep transformations spreading over long periods or condensed into sudden status revolutions may also occur, thus determining the passage from one social formation to another.

The traditional knowledge system has been drawn up on the usual classification of the social groupings adopted in the fields of archaeology and anthropology: hunter-gatherers; farmer-breeders and metal-using agro-pastoralists. These three categories are completed by two superior syntheses composed of complex traditional social systems intensifying and integrating knowledge: oases and urban ecosystems. In them the previous social groupings technologies are stratified and variously combined, according to the different social and environmental conditions.

The first synthesis of complexity is the oasis intended as an artificial accomplishment deriving from a perfect knowledge of the environment. In the desert, dryness is interrupted by singular situations that give rise to niches and microenvironments contrasting with the overall cycle.

The urban ecosystem is the model of the oasis that has grown into a city. This system consists of large caravan cities in the desert or urban agglomerations that have grown larger than the first oasis model. Favourable geomorphologic circumstances are exploited to create irrigated areas in specific geographic systems. An important capital dominates each landscape unit: isolated basins in the middle of the desert; large plains among the mountain peaks; strips of oases along hydrographic networks, international and intercontinental crossroads. Making the most of the available resources, even traditional habitat systems develop into historical centres of regional importance and with urban features.

The classification chronologically outlines the continuous process of knowledge accumulation and stratification, since the first three social groupings correspond to the passage from the Palaeolithic and Neolithic Ages to the Iron Age and to the upper levels of complexity of oases and urban ecosystems. But even if this is useful for classification purposes it would be misleading as a theoretical definition. The social groupings of our model are not conceived as phases in the evolution of human history but rather as typical conditions of specific ages. They can, however, co-exist within the same historical background and indeed they guarantee continuity, stratification and interpenetration.

Socio-cultural formations that prevailed in early human history still largely exist within human groupings, where the practice of knowledge is similar to that derived from palaeontological and archaeological surveys. Obviously there are differences, but these are largely already present within those communities belonging to the same social grouping and living in the same historical period. The types of social-cultural formation should not be intended as universally shared models: they develop depending on the geographical background and the dominant conceptions. Classification is a scientific principle, but it conceals the succession and stratification, in time, of levels of technology and culture, the different climatic and environmental conditions simultaneously occurring and the synchronic existence in history of human experiences and different social models. Both the environment and a community's conception of the world contribute to the creation and maintenance of specific characteristics. Both these factors continuously vary in time and from one place to another, thus creating and preserving cultural diversity.