Video movie on level canals of Pilat Mountain

Level canals association of Pilat mountain-10 juin 2008

In the past centuries, the biefs, bisses, beals and bealieres, were french words to designate works in charge of supplying water in the paddle wheels and the turbines of the mills,sawmills and factories of weaving.They also made it possible to irrigate fields and meadows.The Romans,in the past,thanks to their aqueducts,already controlled the art of transport of water,while following the level lines.These techniques of another age,however owed and renewable,were too quickly abandoned by the profits of others ,more criticizable. They could ,after reflecting,become the principal and essential tool of the total managment of water,and the durable development.


Many human activities contribute to diminish the part of infiltration compared to the runoff and evaporation. More and more of waterproofed surfaces favour the runoff and contribute to reinforce the destructive effects of the floods downhill. The deforestations and modern agriculture increase the erosion of soils. At the same time, to satisfy the needs in drinking and irrigation water, a discreet but continuous phreatic over-pumping modifies the underground reserves without holding into account the natural capacities of recharge. Finally,there has to be added the disappearance of humid zones, because of the drainage, which constitutes important reservoirs for permanent underground water recharge. We attribute the climatic changes exclusively to the effect greenhouse. But it seems that over-pumping, especially in drought zones, is also responsible for this climatic change .
It is urgent to set up a device global management of water capable, not only to repair these effects, but to create a modern tool of durable development base on all the potentialities of water. The Association " Les Biefs du Pilat" calls the attention to a phenomenon that seems , for the moment,to escape to the reflections of experts and decision-makers.
It is urgent to have a look closer to the consequences of human activities on the water cycle and more particulary to the changes on the distribution of superficial and underground flows.
Naturally, meaning without farming, expressways or parking lots, otherwise said without artificial waterproofed lands, the rain, vegetation and ground would establish an optimum ratio between infiltration, runoff and evaporation, resulting in an ecological balance. What has not been infiltrated to the profit of underground water reserves and what has not been evapored to the profit of the micro-climate, otherwise said the excess, flows , forming the streams, kind of natural drains.
The underground water cycle and the climate, are narrowly linked. It is evident that water falls recharge underground reserves. It is necessary to know that,in return, the soil and its humidity, through which its vegetable cover, when there is one, influences the atmosphere and therefore the climate. As an example, the evapo-transpiration of plants that restores an important amount of water to the atmosphere , in order to maintain a good temperature and favourable humidity for life.
Since the apparition of human activities,of intensive and extended farming,in somes places, we reduce the vegetable cover and more seriously, we drought humid zones by drainage to replace them by prairies. In other places, we increase vegetable growth by over-pumping in order to compensate for the lack of rain. Rain, waterproofed lands, drainage and water pumping have as a consequence to diminish the surface of humid lands, essential interfaces between the soil and atmosphere for the water flux. Thus, the part of infiltration is significantly diminished to the profit of the runoff. In fact, we can have floods while underground spaces are not yet saturated. The most urgent problem is to preserve and to restore aquifers.


The Association proposes to adapt the installations that are the biefs. The biefs are canals which flow through the country by following the bend levels. Formerly, they served to supply mills to produce the hydraulic energy tanks to turbines or wheels, they also allowed to irrigate lands .The water loss, by the bottom of the biefs, were considered as waste. With modern agriculture and industrialisation, the biefs have been abandoned. Today, the need of a global water management could drive us to reconsider this means of water distribution by taking advantage of this defect concerning those losses of water .
The biefs remove the surplus of stream's water to redistribute it laterally, in order to reintroduce the water in the ground by infiltrating it all along the canal. They participate to preserve the resources in water and to delay the flows. Thus, underground water storage during the humid periods will return naturally to the profit of streams during drought periods. A network of biefs ahead of watershed delays the flows, limits the runoff, restores the underground reserves and supports drought downhill streams.
Biefs are useful where groundwater withdrawals consistently exceed recharge to the aquifers. It is important to use this quality water ahead of watersheds and to take advantage of this resource instead of leaving this clean water run downhill to dilute pollution and increase floods. This deep "dynamic storage" allows chemical exchanges, to improve the quality of water. In fact, the biefs can play an active role in runoff and floods or firewoods management tank reservoirs all along the biefs. This water, stored during the stormy periods, will be used again for the functioning of the biefs and also to serve for hydro-electric production. Drinkable water of the cities could directly come from mountains. In the country, farming would dispose abundant water of better quality, for irrigation with less chemical fertilizers. ( Abundant fishing and hunting, green tourism..)
Facing the floods, the droughts and the world-wide crises of the water resources, in addition to the over pumping rate and to the climatic changes, the biefs are a supplementary tool for a durable management of water. Source of new employment, they will be motor of development and new activities linked to agriculture, irrigation, and hydraulic energy . On long term and on a large scale, the water, when widely divided up and redistributed in space and in time by a network of biefs, will restore the water balance with a positive consequences on local and regional climate.

Retour page d'accueil Retour à l'accueil

© All reserved rights 1999 The Biefs of the Pilat