Impact de la conduite des peuplements forestiers sur les ressources en eau

Click to increase image sizeClick to decrease image size

The first part deals with the impact of silviculture on the volume of water available downstream. The "leaf area index" parameter, which is functionally linked with the evapotranspiration of the canopy, looks to be a promising indicator to the forester who wants to control the consumption of water in its stand. However, the examples of practical silviculture aimed at reducing (USA) or increasing (New Zealand) water consumption of forests do not seem to be applicable on a large scale in France. A fine-tuned silviculture, best suited to the french situation, is still to be devised. The second part deals with the impact of silviculture on water quality. The overall quality of waters flowing from french forests is good, but, in some places, acidification is a looming risk. There are many ways by which the silviculturist may increase locally the amount of minerals or solid particles in waters. Preventive measures are now well known and are proven to give good results : they only have to be generally enforced so that the quality of waters flowing from the forests will be guaranteed in the long run. The conclusion presents two challenges that have to be met at the catchment level ; research is needed to develop management tools to be used in selecting zones where action has to take place and the nature of interventions ; on the political level, expertise in getting land-owners participating in the water management activities has to be increased.