Avelon 2010: landscape analysis to prevent pollutant transfers and protect ecosystems within a watershed
(ASET, IPLB, 2010)
How to limit pollutant transfers to aquifers and protected ecosystems ?
Typical landscape of Picardie, France
The watershed of the Avelon River (Oise, France) is mainly comprised of cultivated lands, but also areas and wetlands that are ecologically valuable. Three factors shape the way pollutants are transferred inside the watershed: biotic factors (riparian vegetation, hedges, wooded buttes, ditches, bogs...), abiotic factors (slope, geology, pedology...) and human-related factors (constructions, agricultural practices...). Furthermore the status of pollutant transfers are easily assessed by multiple techniques (GIS, biotic indexes...). As my senior year project, I wanted to use these techniques to describe, diagnose, analyze and understand agricultural-based pollutant transfers within the Avelon watershed in order to prevent and manage them and thus protect ecosystems of the watershed. The primary objective of this study was to provide local community officials with a comprehensive report on the status of ground and riverine waters to meet the requirements of the directive from the DCE that orders the 'good quality' of all water masses within members of the European Community by 2015.
Material and methods
Riparian vegetation of one of the Avelon's tributary affluent
GIS (ArcGIS), along with field confirmation, allowed us to produce several maps to be analyzed:
-Map displaying the land use and landscape composition (land use patches)
-Map displaying the erosion sensitiveness (thanks to terrain and slope)
-Map displaying riparian vegetation classes along the river
Then, I used biotic techniques to measure the quality of waters:
-IBGN index (using riverine living organisms: based on the diversity)
-phytosociology index (plant association: ivy, nettle and brambles indicate a pollution with nitrates)
-Riparian vegetation index
Results and discussion
Oprhys apifera (the Bee orchid) can be found in calcarious slopes of the Oise
The watershed of the Avelon river is rather heterogenous. Zones that are very susceptible to transfer pollutants are found where arable lands are very sensitive and likely to be eroded (sharp slopes, plowed plots, no vegetation cover in winter...). It was demonstrated that these zones are the key to all pollutant transfers and pose an actual threat downstream to both man and wilderness, because no barriers allows a limitation of these pollutants (hedges, walls, ditches, forests and bogs constitute a significant and helpful buffer to all chemical transfers). A poorly diverse riparian vegetation and riverine animals is a sign of erosion of the biodiversity created by a too high pollutant transfer, originating either from far erodible cultivated lands, or cropped areas next to the river.
On the other hand, the Avelon river possesses zones with remarkable water quality (diverse plants and rare animal species), favored by a higher concentration of buffer areas (hedges and flat meadows, inclined to facilitate downwards transfers rather than horizontal ones).
As the left photo shows, watersheds of the Oise like the Avelon's can harbor rare and diverse fauna and flora, which are vital to preserve. The transfer of pollutants to these key environments can cause their eutrophication (major loss of biodiversity: species with a narrow ecological gradient, e. g. that grow in very specific and demanding conditions, die and common species take over the free niches in the ecosystem).
As a consequence, it is essential to take into account the high-risk areas pointed out in this study to improve them. Even if no measures is explicitly taken here, communities and farmers have to promote buffer areas, as well as hedges and wooded zones between fields that also connect rich ecosystems between them. Agricultural solutions should also arise in order to limit chemical sprays in the field (biological control, weed control...), failing which the Avelon river will not reach a good quality and consequently will not meet the requirements of the directive.
This study was really rewarding, because it utilized various techniques and allowed a lot of field work. Furthermore I was able to identify many rare and interesting plant species, and contribute to their conservation.
On the other hand, the Avelon river possesses zones with remarkable water quality (diverse plants and rare animal species), favored by a higher concentration of buffer areas (hedges and flat meadows, inclined to facilitate downwards transfers rather than horizontal ones).
As the left photo shows, watersheds of the Oise like the Avelon's can harbor rare and diverse fauna and flora, which are vital to preserve. The transfer of pollutants to these key environments can cause their eutrophication (major loss of biodiversity: species with a narrow ecological gradient, e. g. that grow in very specific and demanding conditions, die and common species take over the free niches in the ecosystem).
As a consequence, it is essential to take into account the high-risk areas pointed out in this study to improve them. Even if no measures is explicitly taken here, communities and farmers have to promote buffer areas, as well as hedges and wooded zones between fields that also connect rich ecosystems between them. Agricultural solutions should also arise in order to limit chemical sprays in the field (biological control, weed control...), failing which the Avelon river will not reach a good quality and consequently will not meet the requirements of the directive.
This study was really rewarding, because it utilized various techniques and allowed a lot of field work. Furthermore I was able to identify many rare and interesting plant species, and contribute to their conservation.