HydroBASINS lev08 watershed · #2080491200
Bassin de l'Arz
A watershed (drainage basin) is not a body of water — it is the land area where rainfall converges towards a single river that eventually reaches the sea (or an endorheic basin). Boundaries follow ridgelines.
Crosses 3 administrative regions : Ille-et-Vilaine, Loire-Atlantique, Morbihan
Sub-basin area
350km²
Upstream area
3 597,5km²
Discharge
66,18m³/s
Mean elev.
70m
Administrative coverage
Hydrographic chain
▼ Drains into
▲ Receives from 2 basins
3 dept-equivalent regions (GADM L2)
- 327.7 km²93.4% of basin
- 23.2 km²6.6% of basin
- 0.1 km²0.0% of basin
32 communes (GADM L5)Available for FRA, RWA
- Elven51.63 km²79% commune
- Malansac33.18 km²92% commune
- Pluherlin28.52 km²81% commune
- Plaudren26.85 km²66% commune
- Saint-Jacut-les-Pins23.34 km²99% commune
- Molac20.36 km²70% commune
- Allaire20.22 km²48% commune
- Larré16.62 km²97% commune
- Bains-sur-Oust16.09 km²35% commune
- Le Cours14.45 km²95% commune
- Peillac13.14 km²53% commune
- Questembert13.01 km²19% commune
- Monterblanc11.16 km²44% commune
- Saint-Gravé11.13 km²69% commune
- Saint-Vincent-sur-Oust10.70 km²67% commune
- Trédion9.85 km²38% commune
- Redon7.15 km²46% commune
- Saint-Jean-la-Poterie6.66 km²82% commune
- Saint-Perreux5.92 km²100% commune
- La Vraie-Croix2.89 km²18% commune
- Saint-Nolff2.37 km²9% commune
- Plumelec1.42 km²2% commune
- Locqueltas1.29 km²7% commune
- Rochefort-en-Terre1.17 km²100% commune
- Saint-Guyomard0.49 km²2% commune
- Rieux0.47 km²2% commune
- Caden0.40 km²1% commune
- Saint-Gorgon0.35 km²6% commune
- Saint-Nicolas-de-Redon0.08 km²0% commune
- Limerzel0.08 km²0% commune
- Saint-Congard0.03 km²0% commune
- Glénac0.01 km²0% commune
4 intersecting protected areas
Golfe Du Morbihan
IUCN VRegional Nature Park
64.76 km² overlap
Marais de Vilaine
IUCN Not ReportedSpecial Areas of Conservation (Habitats Directive)
13.35 km² overlap
Vallée de l'Arz
IUCN Not ReportedSpecial Areas of Conservation (Habitats Directive)
12.34 km² overlap
Biotope Protection Order
0.07 km² overlap
Computed live · GADM 4.1 × HydroBASINS lev08 × WDPA · cached after first hit.
Species present
2 189 distinct species · 45 757 observations
Source: GBIF Occurrence snapshot 2026-05-01.
Ecological tissue
Sample of 32 species (selected proportionally per kingdom among those with at least one documented interaction here) to keep the graph readable. Hover for details, click to explore the full ecosystem of a species.
ℹ️ The territory contains many more species than displayed and all their documented interactions: the graph is intentionally the structural skeleton (top-N species by composite local score, edges filtered by Serrano 2009 disparity filter α=0.2).
Indicateurs du tissu écologique
Tissu écologique de Bassin de l'Arz : 25 espèces + 7 bulles famille, 72 interactions GloBI documentées sur 4 types (connectance 14.5%, filtre Serrano α=0.2). Les 7 bulles regroupent des espèces visuellement absorbées par famille (≥3 espèces visibles).
Comparaison sur la connectance du réseau local complet vs distribution nationale (toutes les communes françaises).
Hydroclimate (BasinATLAS lev08)
Mean T°
11,3°C
Annual rain
818mm
Moisture idx (CMI)
0,07
Runoff
566mm/an
PET
758mm
AET
565mm
Mean slope
2,3°
Water table
212cm
Forest
3%
Crops
48%
Urban
2%
Protected
0%
HydroATLAS BasinATLAS v10 (Linke et al. 2019) · HydroBASINS lev08 (Lehner & Grill 2013)