HydroBASINS lev08 watershed · #2080022540
Bassin de l'Aa
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 2 administrative regions : Nord, Pas-de-Calais
Sub-basin area
933,9km²
Upstream area
933,9km²
Discharge
17,58m³/s
Mean elev.
81m
Administrative coverage
2 dept-equivalent regions (GADM L2)
- 789.3 km²84.2% of basin
- 147.9 km²15.8% of basin
140 communes (GADM L5)Available for FRA, RWA
- Bourbourg27.76 km²70% commune
- Éperlecques26.10 km²100% commune
- Thiembronne23.37 km²100% commune
- Bourthes22.60 km²100% commune
- Arques19.93 km²88% commune
- Sainte-Marie-Kerque19.04 km²100% commune
- Clairmarais18.16 km²100% commune
- Tournehem-sur-la-Hem18.09 km²96% commune
- Saint-Omer16.60 km²100% commune
- Gravelines15.75 km²76% commune
- Seninghem15.63 km²100% commune
- Renty15.55 km²98% commune
- Saint-Folquin14.88 km²84% commune
- Acquin-Westbécourt14.46 km²100% commune
- Ruminghem13.91 km²100% commune
- Herly13.71 km²81% commune
- Verchocq13.68 km²90% commune
- Licques12.95 km²70% commune
- Campagne-lès-Boulonnais12.77 km²100% commune
- Loon-Plage12.72 km²35% commune
- Wismes12.47 km²100% commune
- Nielles-lès-Bléquin12.20 km²100% commune
- Wavrans-sur-l'Aa12.12 km²100% commune
- Merck-Saint-Liévin12.06 km²100% commune
- Muncq-Nieurlet11.81 km²100% commune
- Mentque-Nortbécourt11.00 km²100% commune
- Noordpeene10.90 km²63% commune
- Bonningues-lès-Ardres10.64 km²100% commune
- Serques10.51 km²100% commune
- Nieurlet10.46 km²100% commune
- Alquines10.27 km²100% commune
- Lumbres10.21 km²100% commune
- Coulomby10.03 km²100% commune
- Quelmes9.92 km²100% commune
- Moringhem9.92 km²100% commune
- Esquerdes9.54 km²100% commune
- Audrehem9.41 km²100% commune
- Ergny9.39 km²100% commune
- Blendecques9.10 km²94% commune
- Alembon8.76 km²95% commune
- Cappelle-Brouck8.71 km²51% commune
- Bléquin8.70 km²100% commune
- Saint-Pierre-Brouck8.67 km²100% commune
- Ledinghem8.51 km²100% commune
- Longuenesse8.49 km²100% commune
- Zutkerque8.01 km²48% commune
- Saint-Georges-sur-l'Aa7.84 km²100% commune
- Vaudringhem7.65 km²100% commune
- Zudausques7.50 km²100% commune
- Tilques7.14 km²100% commune
- Watten7.10 km²91% commune
- Rumilly7.02 km²100% commune
- Audruicq6.65 km²47% commune
- Fauquembergues6.58 km²97% commune
- Clerques6.55 km²94% commune
- Saint-Martin-d'Hardinghem6.54 km²97% commune
- Bouvelinghem6.52 km²100% commune
- Wizernes6.52 km²100% commune
- Wicquinghem6.34 km²91% commune
- Houlle6.24 km²100% commune
- Lederzeele6.20 km²71% commune
- Bainghen6.15 km²94% commune
- Bécourt6.09 km²100% commune
- Elnes6.07 km²100% commune
- Zoteux6.04 km²81% commune
- Surques6.02 km²87% commune
- Sanghen5.95 km²99% commune
- Nordausques5.78 km²100% commune
- Saint-Momelin5.73 km²100% commune
- Tatinghem5.64 km²100% commune
- Hallines5.43 km²100% commune
- Ouve-Wirquin5.22 km²100% commune
- Remilly-Wirquin5.19 km²100% commune
- Rebergues5.13 km²100% commune
- Recques-sur-Hem5.13 km²100% commune
- Haut-Loquin5.04 km²100% commune
- Moulle5.03 km²100% commune
- Renescure4.92 km²26% commune
- Polincove4.87 km²100% commune
- Aix-en-Ergny4.81 km²100% commune
- Escœuilles4.74 km²79% commune
- Leulinghem4.65 km²100% commune
- Saint-Martin-au-Laërt4.65 km²100% commune
- Herbinghen4.41 km²99% commune
- Bayenghem-lès-Éperlecques4.17 km²100% commune
- Craywick4.02 km²55% commune
- Holque3.91 km²100% commune
- Cléty3.90 km²64% commune
- Salperwick3.88 km²100% commune
- Buysscheure3.86 km²62% commune
- Setques3.80 km²100% commune
- Wisques3.72 km²100% commune
- Quesques3.46 km²24% commune
- Avroult3.44 km²72% commune
- Nort-Leulinghem3.44 km²100% commune
- Bayenghem-lès-Seninghem3.35 km²100% commune
- Journy3.29 km²100% commune
- Affringues3.07 km²100% commune
- Avesnes2.99 km²100% commune
- Zouafques2.89 km²74% commune
- Boisdinghem2.87 km²100% commune
- Pihem2.81 km²38% commune
- Vieil-Moutier2.78 km²49% commune
- Saint-Omer-Capelle2.43 km²23% commune
- Oye-Plage2.30 km²6% commune
- Courset2.08 km²20% commune
- Helfaut2.07 km²23% commune
- Grand-Fort-Philippe2.02 km²57% commune
- Senlecques1.97 km²100% commune
- Quercamps1.96 km²100% commune
- Hocquinghen1.90 km²100% commune
- Saint-Martin-Choquel1.84 km²32% commune
- Preures1.79 km²11% commune
- Wulverdinghe1.63 km²55% commune
- Maninghem1.44 km²37% commune
- Vieille-Église1.40 km²7% commune
- Dohem1.37 km²15% commune
- Bavinchove1.25 km²14% commune
- Hucqueliers1.24 km²15% commune
- Ebblinghem1.17 km²12% commune
- Zuytpeene1.12 km²10% commune
- Millam1.09 km²9% commune
- Lottinghen0.99 km²9% commune
- Bezinghem0.87 km²7% commune
- Volckerinckhove0.69 km²7% commune
- Audincthun0.48 km²3% commune
- Staple0.35 km²4% commune
- Doudeauville0.30 km²2% commune
- Colembert0.26 km²2% commune
- Bouquehault0.22 km²3% commune
- Louches0.17 km²1% commune
- Heuringhem0.14 km²3% commune
- Hermelinghen0.12 km²2% commune
- Coupelle-Vieille0.08 km²1% commune
- Desvres0.07 km²1% commune
- Menneville0.07 km²1% commune
- Landrethun-lès-Ardres0.05 km²1% commune
- Nabringhen0.04 km²1% commune
- Boursin0.02 km²0% commune
- Nortkerque0.00 km²0% commune
23 intersecting protected areas
Caps Et Marais D\'Opale
IUCN VRegional Nature Park
580.11 km² overlap
Le Marais audomarois
IUCN Not ReportedWetland of International Importance (Ramsar Site)
37.23 km² overlap
Prairies, marais tourbeux, forêts et bois de la cuvette audomaroise et de ses versants
IUCN Not ReportedSpecial Areas of Conservation (Habitats Directive)
5.61 km² overlap
Biotope Protection Order
4.87 km² overlap
Forêt de Tournehem et pelouses de la cuesta du pays de Licques
IUCN Not ReportedSpecial Areas of Conservation (Habitats Directive)
4.41 km² overlap
Pelouses et bois neutrocalcicoles des cuestas du Boulonnais et du Pays de Licques et forêt de Guines
IUCN Not ReportedSpecial Areas of Conservation (Habitats Directive)
4.22 km² overlap
Pelouses, bois acides à neutrocalcicoles, landes nord-atlantiques du plateau d'Helfaut et système alluvial de la moyenne vallée de l'Aa
IUCN Not ReportedSpecial Areas of Conservation (Habitats Directive)
2.73 km² overlap
Marais audomarois
IUCN IVLand acquired by Conservatoire du Littoral (national seaside and lakeside conservancy)
2.56 km² overlap
Biotope Protection Order
2.34 km² overlap
14 more protected areassorted by overlap area
Biotope Protection Order
1.85 km² overlap
Marais Audomarois
IUCN Not ReportedSpecial Protection Area (Birds Directive)
1.77 km² overlap
Landes Du Plateau D\'Helfaut
IUCN IVBiotope Protection Order
1.74 km² overlap
Étangs Du Romelaëre
IUCN IVNational Nature Reserve
1.05 km² overlap
Plateau Des Landes
IUCN IVRegional Nature Reserve
0.94 km² overlap
Coteau de la Montagne d'Acquin et pelouses du Val de Lumbres
IUCN Not ReportedSpecial Areas of Conservation (Habitats Directive)
0.68 km² overlap
National Nature Reserve
0.54 km² overlap
Land acquired by a regional conservatory of natural areas
0.11 km² overlap
Prairies Du Schoubrouck
IUCN IVRegional Nature Reserve
0.11 km² overlap
Long Chêne
IUCN IVForest Managed Biological Reserve
0.09 km² overlap
Marais Saint-Aldegonde
IUCN IVBiotope Protection Order
0.08 km² overlap
Land acquired by a regional conservatory of natural areas
0.06 km² overlap
Anciennes Carrières De Cléty
IUCN IVRegional Nature Reserve
0.02 km² overlap
Land acquired by a regional conservatory of natural areas
0.02 km² overlap
Computed live · GADM 4.1 × HydroBASINS lev08 × WDPA · cached after first hit.
Species present
6 281 distinct species · 604 342 observations
Source: GBIF Occurrence snapshot 2026-05-01.
Ecological tissue
Sample of 38 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'Aa : 26 espèces dont 4 patrimoniales (LR IUCN CR/EN/VU) reliées par 141 interactions GloBI sur 6 types (connectance 19.0%, filtre Serrano α=0.2). 13 bulles taxonomiques (cascade genre/famille GloBI, ≥3 espèces).
Comparaison sur la connectance du réseau local complet vs distribution nationale (toutes les communes françaises).
Hydroclimate (BasinATLAS lev08)
Mean T°
10,1°C
Annual rain
666mm
Moisture idx (CMI)
0,03
Runoff
555mm/an
PET
647mm
AET
494mm
Mean slope
2,2°
Water table
122cm
Forest
0%
Crops
61%
Urban
7%
Protected
58%
HydroATLAS BasinATLAS v10 (Linke et al. 2019) · HydroBASINS lev08 (Lehner & Grill 2013)