L'Assomption River

The Assomption River (in French Rivière l'Assomption , named after the Assumption of Mary) is the most important waterway in the Lanaudière region of Quebec, Canada. It is over long, and has a drainage basin (watershed) of . Its source is the Mont Tremblant massif. Seven significant rivers flow into the Assomption (de la Boule, Versailles, Noire, la Chaloupe, Ouareau, Saint-Esprit, and Achigan) before it flows into the Rivière des Prairies at Repentigny, Quebec.

About 150,000 people live in the drainage area of this river.

Geography

The L'Assomption River watershed overlaps two natural environments, the Laurentian Mountains and the St-Lawrence lowlands, which cover about a third of the watershed area. Its relief is a uniform plain with some hills—from —dominated by agricultural lands. The texture of the soil is rather fine and rests on an impermeable argillaceous (clay) base.

The Laurentian Mountains form part of the Canadian Shield. They are separated from the lowlands by a well-defined escarpment that rises about . This escarpment has many waterfalls. The Laurentians Mountains have an average height of in the south and in the north. And there are even mountains of over in the Mont Tremblant massif where the L'Assomption River forms.

Hydrography

From north to south the average slope of the river decreases. The steeper slopes of the highlands create a fast current whereas the lowland flats produces a slower flow. Moreover, the river meanders a lot which is especially evident at the town of L'Assomption, almost completely surrounded by a large loop of the river.

The L'Assomption River watershed has 490 lakes of which 24 have a surface area larger than . Most of the lakes are in the Laurentian highlands.

Water quality

Urban and industrial pollution

The water quality of the L'Assomption River is seriously affected by the area's social-economic conditions. Since 1950, the situation has been complicated by the urbanization of the river banks, by diversified agriculture, and by industrialisation along the southern portion of the river. Although the source of pollution has changed since 1950, because of strict environmental laws and the use of water purification equipment, water pollution is still not fully curbed.

Over 150,000 people live in the river's watershed in 43 municipalities, of which the most important are Repentigny, Joliette, Le Gardeur, and L'Assomption. In addition, the northern portion of the river's watershed is a popular vacation area, swelling the population by about 45,000 people during the vacation season.

The majority of the municipalities take their drinking water from the river and provide it to more than 100,000 people. The drinking water supply to other residences and country cottages, distributed over approximately 90 percent of the watershed area, comes from water wells.

Agricultural pollution

Besides the urban and industrial pollution, agricultural pollution also contributes greatly to the environment's contamination.

Agriculture has a dominant position along the river: in 1995 there were 1,305 producers with under cultivation and possessing 73,563 animals.

Agricultural pollution takes several forms: direct pollution (discharge of manure directly in the rivers) and diffused pollution (infiltration of fertilizer products in the groundwater). Diffused pollution is difficult to control because it has a multitude of sources throughout the whole region. Yet without a solution to this problem the water quality of the river will never have the desired quality.

Drainage basin watercourses

Order	Label	Mouth	Coordinates	Length (km)	Source	Coordinates	Region
1	L'Assomption River	Rivière des Prairies		200	L'Assomption Lake		Lanaudière
2	Template:Ill	L'Assomption River		83.8	Template:Ill		Lanaudière
3	Template:Ill	Template:Ill		19.4	Duquette Lake		Laurentides
4	Template:Ill	Template:Ill		10.8	Connely Lake		Laurentides
5	Template:Ill	Template:Ill		20	Lac de la Crosse		Laurentides
6	Template:Ill	Template:Ill		13	Saint-Calixte		Laurentides
7	Template:Ill	L'Assomption River		90.4	Huard Lake		Lanaudière
8	Template:Ill	L'Assomption River		19.2	Saint-Alexis		Lanaudière
9	Ouareau River	L'Assomption River		80	Template:Ill		Lanaudière
10	Template:Ill	Ouareau River		16.9	Racette Lake		Lanaudière Laurentides
11	Template:Ill	Ouareau River		20.9	Lac des Îles		Lanaudière
12	Template:Ill	Template:Ill		10.4	Heroux Lake		Lanaudière
13	Template:Ill	Ouareau River		9.2	Beaulne Lake		Lanaudière
14	Template:Ill	Ouareau River		29.6	Dufresne Lake		Lanaudière Laurentides
15	Template:Ill	Ouareau River		56.5	Couture Lake		Lanaudière
16	Template:Ill	Template:Ill		17.8	Template:Ill		Lanaudière
17	Template:Ill	Template:Ill		15.1	Sainte-Mélanie		Lanaudière
18	Template:Ill	Ouareau River		7.6	Chertsey Lake		Lanaudière
19	Template:Ill	Ouareau River		6.5	Lac du Pin Rouge		Lanaudière
20	Template:Ill	L'Assomption River		12.5	spring		Lanaudière
21	Template:Ill	L'Assomption River		8.7	Lac des Cèdres		Lanaudière
22	Template:Ill	Template:Ill		12.6	Vauvert Lake		Lanaudière
23	Template:Ill	L'Assomption River		14.4	Marguerite Lake		Lanaudière
24	Template:Ill	L'Assomption River		16.9	St-Amour Lake		Lanaudière
25	Template:Ill	L'Assomption River		14.7	Laré Lake		Lanaudière
26	Template:Ill	L'Assomption River		52.6	Lemieux Lake		Lanaudière
27	Template:Ill	Template:Ill		10.8	Lac à Canards		Lanaudière
28	Template:Ill	Template:Ill		16	small lake		Lanaudière
29	Template:Ill	Template:Ill		17	Lac à la Pluie		Lanaudière
30	Template:Ill	L'Assomption River		20.6	Lanoraie		Lanaudière

List of towns crossed

File:Lassomption-vue air.jpg

The large meander of the L'Assomption River at the Town of L'Assomption

• Saint-Côme
• Saint-Alphonse-Rodriguez
• Sainte-Béatrix
• Saint-Jean-de-Matha
• Saint-Félix-de-Valois
• Sainte-Mélanie
• Saint-Ambroise-de-Kildare
• Notre-Dame-de-Lourdes
• Notre-Dame-des-Prairies
• Saint-Charles-Borromée
• Joliette
• Saint-Thomas
• Saint-Paul
• L'Épiphanie
• L'Assomption
• Repentigny
• Charlemagne

External links

• Corporation de l'Aménagement de la Rivière l'Assomption
• De l'Outaragasipi à la Rivière l'Assomption