Question needs much more detail
From its source to its mouth.
It's mouth length is about 185 m
820miles 1300km
The source of the River Waal is the River Rhine and the mouth of the Waal is Boven Merwede. The length of the Waal is 50 miles.
The length of the Yarra River is 242 km, from its source in Mt Baw Baw to its mouth at Port Phillip Bay.
The length of the River Angara is 1,105 miles. This river is located in the country of Russia and its mouth is the Yenisei River.
The mouth of a river is where it meets the sea or ocean. The Amazon river's mouth is actually un-pinpointable because of the rivers amazing length, meaning the mouth covers more than one area.
The river runs however long, all the while picking up sediment, sand, rocks, etc. and continue doing this for the river's length, and at the very end of the river (mouth), all of this sediment is deposited, leaivng sand at the river mouth.
As far as I am familiar, there is no Argus River in Spain. If, perhaps, you meant the Tagus River (Río Tajo in Spanish), the river has its source and most of its length in Spain, but its mouth is in Portugal.
There are two mouths to the Red River of the south and they are the Atchafalaya River and Mississippi River. The Red River is 1,360 miles in length.
The length of the River Angara is 1,105 miles. This river is located in the country of Russia and its mouth is the Yenisei River.
The Pasig River is located in the Philippines. It is 17 miles in length, which is equal to 27 kilometers. The mouth of the Pasig River is Manila Bay.