It rises on the chalk slopes of Eggardon Hill,[1] approximately five miles (8 km) east of Bridport.

It flows west-northwest through the villages of Askerswell to which it gives its name, Uploders, where many cottages have gardens backing onto the river, and Loders.

Here it heads west towards Bradpole, where it is joined by the small Mangerton Brook[1] flowing in from the north.

The Environment Agency measure water quality of the river systems in England.

There are several components that are used to determine this, including biological status, which looks at the quantity and varieties of invertebrates, angiosperms and fish.