[4] The river rises approximately 1,300 feet (400 m) above sea level at Heald Moor,[5] north-west of Todmorden, and drains an area of 369 square miles (957 km2).

The river formed an important transportation system for raw materials and the products of the mills, particularly prior to the development of other infrastructures such as road and railway links to the area.

Wakefield's medieval nine-arched bridge is 320 feet (98 m) long, was built in sandstone between 1342 and 1356, and replaced an earlier wooden structure on the site of an ancient ford.

At Wakefield, a variety of former mill buildings are currently being redeveloped to create a Waterfront project which will combine residential housing, offices, galleries and public spaces.

The last salmon on record was caught at Wakefield in 1850, however there is evidence that they are returning, with sightings on the lower river at Castleford in 2008[21] and alleged catchings much further upstream.

Around Huddersfield, Mirfield and Wakefield are popular areas for coarse fishing, roach, perch, chub, dace, minnows, gudgeon, pike, bream and trout.

The areas upstream of Dewsbury are quickly becoming cleaner and more suited to game and specialised river cyprinids like barbel, as well as general coarse fish that are also doing well.

Recent improvements in reducing the amount of pollution have led to the return of native wildlife, such as the otter and kingfisher to stretches of the river.

Close to its source at Heald Foot, the water is polluted by the remains of past opencast mining activities and a landfill site.

As the river reached Huddersfield, the traditional textile industries created a considerable amount of water pollution, particularly through the processes involved in the production of synthetic dyes and in scouring the wool clean.

The enormous growth of the population over the last hundred years (currently over 800,000 people live within the river's catchment) has caused other problems in relation to sewage.

On Easter Monday, after a long weekend holiday shutdown, the water cleared and the river bottom could actually be seen, looking like a grey wool blanket.

The river has a history of flooding, mainly due to the high sides of its banks in its earlier stages, which cause rapid runoff of water following heavy rain.