Calder Valley

Calder
River
View of the Calder Valley west of Hebden Bridge
Country	England
Metropolitan County	West Yorkshire
Towns/Cities	Todmorden, Hebden Bridge, Sowerby Bridge, Elland, Brighouse, Mirfield, Dewsbury, Wakefield
Source	Heald Moor
- location	Todmorden, Calderdale, West Yorkshire, UK
- elevation	1,312 ft (400 m)
Mouth
- location	River Aire, Castleford, UK
Length	45 mi (72 km)

The River Calder is a river in West Yorkshire, in Northern England.

The Calder rises on the eastern slopes of the Pennines and flows through green countryside, former woollen-mill villages, and large and small towns before joining the River Aire near Castleford.

The river's valley is generally known as the Calder Valley. The name Calderdale usually refers to the large urban and rural borough (centred on Halifax) through which the upper river flows. The lower reaches flow through the boroughs of Kirklees (based on Huddersfield) and Wakefield. However, the river does not flow through the centres of Halifax and Huddersfield, which are on the Calder's main tributaries, Hebble Brook and the River Colne respectively. The only large town centres through which the Calder flows are Brighouse, Mirfield, Dewsbury and the city of Wakefield.

The river itself is only navigable in short sections, but these sections are connected by artificial "cuts" (e.g. Horbury Cut) to form the Calder and Hebble Navigation, a popular leisure waterway which is part of the connected inland waterway network of England and Wales.

The name 'Calder' is thought to come from the early Common Brittonic, meaning 'hard or violent water' (the modern Welsh word for hard is "caled"), or possibly from another Celtic language, meaning river of stones. Another possible explanation is that it is a corruption of "Gauls' der"; "Gauls" being an ancient form of "Celts" and "der" meaning water. Hence Calder would mean the Celts' River. This is possible as the moorlands and rugged valleys of upper Calderdale remained a Celtic area for at least two centuries after the surrounding lowlands became dominated by Anglo-Saxon culture. This history is reflected in the name of a village, Walsden, just inside the border of upper Calderdale, which is probably derived from Wales Dene, or "Valley of the "Welsh" (foreigners)" in Anglo-Saxon. However, there are several rivers in Britain named Calder, which do not necessarily have the same history.