The River Derwent, some 50 odd miles in length, is the longest river in Derbyshire. Apart from it's short passage through the City of Derby it is a completely rural river, finally joining the River Trent just south of Derby. The Derwent's source is at Swain's Greave on Howden Moor on the flank of Bleaklow Hill. It soon flows into the first of 3 large reservoirs, built in the early part of the 20th century to satisfy the growing demand for water from the expanding cities of Derby, Nottingham, Sheffield and Leicester. Howden was the first to be built ( 1901-12 ), Derwent followed ( 1902-16 ) and work then began on the largest, Ladybower, in 1935. It took 10 years to complete ladybower and the historic villages of Derwent and Ashopton were lost in the process. A whole village was created to house the men and their families who had built the early dams, which was colloquially known as 'Tin Town' because of it's corrugated roofs. It's official name was Birchinlee and it housed over 1000 inhabitants at one time.

At Mythorn Bridge, the river Derwent is joined by the river Noe which rises on Mam Tor and flows through the Hope Valley. Flowing on between Win Hill and Lose Hill, the Derwent is soon augumented by waters from Crowden, Grinds Brooks and Jaggers Clough. The river flows on to Hathersage and then turns south again to flow in a wide valley flanked by gritstone edges through the villages of Grindleford, Froggatt and Calver before reaching Baslow. At Calver it flows beneath an 18th century bridge. Calver Mill was first built in 1785, utilizing the power of the Derwent, but destroyed by fire and rebuilt in 1805 when it became a thriving cotton mill employing a large number of local people. It finished producing cotton in 1923 and has had a number of uses since then, including the role of Colditz Castle in the television series, Colditz. It has now been developed into modern flats.

In Baslow at Bridge End, the river Derwent is spanned by a charming, 17th century, 3 arched bridge, beside which is a little stone shelter built for the toll collector. The river Derwent then flows through the grounds of Chatsworth Park, the home of the Duke of Devonshire, in a beautifully landscaped setting, to be joined by the River Wye at Rowsley, coming in from Bakewell.

After passing beneath a 15th century bridge at Darley Dale which carries the road to Winster and then the 4 arched bridge at Matlock, the river carves its way through a ridge of limestone just south of Matlock in order to reach the lower ground to the South. This part of the valley is spectacular, steep-sided, winding and wooded, with high cliffs such as High Tor towering above. Below Rowsley the river valley widens again and passes through the more industrialised area around Darley Dale, to reach Matlock. Here the character of the valley changes abruptly, for the river carves its way through a ridge of limestone in order to reach the lower ground to the South forming some spectacular scenery, the valley now being steep-sided, winding and wooded, with high cliffs such as High Tor towering 350ft above.

The river is now flowing through an area known as the Derwent Valley Mills, a nominated World Heritage Site.Starting with Richard Arkwright's pioneering developments at Masson Mill and Cromford mills, expanding down the Derwent Valley by his friends and business partners; Jedediah Strutt at Belper and Milford and Thomas Evans at Darley Abbey. It continues on to Derby, passing Lombe's Silk Mill. Though largely destroyed by fire in 1910, one can still see the massive stone arches that formed the base of the original five-storey building.

After passing under road and rail bridges in Derby the river meanders up towards the acetate factory at Spondon, then Borrowash, on it's way to a meeting with the Trent at Great Wilne. Part of the river section here is a considerable nature reserve which attracts a wide variety of wildlife.