Just 90km (56 miles) long, the Nidd gets its name from the Celtic word for brilliant. It rises at Nidd Head Spring on the slopes of Great Whernside in the Yorkshire Dales, 595m above sea level. In its first few miles it is dammed three times to create Angram Reservoir, Scar House Reservoir and Gouthwaite Reservoir where compensation flows are released.
The classic pool and riffle upper reaches support good stocks of Brown trout and Grayling. The Nidd can overflow the reservoirs, flooding the caves in the valley in which case the river then flows along the normally dry river bed past Lofthouse through to Gouthwaite Reservoir.
It flows through Pateley Bridge and Knaresborough before going on to join the River Ouse at Nun Monkton near York.